MC68HC908MR32 [FREESCALE]
M68HC08 Microcontrollers; M68HC08微控制器
| 型号： | MC68HC908MR32 |
| 厂家： | 
Freescale |
| 描述： | M68HC08 Microcontrollers |
| 文件： | 总282页 (文件大小：1882K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MC68HC908MR32
MC68HC908MR16
Data Sheet
M68HC08
Microcontrollers
MC68HC908MR32
Rev. 6.1
07/2005
freescale.com
MC68HC908MR32
MC68HC908MR16
Data Sheet
To provide the most up-to-date information, the revision of our documents on the World Wide Web will be
the most current. Your printed copy may be an earlier revision. To verify you have the latest information
available, refer to:
http://freescale.com
Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc.
This product incorporates SuperFlash® technology licensed from SST.
© Freescale Semiconductor, Inc., 2005. All rights reserved.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
3
Revision History
The following revision history table summarizes changes contained in this document. For your
convenience, the page number designators have been linked to the appropriate location.
Revision History
Revision
Level
Page
Number(s)
Date
Description
Figure 2-1. MC68HC908MR32 Memory Map — Added FLASH Block Protect
Register (FLBPR) at address location $FF7E
29
August,
2001
3.0
Figure A-1. MC68HC908MR16 Memory Map — Added FLASH Block Protect
Register (FLBPR) at address location $FF7E
306
October,
2001
4.0
5.0
3.3.3 Conversion Time — Reworked equations and text for clarity.
50
Figure 18-8. Monitor Mode Circuit — PTA7 and connecting circuitry added
279
281
Table 18-2. Monitor Mode Signal Requirements and Options — Switch locations
added to column headings for clarity
December,
2001
Section 16. Timer Interface A (TIMA) — Timer discrepancies corrected throughout
this section.
233
255
Section 17. Timer Interface B (TIMB) — Timer discrepancies corrected throughout
this section.
Reformatted to meet current publication standards
Throughout
2.8.2 FLASH Page Erase Operation — Procedure reworked for clarity
2.8.3 FLASH Mass Erase Operation — Procedure reworked for clarity
2.8.4 FLASH Program Operation — Procedure reworked for clarity
Figure 14-14. SIM Break Status Register (SBSR) — Clarified definition of SBSW bit.
42
42
November,
2003
43
6.0
6.1
207
19.5 DC Electrical Characteristics — Corrected maximum value for monitor mode
entry voltage (on IRQ)
291
292
19.6 FLASH Memory Characteristics — Updated table entries
July,
2005
Updated to meet Freescale identity guidelines.
Throughout
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
4
Freescale Semiconductor
List of Chapters
Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Chapter 2 Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Chapter 3 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Chapter 4 Clock Generator Module (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Chapter 5 Configuration Register (CONFIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Chapter 6 Computer Operating Properly (COP). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75
Chapter 7 Central Processor Unit (CPU). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
Chapter 8 External Interrupt (IRQ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
Chapter 9 Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
Chapter 10 Input/Output (I/O) Ports (PORTS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
Chapter 11 Power-On Reset (POR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
Chapter 12 Pulse-Width Modulator for Motor Control (PWMMC) . . . . . . . . . . . . . . . . . . .115
Chapter 13 Serial Communications Interface Module (SCI) . . . . . . . . . . . . . . . . . . . . . . .157
Chapter 14 System Integration Module (SIM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181
Chapter 15 Serial Peripheral Interface Module (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195
Chapter 16 Timer Interface A (TIMA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215
Chapter 17 Timer Interface B (TIMB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .235
Chapter 18 Development Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251
Chapter 19 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .265
Chapter 20 Ordering Information and Mechanical Specifications . . . . . . . . . . . . . . . . . .275
Appendix A MC68HC908MR16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
5
List of Chapters
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
6
Freescale Semiconductor
Table of Contents
Chapter 1
General Description
1.1
1.2
1.3
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.4
Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Power Supply Pins (VDD and VSS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Oscillator Pins (OSC1 and OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
External Reset Pin (RST). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
External Interrupt Pin (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
CGM Power Supply Pins (VDDA and VSSAD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Analog Power Supply Pins (VDDAD and VSSAD). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
ADC Voltage Decoupling Capacitor Pin (VREFH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Port A Input/Output (I/O) Pins (PTA7–PTA0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Port B I/O Pins (PTB7/ATD7–PTB0/ATD0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Port C I/O Pins (PTC6–PTC2 and PTC1/ATD9–PTC0/ATD8). . . . . . . . . . . . . . . . . . . . . . . 23
Port D Input-Only Pins (PTD6/IS3–PTD4/IS1 and PTD3/FAULT4–PTD0/FAULT1) . . . . . . 23
PWM Pins (PWM6–PWM1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
PWM Ground Pin (PWMGND). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Port E I/O Pins (PTE7/TCH3A–PTE3/TCLKA and PTE2/TCH1B–PTE0/TCLKB) . . . . . . . . 24
Port F I/O Pins (PTF5/TxD–PTF4/RxD and PTF3/MISO–PTF0/SPSCK) . . . . . . . . . . . . . . 24
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
1.4.8
1.4.9
1.4.10
1.4.11
1.4.12
1.4.13
1.4.14
1.4.15
1.4.16
1.4.17
Chapter 2
Memory
2.1
2.2
2.3
2.4
2.5
2.6
2.7
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
I/O Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Monitor ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Random-Access Memory (RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.8
FLASH Memory (FLASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
FLASH Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
FLASH Page Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
FLASH Mass Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
FLASH Program Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
FLASH Block Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
FLASH Block Protect Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.8.1
2.8.2
2.8.3
2.8.4
2.8.5
2.8.6
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
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Table of Contents
2.8.7
2.8.8
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Chapter 3
Analog-to-Digital Converter (ADC)
3.1
3.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Continuous Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Result Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Monotonicity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.4
3.5
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.6
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
ADC Analog Power Pin (VDDAD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
ADC Analog Ground Pin (VSSAD). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
ADC Voltage Reference Pin (VREFH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
ADC Voltage In (ADVIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
ADC External Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.6.1
3.6.2
3.6.3
3.6.4
3.6.5
3.6.6
3.6.6.1
3.6.6.2
3.6.6.3
VREFH and VREFL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
ANx. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Grounding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.7
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
ADC Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
ADC Data Register High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
ADC Data Register Low. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
ADC Clock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.7.1
3.7.2
3.7.3
3.7.4
Chapter 4
Clock Generator Module (CGM)
4.1
4.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.3
4.3.1
4.3.2
4.3.2.1
4.3.2.2
4.3.2.3
4.3.2.4
4.3.2.5
4.3.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Crystal Oscillator Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Phase-Locked Loop Circuit (PLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Acquisition and Tracking Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Manual and Automatic PLL Bandwidth Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Programming the PLL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Special Programming Exceptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.3.4
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
4.4
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Oscillator Enable Signal (SIMOSCEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Crystal Output Frequency Signal (CGMXCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
CGM Base Clock Output (CGMOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4.4.6
4.4.7
4.4.8
4.5
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
PLL Programming Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.5.1
4.5.2
4.5.3
4.6
4.7
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
4.8
Acquisition/Lock Time Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Acquisition/Lock Time Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Parametric Influences on Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Choosing a Filter Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Reaction Time Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.8.1
4.8.2
4.8.3
4.8.4
Chapter 5
Configuration Register (CONFIG)
5.1
5.2
5.3
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Chapter 6
Computer Operating Properly (COP)
6.1
6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
6.3
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Reset Vector Fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.4
6.5
6.6
6.7
6.8
COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Monitor Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
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Chapter 7
Central Processor Unit (CPU)
7.1
7.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
7.3
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
7.3.1
7.3.2
7.3.3
7.3.4
7.3.5
7.4
Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
7.5
7.5.1
7.5.2
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
7.6
7.7
7.8
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Chapter 8
External Interrupt (IRQ)
8.1
8.2
8.3
8.4
8.5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
IRQ Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
IRQ Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Chapter 9
Low-Voltage Inhibit (LVI)
9.1
9.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
9.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Forced Reset Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
False Reset Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
LVI Trip Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
9.3.1
9.3.2
9.3.3
9.3.4
9.4
9.5
9.6
9.7
LVI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
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Chapter 10
Input/Output (I/O) Ports (PORTS)
10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
10.2 Port A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
10.2.1
10.2.2
Port A Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Data Direction Register A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
10.3 Port B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
10.3.1
10.3.2
Port B Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Data Direction Register B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
10.4 Port C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
10.4.1
10.4.2
Port C Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Data Direction Register C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
10.5 Port D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
10.6 Port E. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
10.6.1
10.6.2
Port E Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Data Direction Register E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
10.7 Port F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
10.7.1
10.7.2
Port F Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Data Direction Register F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Chapter 11
Power-On Reset (POR)
11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
11.2 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Chapter 12
Pulse-Width Modulator for Motor Control (PWMMC)
12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
12.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
12.3 Timebase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
12.3.1
12.3.2
Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
12.4 PWM Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
12.4.1
12.4.2
Load Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
PWM Data Overflow and Underflow Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
12.5 Output Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
12.5.1
12.5.2
12.5.3
12.5.4
12.5.5
Selecting Six Independent PWMs or Three Complementary PWM Pairs . . . . . . . . . . . . . 126
Dead-Time Insertion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Top/Bottom Correction with Motor Phase Current Polarity Sensing . . . . . . . . . . . . . . . . . 130
Output Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
PWM Output Port Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
12.6 Fault Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
12.6.1
Fault Condition Input Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Fault Pin Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Automatic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Manual Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
12.6.1.1
12.6.1.2
12.6.1.3
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12.6.2
12.6.3
Software Output Disable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Output Port Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
12.7 Initialization and the PWMEN Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
12.8 PWM Operation in Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
12.9 Control Logic Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
12.9.1
12.9.2
12.9.3
12.9.4
12.9.5
12.9.6
12.9.7
12.9.8
12.9.9
12.9.10
12.9.11
PWM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
PWM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
PWMx Value Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
PWM Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
PWM Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Dead-Time Write-Once Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
PWM Disable Mapping Write-Once Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Fault Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Fault Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Fault Acknowledge Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
PWM Output Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
12.10 PWM Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Chapter 13
Serial Communications Interface Module (SCI)
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
13.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
13.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
13.3.1
13.3.2
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Inversion of Transmitted Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Transmitter Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Receiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Receiver Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
13.3.2.1
13.3.2.2
13.3.2.3
13.3.2.4
13.3.2.5
13.3.2.6
13.3.3
13.3.3.1
13.3.3.2
13.3.3.3
13.3.3.4
13.3.3.5
13.3.3.6
13.3.3.7
13.4 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
13.5 SCI During Break Module Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
13.6 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
13.6.1
13.6.2
PTF5/TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
PTF4/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
13.7 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
13.7.1
13.7.2
SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
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13.7.3
13.7.4
13.7.5
13.7.6
13.7.7
SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
SCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
SCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
Chapter 14
System Integration Module (SIM)
14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
14.2 SIM Bus Clock Control and Generation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
14.2.1
14.2.2
14.2.3
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
Clock Startup from POR or LVI Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
Clocks in Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
14.3 Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
14.3.1
14.3.2
External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
Power-On Reset (POR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Computer Operating Properly (COP) Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
Forced Monitor Mode Entry Reset (MENRST). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
14.3.2.1
14.3.2.2
14.3.2.3
14.3.2.4
14.3.2.5
14.3.2.6
14.4 SIM Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
14.4.1
14.4.2
SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
14.5 Exception Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
14.5.1
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
Software Interrupt (SWI) Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
14.5.1.1
14.5.1.2
14.5.2
14.6 Low-Power Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
14.6.1
14.6.2
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
14.7 SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
14.7.1
14.7.2
14.7.3
SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
Chapter 15
Serial Peripheral Interface Module (SPI)
15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
15.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
15.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
15.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
15.4.1
15.4.2
Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
15.5 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
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15.5.1
15.5.2
15.5.3
15.5.4
Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
15.6 Error Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
15.6.1
15.6.2
Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
15.7 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
15.8 Resetting the SPI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
15.9 Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
15.10 Low-Power Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
15.11 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
15.11.1
15.11.2
15.11.3
15.11.4
15.11.5
MISO (Master In/Slave Out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
MOSI (Master Out/Slave In). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
SPSCK (Serial Clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
SS (Slave Select). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
VSS (Clock Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
15.12 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
15.12.1
15.12.2
15.12.3
SPI Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
SPI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Chapter 16
Timer Interface A (TIMA)
16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
16.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
16.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
16.3.1
16.3.2
16.3.3
16.3.3.1
16.3.3.2
16.3.4
16.3.4.1
16.3.4.2
16.3.4.3
TIMA Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
Pulse-Width Modulation (PWM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
PWM Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
16.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
16.5 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
16.6 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
16.6.1
16.6.2
TIMA Clock Pin (PTE3/TCLKA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
TIMA Channel I/O Pins (PTE4/TCH0A–PTE7/TCH3A) . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
16.7 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
16.7.1
16.7.2
16.7.3
16.7.4
16.7.5
TIMA Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
TIMA Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
TIMA Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
TIMA Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
TIMA Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
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Timer Interface B (TIMB)
17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
17.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
17.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
17.3.1
17.3.2
17.3.3
17.3.3.1
17.3.3.2
17.3.4
17.3.4.1
17.3.4.2
17.3.4.3
TIMB Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
Pulse-Width Modulation (PWM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
PWM Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
17.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
17.5 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
17.6 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
17.6.1
17.6.2
TIMB Clock Pin (PTE0/TCLKB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
TIMB Channel I/O Pins (PTE1/TCH0B–PTE2/TCH1B) . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
17.7 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
17.7.1
17.7.2
17.7.3
17.7.4
17.7.5
TIMB Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
TIMB Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
TIMB Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
TIMB Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
TIMB Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
Chapter 18
Development Support
18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
18.2 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
18.2.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
Flag Protection During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
TIM1 and TIM2 During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Break Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
18.2.1.1
18.2.1.2
18.2.1.3
18.2.1.4
18.2.2
18.2.2.1
18.2.2.2
18.2.3
18.2.3.1
18.2.3.2
18.2.3.3
18.2.3.4
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
15
Table of Contents
18.3 Monitor ROM (MON) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
18.3.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
Entering Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
Normal Monitor Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
Forced Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Echoing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
Baud Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
18.3.1.1
18.3.1.2
18.3.1.3
18.3.1.4
18.3.1.5
18.3.1.6
18.3.1.7
18.3.1.8
18.3.2
Chapter 19
Electrical Specifications
19.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
19.2 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
19.3 Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
19.4 Thermal Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
19.5 DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
19.6 FLASH Memory Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
19.7 Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
19.8 Serial Peripheral Interface Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
19.9 TImer Interface Module Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
19.10 Clock Generation Module Component Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
19.11 CGM Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
19.12 CGM Acquisition/Lock Time Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
19.13 Analog-to-Digital Converter (ADC) Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
Chapter 20
Ordering Information and Mechanical Specifications
20.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
20.2 Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
20.3 64-Pin Plastic Quad Flat Pack (QFP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
20.4 56-Pin Shrink Dual In-Line Package (SDIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
Appendix A
MC68HC908MR16
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
16
Freescale Semiconductor
Chapter 1
General Description
1.1 Introduction
The MC68HC908MR32 is a member of the low-cost, high-performance M68HC08 Family of 8-bit
microcontroller units (MCUs). All MCUs in the family use the enhanced M68HC08 central processor unit
(CPU08) and are available with a variety of modules, memory sizes and types, and package types.
The information contained in this document pertains to the MC68HC908MR16 with the exceptions shown
in Appendix A MC68HC908MR16.
1.2 Features
Features include:
•
•
•
•
High-performance M68HC08 architecture
Fully upward-compatible object code with M6805, M146805, and M68HC05 Families
8-MHz internal bus frequency
On-chip FLASH memory with in-circuit programming capabilities of FLASH program memory:
MC68HC908MR32 — 32 Kbytes
MC68HC908MR16 — 16 Kbytes
•
•
•
•
•
•
•
•
•
•
•
•
On-chip programming firmware for use with host personal computer
FLASH data security(1)
768 bytes of on-chip random-access memory (RAM)
12-bit, 6-channel center-aligned or edge-aligned pulse-width modulator (PWMMC)
Serial peripheral interface module (SPI)
Serial communications interface module (SCI)
16-bit, 4-channel timer interface module (TIMA)
16-bit, 2-channel timer interface module (TIMB)
Clock generator module (CGM)
Low-voltage inhibit (LVI) module with software selectable trip points
10-bit, 10-channel analog-to-digital converter (ADC)
System protection features:
–
–
–
–
Optional computer operating properly (COP) reset
Low-voltage detection with optional reset
Illegal opcode or address detection with optional reset
Fault detection with optional PWM disabling
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
17
General Description
•
Available packages:
–
–
64-pin plastic quad flat pack (QFP)
56-pin shrink dual in-line package (SDIP)
•
•
•
•
Low-power design, fully static with wait mode
Master reset pin (RST) and power-on reset (POR)
Stop mode as an option
Break module (BRK) supports setting the in-circuit simulator (ICS) single break point
Features of the CPU08 include:
•
•
•
•
•
•
•
•
•
•
Enhanced M68HC05 programming model
Extensive loop control functions
16 addressing modes (eight more than the M68HC05)
16-bit index register and stack pointer
Memory-to-memory data transfers
Fast 8 × 8 multiply instruction
Fast 16/8 divide instruction
Binary-coded decimal (BCD) instructions
Optimization for controller applications
C language support
1.3 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908MR32.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
18
Freescale Semiconductor
INTERNAL BUS
M68HC08 CPU
PTA7–PTA0
CPU
REGISTERS
ARITHMETIC/LOGIC
UNIT
LOW-VOLTAGE INHIBIT
MODULE
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
COMPUTER OPERATING PROPERLY
MODULE
CONTROL AND STATUS REGISTERS — 112 BYTES
USER FLASH — 32,256 BYTES
TIMER INTERFACE
MODULE A
USER RAM — 768 BYTES
PTC6
PTC5
TIMER INTERFACE
MODULE B
PTC4
MONITOR ROM — 240 BYTES
PTC3
PTC2
PTC1/ATD9(1)
SERIAL COMMUNICATIONS INTERFACE
MODULE
USER FLASH VECTOR SPACE — 46 BYTES
PTC0/ATD8
OSC1
PTD6/IS3
CLOCK GENERATOR
MODULE
OSC2
SERIAL PERIPHERAL INTERFACE
MODULE(2)
PTD5/IS2
CGMXFC
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
POWER-ON RESET
MODULE
SYSTEM INTEGRATION
MODULE
RST
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
IRQ
MODULE
IRQ
SINGLE BREAK
MODULE
VDDAD
(3)
VSSAD
ANALOG-TO-DIGITAL CONVERTER
MODULE
(3)
VREFL
VREFH
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PWMGND
PULSE-WIDTH MODULATOR
MODULE
PWM6–PWM1
PTF1/SS(1)
PTF0/SPSCK(1)
VSS
VDD
POWER
VDDAD
VSSAD
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 1-1. MCU Block Diagram
General Description
1.4 Pin Assignments
Figure 1-2 shows the 64-pin QFP pin assignments and Figure 1-3 shows the 56-pin SDIP pin
assignments.
PTB2/ATD2
PTB3/ATD3
PTB4/ATD4
PTB5/ATD5
PTB6/ATD6
PTB7/ATD7
PTC0/ATD8
PTC1/ATD9
VDDAD
IRQ
1
48
PTF5/TxD
PTF4/RxD
PTF3/MISO
PTF2/MOSI
PTF1/SS
2
47
46
45
44
43
42
41
40
39
38
37
36
35
34
3
4
5
6
PTF0/SPSCK
VSS
7
8
VDD
9
VSSAD
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B
PTE1/TCH0B
10
11
12
13
14
15
VREFL
VREFH
PTC2
PTC3
PTC4
PTC5
16
33
Figure 1-2. 64-Pin QFP Pin Assignments
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
20
Freescale Semiconductor
Pin Assignments
PTA2
PTA3
PTA1
1
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
PTA0
2
PTA4
VSSA
3
PTA5
OSC2
4
PTA6
OSC1
5
PTA7
CGMXFC
VDDA
6
PTB0/ATD0
PTB1/ATD1
PTB2/ATD2
PTB3/ATD3
PTB4/ATD4
PTB5/ATD5
PTB6/ATD5
PTB7/ATD7
PTC0/ATD8
VDDAD
7
RST
8
IRQ
9
PTF5/TxD
PTF4/RxD
VSS
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
VDD
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
NC
VSSAD/VREFL
VREFH
PTC2
PTC3
PWM6
PTC4
PWM5
PTC5
PWMGND
PWM4
PTC6
PTD0/FAULT1
PTD1/FAULT2
PTD2/FAULT3
PTD3/FAULT4
PTD4/IS1
PWM3
PWM2
PWM1
PTD6/IS3
PTD5/IS2
Note:
PTC1, PTE0, PTE1, PTE2, PTF0, PTF1, PTF2, and PTF3
are removed from this package.
Figure 1-3. 56-Pin SDIP Pin Assignments
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
21
General Description
1.4.1 Power Supply Pins (V and V )
DD
SS
VDD and VSS are the power supply and ground pins. The MCU operates from a single power supply.
Fast signal transitions on MCU pins place high, short-duration current demands on the power supply. To
prevent noise problems, take special care to provide power supply bypassing at the MCU as Figure 1-4
shows. Place the C1 bypass capacitor as close to the MCU as possible. Use a high-frequency-response
ceramic capacitor for C1. C2 is an optional bulk current bypass capacitor for use in applications that
require the port pins to source high-current levels.
MCU
VDD
VSS
C1
0.1 µF
+
C2
1–10 µF
VDD
Note: Component values shown represent typical applications.
Figure 1-4. Power Supply Bypassing
1.4.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections for the on-chip oscillator circuit. For more detailed
information, see Chapter 4 Clock Generator Module (CGM).
1.4.3 External Reset Pin (RST)
A logic 0 on the RST pin forces the MCU to a known startup state. RST is bidirectional, allowing a reset
of the entire system. It is driven low when any internal reset source is asserted. See Chapter 14 System
Integration Module (SIM).
1.4.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. See Chapter 8 External Interrupt (IRQ).
1.4.5 CGM Power Supply Pins (V
and V
)
DDA
SSAD
VDDA and VSSAD are the power supply pins for the analog portion of the clock generator module (CGM).
Decoupling of these pins should be per the digital supply. See Chapter 4 Clock Generator Module (CGM).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
22
Freescale Semiconductor
Pin Assignments
1.4.6 External Filter Capacitor Pin (CGMXFC)
CGMXFC is an external filter capacitor connection for the CGM. See Chapter 4 Clock Generator Module
(CGM).
1.4.7 Analog Power Supply Pins (V
and V
)
SSAD
DDAD
VDDAD and VSSAD are the power supply pins for the analog-to-digital converter. Decoupling of these pins
should be per the digital supply. See Chapter 3 Analog-to-Digital Converter (ADC).
1.4.8 ADC Voltage Decoupling Capacitor Pin (V
)
REFH
VREFH is the power supply for setting the reference voltage. Connect the VREFH pin to the same voltage
potential as VDDAD. See Chapter 3 Analog-to-Digital Converter (ADC).
1.4.9 ADC Voltage Reference Low Pin (V
)
REFL
VREFL is the lower reference supply for the ADC. Connect the VREFL pin to the same voltage potential as
VSSAD. See Chapter 3 Analog-to-Digital Converter (ADC).
1.4.10 Port A Input/Output (I/O) Pins (PTA7–PTA0)
PTA7–PTA0 are general-purpose bidirectional input/output (I/O) port pins. See Chapter 10 Input/Output
(I/O) Ports (PORTS).
1.4.11 Port B I/O Pins (PTB7/ATD7–PTB0/ATD0)
Port B is an 8-bit special function port that shares all eight pins with the analog-to-digital converter (ADC).
See Chapter 3 Analog-to-Digital Converter (ADC) and Chapter 10 Input/Output (I/O) Ports (PORTS).
1.4.12 Port C I/O Pins (PTC6–PTC2 and PTC1/ATD9–PTC0/ATD8)
PTC6–PTC2 are general-purpose bidirectional I/O port pins Chapter 10 Input/Output (I/O) Ports
(PORTS). PTC1/ATD9–PTC0/ATD8 are special function port pins that are shared with the
analog-to-digital converter (ADC). See Chapter 3 Analog-to-Digital Converter (ADC) and Chapter 10
Input/Output (I/O) Ports (PORTS).
1.4.13 Port D Input-Only Pins (PTD6/IS3–PTD4/IS1 and PTD3/FAULT4–PTD0/FAULT1)
PTD6/IS3–PTD4/IS1 are special function input-only port pins that also serve as current sensing pins for
the pulse-width modulator module (PWMMC). PTD3/FAULT4–PTD0/FAULT1 are special function port
pins that also serve as fault pins for the PWMMC. See Chapter 12 Pulse-Width Modulator for Motor
Control (PWMMC) and Chapter 10 Input/Output (I/O) Ports (PORTS).
1.4.14 PWM Pins (PWM6–PWM1)
PWM6–PWM1 are dedicated pins used for the outputs of the pulse-width modulator module (PWMMC).
These are high-current sink pins. See Chapter 12 Pulse-Width Modulator for Motor Control (PWMMC)
and Chapter 19 Electrical Specifications.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
23
General Description
1.4.15 PWM Ground Pin (PWMGND)
PWMGND is the ground pin for the pulse-width modulator module (PWMMC). This dedicated ground pin
is used as the ground for the six high-current PWM pins. See Chapter 12 Pulse-Width Modulator for Motor
Control (PWMMC).
1.4.16 Port E I/O Pins (PTE7/TCH3A–PTE3/TCLKA and PTE2/TCH1B–PTE0/TCLKB)
Port E is an 8-bit special function port that shares its pins with the two timer interface modules (TIMA and
TIMB). See Chapter 16 Timer Interface A (TIMA), Chapter 17 Timer Interface B (TIMB), and Chapter 10
Input/Output (I/O) Ports (PORTS).
1.4.17 Port F I/O Pins (PTF5/TxD–PTF4/RxD and PTF3/MISO–PTF0/SPSCK)
Port F is a 6-bit special function port that shares two of its pins with the serial communications interface
module (SCI) and four of its pins with the serial peripheral interface module (SPI). See Chapter 15 Serial
Peripheral Interface Module (SPI), Chapter 13 Serial Communications Interface Module (SCI), and
Chapter 10 Input/Output (I/O) Ports (PORTS).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
24
Freescale Semiconductor
Chapter 2
Memory
2.1 Introduction
The central processor unit (CPU08) can address 64 Kbytes of memory space. The memory map, shown
in Figure 2-1, includes:
•
•
•
•
32 Kbytes of FLASH
768 bytes of random-access memory (RAM)
46 bytes of user-defined vectors
240 bytes of monitor read-only memory (ROM)
2.2 Unimplemented Memory Locations
Some addresses are unimplemented. Accessing an unimplemented address can cause an illegal address
reset. In the memory map and in the input/output (I/O) register summary, unimplemented addresses are
shaded.
Some I/O bits are read only; the write function is unimplemented. Writing to a read-only I/O bit has no
effect on microcontroller unit (MCU) operation. In register figures, the write function of read-only bits is
shaded.
Similarly, some I/O bits are write only; the read function is unimplemented. Reading of write-only I/O bits
has no effect on MCU operation. In register figures, the read function of write-only bits is shaded.
2.3 Reserved Memory Locations
Some addresses are reserved. Writing to a reserved address can have unpredictable effects on MCU
operation. In the memory map (Figure 2-1) and in the I/O register summary (Figure 2-2) reserved
addresses are marked with the word reserved.
Some I/O bits are reserved. Writing to a reserved bit can have unpredictable effects on MCU operation.
In register figures, reserved bits are marked with the letter R.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
25
Memory
2.4 I/O Section
Addresses $0000–$005F, shown in Figure 2-2, contain most of the control, status, and data registers.
Additional I/O registers have these addresses:
•
•
•
•
•
•
•
•
•
•
$FE00, SIM break status register (SBSR)
$FE01, SIM reset status register (SRSR)
$FE03, SIM break flag control register (SBFCR)
$FE07, FLASH control register (FLCR)
$FE0C, Break address register high (BRKH)
$FE0D, Break address register low (BRKL)
$FE0E, Break status and control register (BRKSCR)
$FE0F, LVI status and control register (LVISCR)
$FF7E, FLASH block protect register (FLBPR)
$FFFF, COP control register (COPCTL)
2.5 Memory Map
Figure 2-1 shows the memory map for the MC68HC908MR32 while the memory map for the
MC68HC908MR16 is shown in Appendix A MC68HC908MR16
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
26
Freescale Semiconductor
Memory Map
$0000
↓
$005F
I/O REGISTERS — 96 BYTES
RAM — 768 BYTES
$0060
↓
$035F
$0360
↓
$7FFF
UNIMPLEMENTED — 31,904 BYTES
FLASH — 32,256 BYTES
$8000
↓
$FDFF
$FE00
$FE01
SIM BREAK STATUS REGISTER (SBSR)
SIM RESET STATUS REGISTER (SRSR)
RESERVED
$FE02
$FE03
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
RESERVED
$FE04
$FE05
$FE06
$FE07
$FE08
RESERVED
RESERVED
RESERVED
FLASH CONTROL REGISTER (FLCR)
UNIMPLEMENTED
$FE09
$FE0A
$FE0B
$FE0C
$FE0D
$FE0E
$FE0F
UNIMPLEMENTED
UNIMPLEMENTED
SIM BREAK ADDRESS REGISTER HIGH (BRKH)
SIM BREAK ADDRESS REGISTER LOW (BRKL)
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
LVI STATUS AND CONTROL REGISTER (LVISCR)
$FE10
↓
$FEFF
MONITOR ROM — 240 BYTES
$FF00
↓
$FF7D
UNIMPLEMENTED — 126 BYTES
FLASH BLOCK PROTECT REGISTER (FLBPR)
UNIMPLEMENTED — 83 BYTES
$FF7E
$FF7F
↓
$FFD1
$FFD2
↓
$FFFF
VECTORS — 46 BYTES
Figure 2-1. MC68HC908MR32 Memory Map
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
27
Memory
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
(PTA) Write:
Port A Data Register
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
$0000
See page 103.
Reset:
Read:
Unaffected by reset
PTB4 PTB3
Unaffected by reset
PTC4 PTC3
Unaffected by reset
Port B Data Register
PTB7
PTB6
PTC6
PTB5
PTC5
PTB2
PTC2
PTB1
PTC1
PTB0
PTC0
$0001
$0002
$0003
$0004
$0005
(PTB) Write:
See page 104.
Reset:
Read:
0
Port C Data Register
(PTC) Write:
R
See page 106.
Reset:
Read:
0
PTD6
R
PTD5
R
PTD4
R
PTD3
R
PTD2
R
PTD1
R
PTD0
R
Port D Data Register
(PTD) Write:
R
See page 107.
Reset:
Read:
Unaffected by reset
Data Direction Register A
DDRA7 DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1 DDRA0
(DDRA) Write:
See page 103.
Reset:
Read:
0
0
0
DDRB5
0
0
DDRB4
0
0
DDRB3
0
0
DDRB2
0
0
0
Data Direction Register B
DDRB7 DDRB6
DDRB1 DDRB0
(DDRB) Write:
See page 105.
Reset:
Read:
0
0
0
DDRC6
0
0
0
Data Direction Register C
DDRC5
0
DDRC4
0
DDRC3
0
DDRC2
0
DDRC1 DDRC0
$0006
$0007
(DDRC) Write:
R
0
See page 106.
Reset:
0
0
Unimplemented
Read:
Port E Data Register
PTE7
PTE6
PTE5
PTF5
PTE4
PTE3
PTE2
PTF2
PTE1
PTF1
PTE0
PTF0
$0008
$0009
(PTE) Write:
See page 108.
Reset:
Read:
Unaffected by reset
PTF4 PTF3
Unaffected by reset
0
0
Port F Data Register
(PTF) Write:
R
R
See page 110.
Reset:
$000A
$000B
Unimplemented
Unimplemented
Read:
Data Direction Register E
DDRE7 DDRE6
DDRE5
DDRE4
0
DDRE3
0
DDRE2
DDRE1 DDRE0
$000C
(DDRE) Write:
See page 109.
Reset:
Read:
0
0
0
0
0
DDRF5
0
0
DDRF2
0
0
DDRF1
0
0
DDRF0
0
Data Direction Register F
DDRF4
DDRF3
$000D
(DDRF) Write:
See page 110.
R
R
Reset:
0
0
U = Unaffected X = Indeterminate
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 1 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
28
Freescale Semiconductor
Memory Map
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read: TOF
0
TRST
0
0
R
TIMA Status/Control Register
TOIE
TSTOP
PS2
PS1
PS0
$000E
(TASC) Write:
0
0
See page 226.
TIMA Counter Register High
See page 227.
Reset:
0
Bit 14
R
1
Bit 13
R
0
0
Bit 10
R
0
Bit 9
R
0
Bit 8
R
Read: Bit 15
Bit 12
R
Bit 11
R
$000F
$0010
$0011
$0012
$0013
$0014
$0015
$0016
$0017
$0018
$0019
(TACNTH) Write:
R
0
Reset:
0
0
0
0
0
0
0
Read: Bit 7
Bit 6
R
Bit 5
R
Bit 4
R
Bit 3
R
Bit 2
R
Bit 1
R
Bit 0
R
TIMA Counter Register Low
See page 227.
(TACNTL) Write:
R
0
Reset:
Read:
0
0
0
0
0
0
0
TIMA Counter Modulo
Bit 15
1
14
1
13
1
12
1
11
1
10
1
9
1
Bit 8
1
Register High (TAMODH) Write:
See page 228.
Reset:
Read:
TIMA Counter Modulo
Register Low (TAMODL) Write:
Bit 7
Bit 6
1
Bit 5
1
Bit 4
1
Bit 3
1
Bit 2
1
Bit 1
1
Bit 0
1
See page 228.
Reset:
1
Read: CH0F
TIMA Channel 0 Status/Control
See page 229.
CH0IE
0
MS0B
0
MS0A
0
ELS0B
0
ELS0A
0
TOV0 CH0MAX
Register (TASC0) Write:
0
0
Reset:
Read:
0
0
TIMA Channel 0 Register High
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
(TACH0H) Write:
See page 232.
Reset:
Read:
Indeterminate after reset
Bit 4 Bit 3
Indeterminate after reset
TIMA Channel 0 Register Low
Bit 7
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
(TACH0L) Write:
See page 232.
Reset:
Read: CH1F
0
R
0
TIMA Channel 1 Status/Control
See page 232.
CH1IE
0
MS1A
0
ELS1B
0
ELS1A
0
TOV1 CH1MAX
Register (TASC1) Write:
0
0
Reset:
Read:
0
0
TIMA Channel 1 Register High
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
(TACH1H) Write:
See page 232.
Reset:
Read:
Indeterminate after reset
Bit 4 Bit 3
Indeterminate after reset
TIMA Channel 1 Register Low
Bit 7
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
(TACH1L) Write:
See page 232.
Reset:
Read: CH2F
TIMA Channel 2 Status/Control
See page 229.
CH2IE
MS2B
0
MS2A
ELS2B
ELS2A
0
TOV2 CH2MAX
Register (TASC2) Write:
0
0
Reset:
0
0
0
0
0
U = Unaffected X = Indeterminate
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 2 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
29
Memory
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
TIMA Channel 2 Register High
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
$001A
$001B
$001C
$001D
$001E
$001F
$0020
$0021
$0022
$0023
$0024
$0025
(TACH2H) Write:
See page 232.
Reset:
Read:
Indeterminate after reset
Bit 4 Bit 3
Indeterminate after reset
TIMA Channel 2 Register Low
Bit 7
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
(TACH2L) Write:
See page 232.
Reset:
Read: CH3F
0
R
0
TIMA Channel 3 Status/Control
See page 229.
CH3IE
0
MS3A
0
ELS3B
0
ELS3A
0
TOV3 CH3MAX
Register (TASC3) Write:
0
0
Reset:
Read:
0
0
TIMA Channel 3 Register High
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
(TACH3H) Write:
See page 232.
Reset:
Read:
Indeterminate after reset
Bit 4 Bit 3
Indeterminate after reset
TIMA Channel 3 Register Low
Bit 7
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
(TACH3L) Write:
See page 232.
Reset:
Read:
Configuration Register
EDGE BOTNEG TOPNEG
INDEP
LVIRST
1
LVIPWR STOPE
COPD
(CONFIG) Write:
See page 74.
Reset:
0
DISX
0
0
DISY
0
0
0
PWMF
0
1
ISENS0
0
0
LDOK
0
0
Read:
PWM Control Register 1
PWMINT
ISENS1
0
PWMEN
(PCTL1) Write:
See page 146.
Reset:
Read:
0
0
0
PRSC0
0
PWM Control Register 2
LDFQ1
0
LDFQ0
0
IPOL1
0
IPOL2
0
IPOL3
0
PRSC1
0
(PCTL2) Write:
See page 148.
Reset:
Read:
0
Fault Control Register
FINT4 FMODE4
FINT3
FMODE3
FINT2
FMODE2
FINT1 FMODE1
(FCR) Write:
See page 150.
Reset:
Read: FPIN4
(FSR) Write:
0
0
0
0
0
0
0
0
FFLAG4
FPIN3
FFLAG3
FPIN2
FFLAG2
FPIN1
FFLAG1
Fault Status Register
See page 152.
Reset:
Read:
U
0
0
U
0
DT5
U
0
DT3
U
0
DT1
0
FTACK4
0
DT6
DT4
DT2
Fault Acknowledge Register
(FTACK) Write:
FTACK3
0
FTACK2
0
FTACK1
0
See page 153.
Reset:
Read:
0
0
0
OUT6
0
0
0
OUT2
0
PWM Output Control Register
OUTCTL
OUT5
OUT4
OUT3
0
OUT1
(PWMOUT) Write:
See page 154.
Reset:
0
0
0
0
0
U = Unaffected X = Indeterminate
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 3 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
30
Freescale Semiconductor
Memory Map
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
PWM Counter Register High
$0026
(PCNTH) Write:
See page 143.
Reset:
0
0
0
0
0
0
0
0
Read: Bit 7
(PCNTL) Write:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
PWM Counter Register Low
$0027
$0028
$0029
$002A
$002B
$002C
$002D
$002E
$002F
$0030
See page 143.
Reset:
Read:
0
0
0
0
0
0
0
0
0
Bit 11
X
0
Bit 10
X
0
Bit 9
X
0
Bit 8
X
PWM Counter Modulo Register
High (PMODH) Write:
See page 144.
Reset:
0
Bit 7
X
0
Bit 6
X
0
Bit 5
X
0
Bit 4
X
Read:
PWM Counter Modulo Register
Bit 3
X
Bit 2
X
Bit 1
X
Bit 0
X
Low (PMODL) Write:
See page 144.
Reset:
Read:
PWM 1 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL1H) Write:
See page 145.
Reset:
Read:
PWM 1 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PVAL1L) Write:
See page 145.
Reset:
Read:
PWM 2 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL2H) Write:
See page 145.
Reset:
Read:
PWM 2 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PVAL2L) Write:
See page 145.
Reset:
Read:
PWM 3 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL3H) Write:
See page 145.
Reset:
Read:
PWM 3 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PVAL3L) Write:
See page 145.
Reset:
Read:
PWM 4 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL4H) Write:
See page 145.
Reset:
Read:
PWM 4 Value Register Low
Bit 7
Bit 6
Bit 5
0
Bit 4
Bit 3
Bit 2
0
Bit 1
Bit 0
$0031
(PVAL4L) Write:
See page 145.
Reset:
0
0
0
0
0
0
U = Unaffected X = Indeterminate
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 4 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
31
Memory
Addr.
Register Name
Bit 7
Bit 15
0
6
Bit 14
0
5
Bit 13
0
4
Bit 12
0
3
Bit 11
0
2
Bit 10
0
1
Bit 9
0
Bit 0
Bit 8
0
Read:
PWM 5 Value Register High
$0032
$0033
$0034
$0035
$0036
$0037
$0038
$0039
$003A
$003B
$003C
(PMVAL5H) Write:
See page 145.
Reset:
Read:
PWM 5 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PVAL5L) Write:
See page 145.
Reset:
Read:
PWM 6 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL6H) Write:
See page 145.
Reset:
Read:
PWM 6 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PMVAL6L) Write:
See page 145.
Reset:
Read:
Dead-Time Write-Once
Register (DEADTM) Write:
Bit 7
1
Bit 6
1
Bit 5
1
Bit 4
1
Bit 3
1
Bit 2
1
Bit 1
1
Bit 0
1
See page 150.
Reset:
Read:
PWM Disable Mapping
Write-Once Register (DISMAP) Write:
Bit 7
1
Bit 6
1
Bit 5
1
Bit 4
1
Bit 3
1
Bit 2
1
Bit 1
1
Bit 0
1
See page 137.
Reset:
Read:
SCI Control Register 1
LOOPS
0
ENSCI
0
TXINV
0
M
WAKE
0
ILTY
0
PEN
0
PTY
0
(SCC1) Write:
See page 169.
Reset:
0
Read:
SCI Control Register 2
SCTIE
TCIE
0
SCRIE
ILIE
TE
RE
0
RWU
0
SBK
0
(SCC2) Write:
See page 171.
Reset:
0
R8
R
0
0
0
0
0
Read:
SCI Control Register 3
T8
ORIE
NEIE
FEIE
PEIE
(SCC3) Write:
See page 173.
Reset:
R
R
U
U
TC
R
0
0
0
OR
R
0
NF
R
0
FE
R
0
PE
R
Read: SCTE
SCRF
R
IDLE
R
SCI Status Register 1
See page 174.
(SCS1) Write:
R
1
Reset:
Read:
1
0
0
0
0
0
0
0
0
0
0
0
0
BKF
R
RPF
R
SCI Status Register 2
(SCS2) Write:
R
R
R
R
R
R
See page 176.
Reset:
Read:
0
0
0
0
0
0
0
0
R7
T7
R6
T6
R5
T5
R4
T4
R3
T3
R2
T2
R1
T1
R0
T0
SCI Data Register
$003D
(SCDR) Write:
See page 177.
Reset:
Unaffected by reset
Bold = Buffered
U = Unaffected X = Indeterminate
R
= Reserved
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 5 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
32
Freescale Semiconductor
Memory Map
Addr.
Register Name
Bit 7
6
0
5
4
3
0
2
1
Bit 0
SCR0
0
Read:
0
R
0
SCI Baud Rate Register
SCP1
SCP0
SCR2
SCR1
0
$003E
(SCBR) Write:
R
0
R
See page 177.
Reset:
Read:
0
0
0
0
0
0
0
0
0
IRQF
IRQ Status/Control Register
IMASK1 MODE1
$003F
$0040
$0041
$0042
$0043
$0044
$0045
$0046
(ISCR) Write:
See page 94.
R
0
R
0
R
0
R
0
ACK1
0
Reset:
0
0
0
Read: COCO
ADC Status and Control
Register (ADSCR) Write:
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1 ADCH0
R
0
See page 52.
Reset:
0
0
0
0
1
0
1
0
1
0
1
AD9
R
1
AD8
R
Read:
0
ADC Data Register High
Right Justified Mode (ADRH) Write:
R
R
R
R
R
R
See page 54.
Reset:
Unaffected by reset
Read: AD7
AD6
R
AD5
R
AD4
R
AD3
R
AD2
R
AD1
R
AD0
R
ADC Data Register Low
Right Justified Mode (ADRL) Write:
R
See page 54.
Reset:
Unaffected by reset
Read:
0
R
0
ADC Clock Register
ADIV2
ADIV1
ADIV0
0
ADICLK
0
MODE1
0
MODE0
1
0
0
(ADCLK) Write:
See page 55.
Reset:
0
SPRIE
0
0
Read:
SPI Control Register
R
0
SPMSTR
CPOL
CPHA
SPWOM
0
SPE
0
SPTIE
0
(SPCR) Write:
See page 211.
Reset:
1
OVRF
R
0
MODF
R
1
SPTE
R
Read: SPRF
SPI Status and Control
Register (SPSCR) Write:
ERRIE
MODFEN
SPR1
SPR0
R
0
See page 212.
Reset:
0
0
0
1
0
0
0
Read:
R7
T7
R6
T6
R5
T5
R4
T4
R3
T3
R2
T2
R1
T1
R0
T0
SPI Data Register
(SPDR) Write:
See page 214.
Reset:
Unaffected by reset
$0047
↓
Unimplemented
$0050
Read: TOF
0
TRST
0
0
TIMB Status/Control Register
See page 244.
TOIE
TSTOP
PS2
PS1
PS0
$0051
$0052
(TBSC) Write:
0
0
R
Reset:
0
1
Bit 13
R
0
0
Bit 10
R
0
Bit 9
R
0
Bit 8
R
Read: Bit 15
Bit 14
Bit 12
R
Bit 11
TIMB Counter Register High
See page 246.
(TBCNTH) Write:
R
0
R
R
0
Reset:
0
0
0
0
0
0
U = Unaffected X = Indeterminate
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 6 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
33
Memory
Addr.
Register Name
Bit 7
6
Bit 6
R
5
Bit 5
R
4
Bit 4
R
3
Bit 3
R
2
Bit 2
R
1
Bit 1
R
Bit 0
Bit 0
R
Read: Bit 7
TIMB Counter Register Low
$0053
$0054
$0055
$0056
$0057
$0058
$0059
$005A
$005B
$005C
$005D
(TBCNTL) Write:
R
0
See page 246.
Reset:
Read:
0
0
0
0
0
0
0
TIMB Counter Modulo Register
Bit 15
1
Bit 14
1
Bit 13
1
Bit 12
1
Bit 11
1
Bit 10
1
Bit 9
1
Bit 8
1
High (TBMODH) Write:
See page 246.
Reset:
Read:
TIMB Counter Modulo Register
Bit 7
Bit 6
1
Bit 5
1
Bit 4
1
Bit 3
1
Bit 2
1
Bit 1
1
Bit 0
1
Low (TBMODL) Write:
See page 246.
Reset:
1
Read: CH0F
TIMB Channel 0 Status/Control
See page 247.
CH0IE
0
MS0B
0
MS0A
0
ELS0B
0
ELS0A
0
TOV0 CH0MAX
Register (TBSC0) Write:
0
0
Reset:
Read:
0
0
TIMB Channel 0 Register High
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
(TBCH0H) Write:
See page 250.
Reset:
Read:
Indeterminate after reset
Bit 4 Bit 3
Indeterminate after reset
TIMB Channel 0 Register Low
Bit 7
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
(TBCH0L) Write:
See page 250.
Reset:
Read: CH1F
0
R
0
TIMB Channel 1 Status/Control
See page 247.
CH1IE
0
MS1A
0
ELS1B
0
ELS1A
0
TOV1 CH1MAX
Register (TBSC1) Write:
0
0
Reset:
Read:
0
0
TIMB Channel 1 Register High
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
(TBCH1H) Write:
See page 250.
Reset:
Read:
Indeterminate after reset
Bit 4 Bit 3
TIMB Channel 1 Register Low
Bit 7
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
(TBCH1L) Write:
See page 250.
Reset:
Read:
Indeterminate after reset
PLLF
1
1
R
1
1
R
1
1
R
1
PLL Control Register
PLLIE
PLLON
BCS
(PCTL) Write:
R
R
See page 66.
Reset:
Read:
0
AUTO
0
0
LOCK
R
1
ACQ
0
0
XLD
0
1
0
0
0
0
PLL Bandwidth Control
Register (PBWC) Write:
See page 67.
Reset:
R
0
R
0
R
0
R
0
0
Read:
PLL Programming Register
MUL7
0
MUL6
1
MUL5
1
MUL4
0
VRS7
0
VRS6
1
VRS5
1
VRS4
0
$005E
$005F
(PPG) Write:
See page 68.
Reset:
Unimplemented
U = Unaffected X = Indeterminate
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 7 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
34
Freescale Semiconductor
Memory Map
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
SIM Break Status Register
R
R
R
R
R
R
BW
R
$FE00
(SBSR) Write:
See page 191.
Reset:
Read: POR
0
LVI
R
PIN
R
COP
R
ILOP
ILAD
R
MENRST
0
R
0
SIM Reset Status Register
See page 192.
$FE01
$FE03
(SRSR) Write:
R
1
R
0
R
0
Reset:
Read:
0
0
0
0
SIM Break Flag Control
BCFE
R
R
R
R
R
R
R
Register (SBFCR) Write:
See page 193.
Reset:
0
0
FLASH Control Register Read:
(FLCR)
0
0
0
0
0
0
HVEN
0
MASS
0
ERASE
0
PGM
0
Write:
$FE08
See page 38.
Reset:
0
Read:
Break Address Register High
Bit 15
0
14
13
0
12
0
11
0
10
0
9
0
1
Bit 8
0
$FE0C
$FE0D
$FE0E
$FE0F
$FF7E
(BRKH) Write:
See page 254.
Reset:
0
Read:
Break Address Register Low
Bit 7
0
6
0
5
4
3
2
Bit 0
(BRKL) Write:
See page 254.
Reset:
0
0
0
0
0
0
0
0
0
0
0
0
Read:
Break Status and Control
Register (BRKSCR) Write:
BRKE
BRKA
See page 254.
Reset:
0
0
0
0
TRPSEL
0
0
0
0
0
0
0
0
0
0
0
Read: LVIOUT
LVI Status and Control Register
See page 99.
(LVISCR) Write:
R
0
R
0
R
0
R
0
R
0
R
0
R
0
Reset:
Read:
FLASH Block Protect Register
BPR7
0
BPR6
0
BPR5
0
BPR4
0
BPR3
0
BPR2
0
BPR1
0
BPR0
0
(FLBPR) Write:
See page 43.
Reset:
Read:
Low byte of reset vector
Clear COP counter
Unaffected by reset
COP Control Register
$FFFF
(COPCTL) Write:
See page 77.
Reset:
U = Unaffected X = Indeterminate
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 8 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
35
Memory
Table 2-1 is a list of vector locations.
Table 2-1. Vector Addresses
Address
$FFD2
$FFD3
$FFD4
$FFD5
$FFD6
$FFD7
$FFD8
Vector
SCI transmit vector (high)
SCI transmit vector (low)
SCI receive vector (high)
SCI receive vector (low)
SCI error vector (high)
SCI error vector (low)
SPI transmit vector (high)(1)
SPI transmit vector (low)(1)
SPI receive vector (high)(1)
$FFD9
$FFDA
SPI receive vector (low)(1)
A/D vector (high)
$FFDB
$FFDC
$FFDD
$FFDE
$FFDF
$FFE0
$FFE1
$FFE2
$FFE3
$FFE4
$FFE5
$FFE6
$FFE7
$FFE8
$FFE9
$FFEA
$FFEB
$FFEC
$FFED
A/D vector (low)
TIMB overflow vector (high)
TIMB overflow vector (low)
TIMB channel 1 vector (high)
TIMB channel 1 vector (low)
TIMB channel 0 vector (high)
TIMB channel 0 vector (low)
TIMA overflow vector (high)
TIMA overflow vector (low)
TIMA channel 3 vector (high)
TIMA channel 3 vector (low)
TIMA channel 2 vector (high)
TIMA channel 2 vector (low)
TIMA channel 1 vector (high)
TIMA channel 1 vector (low)
TIMA channel 0 vector (high)
TIMA channel 0 vector (low)
1. The SPI module is not available in the 56-pin SDIP package.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
36
Freescale Semiconductor
Monitor ROM
Table 2-1. Vector Addresses (Continued)
Address
$FFEE
$FFEF
$FFF0
$FFF1
$FFF2
$FFF3
$FFF4
$FFF5
$FFF6
$FFF7
$FFF8
$FFF9
$FFFA
$FFFB
$FFFC
$FFFD
$FFFE
$FFFF
Vector
PWMMC vector (high)
PWMMC vector (low)
FAULT 4 (high)
FAULT 4 (low)
FAULT 3 (high)
FAULT 3 (low)
FAULT 2 (high)
FAULT 2 (low)
FAULT 1 (high)
FAULT 1 (low)
PLL vector (high)
PLL vector (low)
IRQ vector (high)
IRQ vector (low)
SWI vector (high)
SWI vector (low)
Reset vector (high)
Reset vector (low)
2.6 Monitor ROM
The 240 bytes at addresses $FE10–$FEFF are reserved ROM addresses that contain the instructions for
the monitor functions. See 18.3 Monitor ROM (MON).
2.7 Random-Access Memory (RAM)
Addresses $0060–$035F are RAM locations. The location of the stack RAM is programmable. The 16-bit
stack pointer allows the stack to be anywhere in the 64-Kbyte memory space.
NOTE
For correct operation, the stack pointer must point only to RAM locations.
Within page zero are 160 bytes of RAM. Because the location of the stack RAM is programmable, all page
zero RAM locations can be used for input/output (I/O) control and user data or code. When the stack
pointer is moved from its reset location at $00FF, direct addressing mode instructions can access
efficiently all page zero RAM locations. Page zero RAM, therefore, provides ideal locations for frequently
accessed global variables.
Before processing an interrupt, the central processor unit (CPU) uses five bytes of the stack to save the
contents of the CPU registers.
NOTE
For M68HC05 and M1468HC05 compatibility, the H register is not stacked.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
37
Memory
During a subroutine call, the CPU uses two bytes of the stack to store the return address. The stack
pointer decrements during pushes and increments during pulls.
NOTE
Be careful when using nested subroutines. The CPU may overwrite data in
the RAM during a subroutine or during the interrupt stacking operation.
2.8 FLASH Memory (FLASH)
The FLASH memory is an array of 32,256 bytes with an additional 46 bytes of user vectors and one byte
of block protection.
NOTE
An erased bit reads as a 1 and a programmed bit reads as a 0.
Program and erase operations are facilitated through control bits in a memory mapped register. Details
for these operations appear later in this section.
Memory in the FLASH array is organized into two rows per page. The page size is 128 bytes per page.
The minimum erase page size is 128 bytes. Programming is performed on a row basis, 64 bytes at a time.
The address ranges for the user memory and vectors are:
•
•
•
•
$8000–$FDFF, user memory
$FF7E, block protect register (FLBPR)
$FE08, FLASH control register (FLCR)
$FFD2–$FFFF, reserved for user-defined interrupt and reset vectors
Programming tools are available from Freescale. Contact a local Freescale representative for more
information.
NOTE
A security feature prevents viewing of the FLASH contents.(1)
2.8.1 FLASH Control Register
The FLASH control register (FLCR) controls FLASH program and erase operations.
Address:
$FE08
Bit 7
0
6
0
5
0
4
0
3
HVEN
0
2
MASS
0
1
ERASE
0
Bit 0
PGM
0
Read:
Write:
Reset:
0
0
0
0
= Unimplemented
Figure 2-3. FLASH Control Register (FLCR)
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
38
Freescale Semiconductor
FLASH Memory (FLASH)
HVEN — High-Voltage Enable Bit
This read/write bit enables the charge pump to drive high voltages for program and erase operations
in the array. HVEN can only be set if either PGM = 1 or ERASE = 1 and the proper sequence for
program or erase is followed.
1 = High voltage enabled to array and charge pump on
0 = High voltage disabled to array and charge pump off
MASS — Mass Erase Control Bit
Setting this read/write bit configures the 32-Kbyte FLASH array for mass erase operation. Mass erase
is disabled if any FLASH block is protected
1 = MASS erase operation selected
0 = MASS erase operation unselected
ERASE — Erase Control Bit
This read/write bit configures the memory for erase operation. ERASE is interlocked with the PGM bit
such that both bits cannot be equal to 1 or set to 1 at the same time.
1 = Erase operation selected
0 = Erase operation unselected
PGM — Program Control Bit
This read/write bit configures the memory for program operation. PGM is interlocked with the ERASE
bit such that both bits cannot be equal to 1 or set to 1 at the same time.
1 = Program operation selected
0 = Program operation unselected
2.8.2 FLASH Page Erase Operation
Use this step-by-step procedure to erase a page (128 bytes) of FLASH memory.
1. Set the ERASE bit and clear the MASS bit in the FLASH control register.
2. Read the FLASH block protect register.
3. Write any data to any FLASH location within the address range of the block to be erased.
4. Wait for a time, tNVS (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tErase (minimum 1 ms or 4 ms).
7. Clear the ERASE bit.
8. Wait for a time, tNVH (minimum 5 µs).
9. Clear the HVEN bit.
10. After time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps.
In applications that require more than 1000 program/erase cycles, use the 4 ms page erase specification
to get improved long-term reliability. Any application can use this 4 ms page erase specification. However,
in applications where a FLASH location will be erased and reprogrammed less than 1000 times, and
speed is important, use the 1 ms page erase specification to get a shorter cycle time.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
39
Memory
2.8.3 FLASH Mass Erase Operation
Use this step-by-step procedure to erase the entire FLASH memory.
1. Set both the ERASE bit and the MASS bit in the FLASH control register.
2. Read the FLASH block protect register.
3. Write any data to any FLASH address(1) within the FLASH memory address range.
4. Wait for a time, tNVS (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tMErase (minimum 4 ms).
7. Clear the ERASE and MASS bits.
NOTE
Mass erase is disabled whenever any block is protected (FLBPR does not
equal $FF).
8. Wait for a time, tNVHL (minimum 100 µs).
9. Clear the HVEN bit.
10. After time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps.
1. When in monitor mode, with security sequence failed (see 18.3.2 Security), write to the FLASH block protect register instead
of any FLASH address.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
40
Freescale Semiconductor
FLASH Memory (FLASH)
2.8.4 FLASH Program Operation
Use the following step-by-step procedure to program a row of FLASH memory. Figure 2-4 shows a
flowchart of the programming algorithm.
NOTE
Only bytes which are currently $FF may be programmed.
1. Set the PGM bit. This configures the memory for program operation and enables the latching of
address and data for programming.
2. Read the FLASH block protect register.
3. Write any data to any FLASH location within the address range desired.
4. Wait for a time, tNVS (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tPGS (minimum 5 µs).
7. Write data to the FLASH address being programmed(1).
8. Wait for time, tPROG (minimum 30 µs).
9. Repeat step 7 and 8 until all desired bytes within the row are programmed.
10. Clear the PGM bit(1).
11. Wait for time, tNVH (minimum 5 µs).
12. Clear the HVEN bit.
13. After time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
NOTE
The COP register at location $FFFF should not be written between steps
5-12, when the HVEN bit is set. Since this register is located at a valid
FLASH address, unpredictable behavior may occur if this location is written
while HVEN is set.
This program sequence is repeated throughout the memory until all data is programmed.
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps. Do not exceed tPROG maximum, see 19.6 FLASH
Memory Characteristics.
1. The time between each FLASH address change, or the time between the last FLASH address programmed to clearing PGM
bit, must not exceed the maximum programming time, tPROG maximum.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
41
Memory
1
2
3
ALGORITHM FOR PROGRAMMING
A ROW (64 BYTES) OF FLASH MEMORY
SET PGM BIT
READ THE FLASH BLOCK PROTECT REGISTER
WRITE ANY DATA TO ANY FLASH ADDRESS
WITHIN THE ROW ADDRESS RANGE DESIRED
4
5
6
WAIT FOR A TIME, tNVS
SET HVEN BIT
WAIT FOR A TIME, tPGS
7
8
WRITE DATA TO THE FLASH ADDRESS
TO BE PROGRAMMED
WAIT FOR A TIME, tPROG
COMPLETED
YES
PROGRAMMING
THIS ROW?
NO
10
CLEAR PGM BIT
WAIT FOR A TIME, tNVH
CLEAR HVEN BIT
11
12
Note:
The time between each FLASH address change (step 7 to step 7), or
the time between the last FLASH address programmed
to clearing PGM bit (step 7 to step 10)
must not exceed the maximum programming
time, tPROG max.
13
WAIT FOR A TIME, tRCV
END OF PROGRAMMING
This row program algorithm assumes the row/s
to be programmed are initially erased.
Figure 2-4. FLASH Programming Flowchart
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
42
Freescale Semiconductor
FLASH Memory (FLASH)
2.8.5 FLASH Block Protection
Due to the ability of the on-board charge pump to erase and program the FLASH memory in the target
application, provision is made for protecting a block of memory from unintentional erase or program
operations due to system malfunction. This protection is done by using a FLASH block protect register
(FLBPR).
The FLBPR determines the range of the FLASH memory which is to be protected. The range of the
protected area starts from a location defined by FLBPR and ends at the bottom of the FLASH memory
($FFFF). When the memory is protected, the HVEN bit cannot be set in either ERASE or PROGRAM
operations.
NOTE
In performing a program or erase operation, the FLASH block protect
register must be read after setting the PGM or ERASE bit and before
asserting the HVEN bit
When the FLBPR is programmed with all 0s, the entire memory is protected from being programmed and
erased. When all the bits are erased (all 1s), the entire memory is accessible for program and erase.
When bits within the FLBPR are programmed, they lock a block of memory, whose address ranges are
shown in 2.8.6 FLASH Block Protect Register. Once the FLBPR is programmed with a value other than
$FF, any erase or program of the FLBPR or the protected block of FLASH memory is prohibited. Mass
erase is disabled whenever any block is protected (FLBPR does not equal $FF). The FLBPR itself can be
erased or programmed only with an external voltage, VTST, present on the IRQ pin. This voltage also
allows entry from reset into the monitor mode.
2.8.6 FLASH Block Protect Register
The FLASH block protect register (FLBPR) is implemented as a byte within the FLASH memory, and
therefore can be written only during a programming sequence of the FLASH memory. The value in this
register determines the starting location of the protected range within the FLASH memory.
Address:
$FF7E
Bit 7
6
BPR6
0
5
BPR5
0
4
BPR4
0
3
BPR3
0
2
BPR2
0
1
BPR1
0
Bit 0
BPR0
0
Read:
Write:
Reset:
BPR7
0
U = Unaffected by reset. Initial value from factory is 1.
Write to this register by a programming sequence to the FLASH memory.
Figure 2-5. FLASH Block Protect Register (FLBPR)
BPR[7:0] — FLASH Block Protect Bits
These eight bits represent bits [14:7] of a 16-bit memory address. Bit 15 is 1 and bits [6:0] are 0s.
The resultant 16-bit address is used for specifying the start address of the FLASH memory for block
protection. The FLASH is protected from this start address to the end of FLASH memory at $FFFF.
With this mechanism, the protect start address can be XX00 and XX80 (128 bytes page boundaries)
within the FLASH memory.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
43
Memory
16-BIT MEMORY ADDRESS
START ADDRESS OF FLASH
BLOCK PROTECT
0
0
0
0
0
0
0
FLBPR VALUE
1
Figure 2-6. FLASH Block Protect Start Address
Refer to Table 2-2 for examples of the protect start address.
Table 2-2. Examples of Protect Start Address
BPR[7:0]
$00
Start of Address of Protect Range
The entire FLASH memory is protected.
$8080 (1000 0000 1000 0000)
$8100 (1000 0001 0000 0000)
and so on...
$01 (0000 0001)
$02 (0000 0010)
$FE (1111 1110)
$FF00 (1111 1111 0000 0000)
$FF
The entire FLASH memory is not protected.
Note: The end address of the protected range is always $FFFF.
2.8.7 Wait Mode
Putting the MCU into wait mode while the FLASH is in read mode does not affect the operation of the
FLASH memory directly, but there will not be any memory activity since the CPU is inactive.
The WAIT instruction should not be executed while performing a program or erase operation on the
FLASH. Otherwise, the operation will discontinue, and the FLASH will be on standby mode.
2.8.8 Stop Mode
Putting the MCU into stop mode while the FLASH is in read mode does not affect the operation of the
FLASH memory directly, but there will not be any memory activity since the CPU is inactive.
The STOP instruction should not be executed while performing a program or erase operation on the
FLASH, otherwise the operation will discontinue, and the FLASH will be on standby mode
NOTE
Standby mode is the power-saving mode of the FLASH module in which all
internal control signals to the FLASH are inactive and the current
consumption of the FLASH is at a minimum.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
44
Freescale Semiconductor
Chapter 3
Analog-to-Digital Converter (ADC)
3.1 Introduction
This section describes the 10-bit analog-to-digital converter (ADC).
3.2 Features
Features of the ADC module include:
•
•
•
•
•
•
•
•
•
10 channels with multiplexed input
Linear successive approximation
10-bit resolution, 8-bit accuracy
Single or continuous conversion
Conversion complete flag or conversion complete interrupt
Selectable ADC clock
Left or right justified result
Left justified sign data mode
High impedance buffered ADC input
3.3 Functional Description
Ten ADC channels are available for sampling external sources at pins PTC1/ATD9:PTC0/ATD8 and
PTB7/ATD7:PTB0/ATD0. To achieve the best possible accuracy, these pins are implemented as
input-only pins when the analog-to-digital (A/D) feature is enabled. An analog multiplexer allows the single
ADC to select one of the 10 ADC channels as ADC voltage IN (ADCVIN). ADCVIN is converted by the
successive approximation algorithm. When the conversion is completed, the ADC places the result in the
ADC data register (ADRH and ADRL) and sets a flag or generates an interrupt. See Figure 3-2.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
45
INTERNAL BUS
M68HC08 CPU
PTA7–PTA0
CPU
REGISTERS
ARITHMETIC/LOGIC
UNIT
LOW-VOLTAGE INHIBIT
MODULE
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
COMPUTER OPERATING PROPERLY
MODULE
CONTROL AND STATUS REGISTERS — 112 BYTES
USER FLASH — 32,256 BYTES
TIMER INTERFACE
MODULE A
USER RAM — 768 BYTES
PTC6
PTC5
TIMER INTERFACE
MODULE B
PTC4
MONITOR ROM — 240 BYTES
PTC3
PTC2
PTC1/ATD9(1)
SERIAL COMMUNICATIONS INTERFACE
MODULE
USER FLASH VECTOR SPACE — 46 BYTES
PTC0/ATD8
OSC1
PTD6/IS3
CLOCK GENERATOR
MODULE
OSC2
SERIAL PERIPHERAL INTERFACE
MODULE(2)
PTD5/IS2
CGMXFC
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
POWER-ON RESET
MODULE
SYSTEM INTEGRATION
MODULE
RST
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
IRQ
MODULE
IRQ
SINGLE BREAK
MODULE
VDDA
(3)
VSSA
ANALOG-TO-DIGITAL CONVERTER
MODULE
(3)
VREFL
VREFH
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PWMGND
PULSE-WIDTH MODULATOR
MODULE
PWM6–PWM1
PTF1/SS(1)
PTF0/SPSCK(1)
VSS
VDD
POWER
VDDAD
VSSAD
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 3-1. Block Diagram Highlighting ADC Block and Pins
Functional Description
INTERNAL
DATA BUS
PTB/Cx
ADC CHANNEL x
READ PTB/PTC
DISABLE
ADC DATA REGISTERS
CONVERSION
COMPLETE
ADC VOLTAGE IN
ADVIN
INTERRUPT
LOGIC
CHANNEL
SELECT
ADC
ADCH[4:0]
AIEN
COCO
ADC CLOCK
CGMXCLK
CLOCK
GENERATOR
BUS CLOCK
ADIV[2:0]
ADICLK
Figure 3-2. ADC Block Diagram
3.3.1 ADC Port I/O Pins
PTC1/ATD9:PTC0/ATD8 and PTB7/ATD7:PTB0/ATD0 are general-purpose I/O pins that are shared with
the ADC channels.
The channel select bits define which ADC channel/port pin will be used as the input signal. The ADC
overrides the port logic when that port is selected by the ADC multiplexer. The remaining ADC
channels/port pins are controlled by the port logic and can be used as general-purpose input/output (I/O)
pins. Writes to the port register or DDR will not have any effect on the port pin that is selected by the ADC.
Read of a port pin which is in use by the ADC will return a 0.
3.3.2 Voltage Conversion
When the input voltage to the ADC equals VREFH, the ADC converts the signal to $3FF (full scale). If the
input voltage equals VREFL, the ADC converts it to $000. Input voltages between VREFH and VREFL are
straight-line linear conversions. All other input voltages will result in $3FF if greater than VREFH and $000
if less than VREFL
.
NOTE
Input voltage should not exceed the analog supply voltages. See
19.13 Analog-to-Digital Converter (ADC) Characteristics.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
47
Analog-to-Digital Converter (ADC)
3.3.3 Conversion Time
Conversion starts after a write to the ADSCR. A conversion is between 16 and 17 ADC clock cycles,
therefore:
16 to17 ADC Cycles
Conversion time =
ADC Frequency
Number of Bus Cycles = Conversion Time x CPU Bus Frequency
The ADC conversion time is determined by the clock source chosen and the divide ratio selected. The
clock source is either the bus clock or CGMXCLK and is selectable by ADICLK located in the ADC clock
register. For example, if CGMXCLK is 4 MHz and is selected as the ADC input clock source, the ADC
input clock divide-by-4 prescale is selected and the CPU bus frequency is 8 MHz:
16 to 17 ADC Cycles
Conversion Time =
= 16 to 17 µs
4 MHz/4
Number of bus cycles = 16 µs x 8 MHz = 128 to 136 cycles
NOTE
The ADC frequency must be between fADIC minimum and fADIC maximum
to meet A/D specifications. See 19.13 Analog-to-Digital Converter (ADC)
Characteristics.
Since an ADC cycle may be comprised of several bus cycles (eight, 136 minus 128, in the previous
example) and the start of a conversion is initiated by a bus cycle write to the ADSCR, from zero to eight
additional bus cycles may occur before the start of the initial ADC cycle. This results in a fractional ADC
cycle and is represented as the 17th cycle.
3.3.4 Continuous Conversion
In continuous conversion mode, the ADC data registers ADRH and ADRL will be filled with new data after
each conversion. Data from the previous conversion will be overwritten whether that data has been read
or not. Conversions will continue until the ADCO bit is cleared. The COCO bit is set after each conversion
and will stay set until the next read of the ADC data register.
When a conversion is in process and the ADSCR is written, the current conversion data should be
discarded to prevent an incorrect reading.
3.3.5 Result Justification
The conversion result may be formatted in four different ways:
1. Left justified
2. Right justified
3. Left Justified sign data mode
4. 8-bit truncation mode
All four of these modes are controlled using MODE0 and MODE1 bits located in the ADC clock register
(ADCR).
Left justification will place the eight most significant bits (MSB) in the corresponding ADC data register
high, ADRH. This may be useful if the result is to be treated as an 8-bit result where the two least
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
48
Freescale Semiconductor
Functional Description
significant bits (LSB), located in the ADC data register low, ADRL, can be ignored. However, ADRL must
be read after ADRH or else the interlocking will prevent all new conversions from being stored.
Right justification will place only the two MSBs in the corresponding ADC data register high, ADRH, and
the eight LSBs in ADC data register low, ADRL. This mode of operation typically is used when a 10-bit
unsigned result is desired.
Left justified sign data mode is similar to left justified mode with one exception. The MSB of the 10-bit
result, AD9 located in ADRH, is complemented. This mode of operation is useful when a result,
represented as a signed magnitude from mid-scale, is needed. Finally, 8-bit truncation mode will place
the eight MSBs in ADC data register low, ADRL. The two LSBs are dropped. This mode of operation is
used when compatibility with 8-bit ADC designs are required. No interlocking between ADRH and ADRL
is present.
NOTE
Quantization error is affected when only the most significant eight bits are
used as a result. See Figure 3-3.
8-BIT 10-BIT
RESULT RESULT
IDEAL 8-BIT CHARACTERISTIC
WITH QUANTIZATION = 1/2
10-BIT TRUNCATED
TO 8-BIT RESULT
003
00B
00A
IDEAL 10-BIT CHARACTERISTIC
WITH QUANTIZATION = 1/2
009
008
007
006
005
004
003
002
001
000
002
001
000
WHEN TRUNCATION IS USED,
ERROR FROM IDEAL 8-BIT = 3/8 LSB
DUE TO NON-IDEAL QUANTIZATION.
INPUT VOLTAGE
1/2
2 1/2
4 1/2
6 1/2
8 1/2
REPRESENTED AS 10-BIT
9 1/2
INPUT VOLTAGE
1 1/2
3 1/2
5 1/2
7 1/2
1/2
1 1/2
2 1/2
REPRESENTED AS 8-BIT
Figure 3-3. 8-Bit Truncation Mode Error
3.3.6 Monotonicity
The conversion process is monotonic and has no missing codes.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
49
Analog-to-Digital Converter (ADC)
3.4 Interrupts
When the AIEN bit is set, the ADC module is capable of generating a CPU interrupt after each ADC
conversion. A CPU interrupt is generated if the COCO bit is at 0. The COCO bit is not used as a
conversion complete flag when interrupts are enabled.
3.5 Wait Mode
The WAIT instruction can put the MCU in low power-consumption standby mode.
The ADC continues normal operation during wait mode. Any enabled CPU interrupt request from the ADC
can bring the MCU out of wait mode. If the ADC is not required to bring the MCU out of wait mode, power
down the ADC by setting ADCH[4:0] in the ADC status and control register before executing the WAIT
instruction.
3.6 I/O Signals
The ADC module has 10 input signals that are shared with port B and port C.
3.6.1 ADC Analog Power Pin (V
)
DDAD
The ADC analog portion uses VDDAD as its power pin. Connect the VDDAD pin to the same voltage
potential as VDD. External filtering may be necessary to ensure clean VDDAD for good results.
NOTE
Route VDDAD carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
3.6.2 ADC Analog Ground Pin (V
)
SSAD
The ADC analog portion uses VSSAD as its ground pin. Connect the VSSAD pin to the same voltage
potential as VSS.
3.6.3 ADC Voltage Reference Pin (V
)
REFH
VREFH is the power supply for setting the reference voltage VREFH. Connect the VREFH pin to the same
voltage potential as VDDAD. There will be a finite current associated with VREFH. See Chapter 19 Electrical
Specifications.
NOTE
Route VREFH carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
3.6.4 ADC Voltage Reference Low Pin (V
)
REFL
VREFL is the lower reference supply for the ADC. Connect the VREFL pin to the same voltage potential as
VSSAD. A finite current will be associated with VREFL. See Chapter 19 Electrical Specifications.
NOTE
In the 56-pin shrink dual in-line package (SDIP), VREFL and VSSAD are tied
together.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
50
Freescale Semiconductor
I/O Registers
3.6.5 ADC Voltage In (ADVIN)
ADVIN is the input voltage signal from one of the 10 ADC channels to the ADC module.
3.6.6 ADC External Connections
This section describes the ADC external connections: VREFH and VREFL, ANx, and grounding.
3.6.6.1 VREFH and VREFL
Both ac and dc current are drawn through the VREFH and VREFL loop. The AC current is in the form of
current spikes required to supply charge to the capacitor array at each successive approximation step.
The current flows through the internal resistor string. The best external component to meet both these
current demands is a capacitor in the 0.01 µF to 1 µF range with good high frequency characteristics. This
capacitor is connected between VREFH and VREFL and must be placed as close as possible to the
package pins. Resistance in the path is not recommended because the dc current will cause a voltage
drop which could result in conversion errors.
3.6.6.2 ANx
Empirical data shows that capacitors from the analog inputs to VREFL improve ADC performance. 0.01-µF
and 0.1-µF capacitors with good high-frequency characteristics are sufficient. These capacitors must be
placed as close as possible to the package pins.
3.6.6.3 Grounding
In cases where separate power supplies are used for analog and digital power, the ground connection
between these supplies should be at the VSSAD pin. This should be the only ground connection between
these supplies if possible. The VSSA pin makes a good single point ground location. Connect the VREFL
pin to the same potential as VSSAD at the single point ground location.
3.7 I/O Registers
These I/O registers control and monitor operation of the ADC:
•
•
•
ADC status and control register, ADSCR
ADC data registers, ADRH and ARDL
ADC clock register, ADCLK
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
51
Analog-to-Digital Converter (ADC)
3.7.1 ADC Status and Control Register
This section describes the function of the ADC status and control register (ADSCR). Writing ADSCR
aborts the current conversion and initiates a new conversion.
Address: $0040
Bit 7
6
5
ADCO
0
4
ADCH4
1
3
ADCH3
1
2
ADCH2
1
1
ADCH1
1
Bit 0
ADCH0
1
Read:
Write:
Reset:
COCO
AIEN
R
0
0
R
= Reserved
Figure 3-4. ADC Status and Control Register (ADSCR)
COCO — Conversions Complete Bit
In non-interrupt mode (AIEN = 0), COCO is a read-only bit that is set at the end of each conversion.
COCO will stay set until cleared by a read of the ADC data register. Reset clears this bit.
In interrupt mode (AIEN = 1), COCO is a read-only bit that is not set at the end of a conversion. It
always reads as a 0.
1 = Conversion completed (AIEN = 0)
0 = Conversion not completed (AIEN = 0) or CPU interrupt enabled
(AIEN = 1)
NOTE
The write function of the COCO bit is reserved. When writing to the ADSCR
register, always have a 0 in the COCO bit position.
AIEN — ADC Interrupt Enable Bit
When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is
cleared when the data register is read or the status/control register is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the ADR register at the end of each
conversion. Only one conversion is allowed when this bit is cleared. Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
ADCH[4:0] — ADC Channel Select Bits
ADCH4, ADCH3, ADCH2, ADCH1, and ADCH0 form a 5-bit field which is used to select one of 10 ADC
channels. The ADC channels are detailed in Table 3-1.
NOTE
Take care to prevent switching noise from corrupting the analog signal
when simultaneously using a port pin as both an analog and digital input.
The ADC subsystem is turned off when the channel select bits are all set to 1. This feature allows for
reduced power consumption for the MCU when the ADC is not used.
NOTE
Recovery from the disabled state requires one conversion cycle to stabilize.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
52
Freescale Semiconductor
I/O Registers
The voltage levels supplied from internal reference nodes as specified in Table 3-1 are used to verify
the operation of the ADC both in production test and for user applications.
Table 3-1. Mux Channel Select
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
Input Select
PTB0/ATD0
PTB1/ATD1
PTB2/ATD2
PTB3/ATD3
PTB4/ATD4
PTB5/ATD5
PTB6/ATD6
PTB7/ATD7
PTC0/ATD8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
0
1
0
1
PTC1/ATD9(1)
Unused(2)
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
1
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
0
Ø
Ø
Ø
Ø
Ø
Ø
Unused(2)
Reserved(3)
1
1
0
1
1
Unused(2)
VREFH
1
1
1
1
1
1
1
1
1
1
1
1
0
0
1
1
0
1
0
1
VREFL
ADC power off
1. ATD9 is not available in the 56-pin SDIP package.
2. Used for factory testing.
3. If any unused channels are selected, the resulting ADC conversion will be unknown.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
53
Analog-to-Digital Converter (ADC)
3.7.2 ADC Data Register High
In left justified mode, this 8-bit result register holds the eight MSBs of the 10-bit result. This register is
updated each time an ADC single channel conversion completes. Reading ADRH latches the contents of
ADRL until ADRL is read. Until ADRL is read, all subsequent ADC results will be lost.
Address:
$0041
Bit 7
AD9
R
6
AD8
R
5
AD7
R
4
AD6
R
3
AD5
R
2
AD4
R
1
AD3
R
Bit 0
AD2
R
Read:
Write:
Reset:
Unaffected by reset
R
= Reserved
Figure 3-5. ADC Data Register High (ADRH) Left Justified Mode
In right justified mode, this 8-bit result register holds the two MSBs of the 10-bit result. All other bits read
as 0. This register is updated each time a single channel ADC conversion completes. Reading ADRH
latches the contents of ADRL until ADRL is read. Until ADRL is read, all subsequent ADC results will be
lost.
Address:
$0041
Bit 7
0
6
0
5
0
4
0
3
0
2
0
1
AD9
R
Bit 0
AD8
R
Read:
Write:
Reset:
R
R
R
R
R
R
Unaffected by reset
R
= Reserved
Figure 3-6. ADC Data Register High (ADRH) Right Justified Mode
3.7.3 ADC Data Register Low
In left justified mode, this 8-bit result register holds the two LSBs of the 10-bit result. All other bits read as
0. This register is updated each time a single channel ADC conversion completes. Reading ADRH latches
the contents of ADRL until ADRL is read. Until ADRL is read, all subsequent ADC results will be lost.
Address:
$0042
Bit 7
AD1
R
6
AD0
R
5
0
4
0
3
0
2
0
1
0
Bit 0
0
Read:
Write:
Reset:
R
R
R
R
R
R
Unaffected by reset
R
= Reserved
Figure 3-7. ADC Data Register Low (ADRL) Left Justified Mode
In right justified mode, this 8-bit result register holds the eight LSBs of the 10-bit result. This register is
updated each time an ADC conversion completes. Reading ADRH latches the contents of ADRL until
ADRL is read. Until ADRL is read, all subsequent ADC results will be lost.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
54
Freescale Semiconductor
I/O Registers
Address:
$0042
Bit 7
AD7
R
6
AD6
R
5
AD5
R
4
AD4
R
3
AD3
R
2
AD2
R
1
AD1
R
Bit 0
AD0
R
Read:
Write:
Reset:
Unaffected by reset
R
= Reserved
Figure 3-8. ADC Data Register Low (ADRL) Right Justified Mode
In 8-bit mode, this 8-bit result register holds the eight MSBs of the 10-bit result. This register is updated
each time an ADC conversion completes. In 8-bit mode, this register contains no interlocking with ADRH.
Address:
$0042
Bit 7
AD9
R
6
AD8
R
5
AD7
R
4
AD6
R
3
AD5
R
2
AD4
R
1
AD3
R
Bit 0
AD2
R
Read:
Write:
Reset:
Unaffected by reset
R
= Reserved
Figure 3-9. ADC Data Register Low (ADRL) 8-Bit Mode
3.7.4 ADC Clock Register
This register selects the clock frequency for the ADC, selecting between modes of operation.
Address:
$0043
Bit 7
6
5
ADIV0
0
4
ADICLK
0
3
MODE1
0
2
MODE0
1
1
0
0
Bit 0
0
Read:
Write:
Reset:
ADIV2
ADIV1
R
0
0
0
R
= Reserved
Figure 3-10. ADC Clock Register (ADCLK)
ADIV2:ADIV0 — ADC Clock Prescaler Bits
ADIV2, ADIV1, and ADIV0 form a 3-bit field which selects the divide ratio used by the ADC to generate
the internal ADC clock. Table 3-2 shows the available clock configurations.
Table 3-2. ADC Clock Divide Ratio
ADIV2
ADIV1
ADIV0
ADC Clock Rate
ADC input clock ÷ 1
ADC input clock ÷ 2
ADC input clock ÷ 4
ADC input clock ÷ 8
ADC input clock ÷ 16
0
0
0
0
1
0
0
1
1
X
0
1
0
1
X
X = don’t care
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
55
Analog-to-Digital Converter (ADC)
ADICLK — ADC Input Clock Select Bit
ADICLK selects either bus clock or CGMXCLK as the input clock source to generate the internal ADC
clock. Reset selects CGMXCLK as the ADC clock source.
If the external clock (CGMXCLK) is equal to or greater than 1 MHz, CGMXCLK can be used as the
clock source for the ADC. If CGMXCLK is less than 1 MHz, use the PLL-generated bus clock as the
clock source. As long as the internal ADC clock is at fADIC, correct operation can be guaranteed. See
19.13 Analog-to-Digital Converter (ADC) Characteristics.
1 = Internal bus clock
0 = External clock, CGMXCLK
CGMXCLK or bus frequency
fADIC
=
ADIV[2:0]
MODE1:MODE0 — Modes of Result Justification Bits
MODE1:MODE0 selects among four modes of operation. The manner in which the ADC conversion
results will be placed in the ADC data registers is controlled by these modes of operation. Reset returns
right-justified mode.
00 = 8-bit truncation mode
01 = Right justified mode
10 = Left justified mode
11 = Left justified sign data mode
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
56
Freescale Semiconductor
Chapter 4
Clock Generator Module (CGM)
4.1 Introduction
This section describes the clock generator module (CGM, version A). The CGM generates the crystal
clock signal, CGMXCLK, which operates at the frequency of the crystal. The CGM also generates the
base clock signal, CGMOUT, from which the system integration module (SIM) derives the system clocks.
CGMOUT is based on either the crystal clock divided by two or the phase-locked loop (PLL) clock,
CGMVCLK, divided by two. The PLL is a frequency generator designed for use with crystals or ceramic
resonators. The PLL can generate an 8-MHz bus frequency without using a 32-MHz external clock.
4.2 Features
Features of the CGM include:
•
•
•
•
•
PLL with output frequency in integer multiples of the crystal reference
Programmable hardware voltage-controlled oscillator (VCO) for low-jitter operation
Automatic bandwidth control mode for low-jitter operation
Automatic frequency lock detector
Central processor unit (CPU) interrupt on entry or exit from locked condition
4.3 Functional Description
The CGM consists of three major submodules:
1. Crystal oscillator circuit — The crystal oscillator circuit generates the constant crystal frequency
clock, CGMXCLK.
2. Phase-locked loop (PLL) — The PLL generates the programmable VCO frequency clock,
CGMVCLK.
3. Base clock selector circuit — This software-controlled circuit selects either CGMXCLK divided by
two or the VCO clock, CGMVCLK, divided by two as the base clock, CGMOUT. The SIM derives
the system clocks from CGMOUT.
Figure 4-1 shows the structure of the CGM.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
57
Clock Generator Module (CGM)
CRYSTAL OSCILLATOR
OSC2
CGMXCLK
CGMOUT
TO SIM
TO SIM
CLOCK
SELECT
CIRCUIT
OSC1
A
B
÷ 2
S*
*WHEN S = 1, CGMOUT = B
SIMOSCEN
CGMRDV
CGMRCLK
BCS
USER MODE
VDDA
CGMXFC
VSS
PTC2
VRS[7:4]
MONITOR MODE
VOLTAGE
CONTROLLED
OSCILLATOR
PHASE
DETECTOR
LOOP
FILTER
PLL ANALOG
CGMINT
LOCK
DETECTOR
BANDWIDTH
CONTROL
INTERRUPT
CONTROL
LOCK
AUTO
ACQ
PLLIE
PLLF
MUL[7:4]
CGMVDV
CGMVCLK
FREQUENCY
DIVIDER
Figure 4-1. CGM Block Diagram
Addr.
Register Name
Bit 7
PLLIE
0
6
PLLF
R
5
PLLON
1
4
BCS
0
3
2
1
1
1
Bit 0
Read:
1
R
1
1
R
1
PLL Control Register
(PCTL) Write:
$005C
R
1
R
1
See page 66.
Reset:
Read:
0
LOCK
R
0
0
0
0
PLL Bandwidth Control Register
AUTO
0
ACQ
0
XLD
0
$005D
$005E
(PBWC) Write:
R
0
R
0
R
0
R
0
See page 67.
Reset:
Read:
0
PLL Programming Register
MUL7
MUL6
MUL5
1
MUL4
0
VRS7
0
VRS6
1
VRS5
1
VRS4
0
(PPG) Write:
See page 68.
Reset:
0
1
R
= Reserved
Figure 4-2. CGM I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
58
Freescale Semiconductor
Functional Description
4.3.1 Crystal Oscillator Circuit
The crystal oscillator circuit consists of an inverting amplifier and an external crystal. The OSC1 pin is the
input to the amplifier and the OSC2 pin is the output. The SIMOSCEN signal from the system integration
module (SIM) enables the crystal oscillator circuit.
The CGMXCLK signal is the output of the crystal oscillator circuit and runs at a rate equal to the crystal
frequency. CGMXCLK is then buffered to produce CGMRCLK, the PLL reference clock.
CGMXCLK can be used by other modules which require precise timing for operation. The duty cycle of
CGMXCLK is not guaranteed to be 50 percent and depends on external factors, including the crystal and
related external components.
An externally generated clock also can feed the OSC1 pin of the crystal oscillator circuit. Connect the
external clock to the OSC1 pin and let the OSC2 pin float.
4.3.2 Phase-Locked Loop Circuit (PLL)
The PLL is a frequency generator that can operate in either acquisition mode or tracking mode, depending
on the accuracy of the output frequency. The PLL can change between acquisition and tracking modes
either automatically or manually.
4.3.2.1 PLL Circuits
The PLL consists of these circuits:
•
•
•
•
•
Voltage-controlled oscillator (VCO)
Modulo VCO frequency divider
Phase detector
Loop filter
Lock detector
The operating range of the VCO is programmable for a wide range of frequencies and for maximum
immunity to external noise, including supply and CGMXFC noise. The VCO frequency is bound to a range
from roughly one-half to twice the center-of-range frequency, fVRS. Modulating the voltage on the
CGMXFC pin changes the frequency within this range. By design, fVRS is equal to the nominal
center-of-range frequency, fNOM, (4.9152 MHz) times a linear factor, L or (L) fNOM
CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK. CGMRCLK runs at a frequency,
RCLK, and is fed to the PLL through a buffer. The buffer output is the final reference clock, CGMRDV,
running at a frequency, fRDV = fRCLK
.
f
.
The VCO’s output clock, CGMVCLK, running at a frequency, fVCLK, is fed back through a programmable
modulo divider. The modulo divider reduces the VCO clock by a factor, N. The divider’s output is the VCO
feedback clock, CGMVDV, running at a frequency, fVDV = fVCLK/N. (See 4.3.2.4 Programming the PLL for
more information.)
The phase detector then compares the VCO feedback clock, CGMVDV, with the final reference clock,
CGMRDV. A correction pulse is generated based on the phase difference between the two signals. The
loop filter then slightly alters the dc voltage on the external capacitor connected to CGMXFC based on
the width and direction of the correction pulse. The filter can make fast or slow corrections depending on
its mode, described in 4.3.2.2 Acquisition and Tracking Modes. The value of the external capacitor and
the reference frequency determines the speed of the corrections and the stability of the PLL.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
59
Clock Generator Module (CGM)
The lock detector compares the frequencies of the VCO feedback clock, CGMVDV, and the final
reference clock, CGMRDV. Therefore, the speed of the lock detector is directly proportional to the final
reference frequency, fRDV. The circuit determines the mode of the PLL and the lock condition based on
this comparison.
4.3.2.2 Acquisition and Tracking Modes
The PLL filter is manually or automatically configurable into one of two operating modes:
1. Acquisition mode — In acquisition mode, the filter can make large frequency corrections to the
VCO. This mode is used at PLL startup or when the PLL has suffered a severe noise hit and the
VCO frequency is far off the desired frequency. When in acquisition mode, the ACQ bit is clear in
the PLL bandwidth control register. See 4.5.2 PLL Bandwidth Control Register.
2. Tracking mode — In tracking mode, the filter makes only small corrections to the frequency of the
VCO. PLL jitter is much lower in tracking mode, but the response to noise is also slower. The PLL
enters tracking mode when the VCO frequency is nearly correct, such as when the PLL is selected
as the base clock source. See 4.3.3 Base Clock Selector Circuit. The PLL is automatically in
tracking mode when not in acquisition mode or when the ACQ bit is set.
4.3.2.3 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter manually or automatically.
In automatic bandwidth control mode (AUTO = 1), the lock detector automatically switches between
acquisition and tracking modes. Automatic bandwidth control mode also is used to determine when the
VCO clock, CGMVCLK, is safe to use as the source for the base clock, CGMOUT. See 4.5.2 PLL
Bandwidth Control Register. If PLL interrupts are enabled, the software can wait for a PLL interrupt
request and then check the LOCK bit. If interrupts are disabled, software can poll the LOCK bit
continuously (during PLL startup, usually) or at periodic intervals. In either case, when the LOCK bit is set,
the VCO clock is safe to use as the source for the base clock. See 4.3.3 Base Clock Selector Circuit. If
the VCO is selected as the source for the base clock and the LOCK bit is clear, the PLL has suffered a
severe noise hit and the software must take appropriate action, depending on the application. See 4.6
Interrupts for information and precautions on using interrupts.
These conditions apply when the PLL is in automatic bandwidth control mode:
•
The ACQ bit (see 4.5.2 PLL Bandwidth Control Register) is a read-only indicator of the mode of the
filter. For more information, see 4.3.2.2 Acquisition and Tracking Modes.
•
The ACQ bit is set when the VCO frequency is within a certain tolerance, ∆TRK, and is cleared when
the VCO frequency is out of a certain tolerance, ∆UNT. For more information, see 4.8
Acquisition/Lock Time Specifications.
•
•
The LOCK bit is a read-only indicator of the locked state of the PLL.
The LOCK bit is set when the VCO frequency is within a certain tolerance, ∆Lock, and is cleared
when the VCO frequency is out of a certain tolerance, ∆UNL. For more information, see 4.8
Acquisition/Lock Time Specifications.
•
CPU interrupts can occur if enabled (PLLIE = 1) when the PLL’s lock condition changes, toggling
the LOCK bit. For more information, see 4.5.1 PLL Control Register.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
60
Freescale Semiconductor
Functional Description
The PLL also may operate in manual mode (AUTO = 0). Manual mode is used by systems that do not
require an indicator of the lock condition for proper operation. Such systems typically operate well below
f
BUSMAX and require fast startup. These conditions apply when in manual mode:
•
•
ACQ is a writable control bit that controls the mode of the filter. Before turning on the PLL in manual
mode, the ACQ bit must be clear.
Before entering tracking mode (ACQ = 1), software must wait a given time, tACQ (see 4.8
Acquisition/Lock Time Specifications), after turning on the PLL by setting PLLON in the PLL control
register (PCTL).
•
Software must wait a given time, tAL, after entering tracking mode before selecting the PLL as the
clock source to CGMOUT (BCS = 1).
•
•
The LOCK bit is disabled.
CPU interrupts from the CGM are disabled.
4.3.2.4 Programming the PLL
Use this 9-step procedure to program the PLL. Table 4-1 lists the variables used and their meaning.
Table 4-1. Variable Definitions
Variable
Definition
Desired bus clock frequency
fBUSDES
fVCLKDES
fRCLK
fVCLK
fBUS
Desired VCO clock frequency
Chosen reference crystal frequency
Calculated VCO clock frequency
Calculated bus clock frequency
Nominal VCO center frequency
Shifted FCO center frequency
fNOM
fVRS
1. Choose the desired bus frequency, fBUSDES
Example: fBUSDES = 8 MHz
.
2. Calculate the desired VCO frequency, fVCLKDES
.
f
VCLKDES = 4 x fBUSDES
Example: fVCLKDES = 4 x 8 MHz = 32 MHz
3. Using a reference frequency, fRCLK, equal to the crystal frequency, calculate the VCO frequency
multiplier, N. Round the result to the nearest integer.
fVCLKDES
N =
fRCLK
32 MHz
4 MHz
Example: N =
= 8 MHz
4. Calculate the VCO frequency, fVCLK
.
fVCLK = N x fRCLK
Example: fVCLK = 8 x 4 MHz = 32 MHz
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
61
Clock Generator Module (CGM)
5. Calculate the bus frequency, fBUS, and compare fBUS with fBUSDES
fVCLK
.
fBUS
=
4
32 MHz
4 MHz
Example: N =
= 8 MHz
6. If the calculated fBUS is not within the tolerance limits of the application, select another fBUSDES or
another fRCLK
.
7. Using the value 4.9152 MHz for fNOM, calculate the VCO linear range multiplier, L. The linear range
multiplier controls the frequency range of the PLL.
fVCLK
fNOM
)
(
L = round
32 MHz
4.9152 MHz
Example: L =
= 7 MHz
8. Calculate the VCO center-of-range frequency, fVRS. The center-or-range frequency is the midpoint
between the minimum and maximum frequencies attainable by the PLL.
f
VRS = L x fNOM
Example: fVRS = 7 x 4.9152 MHz = 34.4 MHz
For proper operation,
fNOM
fVRS – fVCLK | ≤
2
CAUTION
Exceeding the recommended maximum bus frequency or VCO frequency can crash the MCU.
9. Program the PLL registers accordingly:
a. In the upper four bits of the PLL programming register (PPG), program the binary equivalent
of N.
b. In the lower four bits of the PLL programming register (PPG), program the binary equivalent
of L.
4.3.2.5 Special Programming Exceptions
The programming method described in 4.3.2.4 Programming the PLL does not account for possible
exceptions. A value of 0 for N or L is meaningless when used in the equations given. To account for these
exceptions:
•
•
A 0 value for N is interpreted exactly the same as a value of 1.
A 0 value for L disables the PLL and prevents its selection as the source for the base clock. See
4.3.3 Base Clock Selector Circuit.
4.3.3 Base Clock Selector Circuit
This circuit is used to select either the crystal clock, CGMXCLK, or the VCO clock, CGMVCLK, as the
source of the base clock, CGMOUT. The two input clocks go through a transition control circuit that waits
up to three CGMXCLK cycles and three CGMVCLK cycles to change from one clock source to the other.
During this time, CGMOUT is held in stasis. The output of the transition control circuit is then divided by
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
62
Freescale Semiconductor
Functional Description
two to correct the duty cycle. Therefore, the bus clock frequency, which is one-half of the base clock
frequency, is one-fourth the frequency of the selected clock (CGMXCLK or CGMVCLK).
The BCS bit in the PLL control register (PCTL) selects which clock drives CGMOUT. The VCO clock
cannot be selected as the base clock source if the PLL is not turned on. The PLL cannot be turned off if
the VCO clock is selected. The PLL cannot be turned on or off simultaneously with the selection or
deselection of the VCO clock. The VCO clock also cannot be selected as the base clock source if the
factor L is programmed to a 0. This value would set up a condition inconsistent with the operation of the
PLL, so that the PLL would be disabled and the crystal clock would be forced as the source of the base
clock.
4.3.4 CGM External Connections
In its typical configuration, the CGM requires seven external components. Five of these are for the crystal
oscillator and two are for the PLL.
The crystal oscillator is normally connected in a Pierce oscillator configuration, as shown in Figure 4-3.
Figure 4-3 shows only the logical representation of the internal components and may not represent actual
circuitry.
SIMOSCEN
CGMXCLK
OSC1
OSC2
RS*
VSS
CGMXFC
CF
VDDA
VDD
CBYP
RB
X1
*RS can be 0 (shorted) when used with
higher frequency crystals. Refer to
manufacturer’s data.
C1
C2
Figure 4-3. CGM External Connections
The oscillator configuration uses five components:
1. Crystal, X1
2. Fixed capacitor, C1
3. Tuning capacitor, C2 (can also be a fixed capacitor)
4. Feedback resistor, RB
5. Series resistor, RS (optional)
The series resistor (RS) is included in the diagram to follow strict Pierce oscillator guidelines and may not
be required for all ranges of operation, especially with high-frequency crystals. Refer to the crystal
manufacturer’s data for more information.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
63
Clock Generator Module (CGM)
Figure 4-3 also shows the external components for the PLL:
•
•
Bypass capacitor, CBYP
Filter capacitor, CF
NOTE
Routing should be done with great care to minimize signal cross talk and
noise. (See 4.8 Acquisition/Lock Time Specifications for routing information
and more information on the filter capacitor’s value and its effects on PLL
performance.)
4.4 I/O Signals
This section describes the CGM input/output (I/O) signals.
4.4.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is an input to the crystal oscillator amplifier.
4.4.2 Crystal Amplifier Output Pin (OSC2)
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
4.4.3 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase corrections. A small external capacitor is
connected to this pin.
NOTE
To prevent noise problems, CF should be placed as close to the CGMXFC
pin as possible, with minimum routing distances and no routing of other
signals across the CF connection.
4.4.4 PLL Analog Power Pin (V
)
DDA
VDDA is a power pin used by the analog portions of the PLL. Connect the VDDA pin to the same voltage
potential as the VDD pin.
NOTE
Route VDDA carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
4.4.5 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM) and enables the oscillator and
PLL.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
64
Freescale Semiconductor
CGM Registers
4.4.6 Crystal Output Frequency Signal (CGMXCLK)
CGMXCLK is the crystal oscillator output signal. It runs at the full speed of the crystal (fXCLK) and comes
directly from the crystal oscillator circuit. Figure 4-3 shows only the logical relation of CGMXCLK to OSC1
and OSC2 and may not represent the actual circuitry. The duty cycle of CGMXCLK is unknown and may
depend on the crystal and other external factors. Also, the frequency and amplitude of CGMXCLK can be
unstable at startup.
4.4.7 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM, which generates the MCU clocks.
CGMOUT is a 50 percent duty cycle clock running at twice the bus frequency. CGMOUT is software
programmable to be either the oscillator output, CGMXCLK, divided by two or the VCO clock, CGMVCLK,
divided by two.
4.4.8 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.
4.5 CGM Registers
These registers control and monitor operation of the CGM:
•
•
•
PLL control register (PCTL) — see 4.5.1 PLL Control Register
PLL bandwidth control register (PBWC) — see 4.5.2 PLL Bandwidth Control Register
PLL programming register (PPG) — see 4.5.3 PLL Programming Register
Figure 4-4 is a summary of the CGM registers.
Addr.
Register Name
Bit 7
PLLIE
0
6
PLLF
R
5
PLLON
1
4
BCS
0
3
1
2
1
1
1
Bit 0
Read:
PLL Control Register
(PCTL) Write:
1
R
1
$005C
R
1
R
1
R
1
See page 66.
Reset:
Read:
0
LOCK
R
0
0
0
0
PLL Bandwidth Control Register
AUTO
0
ACQ
0
XLD
0
$005D
$005E
Notes:
(PBWC) Write:
R
0
R
0
R
0
R
0
See page 67.
Reset:
Read:
0
PLL Programming Register
MUL7
MUL6
MUL5
1
MUL4
0
VRS7
0
VRS6
1
VRS5
1
VRS4
0
(PPG) Write:
See page 68.
Reset:
0
1
= Reserved
R
1. When AUTO = 0, PLLIE is forced to logic 0 and is read-only.
2. When AUTO = 0, PLLF and LOCK read as logic 0.
3. When AUTO = 1, ACQ is read-only.
4. When PLLON = 0 or VRS[7:4] = $0, BCS is forced to logic 0 and is read-only.
5. When PLLON = 1, the PLL programming register is read-only.
6. When BCS = 1, PLLON is forced set and is read-only.
Figure 4-4. CGM I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
65
Clock Generator Module (CGM)
4.5.1 PLL Control Register
The PLL control register (PCTL) contains the interrupt enable and flag bits, the on/off switch, and the base
clock selector bit.
Address:
$005C
Bit 7
6
5
PLLON
1
4
BCS
0
3
1
2
1
1
1
Bit 0
1
Read:
Write:
Reset:
PLLF
PLLIE
R
R
1
R
1
R
1
R
0
0
1
= Reserved
R
Figure 4-5. PLL Control Register (PCTL)
PLLIE — PLL Interrupt Enable Bit
This read/write bit enables the PLL to generate an interrupt request when the LOCK bit toggles, setting
the PLL flag, PLLF. When the AUTO bit in the PLL bandwidth control register (PBWC) is clear, PLLIE
cannot be written and reads as logic 0. Reset clears the PLLIE bit.
1 = PLL interrupts enabled
0 = PLL interrupts disabled
PLLF — PLL Interrupt Flag
This read-only bit is set whenever the LOCK bit toggles. PLLF generates an interrupt request if the
PLLIE bit also is set. PLLF always reads as logic 0 when the AUTO bit in the PLL bandwidth control
register (PBWC) is clear. Clear the PLLF bit by reading the PLL control register. Reset clears the PLLF
bit.
1 = Change in lock condition
0 = No change in lock condition
NOTE
Do not inadvertently clear the PLLF bit. Any read or read-modify-write
operation on the PLL control register clears the PLLF bit.
PLLON — PLL On Bit
This read/write bit activates the PLL and enables the VCO clock, CGMVCLK. PLLON cannot be
cleared if the VCO clock is driving the base clock, CGMOUT (BCS = 1). See 4.3.3 Base Clock Selector
Circuit. Reset sets this bit so that the loop can stabilize as the MCU is powering up.
1 = PLL on
0 = PLL off
BCS — Base Clock Select Bit
This read/write bit selects either the crystal oscillator output, CGMXCLK, or the VCO clock,
CGMVCLK, as the source of the CGM output, CGMOUT. CGMOUT frequency is one-half the
frequency of the selected clock. BCS cannot be set while the PLLON bit is clear. After toggling BCS,
it may take up to three CGMXCLK and three CGMVCLK cycles to complete the transition from one
source clock to the other. During the transition, CGMOUT is held in stasis. See 4.3.3 Base Clock
Selector Circuit. Reset clears the BCS bit.
1 = CGMVCLK divided by two drives CGMOUT
0 = CGMXCLK divided by two drives CGMOUT
NOTE
PLLON and BCS have built-in protection that prevents the base clock
selector circuit from selecting the VCO clock as the source of the base clock
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
66
Freescale Semiconductor
CGM Registers
if the PLL is off. Therefore, PLLON cannot be cleared when BCS is set, and
BCS cannot be set when PLLON is clear. If the PLL is off (PLLON = 0),
selecting CGMVCLK requires two writes to the PLL control register. See
4.3.3 Base Clock Selector Circuit.
PCTL[3:0] — Unimplemented Bits
These bits provide no function and always read as logic 1s.
4.5.2 PLL Bandwidth Control Register
The PLL bandwidth control register (PBWC):
•
•
•
•
Selects automatic or manual (software-controlled) bandwidth control mode
Indicates when the PLL is locked
In automatic bandwidth control mode, indicates when the PLL is in acquisition or tracking mode
In manual operation, forces the PLL into acquisition or tracking mode
Address: $005D
Bit 7
6
5
ACQ
0
4
XLD
0
3
0
2
0
1
0
Bit 0
0
Read:
Write:
Reset:
LOCK
AUTO
R
R
0
R
0
R
0
R
0
0
0
= Reserved
R
Figure 4-6. PLL Bandwidth Control Register (PBWC)
AUTO — Automatic Bandwidth Control Bit
This read/write bit selects automatic or manual bandwidth control. When initializing the PLL for manual
operation (AUTO = 0), clear the ACQ bit before turning on the PLL. Reset clears the AUTO bit.
1 = Automatic bandwidth control
0 = Manual bandwidth control
LOCK — Lock Indicator Bit
When the AUTO bit is set, LOCK is a read-only bit that becomes set when the VCO clock, CGMVCLK,
is locked (running at the programmed frequency). When the AUTO bit is clear, LOCK reads as logic 0
and has no meaning. Reset clears the LOCK bit.
1 = VCO frequency correct or locked
0 = VCO frequency incorrect or unlocked
ACQ — Acquisition Mode Bit
When the AUTO bit is set, ACQ is a read-only bit that indicates whether the PLL is in acquisition mode
or tracking mode. When the AUTO bit is clear, ACQ is a read/write bit that controls whether the PLL is
in acquisition or tracking mode.
In automatic bandwidth control mode (AUTO = 1), the last-written value from manual operation is
stored in a temporary location and is recovered when manual operation resumes. Reset clears this bit,
enabling acquisition mode.
1 = Tracking mode
0 = Acquisition mode
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
67
Clock Generator Module (CGM)
XLD — Crystal Loss Detect Bit
When the VCO output, CGMVCLK, is driving CGMOUT, this read/write bit can indicate whether the
crystal reference frequency is active or not. To check the status of the crystal reference, follow these
steps:
1. Write a logic 1 to XLD.
2. Wait N × 4 cycles. (N is the VCO frequency multiplier.)
3. Read XLD.
The crystal loss detect function works only when the BCS bit is set, selecting CGMVCLK to drive
CGMOUT. When BCS is clear, XLD always reads as logic 0.
1 = Crystal reference is not active.
0 = Crystal reference is active.
PBWC[3:0] — Reserved for Test
These bits enable test functions not available in user mode. To ensure software portability from
development systems to user applications, software should write 0s to PBWC[3:0] whenever writing to
PBWC.
4.5.3 PLL Programming Register
The PLL programming register (PPG) contains the programming information for the modulo feedback
divider and the programming information for the hardware configuration of the VCO.
Address: $005E
Bit 7
MUL7
0
6
MUL6
1
5
MUL5
1
4
MUL4
0
3
VRS7
0
2
VRS6
1
1
VRS5
1
Bit 0
VRS4
0
Read:
Write:
Reset:
Figure 4-7. PLL Programming Register (PPG)
MUL[7:4] — Multiplier Select Bits
These read/write bits control the modulo feedback divider that selects the VCO frequency multiplier,
N. See 4.3.2.1 PLL Circuits and 4.3.2.4 Programming the PLL. A value of $0 in the multiplier select bits
configures the modulo feedback divider the same as a value of $1. Reset initializes these bits to $6 to
give a default multiply value of 6.
Table 4-2. VCO Frequency Multiplier (N) Selection
MUL7:MUL6:MUL5:MUL4
VCO Frequency Multiplier (N)
0000
0001
0010
0011
1
1
2
3
1101
1110
1111
13
14
15
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
68
Freescale Semiconductor
Interrupts
NOTE
The multiplier select bits have built-in protection that prevents them from
being written when the PLL is on (PLLON = 1).
VRS[7:4] — VCO Range Select Bits
These read/write bits control the hardware center-of-range linear multiplier L, which controls the
hardware center-of-range frequency fVRS. See 4.3.2.1 PLL Circuits, 4.3.2.4 Programming the PLL and
4.5.1 PLL Control Register. VRS[7:4] cannot be written when the PLLON bit in the PLL control register
(PCTL) is set. See 4.3.2.5 Special Programming Exceptions. A value of $0 in the VCO range select
bits disables the PLL and clears the BCS bit in the PCTL. See 4.3.3 Base Clock Selector Circuit and
4.3.2.5 Special Programming Exceptions for more information.
Reset initializes the bits to $6 to give a default range multiply value of 6.
NOTE
The VCO range select bits have built-in protection that prevents them from
being written when the PLL is on (PLLON = 1) and prevents selection of the
VCO clock as the source of the base clock (BCS = 1) if the VCO range
select bits are all clear.
The VCO range select bits must be programmed correctly. Incorrect
programming may result in failure of the PLL to achieve lock.
4.6 Interrupts
When the AUTO bit is set in the PLL bandwidth control register (PBWC), the PLL can generate a CPU
interrupt request every time the LOCK bit changes state. The PLLIE bit in the PLL control register (PCTL)
enables CPU interrupts from the PLL. PLLF, the interrupt flag in the PCTL, becomes set whether
interrupts are enabled or not. When the AUTO bit is clear, CPU interrupts from the PLL are disabled and
PLLF reads as logic 0.
Software should read the LOCK bit after a PLL interrupt request to see if the request was due to an entry
into lock or an exit from lock. When the PLL enters lock, the VCO clock, CGMVCLK, divided by two can
be selected as the CGMOUT source by setting BCS in the PCTL. When the PLL exits lock, the VCO clock
frequency is corrupt, and appropriate precautions should be taken. If the application is not
frequency-sensitive, interrupts should be disabled to prevent PLL interrupt service routines from impeding
software performance or from exceeding stack limitations.
NOTE
Software can select the CGMVCLK divided by two as the CGMOUT source
even if the PLL is not locked (LOCK = 0). Therefore, software should make
sure the PLL is locked before setting the BCS bit.
4.7 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
The WAIT instruction does not affect the CGM. Before entering wait mode, software can disengage and
turn off the PLL by clearing the BCS and PLLON bits in the PLL control register (PCTL). Less
power-sensitive applications can disengage the PLL without turning it off. Applications that require the
PLL to wake the MCU from wait mode also can deselect the PLL output without turning off the PLL.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
69
Clock Generator Module (CGM)
4.8 Acquisition/Lock Time Specifications
The acquisition and lock times of the PLL are, in many applications, the most critical PLL design
parameters. Proper design and use of the PLL ensures the highest stability and lowest acquisition/lock
times.
4.8.1 Acquisition/Lock Time Definitions
Typical control systems refer to the acquisition time or lock time as the reaction time, within specified
tolerances, of the system to a step input. In a PLL, the step input occurs when the PLL is turned on or
when it suffers a noise hit. The tolerance is usually specified as a percent of the step input or when the
output settles to the desired value plus or minus a percent of the frequency change. Therefore, the
reaction time is constant in this definition, regardless of the size of the step input. For example, consider
a system with a 5 percent acquisition time tolerance. If a command instructs the system to change from
0 Hz to 1 MHz, the acquisition time is the time taken for the frequency to reach 1 MHz 50 kHz.
Fifty kHz = 5% of the 1-MHz step input. If the system is operating at 1 MHz and suffers a –100-kHz noise
hit, the acquisition time is the time taken to return from 900 kHz to 1 MHz 5 kHz. Five kHz = 5% of the
100-kHz step input.
Other systems refer to acquisition and lock times as the time the system takes to reduce the error between
the actual output and the desired output to within specified tolerances. Therefore, the acquisition or lock
time varies according to the original error in the output. Minor errors may not even be registered. Typical
PLL applications prefer to use this definition because the system requires the output frequency to be
within a certain tolerance of the desired frequency regardless of the size of the initial error.
The discrepancy in these definitions makes it difficult to specify an acquisition or lock time for a typical
PLL. Therefore, the definitions for acquisition and lock times for this module are:
•
Acquisition time, tACQ, is the time the PLL takes to reduce the error between the actual output
frequency and the desired output frequency to less than the tracking mode entry tolerance, ∆TRK
.
Acquisition time is based on an initial frequency error, (fDES – fORIG)/fDES, of not more than 100
percent. In automatic bandwidth control mode (see 4.3.2.3 Manual and Automatic PLL Bandwidth
Modes), acquisition time expires when the ACQ bit becomes set in the PLL bandwidth control
register (PBWC).
•
Lock time, tLock, is the time the PLL takes to reduce the error between the actual output frequency
and the desired output frequency to less than the lock mode entry tolerance, ∆Lock. Lock time is
based on an initial frequency error, (fDES – fORIG)/fDES, of not more than 100 percent. In automatic
bandwidth control mode, lock time expires when the LOCK bit becomes set in the PLL bandwidth
control register (PBWC). See 4.3.2.3 Manual and Automatic PLL Bandwidth Modes.
Obviously, the acquisition and lock times can vary according to how large the frequency error is and may
be shorter or longer in many cases.
4.8.2 Parametric Influences on Reaction Time
Acquisition and lock times are designed to be as short as possible while still providing the highest possible
stability. These reaction times are not constant, however. Many factors directly and indirectly affect the
acquisition time.
The most critical parameter which affects the reaction times of the PLL is the reference frequency, fRDV
.
This frequency is the input to the phase detector and controls how often the PLL makes corrections. For
stability, the corrections must be small compared to the desired frequency, so several corrections are
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
70
Freescale Semiconductor
Acquisition/Lock Time Specifications
required to reduce the frequency error. Therefore, the slower the reference the longer it takes to make
these corrections. This parameter is also under user control via the choice of crystal frequency, fXCLK
.
Another critical parameter is the external filter capacitor. The PLL modifies the voltage on the VCO by
adding or subtracting charge from this capacitor. Therefore, the rate at which the voltage changes for a
given frequency error (thus change in charge) is proportional to the capacitor size. The size of the
capacitor also is related to the stability of the PLL. If the capacitor is too small, the PLL cannot make small
enough adjustments to the voltage and the system cannot lock. If the capacitor is too large, the PLL may
not be able to adjust the voltage in a reasonable time. See 4.8.3 Choosing a Filter Capacitor.
Also important is the operating voltage potential applied to VDDA. The power supply potential alters the
characteristics of the PLL. A fixed value is best. Variable supplies, such as batteries, are acceptable if
they vary within a known range at very slow speeds. Noise on the power supply is not acceptable,
because it causes small frequency errors which continually change the acquisition time of the PLL.
Temperature and processing also can affect acquisition time because the electrical characteristics of the
PLL change. The part operates as specified as long as these influences stay within the specified limits.
External factors, however, can cause drastic changes in the operation of the PLL. These factors include
noise injected into the PLL through the filter capacitor filter, capacitor leakage, stray impedances on the
circuit board, and even humidity or circuit board contamination.
4.8.3 Choosing a Filter Capacitor
As described in 4.8.2 Parametric Influences on Reaction Time, the external filter capacitor, CF, is critical
to the stability and reaction time of the PLL. The PLL is also dependent on reference frequency and supply
voltage. The value of the capacitor must, therefore, be chosen with supply potential and reference
frequency in mind. For proper operation, the external filter capacitor must be chosen according to this
equation:
V
⎛
⎜
⎝
⎞
⎟
⎠
DDA
--------------
C
= C
FACT
F
f
RDV
For acceptable values of CFACT, see 4.8 Acquisition/Lock Time Specifications. For the value of VDDA
,
choose the voltage potential at which the MCU is operating. If the power supply is variable, choose a value
near the middle of the range of possible supply values.
This equation does not always yield a commonly available capacitor size, so round to the nearest
available size. If the value is between two different sizes, choose the higher value for better stability.
Choosing the lower size may seem attractive for acquisition time improvement, but the PLL can become
unstable. Also, always choose a capacitor with a tight tolerance ( 20 percent or better) and low
dissipation.
4.8.4 Reaction Time Calculation
The actual acquisition and lock times can be calculated using the equations here. These equations yield
nominal values under these conditions:
•
•
•
•
Correct selection of filter capacitor, CF, see 4.8.3 Choosing a Filter Capacitor
Room temperature operation
Negligible external leakage on CGMXFC
Negligible noise
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
71
Clock Generator Module (CGM)
The K factor in the equations is derived from internal PLL parameters. KACQ is the K factor when the PLL
is configured in acquisition mode, and KTRK is the K factor when the PLL is configured in tracking mode.
See 4.3.2.2 Acquisition and Tracking Modes.
V
⎛
⎜
⎝
⎞
8
DDA
⎛
⎞
⎠
-------------- --------------
t
=
⎟
ACQ
⎝
f
K
⎠
RDV
ACQ
V
⎛
⎜
⎝
⎞
4
DDA
⎛
⎞
⎠
-------------- -------------
t
=
⎟
AL
⎝
f
K
⎠
RDV
TRK
t
= t
+ t
ACQ AL
Lock
NOTE
The inverse proportionality between the lock time and the reference
frequency.
In automatic bandwidth control mode, the acquisition and lock times are quantized into units based on the
reference frequency. See 4.3.2.3 Manual and Automatic PLL Bandwidth Modes A certain number of clock
cycles, nACQ, is required to ascertain that the PLL is within the tracking mode entry tolerance, ∆TRK
,
before exiting acquisition mode. A certain number of clock cycles, nTRK, is required to ascertain that the
PLL is within the lock mode entry tolerance, ∆Lock. Therefore, the acquisition time, tACQ, is an integer
multiple of nACQ RDV, and the acquisition to lock time, tAL, is an integer multiple of nTRK/fRDV. Also, since
/f
the average frequency over the entire measurement period must be within the specified tolerance, the
total time usually is longer than tLock as calculated in the previous example.
In manual mode, it is usually necessary to wait considerably longer than tLock before selecting the PLL
clock (see 4.3.3 Base Clock Selector Circuit) because the factors described in 4.8.2 Parametric
Influences on Reaction Time may slow the lock time considerably.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
72
Freescale Semiconductor
Chapter 5
Configuration Register (CONFIG)
5.1 Introduction
This section describes the configuration register (CONFIG). This register contains bits that configure
these options:
•
•
•
•
•
•
•
Resets caused by the low-voltage inhibit (LVI) module
Power to the LVI module
Computer operating properly (COP) module
Top-side pulse-width modulator (PWM) polarity
Bottom-side PWM polarity
Edge-aligned versus center-aligned PWMs
Six independent PWMs versus three complementary PWM pairs
5.2 Functional Description
The configuration register (CONFIG) is used in the initialization of various options. The configuration
register can be written once after each reset. All of the configuration register bits are cleared during reset.
Since the various options affect the operation of the microcontroller unit (MCU), it is recommended that
this register be written immediately after reset. The configuration register is located at $001F and may be
read at anytime.
NOTE
On a FLASH device, the options are one-time writeable by the user after
each reset. The registers are not in the FLASH memory but are special
registers containing one-time writeable latches after each reset. Upon a
reset, the configuration register defaults to predetermined settings as
shown in Figure 5-1.
If the LVI module and the LVI reset signal are enabled, a reset occurs when
VDD falls to a voltage, VLVRx, and remains at or below that level for at least
nine consecutive central processor unit (CPU) cycles. Once an LVI reset
occurs, the MCU remains in reset until VDD rises to a voltage, VLVRX
.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
73
Configuration Register (CONFIG)
5.3 Configuration Register
Address:
$001F
Bit 7
6
5
4
INDEP
0
3
LVIRST
1
2
LVIPWR
1
1
STOPE
0
Bit 0
COPD
0
Read:
Write:
Reset:
EDGE
0
BOTNEG TOPNEG
0
0
Figure 5-1. Configuration Register (CONFIG)
EDGE — Edge-Align Enable Bit
EDGE determines if the motor control PWM will operate in edge-aligned mode or center-aligned mode.
See Chapter 12 Pulse-Width Modulator for Motor Control (PWMMC).
1 = Edge-aligned mode enabled
0 = Center-aligned mode enabled
BOTNEG — Bottom-Side PWM Polarity Bit
BOTNEG determines if the bottom-side PWMs will have positive or negative polarity. See Chapter 12
Pulse-Width Modulator for Motor Control (PWMMC).
1 = Negative polarity
0 = Positive polarity
TOPNEG — Top-Side PWM Polarity Bit
TOPNEG determines if the top-side PWMs will have positive or negative polarity. See Chapter 12
Pulse-Width Modulator for Motor Control (PWMMC).
1 = Negative polarity
0 = Positive polarity
INDEP — Independent Mode Enable Bit
INDEP determines if the motor control PWMs will be six independent PWMs or three complementary
PWM pairs. See Chapter 12 Pulse-Width Modulator for Motor Control (PWMMC).
1 = Six independent PWMs
0 = Three complementary PWM pairs
LVIRST — LVI Reset Enable Bit
LVIRST enables the reset signal from the LVI module. See
Chapter 9 Low-Voltage Inhibit (LVI).
1 = LVI module resets enabled
0 = LVI module resets disabled
LVIPWR — LVI Power Enable Bit
LVIPWR enables the LVI module. Chapter 9 Low-Voltage Inhibit (LVI)
1 = LVI module power enabled
0 = LVI module power disabled
STOPE — Stop Enable Bit
Writing a 0 or a 1 to bit 1 has no effect on MCU operation. Bit 1 operates the same as the other bits
within this write-once register operate.
1 = STOP mode enabled
0 = STOP mode disabled
COPD — COP Disable Bit
COPD disables the COP module. See Chapter 6 Computer Operating Properly (COP).
1 = COP module disabled
0 = COP module enabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
74
Freescale Semiconductor
Chapter 6
Computer Operating Properly (COP)
6.1 Introduction
This section describes the computer operating properly module, a free-running counter that generates a
reset if allowed to overflow. The computer operating properly (COP) module helps software recover from
runaway code. Prevent a COP reset by periodically clearing the COP counter.
6.2 Functional Description
Figure 6-1 shows the structure of the COP module. A summary of the input/output (I/O) register is shown
in Figure 6-2.
SIM
SIM RESET CIRCUIT
13-BIT SIM COUNTER
CGMXCLK
SIM RESET STATUS REGISTER
INTERNAL RESET SOURCES(1)
RESET VECTOR FETCH
COPCTL WRITE
COP MODULE
6-BIT COP COUNTER
COPD (FROM CONFIG)
RESET
CLEAR
COP COUNTER
COPCTL WRITE
Note 1. See 14.3.2 Active Resets from Internal Sources.
Figure 6-1. COP Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
75
Computer Operating Properly (COP)
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
(COPCTL) Write:
See page 77.
Low byte of reset vector
Clear COP counter
Unaffected by reset
COP Control Register
$FFFF
Reset:
Figure 6-2. COP I/O Register Summary
The COP counter is a free-running, 6-bit counter preceded by the 13-bit system integration module (SIM)
counter. If not cleared by software, the COP counter overflows and generates an asynchronous reset after
218–24 CGMXCLK cycles. With a 4.9152-MHz crystal, the COP timeout period is 53.3 ms. Writing any
value to location $FFFF before overflow occurs clears the COP counter and prevents reset.
A COP reset pulls the RST pin low for 32 CGMXCLK cycles and sets the COP bit in the SIM reset status
register (SRSR). See 14.7.2 SIM Reset Status Register.
NOTE
Place COP clearing instructions in the main program and not in an interrupt
subroutine. Such an interrupt subroutine could keep the COP from
generating a reset even while the main program is not working properly.
6.3 I/O Signals
This section describes the signals shown in Figure 6-1.
6.3.1 CGMXCLK
CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency is equal to the crystal frequency.
6.3.2 COPCTL Write
Writing any value to the COP control register (COPCTL) (see 6.4 COP Control Register) clears the COP
counter and clears bits 12–4 of the SIM counter. Reading the COP control register returns the reset
vector.
6.3.3 Power-On Reset
The power-on reset (POR) circuit in the SIM clears the SIM counter 4096 CGMXCLK cycles after
power-up.
6.3.4 Internal Reset
An internal reset clears the SIM counter and the COP counter.
6.3.5 Reset Vector Fetch
A reset vector fetch occurs when the vector address appears on the data bus. A reset vector fetch clears
the SIM counter.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
76
Freescale Semiconductor
COP Control Register
6.3.6 COPD (COP Disable)
The COPD signal reflects the state of the COP disable bit (COPD) in the configuration register (CONFIG).
See Chapter 5 Configuration Register (CONFIG).
6.4 COP Control Register
The COP control register is located at address $FFFF and overlaps the reset vector. Writing any value to
$FFFF clears the COP counter and starts a new timeout period. Reading location $FFFF returns the low
byte of the reset vector.
Address:
$FFFF
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Low byte of reset vector
Clear COP counter
Unaffected by reset
Figure 6-3. COP Control Register (COPCTL)
6.5 Interrupts
The COP does not generate CPU interrupt requests.
6.6 Monitor Mode
The COP is disabled in monitor mode when VHI is present on the IRQ pin or on the RST pin.
6.7 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
The COP continues to operate during wait mode.
6.8 Stop Mode
Stop mode turns off the CGMXCLK input to the COP and clears the COP prescaler. Service the COP
immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering
or exiting stop mode.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
77
Computer Operating Properly (COP)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
78
Freescale Semiconductor
Chapter 7
Central Processor Unit (CPU)
7.1 Introduction
The M68HC08 CPU (central processor unit) is an enhanced and fully object-code-compatible version of
the M68HC05 CPU. The CPU08 Reference Manual (document order number CPU08RM/AD) contains a
description of the CPU instruction set, addressing modes, and architecture.
7.2 Features
Features of the CPU include:
•
•
•
•
•
•
•
•
•
•
Object code fully upward-compatible with M68HC05 Family
16-bit stack pointer with stack manipulation instructions
16-bit index register with x-register manipulation instructions
8-MHz CPU internal bus frequency
64-Kbyte program/data memory space
16 addressing modes
Memory-to-memory data moves without using accumulator
Fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions
Enhanced binary-coded decimal (BCD) data handling
Modular architecture with expandable internal bus definition for extension of addressing range
beyond 64 Kbytes
•
Low-power stop and wait modes
7.3 CPU Registers
Figure 7-1 shows the five CPU registers. CPU registers are not part of the memory map.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
79
Central Processor Unit (CPU)
7
0
0
0
0
ACCUMULATOR (A)
15
15
15
H
X
INDEX REGISTER (H:X)
STACK POINTER (SP)
PROGRAM COUNTER (PC)
CONDITION CODE REGISTER (CCR)
7
0
V
1
1
H
I
N
Z
C
CARRY/BORROW FLAG
ZERO FLAG
NEGATIVE FLAG
INTERRUPT MASK
HALF-CARRY FLAG
TWO’S COMPLEMENT OVERFLOW FLAG
Figure 7-1. CPU Registers
7.3.1 Accumulator
The accumulator is a general-purpose 8-bit register. The CPU uses the accumulator to hold operands and
the results of arithmetic/logic operations.
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Unaffected by reset
Figure 7-2. Accumulator (A)
7.3.2 Index Register
The 16-bit index register allows indexed addressing of a 64-Kbyte memory space. H is the upper byte of
the index register, and X is the lower byte. H:X is the concatenated 16-bit index register.
In the indexed addressing modes, the CPU uses the contents of the index register to determine the
conditional address of the operand.
The index register can serve also as a temporary data storage location.
Bit
15 14 13 12 11 10
Bit
0
9
0
8
0
7
6
5
4
3
2
1
Read:
Write:
Reset:
0
0
0
0
0
0
X
X
X
X
X
X
X
X
X = Indeterminate
Figure 7-3. Index Register (H:X)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
80
Freescale Semiconductor
CPU Registers
7.3.3 Stack Pointer
The stack pointer is a 16-bit register that contains the address of the next location on the stack. During a
reset, the stack pointer is preset to $00FF. The reset stack pointer (RSP) instruction sets the least
significant byte to $FF and does not affect the most significant byte. The stack pointer decrements as data
is pushed onto the stack and increments as data is pulled from the stack.
In the stack pointer 8-bit offset and 16-bit offset addressing modes, the stack pointer can function as an
index register to access data on the stack. The CPU uses the contents of the stack pointer to determine
the conditional address of the operand.
Bit
15 14 13 12 11 10
Bit
0
9
8
7
6
5
4
3
2
1
Read:
Write:
Reset:
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Figure 7-4. Stack Pointer (SP)
NOTE
The location of the stack is arbitrary and may be relocated anywhere in
random-access memory (RAM). Moving the SP out of page 0 ($0000 to
$00FF) frees direct address (page 0) space. For correct operation, the
stack pointer must point only to RAM locations.
7.3.4 Program Counter
The program counter is a 16-bit register that contains the address of the next instruction or operand to be
fetched.
Normally, the program counter automatically increments to the next sequential memory location every
time an instruction or operand is fetched. Jump, branch, and interrupt operations load the program
counter with an address other than that of the next sequential location.
During reset, the program counter is loaded with the reset vector address located at $FFFE and $FFFF.
The vector address is the address of the first instruction to be executed after exiting the reset state.
Bit
15 14 13 12 11 10
Bit
0
9
8
7
6
5
4
3
2
1
Read:
Write:
Reset:
Loaded with vector from $FFFE and $FFFF
Figure 7-5. Program Counter (PC)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
81
Central Processor Unit (CPU)
7.3.5 Condition Code Register
The 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the
instruction just executed. Bits 6 and 5 are set permanently to 1. The following paragraphs describe the
functions of the condition code register.
Bit 7
6
1
1
5
1
1
4
H
X
3
2
N
X
1
Z
X
Bit 0
Read:
Write:
Reset:
V
I
C
X
1
X
X = Indeterminate
Figure 7-6. Condition Code Register (CCR)
V — Overflow Flag
The CPU sets the overflow flag when a two's complement overflow occurs. The signed branch
instructions BGT, BGE, BLE, and BLT use the overflow flag.
1 = Overflow
0 = No overflow
H — Half-Carry Flag
The CPU sets the half-carry flag when a carry occurs between accumulator bits 3 and 4 during an
add-without-carry (ADD) or add-with-carry (ADC) operation. The half-carry flag is required for
binary-coded decimal (BCD) arithmetic operations. The DAA instruction uses the states of the H and
C flags to determine the appropriate correction factor.
1 = Carry between bits 3 and 4
0 = No carry between bits 3 and 4
I — Interrupt Mask
When the interrupt mask is set, all maskable CPU interrupts are disabled. CPU interrupts are enabled
when the interrupt mask is cleared. When a CPU interrupt occurs, the interrupt mask is set
automatically after the CPU registers are saved on the stack, but before the interrupt vector is fetched.
1 = Interrupts disabled
0 = Interrupts enabled
NOTE
To maintain M6805 Family compatibility, the upper byte of the index
register (H) is not stacked automatically. If the interrupt service routine
modifies H, then the user must stack and unstack H using the PSHH and
PULH instructions.
After the I bit is cleared, the highest-priority interrupt request is serviced first.
A return-from-interrupt (RTI) instruction pulls the CPU registers from the stack and restores the
interrupt mask from the stack. After any reset, the interrupt mask is set and can be cleared only by the
clear interrupt mask software instruction (CLI).
N — Negative Flag
The CPU sets the negative flag when an arithmetic operation, logic operation, or data manipulation
produces a negative result, setting bit 7 of the result.
1 = Negative result
0 = Non-negative result
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
82
Freescale Semiconductor
Arithmetic/Logic Unit (ALU)
Z — Zero Flag
The CPU sets the zero flag when an arithmetic operation, logic operation, or data manipulation
produces a result of $00.
1 = Zero result
0 = Non-zero result
C — Carry/Borrow Flag
The CPU sets the carry/borrow flag when an addition operation produces a carry out of bit 7 of the
accumulator or when a subtraction operation requires a borrow. Some instructions — such as bit test
and branch, shift, and rotate — also clear or set the carry/borrow flag.
1 = Carry out of bit 7
0 = No carry out of bit 7
7.4 Arithmetic/Logic Unit (ALU)
The ALU performs the arithmetic and logic operations defined by the instruction set.
Refer to the CPU08 Reference Manual (document order number CPU08RM/AD) for a description of the
instructions and addressing modes and more detail about the architecture of the CPU.
7.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
7.5.1 Wait Mode
The WAIT instruction:
•
Clears the interrupt mask (I bit) in the condition code register, enabling interrupts. After exit from
wait mode by interrupt, the I bit remains clear. After exit by reset, the I bit is set.
Disables the CPU clock
•
7.5.2 Stop Mode
The STOP instruction:
•
Clears the interrupt mask (I bit) in the condition code register, enabling external interrupts. After
exit from stop mode by external interrupt, the I bit remains clear. After exit by reset, the I bit is set.
•
Disables the CPU clock
After exiting stop mode, the CPU clock begins running after the oscillator stabilization delay.
7.6 CPU During Break Interrupts
If a break module is present on the MCU, the CPU starts a break interrupt by:
•
•
Loading the instruction register with the SWI instruction
Loading the program counter with $FFFC:$FFFD or with $FEFC:$FEFD in monitor mode
The break interrupt begins after completion of the CPU instruction in progress. If the break address
register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately.
A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and returns the MCU
to normal operation if the break interrupt has been deasserted.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
83
Central Processor Unit (CPU)
7.7 Instruction Set Summary
Table 7-1 provides a summary of the M68HC08 instruction set.
Table 7-1. Instruction Set Summary (Sheet 1 of 6)
Effect
on CCR
Source
Form
Operation
Description
V H I N Z C
ADC #opr
IMM
DIR
EXT
IX2
A9 ii
B9 dd
C9 hh ll
D9 ee ff
E9 ff
2
3
4
4
3
2
4
5
ADC opr
ADC opr
ADC opr,X
ADC opr,X
ADC ,X
Add with Carry
A ← (A) + (M) + (C)
ꢀ
ꢀ
ꢀ
ꢀ
–
–
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
IX1
IX
SP1
SP2
F9
ADC opr,SP
ADC opr,SP
9EE9 ff
9ED9 ee ff
ADD #opr
ADD opr
ADD opr
ADD opr,X
ADD opr,X
ADD ,X
ADD opr,SP
ADD opr,SP
IMM
DIR
EXT
IX2
AB ii
BB dd
CB hh ll
DB ee ff
EB ff
FB
9EEB ff
9EDB ee ff
2
3
4
4
3
2
4
5
Add without Carry
A ← (A) + (M)
IX1
IX
SP1
SP2
AIS #opr
AIX #opr
Add Immediate Value (Signed) to SP
Add Immediate Value (Signed) to H:X
–
–
–
–
–
–
–
–
–
–
– IMM
– IMM
A7 ii
AF ii
2
2
SP ← (SP) + (16 « M)
H:X ← (H:X) + (16 « M)
AND #opr
AND opr
IMM
DIR
EXT
A4 ii
B4 dd
C4 hh ll
D4 ee ff
E4 ff
2
3
4
4
3
2
4
5
AND opr
AND opr,X
AND opr,X
AND ,X
AND opr,SP
AND opr,SP
IX2
Logical AND
A ← (A) & (M)
0
–
–
–
–
ꢀ
ꢀ
ꢀ
ꢀ
–
IX1
IX
F4
SP1
SP2
9EE4 ff
9ED4 ee ff
ASL opr
ASLA
DIR
INH
38 dd
48
4
1
1
4
3
5
ASLX
Arithmetic Shift Left
(Same as LSL)
INH
58
C
0
ꢀ
ꢀ
ASL opr,X
ASL ,X
IX1
68 ff
78
b7
b7
b0
b0
IX
ASL opr,SP
SP1
9E68 ff
ASR opr
ASRA
ASRX
ASR opr,X
ASR opr,X
ASR opr,SP
DIR
INH
37 dd
47
4
1
1
4
3
5
INH
57
C
Arithmetic Shift Right
ꢀ
–
–
–
–
ꢀ
ꢀ
ꢀ
IX1
67 ff
77
IX
SP1
9E67 ff
BCC rel
Branch if Carry Bit Clear
PC ← (PC) + 2 + rel ? (C) = 0
–
–
–
– REL
24 rr
3
DIR (b0) 11 dd
DIR (b1) 13 dd
DIR (b2) 15 dd
DIR (b3) 17 dd
DIR (b4) 19 dd
DIR (b5) 1B dd
DIR (b6) 1D dd
DIR (b7) 1F dd
4
4
4
4
4
4
4
4
BCLR n, opr
Clear Bit n in M
Mn ← 0
–
–
–
–
–
–
BCS rel
BEQ rel
Branch if Carry Bit Set (Same as BLO)
Branch if Equal
PC ← (PC) + 2 + rel ? (C) = 1
PC ← (PC) + 2 + rel ? (Z) = 1
–
–
–
–
–
–
–
–
–
–
– REL
– REL
25 rr
27 rr
3
3
Branch if Greater Than or Equal To
(Signed Operands)
BGE opr
BGT opr
–
–
–
–
–
–
–
–
–
–
– REL
– REL
90 rr
92 rr
3
PC ← (PC) + 2 + rel ? (N ⊕ V) = 0
Branch if Greater Than (Signed
Operands)
3
3
PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) = 0
BHCC rel
BHCS rel
BHI rel
Branch if Half Carry Bit Clear
Branch if Half Carry Bit Set
Branch if Higher
PC ← (PC) + 2 + rel ? (H) = 0
PC ← (PC) + 2 + rel ? (H) = 1
PC ← (PC) + 2 + rel ? (C) | (Z) = 0
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
– REL
– REL
– REL
28 rr
29 rr
22 rr
3
3
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
84
Freescale Semiconductor
Instruction Set Summary
Table 7-1. Instruction Set Summary (Sheet 2 of 6)
Effect
on CCR
Source
Form
Operation
Description
V H I N Z C
Branch if Higher or Same
(Same as BCC)
BHS rel
PC ← (PC) + 2 + rel ? (C) = 0
–
–
–
–
–
– REL
24 rr
3
BIH rel
BIL rel
Branch if IRQ Pin High
Branch if IRQ Pin Low
PC ← (PC) + 2 + rel ? IRQ = 1
PC ← (PC) + 2 + rel ? IRQ = 0
–
–
–
–
–
–
–
–
–
–
– REL
– REL
2F rr
2E rr
3
3
BIT #opr
BIT opr
IMM
DIR
EXT
A5 ii
B5 dd
C5 hh ll
D5 ee ff
E5 ff
2
3
4
4
3
2
4
5
BIT opr
BIT opr,X
BIT opr,X
BIT ,X
BIT opr,SP
BIT opr,SP
IX2
Bit Test
(A) & (M)
0
–
–
ꢀ
ꢀ
–
IX1
IX
F5
SP1
SP2
9EE5 ff
9ED5 ee ff
Branch if Less Than or Equal To
(Signed Operands)
BLE opr
–
–
–
–
–
– REL
93 rr
3
PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) = 1
BLO rel
BLS rel
BLT opr
BMC rel
BMI rel
BMS rel
BNE rel
BPL rel
BRA rel
Branch if Lower (Same as BCS)
Branch if Lower or Same
Branch if Less Than (Signed Operands)
Branch if Interrupt Mask Clear
Branch if Minus
PC ← (PC) + 2 + rel ? (C) = 1
PC ← (PC) + 2 + rel ? (C) | (Z) = 1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
– REL
– REL
– REL
– REL
– REL
– REL
– REL
– REL
– REL
25 rr
23 rr
91 rr
2C rr
2B rr
2D rr
26 rr
2A rr
20 rr
3
3
3
3
3
3
3
3
3
PC ← (PC) + 2 + rel ? (N ⊕ V) =1
PC ← (PC) + 2 + rel ? (I) = 0
PC ← (PC) + 2 + rel ? (N) = 1
PC ← (PC) + 2 + rel ? (I) = 1
PC ← (PC) + 2 + rel ? (Z) = 0
PC ← (PC) + 2 + rel ? (N) = 0
PC ← (PC) + 2 + rel
Branch if Interrupt Mask Set
Branch if Not Equal
Branch if Plus
Branch Always
DIR (b0) 01 dd rr
DIR (b1) 03 dd rr
DIR (b2) 05 dd rr
DIR (b3) 07 dd rr
DIR (b4) 09 dd rr
DIR (b5) 0B dd rr
DIR (b6) 0D dd rr
DIR (b7) 0F dd rr
5
5
5
5
5
5
5
5
BRCLR n,opr,rel Branch if Bit n in M Clear
PC ← (PC) + 3 + rel ? (Mn) = 0
PC ← (PC) + 2
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
ꢀ
BRN rel
Branch Never
– REL
21 rr
3
DIR (b0) 00 dd rr
DIR (b1) 02 dd rr
DIR (b2) 04 dd rr
DIR (b3) 06 dd rr
DIR (b4) 08 dd rr
DIR (b5) 0A dd rr
DIR (b6) 0C dd rr
DIR (b7) 0E dd rr
5
5
5
5
5
5
5
5
BRSET n,opr,rel Branch if Bit n in M Set
PC ← (PC) + 3 + rel ? (Mn) = 1
ꢀ
DIR (b0) 10 dd
DIR (b1) 12 dd
DIR (b2) 14 dd
DIR (b3) 16 dd
DIR (b4) 18 dd
DIR (b5) 1A dd
DIR (b6) 1C dd
DIR (b7) 1E dd
4
4
4
4
4
4
4
4
BSET n,opr
BSR rel
Set Bit n in M
Mn ← 1
–
–
–
–
–
–
PC ← (PC) + 2; push (PCL)
SP ← (SP) – 1; push (PCH)
SP ← (SP) – 1
Branch to Subroutine
–
–
–
–
–
–
–
–
–
–
– REL
AD rr
4
PC ← (PC) + rel
CBEQ opr,rel
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 3 + rel ? (X) – (M) = $00
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 2 + rel ? (A) – (M) = $00
PC ← (PC) + 4 + rel ? (A) – (M) = $00
DIR
31 dd rr
41 ii rr
51 ii rr
61 ff rr
71 rr
5
4
4
5
4
6
CBEQA #opr,rel
CBEQX #opr,rel
CBEQ opr,X+,rel
CBEQ X+,rel
IMM
IMM
Compare and Branch if Equal
–
IX1+
IX+
CBEQ opr,SP,rel
SP1
9E61 ff rr
CLC
CLI
Clear Carry Bit
C ← 0
I ← 0
–
–
–
–
–
0
–
–
–
–
0 INH
– INH
98
9A
1
2
Clear Interrupt Mask
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
85
Central Processor Unit (CPU)
Table 7-1. Instruction Set Summary (Sheet 3 of 6)
Effect
on CCR
Source
Form
Operation
Description
V H I N Z C
CLR opr
CLRA
M ← $00
A ← $00
X ← $00
H ← $00
M ← $00
M ← $00
M ← $00
DIR
INH
INH
3F dd
4F
3
1
1
1
3
2
4
CLRX
5F
CLRH
Clear
0
–
–
–
–
0
1
– INH
IX1
8C
CLR opr,X
CLR ,X
6F ff
7F
IX
SP1
CLR opr,SP
9E6F ff
CMP #opr
CMP opr
CMP opr
CMP opr,X
CMP opr,X
CMP ,X
CMP opr,SP
CMP opr,SP
IMM
DIR
EXT
A1 ii
B1 dd
C1 hh ll
D1 ee ff
E1 ff
2
3
4
4
3
2
4
5
IX2
Compare A with M
(A) – (M)
ꢀ
ꢀ
ꢀ
ꢀ
IX1
IX
F1
SP1
SP2
9EE1 ff
9ED1 ee ff
COM opr
COMA
M ← (M) = $FF – (M)
A ← (A) = $FF – (M)
X ← (X) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
DIR
INH
33 dd
43
4
1
1
4
3
5
COMX
INH
53
Complement (One’s Complement)
Compare H:X with M
0
–
–
–
–
ꢀ
ꢀ
ꢀ
ꢀ
1
COM opr,X
COM ,X
COM opr,SP
IX1
63 ff
73
9E63 ff
IX
SP1
CPHX #opr
CPHX opr
IMM
ꢀ
65 ii ii+1
75 dd
3
4
(H:X) – (M:M + 1)
ꢀ
DIR
CPX #opr
CPX opr
IMM
DIR
EXT
A3 ii
B3 dd
C3 hh ll
D3 ee ff
E3 ff
2
3
4
4
3
2
4
5
CPX opr
CPX ,X
IX2
Compare X with M
(X) – (M)
(A)10
ꢀ
–
–
ꢀ
ꢀ
ꢀ
CPX opr,X
CPX opr,X
CPX opr,SP
CPX opr,SP
IX1
IX
F3
SP1
SP2
9EE3 ff
9ED3 ee ff
DAA
Decimal Adjust A
U
–
–
–
–
–
ꢀ
ꢀ
ꢀ INH
72
2
A ← (A) – 1 or M ← (M) – 1 or X ← (X) – 1
PC ← (PC) + 3 + rel ? (result) ≠ 0
PC ← (PC) + 2 + rel ? (result) ≠ 0
PC ← (PC) + 2 + rel ? (result) ≠ 0
PC ← (PC) + 3 + rel ? (result) ≠ 0
PC ← (PC) + 2 + rel ? (result) ≠ 0
PC ← (PC) + 4 + rel ? (result) ≠ 0
5
3
3
5
4
6
DBNZ opr,rel
DBNZA rel
DIR
INH
3B dd rr
4B rr
DBNZX rel
Decrement and Branch if Not Zero
–
–
– INH
IX1
5B rr
DBNZ opr,X,rel
DBNZ X,rel
6B ff rr
7B rr
IX
SP1
DBNZ opr,SP,rel
9E6B ff rr
DEC opr
DECA
M ← (M) – 1
A ← (A) – 1
X ← (X) – 1
M ← (M) – 1
M ← (M) – 1
M ← (M) – 1
DIR
INH
3A dd
4A
4
1
1
4
3
5
DECX
INH
5A
Decrement
Divide
ꢀ
–
–
–
–
ꢀ
ꢀ
ꢀ
–
DEC opr,X
DEC ,X
DEC opr,SP
IX1
6A ff
7A
9E6A ff
IX
SP1
A ← (H:A)/(X)
DIV
–
–
ꢀ INH
52
7
H ← Remainder
EOR #opr
EOR opr
IMM
DIR
EXT
A8 ii
B8 dd
C8 hh ll
D8 ee ff
E8 ff
2
3
4
4
3
2
4
5
EOR opr
EOR opr,X
EOR opr,X
EOR ,X
EOR opr,SP
EOR opr,SP
IX2
Exclusive OR M with A
0
–
–
–
–
ꢀ
ꢀ
ꢀ
ꢀ
–
A ← (A ⊕ M)
IX1
IX
F8
SP1
SP2
9EE8 ff
9ED8 ee ff
INC opr
INCA
M ← (M) + 1
A ← (A) + 1
X ← (X) + 1
M ← (M) + 1
M ← (M) + 1
M ← (M) + 1
DIR
INH
3C dd
4C
4
1
1
4
3
5
INCX
INH
5C
Increment
ꢀ
–
INC opr,X
INC ,X
IX1
6C ff
7C
IX
INC opr,SP
SP1
9E6C ff
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
86
Freescale Semiconductor
Instruction Set Summary
Table 7-1. Instruction Set Summary (Sheet 4 of 6)
Effect
on CCR
Source
Form
Operation
Description
V H I N Z C
JMP opr
DIR
BC dd
CC hh ll
DC ee ff
EC ff
2
3
4
3
2
JMP opr
JMP opr,X
JMP opr,X
JMP ,X
EXT
Jump
PC ← Jump Address
–
–
–
–
–
–
–
–
–
–
– IX2
IX1
IX
FC
JSR opr
JSR opr
JSR opr,X
JSR opr,X
JSR ,X
DIR
EXT
– IX2
IX1
BD dd
CD hh ll
DD ee ff
ED ff
4
5
6
5
4
PC ← (PC) + n (n = 1, 2, or 3)
Push (PCL); SP ← (SP) – 1
Push (PCH); SP ← (SP) – 1
PC ← Unconditional Address
Jump to Subroutine
IX
FD
LDA #opr
LDA opr
IMM
DIR
EXT
A6 ii
B6 dd
C6 hh ll
D6 ee ff
E6 ff
2
3
4
4
3
2
4
5
LDA opr
LDA opr,X
LDA opr,X
LDA ,X
LDA opr,SP
LDA opr,SP
IX2
Load A from M
Load H:X from M
Load X from M
A ← (M)
H:X ← (M:M + 1)
X ← (M)
0
0
0
–
–
–
–
–
–
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
–
IX1
IX
F6
SP1
SP2
9EE6 ff
9ED6 ee ff
LDHX #opr
LDHX opr
IMM
–
45 ii jj
55 dd
3
4
DIR
LDX #opr
LDX opr
LDX opr
LDX opr,X
LDX opr,X
LDX ,X
LDX opr,SP
LDX opr,SP
IMM
DIR
EXT
AE ii
BE dd
CE hh ll
DE ee ff
EE ff
FE
9EEE ff
9EDE ee ff
2
3
4
4
3
2
4
5
IX2
–
IX1
IX
SP1
SP2
LSL opr
LSLA
DIR
INH
38 dd
48
4
1
1
4
3
5
LSLX
Logical Shift Left
(Same as ASL)
INH
58
C
0
ꢀ
ꢀ
–
–
–
–
ꢀ
ꢀ
ꢀ
ꢀ
LSL opr,X
LSL ,X
LSL opr,SP
IX1
68 ff
78
9E68 ff
b7
b7
b0
b0
IX
SP1
LSR opr
LSRA
DIR
INH
34 dd
44
4
1
1
4
3
5
LSRX
INH
54
0
C
Logical Shift Right
0
ꢀ
LSR opr,X
LSR ,X
IX1
64 ff
74
IX
LSR opr,SP
SP1
9E64 ff
MOV opr,opr
MOV opr,X+
MOV #opr,opr
MOV X+,opr
DD
4E dd dd
5E dd
5
4
4
4
(M)Destination ← (M)Source
DIX+
Move
0
–
–
0
–
–
ꢀ
ꢀ
–
IMD
IX+D
6E ii dd
7E dd
H:X ← (H:X) + 1 (IX+D, DIX+)
X:A ← (X) × (A)
MUL
Unsigned multiply
–
–
0 INH
42
5
NEG opr
NEGA
DIR
INH
30 dd
40
4
1
1
4
3
5
M ← –(M) = $00 – (M)
A ← –(A) = $00 – (A)
X ← –(X) = $00 – (X)
M ← –(M) = $00 – (M)
M ← –(M) = $00 – (M)
NEGX
INH
50
Negate (Two’s Complement)
ꢀ
–
–
ꢀ
ꢀ
ꢀ
NEG opr,X
NEG ,X
NEG opr,SP
IX1
60 ff
70
9E60 ff
IX
SP1
NOP
NSA
No Operation
Nibble Swap A
None
–
–
–
–
–
–
–
–
–
–
– INH
– INH
9D
62
1
3
A ← (A[3:0]:A[7:4])
ORA #opr
ORA opr
IMM
DIR
EXT
AA ii
BA dd
CA hh ll
DA ee ff
EA ff
2
3
4
4
3
2
4
5
ORA opr
ORA opr,X
ORA opr,X
ORA ,X
ORA opr,SP
ORA opr,SP
IX2
Inclusive OR A and M
A ← (A) | (M)
0
–
–
ꢀ
ꢀ
–
IX1
IX
FA
SP1
SP2
9EEA ff
9EDA ee ff
PSHA
PSHH
PSHX
Push A onto Stack
Push H onto Stack
Push X onto Stack
Push (A); SP ← (SP) – 1
Push (H); SP ← (SP) – 1
Push (X); SP ← (SP) – 1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
– INH
– INH
– INH
87
8B
89
2
2
2
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
87
Central Processor Unit (CPU)
Table 7-1. Instruction Set Summary (Sheet 5 of 6)
Effect
on CCR
Source
Form
Operation
Description
V H I N Z C
PULA
PULH
PULX
Pull A from Stack
Pull H from Stack
Pull X from Stack
SP ← (SP + 1); Pull (A)
SP ← (SP + 1); Pull (H)
SP ← (SP + 1); Pull (X)
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
– INH
– INH
– INH
86
8A
88
2
2
2
ROL opr
ROLA
DIR
INH
39 dd
49
4
1
1
4
3
5
ROLX
INH
59
C
Rotate Left through Carry
Rotate Right through Carry
ꢀ
ꢀ
–
–
–
–
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ROL opr,X
ROL ,X
ROL opr,SP
IX1
69 ff
79
9E69 ff
b7
b0
IX
SP1
ROR opr
RORA
DIR
INH
36 dd
46
4
1
1
4
3
5
RORX
INH
56
C
ꢀ
ROR opr,X
ROR ,X
IX1
66 ff
76
b7
b0
IX
ROR opr,SP
SP1
9E66 ff
RSP
Reset Stack Pointer
Return from Interrupt
SP ← $FF
–
–
–
–
–
– INH
9C
1
SP ← (SP) + 1; Pull (CCR)
SP ← (SP) + 1; Pull (A)
SP ← (SP) + 1; Pull (X)
SP ← (SP) + 1; Pull (PCH)
SP ← (SP) + 1; Pull (PCL)
RTI
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ INH
80
7
SP ← SP + 1; Pull (PCH)
SP ← SP + 1; Pull (PCL)
RTS
Return from Subroutine
Subtract with Carry
–
–
–
–
–
–
–
– INH
81
4
SBC #opr
SBC opr
SBC opr
SBC opr,X
SBC opr,X
SBC ,X
SBC opr,SP
SBC opr,SP
IMM
DIR
EXT
A2 ii
B2 dd
C2 hh ll
D2 ee ff
E2 ff
2
3
4
4
3
2
4
5
IX2
A ← (A) – (M) – (C)
ꢀ
ꢀ
ꢀ
ꢀ
IX1
IX
SP1
SP2
F2
9EE2 ff
9ED2 ee ff
SEC
SEI
Set Carry Bit
C ← 1
I ← 1
–
–
–
–
–
1
–
–
–
–
1 INH
– INH
99
9B
1
2
Set Interrupt Mask
STA opr
DIR
EXT
IX2
B7 dd
C7 hh ll
D7 ee ff
E7 ff
3
4
4
3
2
4
5
STA opr
STA opr,X
STA opr,X
STA ,X
STA opr,SP
STA opr,SP
Store A in M
M ← (A)
0
–
–
ꢀ
ꢀ
– IX1
IX
F7
SP1
SP2
9EE7 ff
9ED7 ee ff
STHX opr
Store H:X in M
(M:M + 1) ← (H:X)
0
–
–
–
–
0
ꢀ
ꢀ
– DIR
35 dd
4
Enable Interrupts, Stop Processing,
Refer to MCU Documentation
STOP
I ← 0; Stop Processing
–
–
– INH
8E
1
STX opr
DIR
EXT
IX2
BF dd
CF hh ll
DF ee ff
EF ff
3
4
4
3
2
4
5
STX opr
STX opr,X
STX opr,X
STX ,X
STX opr,SP
STX opr,SP
Store X in M
M ← (X)
0
–
–
–
–
ꢀ
ꢀ
ꢀ
ꢀ
– IX1
IX
FF
SP1
SP2
9EEF ff
9EDF ee ff
SUB #opr
SUB opr
SUB opr
SUB opr,X
SUB opr,X
SUB ,X
SUB opr,SP
SUB opr,SP
IMM
DIR
EXT
A0 ii
B0 dd
C0 hh ll
D0 ee ff
E0 ff
2
3
4
4
3
2
4
5
IX2
Subtract
A ← (A) – (M)
ꢀ
ꢀ
IX1
IX
F0
SP1
SP2
9EE0 ff
9ED0 ee ff
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
88
Freescale Semiconductor
Opcode Map
Table 7-1. Instruction Set Summary (Sheet 6 of 6)
Effect
on CCR
Source
Form
Operation
Description
V H I N Z C
PC ← (PC) + 1; Push (PCL)
SP ← (SP) – 1; Push (PCH)
SP ← (SP) – 1; Push (X)
SP ← (SP) – 1; Push (A)
SWI
Software Interrupt
–
–
1
–
–
– INH
83
9
SP ← (SP) – 1; Push (CCR)
SP ← (SP) – 1; I ← 1
PCH ← Interrupt Vector High Byte
PCL ← Interrupt Vector Low Byte
TAP
TAX
TPA
Transfer A to CCR
Transfer A to X
CCR ← (A)
X ← (A)
A ← (CCR)
ꢀ
–
–
ꢀ
–
–
ꢀ
–
–
ꢀ
–
–
ꢀ
–
–
ꢀ INH
– INH
– INH
84
97
85
2
1
1
Transfer CCR to A
TST opr
TSTA
DIR
INH
3D dd
4D
3
1
1
3
2
4
TSTX
INH
5D
Test for Negative or Zero
(A) – $00 or (X) – $00 or (M) – $00
0
–
–
ꢀ
ꢀ
–
TST opr,X
TST ,X
TST opr,SP
IX1
6D ff
7D
9E6D ff
IX
SP1
TSX
TXA
TXS
Transfer SP to H:X
Transfer X to A
H:X ← (SP) + 1
A ← (X)
(SP) ← (H:X) – 1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
– INH
– INH
– INH
95
9F
94
2
1
2
Transfer H:X to SP
I bit ← 0; Inhibit CPU clocking
WAIT
Enable Interrupts; Wait for Interrupt
–
–
0
–
–
– INH
8F
1
until interrupted
A
Accumulator
n
Any bit
C
Carry/borrow bit
opr Operand (one or two bytes)
PC Program counter
CCR
dd
Condition code register
Direct address of operand
Direct address of operand and relative offset of branch instruction
Direct to direct addressing mode
Direct addressing mode
Direct to indexed with post increment addressing mode
High and low bytes of offset in indexed, 16-bit offset addressing
Extended addressing mode
Offset byte in indexed, 8-bit offset addressing
Half-carry bit
Index register high byte
PCH Program counter high byte
PCL Program counter low byte
REL Relative addressing mode
rel
rr
SP1 Stack pointer, 8-bit offset addressing mode
SP2 Stack pointer 16-bit offset addressing mode
SP Stack pointer
U
V
X
Z
&
|
dd rr
DD
DIR
DIX+
ee ff
EXT
ff
Relative program counter offset byte
Relative program counter offset byte
H
H
Undefined
Overflow bit
Index register low byte
Zero bit
hh ll
I
High and low bytes of operand address in extended addressing
Interrupt mask
Immediate operand byte
Immediate source to direct destination addressing mode
ii
Logical AND
Logical OR
IMD
IMM
INH
IX
Immediate addressing mode
Inherent addressing mode
Indexed, no offset addressing mode
Indexed, no offset, post increment addressing mode
⊕
Logical EXCLUSIVE OR
Contents of
( )
–( ) Negation (two’s complement)
#
IX+
Immediate value
IX+D
IX1
IX1+
IX2
M
Indexed with post increment to direct addressing mode
Indexed, 8-bit offset addressing mode
Indexed, 8-bit offset, post increment addressing mode
Indexed, 16-bit offset addressing mode
Memory location
«
←
?
Sign extend
Loaded with
If
Concatenated with
Set or cleared
Not affected
:
ꢀ
—
N
Negative bit
7.8 Opcode Map
See Table 7-2.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
89
Table 7-2. Opcode Map
Bit Manipulation Branch
Read-Modify-Write
Control
Register/Memory
DIR
DIR
REL
DIR
3
INH
4
INH
IX1
SP1
9E6
IX
7
INH
INH
IMM
A
DIR
B
EXT
C
IX2
SP2
IX1
E
SP1
9EE
IX
F
MSB
0
1
2
5
6
8
9
D
9ED
LSB
5
4
3
4
1
NEGA
INH
1
NEGX
INH
4
5
3
7
3
2
3
4
4
5
3
4
2
0
BRSET0 BSET0
BRA
NEG
NEG
NEG
NEG
RTI
BGE
SUB
SUB
SUB
SUB
SUB
SUB
SUB
SUB
3
DIR
5
2
DIR
4
2
2
2
2
2
2
2
2
REL 2 DIR
1
1
2
IX1 3 SP1 1 IX
5
1
1
INH
2
2
2
2
1
1
REL 2 IMM 2 DIR
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
EXT 3 IX2
4
4
4
4
4
4
4
4
4
4
4
4
SP2 2 IX1
3
3
3
3
3
3
3
3
3
3
3
3
SP1 1 IX
3
BRN
REL 3 DIR
5
4
4
6
4
4
3
BLT
2
3
4
4
5
3
4
2
1
2
BRCLR0 BCLR0
CBEQ CBEQA CBEQX CBEQ
CBEQ
CBEQ
RTS
CMP
CMP
CMP
CMP
CMP
CMP
CMP
CMP
3
DIR
5
2
DIR
4
3
IMM 3 IMM 3 IX1+
4
SP1 2 IX+
INH
REL 2 IMM 2 DIR
EXT 3 IX2
SP2 2 IX1
SP1 1 IX
3
5
7
3
2
DAA
3
BGT
2
SBC
3
SBC
4
SBC
EXT 3 IX2
4
CPX
EXT 3 IX2
4
AND
EXT 3 IX2
4
BIT
EXT 3 IX2
4
LDA
EXT 3 IX2
4
STA
EXT 3 IX2
4
EOR
EXT 3 IX2
4
ADC
EXT 3 IX2
4
ORA
EXT 3 IX2
4
ADD
EXT 3 IX2
3
JMP
EXT 3 IX2
5
JSR
EXT 3 IX2
4
LDX
EXT 3 IX2
4
STX
EXT 3 IX2
4
SBC
5
SBC
SP2 2 IX1
5
CPX
SP2 2 IX1
5
AND
SP2 2 IX1
5
BIT
SP2 2 IX1
5
LDA
SP2 2 IX1
5
STA
SP2 2 IX1
5
EOR
SP2 2 IX1
5
ADC
SP2 2 IX1
3
SBC
4
SBC
SP1 1 IX
4
CPX
SP1 1 IX
4
AND
SP1 1 IX
4
BIT
SP1 1 IX
4
LDA
SP1 1 IX
4
STA
SP1 1 IX
4
EOR
SP1 1 IX
4
ADC
SP1 1 IX
2
SBC
BRSET1 BSET1
BHI
MUL
INH
DIV
INH
NSA
3
DIR
5
2
DIR
4
REL
1
1
1
2
2
3
2
2
2
2
2
INH
1
INH
3
REL 2 IMM 2 DIR
3
BLS
REL 2 DIR
3
BCC
REL 2 DIR
3
BCS
REL 2 DIR
3
BNE
REL 2 DIR
4
1
1
4
COM
IX1
4
LSR
IX1
3
CPHX
IMM
4
ROR
IX1
4
ASR
IX1
4
LSL
IX1
4
ROL
IX1
4
DEC
IX1
5
9
3
BLE
2
CPX
3
CPX
4
CPX
3
CPX
2
CPX
3
BRCLR1 BCLR1
COM
COMA
COMX
COM
COM
SWI
3
DIR
5
2
DIR
4
1
INH
1
INH
3
3
SP1 1 IX
1
1
1
1
1
1
1
1
1
1
INH
REL 2 IMM 2 DIR
4
LSR
1
LSRA
INH
1
LSRX
INH
5
LSR
SP1 1 IX
3
LSR
2
2
2
AND
IMM 2 DIR
3
AND
4
AND
3
AND
2
AND
4
BRSET2 BSET2
TAP
TXS
3
DIR
5
2
DIR
4
1
3
1
INH
INH
2
2
2
2
2
2
2
2
4
3
4
4
1
2
2
BIT
3
BIT
4
BIT
3
BIT
2
BIT
5
BRCLR2 BCLR2
STHX
LDHX
LDHX
CPHX
TPA
TSX
3
DIR
5
2
DIR
4
IMM 2 DIR
2
DIR
3
INH
INH
IMM 2 DIR
4
ROR
1
1
5
2
PULA
INH
2
PSHA
INH
2
PULX
INH
2
PSHX
INH
2
PULH
INH
2
PSHH
INH
1
CLRH
INH
2
LDA
IMM 2 DIR
2
AIS
IMM 2 DIR
2
EOR
IMM 2 DIR
2
ADC
IMM 2 DIR
2
ORA
IMM 2 DIR
2
ADD
IMM 2 DIR
3
LDA
4
LDA
3
LDA
2
LDA
6
BRSET3 BSET3
RORA
RORX
ROR
SP1 1 IX
5
ASR
SP1 1 IX
5
LSL
SP1 1 IX
5
ROL
SP1 1 IX
ROR
3
DIR
5
2
DIR
4
1
INH
1
INH
3
3
3
3
3
4
3
3
3
BEQ
REL 2 DIR
3
4
ASR
1
ASRA
INH
1
LSLA
INH
1
ROLA
INH
1
DECA
INH
1
ASRX
INH
1
LSLX
INH
1
ROLX
INH
1
DECX
INH
3
ASR
1
3
STA
4
STA
3
STA
2
STA
7
BRCLR3 BCLR3
TAX
3
DIR
5
2
DIR
4
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
INH
4
LSL
3
LSL
1
3
EOR
4
EOR
3
EOR
2
EOR
8
BRSET4 BSET4 BHCC
CLC
3
DIR
5
2
DIR
4
2
REL 2 DIR
3
INH
4
ROL
3
ROL
1
3
ADC
4
ADC
3
ADC
2
ADC
9
BRCLR4 BCLR4 BHCS
SEC
3
DIR
5
2
DIR
4
2
2
2
2
2
2
2
REL 2 DIR
INH
3
BPL
REL 2 DIR
3
BMI
REL 3 DIR
4
DEC
5
DEC
SP1 1 IX
3
DEC
2
3
ORA
4
ORA
5
ORA
SP2 2 IX1
5
ADD
SP2 2 IX1
3
ORA
4
ORA
SP1 1 IX
4
ADD
SP1 1 IX
2
ORA
A
B
C
D
E
F
BRSET5 BSET5
CLI
3
DIR
5
2
DIR
4
INH
5
3
3
5
6
4
2
3
ADD
4
ADD
3
ADD
2
ADD
BRCLR5 BCLR5
DBNZ DBNZA DBNZX DBNZ
DBNZ
DBNZ
SEI
3
DIR
5
2
DIR
4
2
1
1
3
1
INH
1
2
1
1
2
1
INH
1
3
2
2
3
2
IX1
4
SP1 2 IX
INH
3
4
INC
5
INC
SP1 1 IX
4
TST
SP1 1 IX
3
INC
1
2
JMP
4
JMP
3
JMP
2
BRSET6 BSET6
BMC
INCA
INCX
INC
RSP
JMP
3
DIR
5
2
DIR
4
REL 2 DIR
INH
1
INH
1
IX1
3
INH
2
DIR
4
2
2
IX1
5
1
1
IX
3
BMS
3
TST
2
TST
1
4
BSR
REL 2 DIR
2
LDX
IMM 2 DIR
2
AIX
IMM 2 DIR
6
JSR
4
JSR
IX
2
LDX
BRCLR6 BCLR6
TSTA
TSTX
TST
NOP
JSR
JSR
3
DIR
5
2
DIR
4
REL 2 DIR
3
INH
5
INH
4
IX1
4
INH
2
2
2
IX1
3
4
1
STOP
INH
1
WAIT
INH
3
LDX
4
LDX
5
LDX
SP2 2 IX1
5
STX
SP2 2 IX1
4
LDX
SP1 1 IX
4
STX
SP1 1 IX
BRSET7 BSET7
BIL
MOV
MOV
MOV
MOV
LDX
*
1
TXA
INH
3
DIR
5
2
DIR
4
REL
3
DD
DIX+
IMD
3
2
IX+D
1
1
4
4
3
3
3
CLR
1
CLRA
INH
1
CLRX
INH
4
CLR
SP1 1 IX
2
CLR
3
STX
4
STX
3
STX
2
STX
BRCLR7 BCLR7
BIH
CLR
IX1
3
DIR
2
DIR
REL 2 DIR
3
1
INH Inherent
REL Relative
SP1 Stack Pointer, 8-Bit Offset
SP2 Stack Pointer, 16-Bit Offset
IX+ Indexed, No Offset with
Post Increment
IX1+ Indexed, 1-Byte Offset with
Post Increment
MSB
LSB
0
High Byte of Opcode in Hexadecimal
Cycles
IMM Immediate
DIR Direct
IX
Indexed, No Offset
IX1 Indexed, 8-Bit Offset
IX2 Indexed, 16-Bit Offset
IMD Immediate-Direct
EXT Extended
DD Direct-Direct
IX+D Indexed-Direct DIX+ Direct-Indexed
*Pre-byte for stack pointer indexed instructions
5
Low Byte of Opcode in Hexadecimal
0
BRSET0 Opcode Mnemonic
DIR Number of Bytes / Addressing Mode
3
Chapter 8
External Interrupt (IRQ)
8.1 Introduction
This section describes the external interrupt (IRQ) module, which supports external interrupt functions.
8.2 Features
Features of the IRQ module include:
•
•
A dedicated external interrupt pin, IRQ
Hysteresis buffers
8.3 Functional Description
A logic 0 applied to any of the external interrupt pins can latch a CPU interrupt request. Figure 8-1 shows
the structure of the IRQ module.
ACK1
VDD
CLR
D
Q
SYNCHRO-
NIZER
IRQ
INTERRUPT
REQUEST
CK
IRQ
IRQ
LATCH
IMASK1
MODE1
TO MODE
SELECT
LOGIC
HIGH
VOLTAGE
DETECT
Figure 8-1. IRQ Module Block Diagram
Addr.
Register Name
Bit 7
0
6
5
0
4
0
3
IRQF
0
2
0
1
Bit 0
Read:
Write:
Reset:
0
IRQ Status/Control Register
(ISCR)
See page 94.
IMASK1 MODE1
$003F
R
R
R
0
R
0
ACK1
0
0
0
0
0
R
= Reserved
Figure 8-2. IRQ I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
91
External Interrupt (IRQ)
Interrupt signals on the IRQ pin are latched into the IRQ1 latch. An interrupt latch remains set until one of
the following actions occurs:
•
Vector fetch — A vector fetch automatically generates an interrupt acknowledge signal that clears
the latch that caused the vector fetch.
•
Software clear — Software can clear an interrupt latch by writing to the appropriate acknowledge
bit in the interrupt status and control register (ISCR). Writing a logic 1 to the ACK1 bit clears the
IRQ1 latch.
•
Reset — A reset automatically clears both interrupt latches.
The external interrupt pins are falling-edge-triggered and are software-configurable to be both
falling-edge and low-level-triggered. The MODE1 bit in the ISCR controls the triggering sensitivity of the
IRQ pin.
When the interrupt pin is edge-triggered only, the interrupt latch remains set until a vector fetch, software
clear, or reset occurs.
When the interrupt pin is both falling-edge and low-level-triggered, the interrupt latch remains set until
both of these occur:
•
•
Vector fetch, software clear, or reset
Return of the interrupt pin to logic 1
The vector fetch or software clear can occur before or after the interrupt pin returns to logic 1. As long as
the pin is low, the interrupt request remains pending.
When set, the IMASK1 bit in the ISCR masks all external interrupt requests. A latched interrupt request
is not presented to the interrupt priority logic unless the IMASK bit is clear.
NOTE
The interrupt mask (I) in the condition code register (CCR) masks all
interrupt requests, including external interrupt requests. (See Figure 8-3.)
8.4 IRQ Pin
A logic 0 on the IRQ pin can latch an interrupt request into the IRQ latch. A vector fetch, software clear,
or reset clears the IRQ latch.
If the MODE1 bit is set, the IRQ pin is both falling-edge-sensitive and low-level- sensitive. With MODE1
set, both of these actions must occur to clear the IRQ1 latch:
•
Vector fetch, software clear, or reset — A vector fetch generates an interrupt acknowledge signal
to clear the latch. Software can generate the interrupt acknowledge signal by writing a logic 1 to
the ACK1 bit in the interrupt status and control register (ISCR). The ACK1 bit is useful in
applications that poll the IRQ pin and require software to clear the IRQ1 latch. Writing to the ACK1
bit can also prevent spurious interrupts due to noise. Setting ACK1 does not affect subsequent
transitions on the IRQ pin. A falling edge that occurs after writing to the ACK1 bit latches another
interrupt request. If the IRQ1 mask bit, IMASK1, is clear, the CPU loads the program counter with
the vector address at locations $FFFA and $FFFB.
•
Return of the IRQ pin to logic 1 — As long as the IRQ pin is at logic 0, the IRQ1 latch remains set.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
92
Freescale Semiconductor
IRQ Pin
FROM RESET
YES
I BIT SET?
NO
YES
INTERRUPT?
NO
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT
INSTRUCTION
YES
SWI
INSTRUCTION?
NO
YES
RTI
INSTRUCTION?
UNSTACK CPU REGISTERS
EXECUTE INSTRUCTION
NO
Figure 8-3. IRQ Interrupt Flowchart
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
93
External Interrupt (IRQ)
A logic 0 on the IRQ pin can latch an interrupt request into the IRQ latch. A vector fetch, software clear,
or reset clears the IRQ latch.
If the MODE1 bit is set, the IRQ pin is both falling-edge-sensitive and low-level- sensitive. With MODE1
set, both of these actions must occur to clear the IRQ1 latch:
•
Vector fetch, software clear, or reset — A vector fetch generates an interrupt acknowledge signal
to clear the latch. Software can generate the interrupt acknowledge signal by writing a logic 1 to
the ACK1 bit in the interrupt status and control register (ISCR). The ACK1 bit is useful in
applications that poll the IRQ pin and require software to clear the IRQ1 latch. Writing to the ACK1
bit can also prevent spurious interrupts due to noise. Setting ACK1 does not affect subsequent
transitions on the IRQ pin. A falling edge that occurs after writing to the ACK1 bit latches another
interrupt request. If the IRQ1 mask bit, IMASK1, is clear, the CPU loads the program counter with
the vector address at locations $FFFA and $FFFB.
•
Return of the IRQ pin to logic 1 — As long as the IRQ pin is at logic 0, the IRQ1 latch remains set.
The vector fetch or software clear and the return of the IRQ pin to logic 1 can occur in any order. The
interrupt request remains pending as long as the IRQ pin is at logic 0.
If the MODE1 bit is clear, the IRQ pin is falling-edge-sensitive only. With MODE1 clear, a vector fetch or
software clear immediately clears the IRQ1 latch.
Use the branch if IRQ pin high (BIH) or branch if IRQ pin low (BIL) instruction to read the logic level on
the IRQ pin.
NOTE
When using the level-sensitive interrupt trigger, avoid false interrupts by
masking interrupt requests in the interrupt routine.
8.5 IRQ Status and Control Register
The IRQ status and control register (ISCR) has these functions:
•
•
•
Clears the IRQ interrupt latch
Masks IRQ interrupt requests
Controls triggering sensitivity of the IRQ interrupt pin
Address:
$003F
Bit 7
0
6
5
0
4
0
3
IRQF
0
2
0
1
IMASK1
0
Bit 0
MODE1
0
Read:
Write:
Reset:
0
R
R
R
0
R
0
ACK1
0
0
0
R
= Reserved
Figure 8-4. IRQ Status and Control Register (ISCR)
ACK1 — IRQ Interrupt Request Acknowledge Bit
Writing a logic 1 to this write-only bit clears the IRQ latch. ACK1 always reads as logic 0. Reset clears
ACK1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
94
Freescale Semiconductor
IRQ Status and Control Register
IMASK1 — IRQ Interrupt Mask Bit
Writing a logic 1 to this read/write bit disables IRQ interrupt requests. Reset clears IMASK1.
1 = IRQ interrupt requests disabled
0 = IRQ interrupt requests enabled
MODE1 — IRQ Edge/Level Select Bit
This read/write bit controls the triggering sensitivity of the IRQ pin. Reset clears MODE1.
1 = IRQ interrupt requests on falling edges and low levels
0 = IRQ interrupt requests on falling edges only
IRQF — IRQ Flag
This read-only bit acts as a status flag, indicating an IRQ event occurred.
1 = External IRQ event occurred.
0 = External IRQ event did not occur.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
95
External Interrupt (IRQ)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
96
Freescale Semiconductor
Chapter 9
Low-Voltage Inhibit (LVI)
9.1 Introduction
This section describes the low-voltage inhibit (LVI) module, which monitors the voltage on the VDD pin
and can force a reset when the VDD voltage falls to the LVI trip voltage.
9.2 Features
Features of the LVI module include:
•
•
•
•
Programmable LVI reset
Programmable power consumption
Digital filtering of VDD pin level
Selectable LVI trip voltage
9.3 Functional Description
Figure 9-1 shows the structure of the LVI module. The LVI is enabled out of reset. The LVI module
contains a bandgap reference circuit and comparator. The LVI power bit, LVIPWR, enables the LVI to
monitor VDD voltage. The LVI reset bit, LVIRST, enables the LVI module to generate a reset when VDD
falls below a voltage, VLVRX, and remains at or below that level for nine or more consecutive CGMXCLK.
VLVRX and VLVHX are determined by the TRPSEL bit in the LVISCR (see Figure 9-2). LVIPWR and
LVIRST are in the configuration register (CONFIG). See Chapter 5 Configuration Register (CONFIG).
VDD
LVIPWR
FROM CONFIG
FROM CONFIG
CPU CLOCK
LVIRST
VDD
DIGITAL FILTER
VDD > LVItrip = 0
DD < LVItrip = 1
LVI RESET
LOW VDD
DETECTOR
V
TRPSEL
ANLGTRIP
LVIOUT
FROM LVISCR
Figure 9-1. LVI Module Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
97
Low-Voltage Inhibit (LVI)
Once an LVI reset occurs, the MCU remains in reset until VDD rises above a voltage, VLVRX + VLVHX
VDD must be above VLVRX + VLVHX for only one CPU cycle to bring the MCU out of reset. See
.
14.3.2.6 Low-Voltage Inhibit (LVI) Reset. The output of the comparator controls the state of the LVIOUT
flag in the LVI status register (LVISCR).
An LVI reset also drives the RST pin low to provide low-voltage protection to external peripheral devices.
See 19.5 DC Electrical Characteristics.
Addr.
Register Name
Bit 7
6
5
TRPSEL
0
4
0
3
0
2
0
1
0
Bit 0
Read: LVIOUT
0
0
R
0
LVI Status and Control Register
See page 99.
$FE0F
(LVISCR) Write:
R
0
R
R
0
R
0
R
0
R
0
Reset:
0
= Reserved
R
Figure 9-2. LVI I/O Register Summary
9.3.1 Polled LVI Operation
In applications that can operate at VDD levels below VLVRX, software can monitor VDD by polling the
LVIOUT bit. In the configuration register, the LVIPWR bit must be 1 to enable the LVI module, and the
LVIRST bit must be 0 to disable LVI resets. See Chapter 5 Configuration Register (CONFIG). TRPSEL
in the LVISCR selects VLVRX
.
9.3.2 Forced Reset Operation
In applications that require VDD to remain above VLVRX, enabling LVI resets allows the LVI module to
reset the MCU when VDD falls to the VLVRX level and remains at or below that level for nine or more
consecutive CPU cycles. In the CONFIG register, the LVIPWR and LVIRST bits must be 1s to enable the
LVI module and to enable LVI resets. TRPSEL in the LVISCR selects VLVRX
.
9.3.3 False Reset Protection
The VDD pin level is digitally filtered to reduce false resets due to power supply noise. In order for the LVI
module to reset the MCU, VDD must remain at or below VLVRX for nine or more consecutive CPU cycles.
VDD must be above VLVRX + VLVHX for only one CPU cycle to bring the MCU out of reset. TRPSEL in the
LVISCR selects VLVRX + VLVHX
.
9.3.4 LVI Trip Selection
The TRPSEL bit allows the user to chose between 5 percent and 10 percent tolerance when monitoring
the supply voltage. The 10 percent option is enabled out of reset. Writing a 1 to TRPSEL will enable 5
percent option.
NOTE
The microcontroller is guaranteed to operate at a minimum supply voltage.
The trip point (VLVR1 or VLVR2) may be lower than this. See 19.5 DC
Electrical Characteristics.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
98
Freescale Semiconductor
LVI Status and Control Register
9.4 LVI Status and Control Register
The LVI status register (LVISCR) flags VDD voltages below the VLVRX level.
Address:
$FE0F
Bit 7
6
5
TRPSEL
0
4
0
3
0
2
0
1
0
Bit 0
0
Read: LVIOUT
0
Write:
R
0
R
R
0
R
0
R
0
R
0
R
Reset:
0
0
= Reserved
R
Figure 9-3. LVI Status and Control Register (LVISCR)
LVIOUT — LVI Output Bit
This read-only flag becomes set when the VDD voltage falls below the VLVRX voltage for 32 to 40
CGMXCLK cycles. See Table 9-1. Reset clears the LVIOUT bit.
Table 9-1. LVIOUT Bit Indication
VDD
LVIOUT
At Level:
For Number of CGMXCLK Cycles:
Any
VDD > VLVRX + VLVHX
0
VDD < VLVRX
VDD < VLVRX
< 32 CGMXCLK cycles
Between 32 & 40 CGMXCLK cycles
> 40 CGMXCLK cycles
Any
0
0 or 1
1
VDD < VLVRX
VLVRX < VDD < VLVRX + VLVHX
Previous value
TRPSEL — LVI Trip Select Bit
This bit selects the LVI trip point. Reset clears this bit.
1 = 5 percent tolerance. The trip point and recovery point are determined by VLVR1 and VLVH1
,
respectively.
0 = 10 percent tolerance. The trip point and recovery point are determined by VLVR2 and VLVH2
,
respectively.
NOTE
If LVIRST and LVIPWR are 0s, note that when changing the tolerance, LVI
reset will be generated if the supply voltage is below the trip point.
9.5 LVI Interrupts
The LVI module does not generate interrupt requests.
9.6 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
With the LVIPWR bit in the configuration register programmed to 1, the LVI module is active after a WAIT
instruction.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
99
Low-Voltage Inhibit (LVI)
With the LVIRST bit in the configuration register programmed to 1, the LVI module can generate a reset
and bring the MCU out of wait mode.
9.7 Stop Mode
If enabled, the LVI module remains active in stop mode. If enabled to generate resets, the LVI module
can generate a reset and bring the MCU out of stop mode.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
100
Freescale Semiconductor
Chapter 10
Input/Output (I/O) Ports (PORTS)
10.1 Introduction
Thirty-seven bidirectional input-output (I/O) pins and seven input pins form six parallel ports. All I/O pins
are programmable as inputs or outputs.
When using the 56-pin package version:
•
•
•
Set the data direction register bits in DDRC such that bit 1 is written to a logic 1 (along with any
other output bits on port C).
Set the data direction register bits in DDRE such that bits 0, 1, and 2 are written to a logic 1 (along
with any other output bits on port E).
Set the data direction register bits in DDRF such that bits 0, 1, 2, and 3 are written to a logic 1 (along
with any other output bits on port F).
NOTE
Connect any unused I/O pins to an appropriate logic level, either VDD or
VSS. Although PWM6–PWM1 do not require termination for proper
operation, termination reduces excess current consumption and the
possibility of electrostatic damage.
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Port A Data Register
(PTA)
See page 103.
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
$0000
Unaffected by reset
PTB4 PTB3
Unaffected by reset
PTC4 PTC3
Unaffected by reset
Port B Data Register
(PTB)
See page 104.
PTB7
PTB6
PTC6
PTB5
PTC5
PTB2
PTC2
PTB1
PTC1
PTB0
PTC0
$0001
$0002
$0003
$0004
0
Port C Data Register
(PTC)
See page 106.
R
0
PTD6
R
PTD5
R
PTD4
R
PTD3
R
PTD2
R
PTD1
R
PTD0
R
Port D Data Register
(PTD)
See page 107.
R
Unaffected by reset
Data Direction Register A
(DDRA)
See page 103.
DDRA7
DDRA6
DDRA5
0
DDRA4
0
DDRA3
DDRA2
0
DDRA1
0
DDRA0
0
0
0
0
R
= Reserved
= Unimplemented
Figure 10-1. I/O Port Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
101
Input/Output (I/O) Ports (PORTS)
Addr.
Register Name
Bit 7
6
DDRB6
0
5
DDRB5
0
4
DDRB4
0
3
DDRB3
0
2
DDRB2
0
1
DDRB1
0
Bit 0
DDRB0
0
Read:
Write:
Reset:
Read:
Write:
Reset:
Data Direction Register B
(DDRB)
See page 105.
DDRB7
$0005
0
0
Data Direction Register C
(DDRC)
See page 106.
DDRC6
0
DDRC5
0
DDRC4
DDRC3
DDRC2
0
DDRC1
0
DDRC0
0
$0006
$0007
R
0
0
0
Unimplemented
Read:
Write:
Reset:
Read:
Write:
Reset:
Port E Data Register
(PTE)
See page 108.
PTE7
PTE6
PTE5
PTF5
PTE4
PTE3
PTE2
PTF2
PTE1
PTF1
PTE0
PTF0
$0008
$0009
Unaffected by reset
PTF4 PTF3
Unaffected by reset
0
0
Port F Data Register
(PTF)
See page 110.
R
R
$000A
$000B
Unimplemented
Unimplemented
Read:
Write:
Reset:
Read:
Write:
Reset:
Data Direction Register E
(DDRE)
See page 109.
DDRE7
DDRE6
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
$000C
$000D
0
0
0
0
0
DDRF5
0
0
DDRF4
0
0
DDRF3
0
0
DDRF2
0
0
DDRF1
0
0
DDRF0
0
Data Direction Register F
(DDRF)
See page 110.
R
R
R
= Reserved
= Unimplemented
Figure 10-1. I/O Port Register Summary (Continued)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
102
Freescale Semiconductor
Port A
10.2 Port A
Port A is an 8-bit, general-purpose, bidirectional I/O port.
10.2.1 Port A Data Register
The port A data register (PTA) contains a data latch for each of the eight port A pins.
Address:
$0000
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
Unaffected by reset
Figure 10-2. Port A Data Register (PTA)
PTA[7:0] — Port A Data Bits
These read/write bits are software programmable. Data direction of each port A pin is under the control
of the corresponding bit in data direction register A. Reset has no effect on port A data.
10.2.2 Data Direction Register A
Data direction register A (DDRA) determines whether each port A pin is an input or an output. Writing a
logic 1 to a DDRA bit enables the output buffer for the corresponding port A pin; a logic 0 disables the
output buffer.
Address:
$0004
Bit 7
6
DDRA6
0
5
DDRA5
0
4
DDRA4
0
3
DDRA3
0
2
DDRA2
0
1
DDRA1
0
Bit 0
DDRA0
0
Read:
Write:
Reset:
DDRA7
0
Figure 10-3. Data Direction Register A (DDRA)
DDRA[7:0] — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears DDRA[7:0], configuring all port A pins
as inputs.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
NOTE
Avoid glitches on port A pins by writing to the port A data register before
changing data direction register A bits from 0 to 1.
Figure 10-4 shows the port A I/O logic.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
103
Input/Output (I/O) Ports (PORTS)
READ DDRA ($0004)
WRITE DDRA ($0004)
WRITE PTA ($0000)
DDRAx
PTAx
RESET
PTAx
READ PTA ($0000)
Figure 10-4. Port A I/O Circuit
When bit DDRAx is a logic 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a
logic 0, reading address $0000 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-1 summarizes the operation of the port A pins.
Table 10-1. Port A Pin Functions
Accesses to DDRA
Read/Write
Accesses to PTA
DDRA Bit
PTA Bit
I/O Pin Mode
Read
Write
X(1)
X
Input, Hi-Z(2)
Output
PTA[7:0](3)
PTA[7:0]
0
DDRA[7:0]
Pin
1
DDRA[7:0]
PTA[7:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
10.3 Port B
Port B is an 8-bit, general-purpose, bidirectional I/O port that shares its pins with the analog-to-digital
convertor (ADC) module.
10.3.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the eight port B pins.
Address:
$0001
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
PTB7
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
Unaffected by reset
Figure 10-5. Port B Data Register (PTB)
PTB[7:0] — Port B Data Bits
These read/write bits are software-programmable. Data direction of each port B pin is under the control
of the corresponding bit in data direction register B. Reset has no effect on port B data.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
104
Freescale Semiconductor
Port B
10.3.2 Data Direction Register B
Data direction register B (DDRB) determines whether each port B pin is an input or an output. Writing a
logic 1 to a DDRB bit enables the output buffer for the corresponding port B pin; a logic 0 disables the
output buffer.
Address:
$0005
Bit 7
6
DDRB6
0
5
DDRB5
0
4
DDRB4
0
3
DDRB3
0
2
DDRB2
0
1
DDRB1
0
Bit 0
DDRB0
0
Read:
Write:
Reset:
DDRB7
0
Figure 10-6. Data Direction Register B (DDRB)
DDRB[7:0] — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears DDRB[7:0], configuring all port B pins
as inputs.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
NOTE
Avoid glitches on port B pins by writing to the port B data register before
changing data direction register B bits from 0 to 1.
Figure 10-7 shows the port B I/O logic.
READ DDRB ($0005)
WRITE DDRB ($0005)
DDRBx
RESET
WRITE PTB ($0001)
PTBx
PTBx
READ PTB ($0001)
Figure 10-7. Port B I/O Circuit
When bit DDRBx is a logic 1, reading address $0001 reads the PTBx data latch. When bit DDRBx is a
logic 0, reading address $0001 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-2 summarizes the operation of the port B pins.
Table 10-2. Port B Pin Functions
Accesses to DDRB
Read/Write
Accesses to PTB
DDRB Bit
PTB Bit
I/O Pin Mode
Read
Write
X(1)
X
Input, Hi-Z(2)
Output
PTB[7:0](3)
0
1
DDRB[7:0]
Pin
DDRB[7:0]
PTB[7:0]
PTB[7:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
105
Input/Output (I/O) Ports (PORTS)
10.4 Port C
Port C is a 7-bit, general-purpose, bidirectional I/O port that shares two of its pins with the analog-to-digital
convertor module (ADC).
10.4.1 Port C Data Register
The port C data register (PTC) contains a data latch for each of the seven port C pins.
Address:
$0002
Bit 7
0
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1
PTC0
R
Unaffected by reset
R
= Reserved
Figure 10-8. Port C Data Register (PTC)
PTC[6:0] — Port C Data Bits
These read/write bits are software-programmable. Data direction of each port C pin is under the control
of the corresponding bit in data direction register C. Reset has no effect on port C data.
10.4.2 Data Direction Register C
Data direction register C (DDRC) determines whether each port C pin is an input or an output. Writing a
logic 1 to a DDRC bit enables the output buffer for the corresponding port C pin; a logic 0 disables the
output buffer.
Address:
$0006
Bit 7
0
6
5
DDRC5
0
4
DDRC4
0
3
DDRC3
0
2
DDRC2
0
1
DDRC1
0
Bit 0
DDRC0
0
Read:
Write:
Reset:
DDRC6
R
0
0
R
= Reserved
Figure 10-9. Data Direction Register C (DDRC)
DDRC[6:0] — Data Direction Register C Bits
These read/write bits control port C data direction. Reset clears DDRC[6:0], configuring all port C pins
as inputs.
1 = Corresponding port C pin configured as output
0 = Corresponding port C pin configured as input
NOTE
Avoid glitches on port C pins by writing to the port C data register before
changing data direction register C bits from 0 to 1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
106
Freescale Semiconductor
Port D
Figure 10-10 shows the port C I/O logic.
READ DDRC ($0006)
WRITE DDRC ($0006)
RESET
DDRCx
PTCx
WRITE PTC ($0002)
PTCx
READ PTC ($0002)
Figure 10-10. Port C I/O Circuit
When bit DDRCx is a logic 1, reading address $0002 reads the PTCx data latch. When bit DDRCx is a
logic 0, reading address $0002 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-3 summarizes the operation of the port C pins.
Table 10-3. Port C Pin Functions
DDRC Bit
PTC Bit
I/O Pin Mode
Accesses to DDRC
Read/Write
Accesses to PTC
Read
Pin
Write
X(1)
X
Input, Hi-Z(2)
Output
PTC[6:0](3)
PTC[6:0]
0
1
DDRC[6:0]
DDRC[6:0]
PTC[6:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
10.5 Port D
Port D is a 7-bit, input-only port that shares its pins with the pulse width modulator for motor control
module (PMC).
The port D data register (PTD) contains a data latch for each of the seven port pins.
Address:
$0003
Bit 7
0
6
PTD6
R
5
PTD5
R
4
PTD4
R
3
PTD3
R
2
PTD2
R
1
PTD1
R
Bit 0
PTD0
R
Read:
Write:
Reset:
R
Unaffected by reset
R
= Reserved
Figure 10-11. Port D Data Register (PTD)
PTD[6:0] — Port D Data Bits
These read/write bits are software programmable. Reset has no effect on port D data.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
107
Input/Output (I/O) Ports (PORTS)
Figure 10-12 shows the port D input logic.
READ PTD ($0003)
PTDx
Figure 10-12. Port D Input Circuit
Reading address $0003 reads the voltage level on the pin. Table 10-4 summarizes the operation of the
port D pins.
Table 10-4. Port D Pin Functions
Accesses to PTD
PTD Bit
Pin Mode
Read
Write
X(1)
Input, Hi-Z(2)
PTD[6:0](3)
Pin
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
10.6 Port E
Port E is an 8-bit, special function port that shares five of its pins with the timer interface module (TIM)
and two of its pins with the serial communications interface module (SCI).
10.6.1 Port E Data Register
The port E data register (PTE) contains a data latch for each of the eight port E pins.
Address:
$0008
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
PTE7
PTE6
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
Unaffected by reset
Figure 10-13. Port E Data Register (PTE)
PTE[7:0] — Port E Data Bits
PTE[7:0] are read/write, software-programmable bits. Data direction of each port E pin is under the
control of the corresponding bit in data direction register E.
NOTE
Data direction register E (DDRE) does not affect the data direction of port
E pins that are being used by the TIMA or TIMB. However, the DDRE bits
always determine whether reading port E returns the states of the latches
or the states of the pins.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
108
Freescale Semiconductor
Port E
10.6.2 Data Direction Register E
Data direction register E (DDRE) determines whether each port E pin is an input or an output. Writing a
logic 1 to a DDRE bit enables the output buffer for the corresponding port E pin; a logic 0 disables the
output buffer.
Address:
$000C
Bit 7
6
DDRE6
0
5
DDRE5
0
4
DDRE4
0
3
DDRE3
0
2
DDRE2
0
1
DDRE1
0
Bit 0
DDRE0
0
Read:
Write:
Reset:
DDRE7
0
Figure 10-14. Data Direction Register E (DDRE)
DDRE[7:0] — Data Direction Register E Bits
These read/write bits control port E data direction. Reset clears DDRE[7:0], configuring all port E pins
as inputs.
1 = Corresponding port E pin configured as output
0 = Corresponding port E pin configured as input
NOTE
Avoid glitches on port E pins by writing to the port E data register before
changing data direction register E bits from 0 to 1.
Figure 10-15 shows the port E I/O logic.
READ DDRE ($000C)
WRITE DDRE ($000C)
DDREx
RESET
WRITE PTE ($0008)
PTEx
PTEx
READ PTE ($0008)
Figure 10-15. Port E I/O Circuit
When bit DDREx is a logic 1, reading address $0008 reads the PTEx data latch. When bit DDREx is a
logic 0, reading address $0008 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-5 summarizes the operation of the port E pins.
Table 10-5. Port E Pin Functions
Accesses to DDRE
Read/Write
Accesses to PTE
DDRE Bit
PTE Bit
I/O Pin Mode
Read
Write
X(1)
X
Input, Hi-Z(2)
Output
PTE[7:0](3)
PTE[7:0]
0
DDRE[7:0]
Pin
1
DDRE[7:0]
PTE[7:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
109
Input/Output (I/O) Ports (PORTS)
10.7 Port F
Port F is a 6-bit, special function port that shares four of its pins with the serial peripheral interface module
(SPI) and two pins with the serial communications interface (SCI).
10.7.1 Port F Data Register
The port F data register (PTF) contains a data latch for each of the six port F pins.
Address:
$0009
Bit 7
0
6
0
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
PTF5
PTF4
PTF3
PTF2
PTF1
PTF0
R
R
Unaffected by reset
R
= Reserved
Figure 10-16. Port F Data Register (PTF)
PTF[5:0] — Port F Data Bits
These read/write bits are software programmable. Data direction of each port F pin is under the control
of the corresponding bit in data direction register F. Reset has no effect on PTF[5:0].
NOTE
Data direction register F (DDRF) does not affect the data direction of port F
pins that are being used by the SPI or SCI module. However, the DDRF bits
always determine whether reading port F returns the states of the latches
or the states of the pins.
10.7.2 Data Direction Register F
Data direction register F (DDRF) determines whether each port F pin is an input or an output. Writing a
logic 1 to a DDRF bit enables the output buffer for the corresponding port F pin; a logic 0 disables the
output buffer.
Address:
$000D
Bit 7
0
6
0
5
DDRF5
0
4
DDRF4
0
3
DDRF3
0
2
DDRF2
0
1
DDRF1
0
Bit 0
DDRF0
0
Read:
Write:
Read:
R
R
R
= Reserved
Figure 10-17. Data Direction Register F (DDRF)
DDRF[5:0] — Data Direction Register F Bits
These read/write bits control port F data direction. Reset clears DDRF[5:0], configuring all port F pins
as inputs.
1 = Corresponding port F pin configured as output
0 = Corresponding port F pin configured as input
NOTE
Avoid glitches on port F pins by writing to the port F data register before
changing data direction register F bits from 0 to 1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
110
Freescale Semiconductor
Port F
Figure 10-18 shows the port F I/O logic.
READ DDRF ($000D)
WRITE DDRF ($000D)
RESET
DDRFx
PTFx
WRITE PTF ($0009)
PTFx
READ PTF ($0009)
Figure 10-18. Port F I/O Circuit
When bit DDRFx is a logic 1, reading address $0009 reads the PTFx data latch. When bit DDRFx is a
logic 0, reading address $0009 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-6 summarizes the operation of the port F pins.
Table 10-6. Port F Pin Functions
Accesses to DDRF
Read/Write
Accesses to PTF
DDRF Bit
PTF Bit
I/O Pin Mode
Read
Write
X(1)
X
Input, Hi-Z(2)
Output
PTF[6:0](3)
PTF[6:0]
0
DDRF[6:0]
Pin
1
DDRF[6:0]
PTF[6:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
111
Input/Output (I/O) Ports (PORTS)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
112
Freescale Semiconductor
Chapter 11
Power-On Reset (POR)
11.1 Introduction
This section describes the power-on reset (POR) module.
11.2 Functional Description
The POR module provides a known, stable signal to the microcontroller unit (MCU) at power-on. This
signal tracks VDD until the MCU generates a feedback signal to indicate that it is properly initialized. At
this time, the POR drives its output low.
The POR is not a brown-out detector, low-voltage detector, or glitch detector. VDD at the POR must go
completely to 0 to reset the microcontroller unit (MCU). To detect power-loss conditions, use a low-voltage
inhibit module (LVI) or other suitable circuit.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
113
Power-On Reset (POR)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
114
Freescale Semiconductor
Chapter 12
Pulse-Width Modulator for Motor Control (PWMMC)
12.1 Introduction
This section describes the pulse-width modulator for motor control (PWMMC, version A). The PWM
module can generate three complementary PWM pairs or six independent PWM signals. These
PWM signals can be center-aligned or edge-aligned. A block diagram of the PWM module is shown in
Figure 12-2.
A12-bit timer PWM counter is common to all six channels. PWM resolution is one clock period for
edge-aligned operation and two clock periods for center-aligned operation. The clock period is dependent
on the internal operating frequency (fOP) and a programmable prescaler. The highest resolution for
edge-aligned operation is 125 ns (fOP = 8 MHz). The highest resolution for center-aligned operation is
250 ns (fOP = 8 MHz).
When generating complementary PWM signals, the module features automatic dead-time insertion to the
PWM output pairs and transparent toggling of PWM data based upon sensed motor phase current
polarity.
A summary of the PWM registers is shown in Figure 12-3.
12.2 Features
Features of the PWMMC include:
•
•
•
•
•
•
•
Three complementary PWM pairs or six independent PWM signals
Edge-aligned PWM signals or center-aligned PWM signals
PWM signal polarity control
20-mA current sink capability on PWM pins
Manual PWM output control through software
Programmable fault protection
Complementary mode featuring:
–
–
Dead-time insertion
Separate top/bottom pulse width correction via current sensing or programmable software bits
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
115
INTERNAL BUS
M68HC08 CPU
PTA7–PTA0
CPU
REGISTERS
ARITHMETIC/LOGIC
UNIT
LOW-VOLTAGE INHIBIT
MODULE
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
COMPUTER OPERATING PROPERLY
MODULE
CONTROL AND STATUS REGISTERS — 112 BYTES
USER FLASH — 32,256 BYTES
TIMER INTERFACE
MODULE A
USER RAM — 768 BYTES
PTC6
PTC5
TIMER INTERFACE
MODULE B
PTC4
MONITOR ROM — 240 BYTES
PTC3
PTC2
SERIAL COMMUNICATIONS INTERFACE
MODULE
PTC1/ATD9(1)
PTC0/ATD8
USER FLASH VECTOR SPACE — 46 BYTES
OSC1
PTD6/IS3
CLOCK GENERATOR
MODULE
OSC2
SERIAL PERIPHERAL INTERFACE
MODULE(2)
PTD5/IS2
CGMXFC
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
POWER-ON RESET
MODULE
SYSTEM INTEGRATION
MODULE
RST
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
IRQ
MODULE
IRQ
SINGLE BREAK
MODULE
VDDA
(3)
VSSA
ANALOG-TO-DIGITAL CONVERTER
MODULE
(3)
VREFL
VREFH
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PWMGND
PULSE-WIDTH MODULATOR
MODULE
PWM6–PWM1
PTF1/SS(1)
PTF0/SPSCK(1)
VSS
VDD
POWER
VDDAD
VSSAD
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 12-1. Block Diagram Highlighting PWMMC Block and Pins
Features
8
CPU BUS
PWM1 PIN
PWM2 PIN
PWM CHANNELS 1 AND 2
PWM CHANNELS 3 AND 4
PWM3 PIN
PWM4 PIN
PWM5 PIN
PWM6 PIN
PWM CHANNELS 5 AND 6
FAULT
INTERRUPT
PINS
4
12
TIMEBASE
3
COIL CURRENT
POLARITY PINS
Figure 12-2. PWM Module Block Diagram
Addr.
Register Name
Bit 7
DISX
0
6
DISY
0
5
4
PWMF
0
3
ISENS1
0
2
1
LDOK
0
Bit 0
PWMEN
0
Read:
PWM Control Register 1
PWMINT
ISENS0
$0020
(PCTL1) Write:
See page 146.
Reset:
Read:
0
0
0
IPOL3
0
PWM Control Register 2
LDFQ1
0
LDFQ0
0
IPOL1
0
IPOL2
0
PRSC1
0
PRSC0
0
$0021
$0022
$0023
$0024
(PCTL2) Write:
See page 148.
Reset:
Read:
0
Fault Control Register
FINT4 FMODE4
FINT3
FMODE3
FINT2
FMODE2
FINT1 FMODE1
(FCR) Write:
See page 150.
Reset:
Read: FPIN4
(FSR) Write:
0
0
0
0
0
0
0
0
FFLAG4
FPIN3
FFLAG3
FPIN2
FFLAG2
FPIN1
FFLAG1
Fault Status Register
See page 152.
Reset:
Read:
U
0
0
U
0
DT5
U
0
DT3
U
0
DT1
0
DT6
DT4
DT2
Fault Acknowledge Register
(FTACK) Write:
See page 153.
Reset:
FTACK4
0
FTACK3
0
FTACK2
0
FTACK1
0
0
0
0
0
R
= Reserved
Bold
= Buffered
X = Indeterminate
Figure 12-3. Register Summary (Sheet 1 of 3)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
117
Pulse-Width Modulator for Motor Control (PWMMC)
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
PWM Output Control
Register (PWMOUT) Write:
0
OUTCTL
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
$0025
See page 154.
Reset:
0
0
0
0
0
0
0
0
0
0
0
0
Read:
Bit 11
Bit 10
Bit 9
Bit 8
PWM Counter Register High
$0026
$0027
$0028
$0029
$002A
$002B
$002C
$002D
$002E
$002F
(PCNTH) Write:
See page 143.
Reset:
0
0
0
0
0
0
0
0
Read: Bit 7
(PCNTL) Write:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
PWM Counter Register Low
See page 143.
Reset:
Read:
0
0
0
0
0
0
0
0
0
Bit 11
X
0
Bit 10
X
0
Bit 9
X
0
Bit 8
X
PWM Counter Modulo Register
High (PMODH) Write:
See page 144.
Reset:
0
Bit 7
X
0
Bit 6
X
0
Bit 5
X
0
Bit 4
X
Read:
PWM Counter Modulo Register
Bit 3
X
Bit 2
X
Bit 1
X
Bit 0
X
Low (PMODL) Write:
See page 144.
Reset:
Read:
PWM 1 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL1H) Write:
See page 145.
Reset:
Read:
PWM 1 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PVAL1L) Write:
See page 145.
Reset:
Read:
PWM 2 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL2H) Write:
See page 145.
Reset:
Read:
PWM 2 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PVAL2L) Write:
See page 145.
Reset:
Read:
PWM 3 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL3H) Write:
See page 145.
Reset:
Read:
PWM 3 Value Register Low
Bit 7
Bit 6
Bit 5
0
Bit 4
Bit 3
Bit 2
0
Bit 1
0
Bit 0
0
(PVAL3L) Write:
See page 145.
Reset:
0
0
0
0
R
= Reserved
Bold
= Buffered
X = Indeterminate
Figure 12-3. Register Summary (Sheet 2 of 3)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
118
Freescale Semiconductor
Features
Addr.
Register Name
Bit 7
Bit 15
0
6
Bit 14
0
5
Bit 13
0
4
Bit 12
0
3
Bit 11
0
2
Bit 10
0
1
Bit 9
0
Bit 0
Bit 8
0
Read:
PWM 4 Value Register High
$0030
(PVAL4H) Write:
See page 145.
Reset:
Read:
PWM 4 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
$0031
$0032
$0033
$0034
$0035
$0036
$0037
(PVAL4L) Write:
See page 145.
Reset:
Read:
PWM 5 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL5H) Write:
See page 145.
Reset:
Read:
PWM 5 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PVAL5L) Write:
See page 145.
Reset:
Read:
PWM 6 Value Register High
Bit 15
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
Bit 9
0
Bit 8
0
(PVAL6H) Write:
See page 145.
Reset:
Read:
PWM 6 Value Register Low
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
(PMVAL6L) Write:
See page 145.
Reset:
Read:
Dead-Time Write-Once
Register (DEADTM) Write:
Bit 7
1
Bit 6
1
Bit 5
1
Bit 4
1
Bit 3
1
Bit 2
1
Bit 1
1
Bit 0
1
See page 150.
Reset:
Read:
PWM Disable Mapping
Write-Once Register Write:
Bit 7
Bit 6
Bit 5
1
Bit 4
Bit 3
Bit 2
1
Bit 1
1
Bit 0
1
(DISMAP) See page 150.
Reset:
1
1
1
1
R
= Reserved
Bold
= Buffered
X = Indeterminate
Figure 12-3. Register Summary (Sheet 3 of 3)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
119
Pulse-Width Modulator for Motor Control (PWMMC)
12.3 Timebase
This section provides a discussion of the timebase.
12.3.1 Resolution
In center-aligned mode, a 12-bit up/down counter is used to create the PWM period. Therefore, the PWM
resolution in center-aligned mode is two clocks (highest resolution is 250 ns @ fOP = 8 MHz) as shown in
Figure 12-4. The up/down counter uses the value in the timer modulus register to determine its maximum
count. The PWM period will equal:
[(timer modulus) x (PWM clock period) x 2].
UP/DOWN COUNTER
MODULUS = 4
PERIOD = 8 X (PWM CLOCK PERIOD)
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
Figure 12-4. Center-Aligned PWM (Positive Polarity)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
120
Freescale Semiconductor
Timebase
For edge-aligned mode, a 12-bit up-only counter is used to create the PWM period. Therefore, the PWM
resolution in edge-aligned mode is one clock (highest resolution is125 ns @ fOP = 8 MHz) as shown in
Figure 12-5. Again, the timer modulus register is used to determine the maximum count. The PWM period
will equal:
(timer modulus) x (PWM clock period)
Center-aligned operation versus edge-aligned operation is determined by the option EDGE. See 5.2
Functional Description.
UP-ONLY COUNTER
MODULUS = 4
PERIOD = 4 X (PWM
CLOCK PERIOD)
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
Figure 12-5. Edge-Aligned PWM (Positive Polarity)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
121
Pulse-Width Modulator for Motor Control (PWMMC)
12.3.2 Prescaler
To permit lower PWM frequencies, a prescaler is provided which will divide the PWM clock frequency by
1, 2, 4, or 8. Table 12-1 shows how setting the prescaler bits in PWM control register 2 affects the PWM
clock frequency. This prescaler is buffered and will not be used by the PWM generator until the LDOK bit
is set and a new PWM reload cycle begins.
Table 12-1. PWM Prescaler
Prescaler Bits
PWM Clock Frequency
PRSC1 and PRSC0
fOP
00
01
10
11
fOP/2
f
OP/4
fOP/8
12.4 PWM Generators
Pulse-width modulator (PWM) generators are discussed in this subsection.
12.4.1 Load Operation
To help avoid erroneous pulse widths and PWM periods, the modulus, prescaler, and PWM value
registers are buffered. New PWM values, counter modulus values, and prescalers can be loaded from
their buffers into the PWM module every one, two, four, or eight PWM cycles. LDFQ1 and LDFQ0 in PWM
control register 2 are used to control this reload frequency, as shown in Table 12-2. When a reload cycle
arrives, regardless of whether an actual reload occurs (as determined by the LDOK bit), the PWM reload
flag bit in PWM control register 1 will be set. If the PWMINT bit in PWM control register 1 is set, a CPU
interrupt request will be generated when PWMF is set. Software can use this interrupt to calculate new
PWM parameters in real time for the PWM module.
Table 12-2. PWM Reload Frequency
Reload Frequency Bits
PWM Reload Frequency
LDFQ1 and LDFQ0
00
01
10
11
Every PWM cycle
Every 2 PWM cycles
Every 4 PWM cycles
Every 8 PWM cycles
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
122
Freescale Semiconductor
PWM Generators
For ease of software, the LDFQx bits are buffered. When the LDFQx bits are changed, the reload
frequency will not change until the previous reload cycle is completed. See Figure 12-6.
NOTE
When reading the LDFQx bits, the value is the buffered value (for example,
not necessarily the value being acted upon).
RELOAD
RELOAD
RELOAD
RELOAD RELOADRELOADRELOAD
CHANGE RELOAD
FREQUENCY TO
EVERY 4 CYCLES
CHANGE RELOAD
FREQUENCY TO
EVERY CYCLE
Figure 12-6. Reload Frequency Change
PWMINT enables CPU interrupt requests as shown in Figure 12-7. When this bit is set, CPU interrupt
requests are generated when the PWMF bit is set. When the PWMINT bit is clear, PWM interrupt requests
are inhibited. PWM reloads will still occur at the reload rate, but no interrupt requests will be generated.
READ PWMF AS 1,
WRITE PWMF AS 0
OR
VDD
RESET
RESET
PWMF
CPU INTERRUPT
REQUEST
D
LATCH
PWM RELOAD
PWMINT
CK
Figure 12-7. PWM Interrupt Requests
To prevent a partial reload of PWM parameters from occurring while the software is still calculating them,
an interlock bit controlled from software is provided. This bit informs the PWM module that all the PWM
parameters have been calculated, and it is “okay” to use them. A new modulus, prescaler, and/or PWM
value cannot be loaded into the PWM module until the LDOK bit in PWM control register 1 is set. When
the LDOK bit is set, these new values are loaded into a second set of registers and used by the PWM
generator at the beginning of the next PWM reload cycle as shown in Figure 12-8, Figure 12-9,
Figure 12-10, and Figure 12-11. After these values are loaded, the LDOK bit is cleared.
NOTE
When the PWM module is enabled (via the PWMEN bit), a load will occur
if the LDOK bit is set. Even if it is not set, an interrupt will occur if the
PWMINT bit is set. To prevent this, the software should clear the PWMINT
bit before enabling the PWM module.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
123
Pulse-Width Modulator for Motor Control (PWMMC)
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP/DOWN
COUNTER
LDOK = 1
MODULUS = 3
PWM VALUE = 2
PWMF SET
LDOK = 1
LDOK = 0
MODULUS = 3
PWM VALUE = 2
PWMF SET
LDOK = 0
MODULUS = 3
PWM VALUE = 1
PWMF SET
MODULUS = 3
PWM VALUE = 1
PWMF SET
PWM
Figure 12-8. Center-Aligned PWM Value Loading
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP/DOWN
COUNTER
LDOK = 1
LDOK = 1
MODULUS = 3
PWM VALUE = 1
PWMF SET
LDOK = 1
MODULUS = 2 MODULUS = 1
PWMVALUE = 1 PWM VALUE = 1
LDOK = 1
LDOK = 0
MODULUS = 2
PWM VALUE = 1
PWMF SET
MODULUS = 2
PWM VALUE = 1
PWMF SET
PWMF SET
PWMF SET
PWM
Figure 12-9. Center-Aligned Loading of Modulus
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP-ONLY
COUNTER
LDOK = 1
MODULUS = 3
PWM VALUE = 2
PWMF SET
LDOK = 1
MODULUS = 3
PWM VALUE = 1 PWM VALUE = 2
LDOK = 0
MODULUS = 3
PWM VALUE = 1
PWMF SET
LDOK = 0
MODULUS = 3
LDOK = 0
MODULUS = 3
PWM VALUE = 1
PWMF SET
PWMF SET
PWMF SET
PWM
Figure 12-10. Edge-Aligned PWM Value Loading
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
124
Freescale Semiconductor
PWM Generators
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP-ONLY
COUNTER
LDOK = 1
LDOK = 1
LDOK = 0
LDOK = 1
MODULUS = 3
PWM VALUE = 2
PWMF SET
MODULUS = 4
PWM VALUE = 2
PWMF SET
MODULUS = 1
PWM VALUE = 2
PWMF SET
MODULUS = 2
PWM VALUE = 2
PWMF SET
PWM
Figure 12-11. Edge-Aligned Modulus Loading
12.4.2 PWM Data Overflow and Underflow Conditions
The PWM value registers are 16-bit registers. Although the counter is only 12 bits, the user may write a
16-bit signed value to a PWM value register. As shown in Figure 12-4 and Figure 12-5, if the PWM value
is less than or equal to zero, the PWM will be inactive for the entire period. Conversely, if the PWM value
is greater than or equal to the timer modulus, the PWM will be active for the entire period. Refer to
Table 12-3.
NOTE
The terms “active” and “inactive” refer to the asserted and negated states
of the PWM signals and should not be confused with the high-impedance
state of the PWM pins.
Table 12-3. PWM Data Overflow and Underflow Conditions
PWMVALxH:PWMVALxL
$0000–$0FFF
Condition
Normal
PWM Value Used
Per register contents
$FFF
$1000–$7FFF
Overflow
Underflow
$8000–$FFFF
$000
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
125
Pulse-Width Modulator for Motor Control (PWMMC)
12.5 Output Control
This subsection discusses output control.
12.5.1 Selecting Six Independent PWMs or Three Complementary PWM Pairs
The PWM outputs can be configured as six independent PWM channels or three complementary channel
pairs. The option INDEP determines which mode is used (see 5.2 Functional Description). If
complementary operation is chosen, the PWM pins are paired as shown in Figure 12-12. Operation of
one pair is then determined by one PWM value register. This type of operation is meant for use in motor
drive circuits such as the one in Figure 12-13.
PWM1 PIN
PWM VALUE REGISTER
PWM VALUE REGISTER
PWM VALUE REGISTER
PWMS 1 AND 2
PWM2 PIN
PWM3 PIN
PWM4 PIN
PWMS 3 AND 4
PWM5 PIN
PWM6 PIN
PWMS 5 AND 6
Figure 12-12. Complementary Pairing
PWM
3
PWM
1
PWM
5
TO
AC
MOTOR
INPUTS
PWM
2
PWM
4
PWM
6
Figure 12-13. Typical AC Motor Drive
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
126
Freescale Semiconductor
Output Control
When complementary operation is used, two additional features are provided:
•
•
Dead-time insertion
Separate top/bottom pulse width correction to correct for distortions caused by the motor drive
characteristics
If independent operation is chosen, each PWM has its own PWM value register.
12.5.2 Dead-Time Insertion
As shown in Figure 12-13, in complementary mode, each PWM pair can be used to drive
top-side/bottom-side transistors.
When controlling dc-to-ac inverters such as this, the top and bottom PWMs in one pair should never be
active at the same time. In Figure 12-13, if PWM1 and PWM2 were on at the same time, large currents
would flow through the two transistors as they discharge the bus capacitor. The IGBTs could be
weakened or destroyed.
Simply forcing the two PWMs to be inversions of each other is not always sufficient. Since a time delay is
associated with turning off the transistors in the motor drive, there must be a dead-time between the
deactivation of one PWM and the activation of the other.
A dead-time can be specified in the dead-time write-once register. This 8-bit value specifies the number
of CPU clock cycles to use for the dead-time. The dead-time is not affected by changes in the PWM period
caused by the prescaler.
Dead-time insertion is achieved by feeding the top PWM outputs of the PWM generator into dead-time
generators, as shown in Figure 12-14. Current sensing determines which PWM value of a PWM generator
pair to use for the top PWM in the next PWM cycle. See 12.5.3 Top/Bottom Correction with Motor Phase
Current Polarity Sensing. When output control is enabled, the odd OUT bits, rather than the PWM
generator outputs, are fed into the dead-time generators. See 12.5.5 PWM Output Port Control.
Whenever an input to a dead-time generator transitions, a dead-time is inserted (for example, both PWMs
in the pair are forced to their inactive state). The bottom PWM signal is generated from the top PWM and
the dead-time. In the case of output control enabled, the odd OUTx bits control the top PWMs, the even
OUTx bits control the bottom PWMs with respect to the odd OUTx bits (see Table 12-6). Figure 12-15
shows the effects of the dead-time insertion.
As seen in Figure 12-15, some pulse width distortion occurs when the dead-time is inserted. The active
pulse widths are reduced. For example, in Figure 12-15, when the PWM value register is equal to two,
the ideal waveform (with no dead-time) has pulse widths equal to four. However, the actual pulse widths
shrink to two after a dead-time of two was inserted. In this example, with the prescaler set to divide by
one and center-aligned operation selected, this distortion can be compensated for by adding or
subtracting half the dead-time value to or from the PWM register value. This correction is further described
in 12.5.3 Top/Bottom Correction with Motor Phase Current Polarity Sensing.
Further examples of dead-time insertion are shown in Figure 12-16 and Figure 12-17. Figure 12-16 shows
the effects of dead-time insertion at the duty cycle boundaries (near 0 percent and 100 percent duty
cycles). Figure 12-17 shows the effects of dead-time insertion on pulse widths smaller than the dead-time.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
127
Pulse-Width Modulator for Motor Control (PWMMC)
OUTPUT CONTROL
(OUTCTL)
OUT2
OUT4
OUT6
MUX
PWMPAIR12
TOP
PWM1
PWM2
PWM (TOP)
(TOP)
(PWM1)
DEAD-TIME
POSTDT (TOP)
PREDT (TOP)
OUTX
BOTTOM
(PWM2)
SELECT
MUX
PWMPAIR34
(TOP)
TOP
(PWM3)
PWM (TOP)
PWM3
PWM4
DEAD-TIME
POSTDT (TOP)
PREDT (TOP)
OUTX
BOTTOM
(PWM4)
SELECT
6
MUX
PWMPAIR56
(TOP)
TOP
(PWM5)
PWM (TOP)
PWM5
PWM6
DEAD-TIME
POSTDT (TOP)
PREDT (TOP)
OUTX
BOTTOM
(PWM6)
SELECT
Figure 12-14. Dead-Time Generators
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
128
Freescale Semiconductor
Output Control
UP/DOWN COUNTER
MODULUS = 4
PWM VALUE = 2
PWM VALUE = 3
PWM VALUE = 2
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
DEAD-TIME = 2
2
2
2
2
PWM2 W/
DEAD-TIME = 2
2
2
Figure 12-15. Effects of Dead-Time Insertion
UP/DOWN COUNTER
MODULUS = 3
PWM VALUE = 1
PWM VALUE = 1
PWM VALUE = 3
PWM VALUE = 3
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
DEAD-TIME = 2
2
2
PWM2 W/
DEAD-TIME = 2
2
2
Figure 12-16. Dead-Time at Duty Cycle Boundaries
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
129
Pulse-Width Modulator for Motor Control (PWMMC)
UP/DOWN COUNTER
MOUDULUS = 3
PWM VALUE = 2
PWM VALUE = 3
PWM VALUE = 2
PWM VALUE = 1
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
3
3
3
DEAD-TIME = 3
PWM2 W/
DEAD-TIME = 3
3
3
3
Figure 12-17. Dead-Time and Small Pulse Widths
12.5.3 Top/Bottom Correction with Motor Phase Current Polarity Sensing
Ideally, when complementary pairs are used, the PWM pairs are inversions of each other, as shown in
Figure 12-18. When PWM1 is active, PWM2 is inactive, and vice versa. In this case, the motor terminal
voltage is never allowed to float and is strictly controlled by the PWM waveforms.
UP/DOWN COUNTER
MODULUS = 4
PWM1
PWM VALUE = 1
PWM2
PWM3
PWM VALUE = 2
PWM4
PWM5
PWM VALUE = 3
PWM6
Figure 12-18. Ideal Complementary Operation (Dead-Time = 0)
However, when dead-time is inserted, the motor voltage is allowed to float momentarily during the
dead-time interval, creating a distortion in the motor current waveform. This distortion is aggravated by
dissimilar turn-on and turn-off delays of each of the transistors.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
130
Freescale Semiconductor
Output Control
For a typical motor drive inverter as shown in Figure 12-13, for a given top/bottom transistor pair, only one
of the transistors will be effective in controlling the output voltage at any given time depending on the
direction of the motor current for that pair. To achieve distortion correction, one of two different correction
factors must be added to the desired PWM value, depending on whether the top or bottom transistor is
controlling the output voltage. Therefore, the software is responsible for calculating both compensated
PWM values and placing them in an odd/even PWM register pair. By supplying the PWM module with
information regarding which transistor (top or bottom) is controlling the output voltage at any given time
(for instance, the current polarity for that motor phase), the PWM module selects either the odd or even
numbered PWM value register to be used by the PWM generator.
Current sensing or programmable software bits are then used to determine which PWM value to use. If
the current sensed at the motor for that PWM pair is positive (voltage on current pin ISx is low) or bit IPOLx
in PWM control register 2 is low, the top PWM value is used for the PWM pair. Likewise, if the current
sensed at the motor for that PWM pair is negative (voltage on current pin ISx is high) or bit IPOLx in PWM
control register 2 is high, the bottom PWM value is used. See Table 12-4.
NOTE
This text assumes the user will provide current sense circuitry which causes
the voltage at the corresponding input pin to be low for positive current and
high for negative current. See Figure 12-19 for current convention. In
addition, it assumes the top PWMs are PWMs 1, 3, and 5 while the bottom
PWMs are PWMs 2, 4, and 6.
Table 12-4. Current Sense Pins
Voltage
Current
on Current
Sense Pin
PWM Value
Register Used
PWMs
Affected
Sense Pin
or Bit
or IPOLx Bit
IS1 or IPOL1
IS1 or IPOL1
Logic 0
Logic 1
PWM value register 1
PWM value register 2
PWMs 1 and 2
PWMs 1 and 2
I+
I-
Figure 12-19. Current Convention
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
131
Pulse-Width Modulator for Motor Control (PWMMC)
To allow for correction based on different current sensing methods or correction controlled by software,
the ISENS1 and ISENS0 bits in PWM control register 1 are provided to choose the correction method.
These bits provide correction according to Table 12-5.
Table 12-5. Correction Methods
Current Correction Bits
Correction Method
ISENS1 and ISENS0
00
Bits IPOL1, IPOL2, and IPOL3 used for correction
01
Current sensing on pins IS1, IS2, and IS3 occurs during the
dead-time.
10
Current sensing on pins IS1, IS2, and IS3 occurs at the half
11
cycle in center-aligned mode and at the end of the cycle in
edge-aligned mode.
If correction is to be done in software or is not necessary, setting ISENS1:ISENS0 = 00 or = 01 causes
the correction to be based on bits IPOL1, IPOL2, and IPOL3 in PWM control register 2. If correction is not
required, the user can initialize the IPOLx bits and then only load one PWM value register per PWM pair.
To allow the user to use a current sense scheme based upon sensed phase voltage during dead-time,
setting ISENS1:ISENS0 = 10 causes the polarity of the Ix pin to be latched when both the top and bottom
PWMs are off (for example, during the dead-time). At the 0 percent and 100 percent duty cycle
boundaries, there is no dead-time so no new current value is sensed.
To accommodate other current sensing schemes, setting ISENS1:ISENS0 = 11 causes the polarity of the
current sense pin to be latched half-way into the PWM cycle in center-aligned mode and at the end of the
cycle in edge-aligned mode. Therefore, even at 0 percent and 100 percent duty cycle, the current is
sensed.
Distortion correction is only available in complementary mode. At the beginning of the PWM period, the
PWM uses this latched current value or polarity bit to decide whether the top PWM value or bottom PWM
value is used. Figure 12-20 shows an example of top/bottom correction for PWMs 1 and 2.
NOTE
The IPOLx bits and the values latched on the ISx pins are buffered so that
only one PWM register is used per PWM cycle. If the IPOLx bits or the
current sense values change during a PWM period, this new value will not
be used until the next PWM period. The ISENSx bits are NOT buffered;
therefore, changing the current sensing method could affect the present
PWM cycle.
When the PWM is first enabled by setting PWMEN, PWM value registers 1, 3, and 5 will be used if the
ISENSx bits are configured for current sensing correction. This is because no current will have previously
been sensed.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
132
Freescale Semiconductor
Output Control
PWM VALUE REG. 1 = 1
PWM VALUE REG. 2 = 2
IS1 NEGATIVE
PWM = 2
IS1 POSITIVE
PWM = 1
IS1 POSITIVE
PWM = 1
IS1 NEGATIVE
PWM = 2
PWM1
PWM2
Figure 12-20. Top/Bottom Correction for PWMs 1 and 2
12.5.4 Output Polarity
The output polarity of the PWMs is determined by two options: TOPNEG and BOTNEG. The top polarity
option, TOPNEG, controls the polarity of PWMs 1, 3, and 5. The bottom polarity option, BOTNEG,
controls the polarity of PWMs 2, 4, and 6. Positive polarity means that when the PWM is active, the PWM
output is high. Conversely, negative polarity means that when the PWM is active, PWM output is low. See
Figure 12-21.
NOTE
Both bits are found in the CONFIG register, which is a write-once register.
This reduces the chances of the software inadvertently changing the
polarity of the PWM signals and possibly damaging the motor drive
hardware.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
133
Pulse-Width Modulator for Motor Control (PWMMC)
CENTER-ALIGNED POSITIVE POLARITY
EDGE-ALIGNED POSITIVE POLARITY
UP-ONLY COUNTER
MODULUS = 4
UP/DOWN COUNTER
MODULUS = 4
PWM <= 0
PWM = 1
PWM = 2
PWM = 3
PWM >= 4
PWM <= 0
PWM = 1
PWM = 2
PWM = 3
PWM >= 4
CENTER-ALIGNED NEGATIVE POLARITY
EDGE-ALIGNED NEGATIVE POLARITY
UP-ONLY COUNTER
MODULUS = 4
UP/DOWN COUNTER
MODULUS = 4
PWM <= 0
PWM = 1
PWM = 2
PWM = 3
PWM >= 4
PWM <= 0
PWM = 1
PWM = 2
PWM = 3
PWM >= 4
Figure 12-21. PWM Polarity
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
134
Freescale Semiconductor
Output Control
12.5.5 PWM Output Port Control
Conditions may arise in which the PWM pins need to be individually controlled. This is made possible by
the PWM output control register (PWMOUT) shown in Figure 12-22.
Address:
$0025
Bit 7
0
6
OUTCTL
0
5
OUT6
0
4
OUT5
0
3
OUT4
0
2
OUT3
0
1
OUT2
0
Bit 0
OUT1
0
Read:
Write:
Reset:
0
= Unimplemented
Figure 12-22. PWM Output Control Register (PWMOUT)
If the OUTCTL bit is set, the PWM pins can be controlled by the OUTx bits. These bits behave according
to Table 12-6.
Table 12-6. OUTx Bits
OUTx Bit
Complementary Mode
1 — PWM1 is active.
Independent Mode
1 — PWM1 is active.
0 — PWM1 is inactive.
OUT1
0 — PWM1 is inactive.
1 — PWM2 is complement of PWM 1.
0 — PWM2 is inactive.
1 — PWM2 is active.
0 — PWM2 is inactive.
OUT2
OUT3
OUT4
OUT5
OUT6
1 — PWM3 is active.
0 — PWM3 is inactive.
1 — PWM3 is active.
0 — PWM3 is inactive.
1 — PWM4 is complement of PWM 3.
0 — PWM4 is inactive.
1 — PWM4 is active.
0 — PWM4 is inactive.
1 — PWM5 is active.
0 — PWM5 is inactive.
1 — PWM5 is active.
0 — PWM5 is inactive.
1 — PWM 6 is complement of PWM 5.
0 — PWM6 is inactive.
1 — PWM6 is active.
0 — PWM6 is inactive.
When OUTCTL is set, the polarity options TOPPOL and BOTPOL will still affect the outputs. In addition,
if complementary operation is in use, the PWM pairs will not be allowed to be active simultaneously, and
dead-time will still not be violated. When OUTCTL is set and complementary operation is in use, the odd
OUTx bits are inputs to the dead-time generators as shown in Figure 12-15. Dead-time is inserted
whenever the odd OUTx bit toggles as shown in Figure 12-23. Although dead-time is not inserted when
the even OUTx bits change, there will be no dead-time violation as shown in Figure 12-24.
Setting the OUTCTL bit does not disable the PWM generator and current sensing circuitry. They continue
to run, but are no longer controlling the output pins. In addition, OUTCTL will control the PWM pins even
when PWMEN = 0. When OUTCTL is cleared, the outputs of the PWM generator become the inputs to
the dead-time and output circuitry at the beginning of the next PWM cycle.
NOTE
To avoid an unexpected dead-time occurrence, it is recommended that the
OUTx bits be cleared prior to entering and prior to exiting individual PWM
output control mode.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
135
Pulse-Width Modulator for Motor Control (PWMMC)
UP/DOWN COUNTER
MODULUS = 4
DEAD-TIME = 2
PWM VALUE = 3
OUTCTL
OUT1
OUT2
PWM1
PWM2
PWM1/PWM2
DEAD-TIME
2
2
2
DEAD-TIME INSERTED AS PART OF DEAD-TIME INSERTED DUE
DEAD-TIME INSERTED
DUE TO CLEARING OF
OUT1 BIT
NORMAL PWM OPERATION AS
CONTROLLED BY CURRENT
SENSING AND PWM GENERATOR
TO SETTING OF OUT1 BIT
Figure 12-23. Dead-Time Insertion During OUTCTL = 1
UP/DOWN COUNTER
MODULUS = 4
DEAD-TIME = 2
PWM VALUE = 3
OUTCTL
OUT1
OUT2
PWM1
PWM2
2
2
2
2
PWM1/PWM2
DEAD-TIME
NO DEAD-TIME INSERTED
BECAUSE OUT1 IS NOT
TOGGLING
DEAD-TIME INSERTED BECAUSE
WHEN OUTCTL WAS SET, THE
STATE OF OUT1 WAS SUCH THAT
PWM1 WAS DIRECTED TO TOGGLE
DEAD-TIME INSERTED
BECAUSE OUT1 TOGGLES,
DIRECTING PWM1 TO
TOGGLE
Figure 12-24. Dead-Time Insertion During OUTCTL = 1
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
136
Freescale Semiconductor
Fault Protection
12.6 Fault Protection
Conditions may arise in the external drive circuitry which require that the PWM signals become inactive
immediately, such as an overcurrent fault condition. Furthermore, it may be desirable to selectively
disable PWM(s) solely with software.
One or more PWM pins can be disabled (forced to their inactive state) by applying a logic high to any of
the four external fault pins or by writing a logic high to either of the disable bits (DISX and DISY in PWM
control register 1). Figure 12-26 shows the structure of the PWM disabling scheme. While the PWM pins
are disabled, they are forced to their inactive state. The PWM generator continues to run — only the
output pins are disabled.
To allow for different motor configurations and the controlling of more than one motor, the PWM disabling
function is organized as two banks, bank X and bank Y. Bank information combines with information from
the disable mapping register to allow selective PWM disabling. Fault pin 1, fault pin 2, and PWM disable
bit X constitute the disabling function of bank X. Fault pin 3, fault pin 4, and PWM disable bit Y constitute
the disabling function of bank Y. Figure 12-25 and Figure 12-27 show the disable mapping write-once
register and the decoding scheme of the bank which selectively disables PWM(s). When all bits of the
disable mapping register are set, any disable condition will disable all PWMs.
A fault can also generate a CPU interrupt. Each fault pin has its own interrupt vector.
Address: $0037
Bit 7
Bit 7
1
6
Bit 6
1
5
Bit 5
1
4
Bit 4
1
3
Bit 3
1
2
Bit 2
1
1
Bit 1
1
Bit 0
Bit 0
1
Read:
Write:
Reset:
Figure 12-25. PWM Disable Mapping Write-Once Register (DISMAP)
12.6.1 Fault Condition Input Pins
A logic high level on a fault pin disables the respective PWM(s) determined by the bank and the disable
mapping register. Each fault pin incorporates a filter to assist in rejecting spurious faults. All of the external
fault pins are software-configurable to re-enable the PWMs either with the fault pin (automatic mode) or
with software (manual mode). Each fault pin has an associated FMODE bit to control the PWM
re-enabling method. Automatic mode is selected by setting the FMODEx bit in the fault control register.
Manual mode is selected when FMODEx is clear.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
137
Pulse-Width Modulator for Motor Control (PWMMC)
DISX
SOFTWARE X DISABLE
CYCLE START
S
R
Q
BANK X
DISABLE
FMODE2
FAULT PIN 2 DISABLE
AUTO
MODE
FPIN2
LOGIC HIGH FOR FAULT
S
R
Q
TWO
ONE
SAMPLE
FILTER
S
R
Q
FFLAG2
SHOT
FAULT
PIN2
MANUAL
MODE
CLEAR BY WRITING 1 TO FTACK4
INTERRUPT REQUEST
FINT2
The example is of fault pin 2 with DISX. Fault pin 4 with DISY is logically similar and affects BANK Y disable.
Note: In manual mode (FMODE = 0), faults 2 and 4 may be cleared only if a logic level low at the input of the fault
pin is present.
CYCLE START
FMODE1
FAULT PIN 1 DISABLE
AUTO
MODE
FPIN1
LOGIC HIGH FOR FAULT
TWO
S
R
Q
BANK X DISABLE
ONE
SHOT
FAULT
PIN1
SAMPLE
FILTER
S
R
Q
FFLAG1
MANUAL
MODE
CLEAR BY WRITING 1 TO FTACK1
INTERRUPT REQUEST
FINT1
The example is of fault pin 1. Fault pin 3 is logically similar and affects BANK Y disable.
Note: In manual mode (FMODE = 0), faults 1 and 3 may be cleared regardless of the logic level at the input of the fault pin.
Figure 12-26. PWM Disabling Scheme
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
138
Freescale Semiconductor
Fault Protection
BIT 7
DISABLE
PWM PIN 1
BIT 6
BIT 5
DISABLE
PWM PIN 2
DISABLE
PWM PIN 3
BIT 4
BIT 3
BANK X
DISABLE
BANK Y
DISABLE
DISABLE
PWM PIN 4
BIT 2
DISABLE
PWM PIN 5
BIT 1
BIT 0
DISABLE
PWM PIN 6
Figure 12-27. PWM Disabling Decode Scheme
12.6.1.1 Fault Pin Filter
Each fault pin incorporates a filter to assist in determining a genuine fault condition. After a fault pin has
been logic low for one CPU cycle, a rising edge (logic high) will be synchronously sampled once per CPU
cycle for two cycles. If both samples are detected logic high, the corresponding FPIN bit and FFLAG bit
will be set. The FPIN bit will remain set until the corresponding fault pin is logic low and synchronously
sampled once in the following CPU cycle.
12.6.1.2 Automatic Mode
In automatic mode, the PWM(s) are disabled immediately once a filtered fault condition is detected (logic
high). The PWM(s) remain disabled until the filtered fault condition is cleared (logic low) and a new PWM
cycle begins as shown in Figure 12-28. Clearing the corresponding FFLAGx event bit will not enable the
PWMs in automatic mode.
The filtered fault pin’s logic state is reflected in the respective FPINx bit. Any write to this bit is overwritten
by the pin state. The FFLAGx event bit is set with each rising edge of the respective fault pin after filtering
has been applied. To clear the FFLAGx bit, the user must write a 1 to the corresponding FTACKx bit.
f the FINTx bit is set, a fault condition resulting in setting the corresponding FFLAG bit will also latch a
CPU interrupt request. The interrupt request latch is not cleared until one of these actions occurs:
•
•
•
The FFLAGx bit is cleared by writing a 1 to the corresponding FTACKx bit.
The FINTx bit is cleared. This will not clear the FFLAGx bit.
A reset automatically clears all four interrupt latches.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
139
Pulse-Width Modulator for Motor Control (PWMMC)
FILTERED FAULT PIN
PWM(S) ENABLED
PWM(S) ENABLED
PWM(S) DISABLED (INACTIVE)
Figure 12-28. PWM Disabling in Automatic Mode
IIf prior to a vector fetch, the interrupt request latch is cleared by one of the actions listed, a CPU interrupt
will no longer be requested. A vector fetch does not alter the state of the PWMs, the FFLAGx event flag,
or FINTx.
NOTE
If the FFLAGx or FINTx bits are not cleared during the interrupt service
routine, the interrupt request latch will not be cleared.
12.6.1.3 Manual Mode
In manual mode, the PWM(s) are disabled immediately once a filtered fault condition is detected (logic
high). The PWM(s) remain disabled until software clears the corresponding FFLAGx event bit and a new
PWM cycle begins. In manual mode, the fault pins are grouped in pairs, each pair sharing common
functionality. A fault condition on pins 1 and 3 may be cleared, allowing the PWM(s) to enable at the start
of a PWM cycle regardless of the logic level at the fault pin. See Figure 12-29. A fault condition on pins 2
and 4 can only be cleared, allowing the PWM(s) to enable, if a logic low level at the fault pin is present at
the start of a PWM cycle. See Figure 12-30.
The function of the fault control and event bits is the same as in automatic mode except that the PWMs
are not re-enabled until the FFLAGx event bit is cleared by writing to the FTACKx bit and the filtered fault
condition is cleared (logic low).
FILTERED FAULT PIN 1 OR 3
PWM(S) ENABLED
PWM(S) ENABLED
PWM(S) DISABLED
FFLAGX CLEARED
Figure 12-29. PWM Disabling in Manual Mode (Example 1)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
140
Freescale Semiconductor
Fault Protection
FILTERED FAULT PIN 2 OR 4
PWM(S) ENABLED
PWM(S) ENABLED
PWM(S) DISABLED
FFLAGX CLEARED
Figure 12-30. PWM Disabling in Manual Mode (Example 2)
12.6.2 Software Output Disable
Setting PWM disable bit DISX or DISY in PWM control register 1 immediately disables the corresponding
PWM pins as determined by the bank and disable mapping register. The PWM pin(s) remain disabled
until the PWM disable bit is cleared and a new PWM cycle begins as shown in Figure 12-31. Setting a
PWM disable bit does not latch a CPU interrupt request, and there are no event flags associated with the
PWM disable bits.
12.6.3 Output Port Control
When operating the PWMs using the OUTx bits (OUTCTL = 1), fault protection applies as described in
this section. Due to the absence of periodic PWM cycles, fault conditions are cleared upon each CPU
cycle and the PWM outputs are re-enabled, provided all fault clearing conditions are satisfied.
DISABLE BIT
PWM(S) ENABLED
PWM(S) DISABLED
PWM(S) ENABLED
Figure 12-31. PWM Software Disable
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
141
Pulse-Width Modulator for Motor Control (PWMMC)
12.7 Initialization and the PWMEN Bit
For proper operation, all registers should be initialized and the LDOK bit should be set before enabling
the PWM via the PWMEN bit. When the PWMEN bit is first set, a reload will occur immediately, setting
the PWMF flag and generating an interrupt if PWMINT is set. In addition, in complementary mode, PWM
value registers 1, 3, and 5 will be used for the first PWM cycle if current sensing is selected.
NOTE
If the LDOK bit is not set when PWMEN is set after a RESET, the prescaler
and PWM values will be 0, but the modulus will be unknown. If the LDOK
bit is not set after the PWMEN bit has been cleared then set (without a
RESET), the modulus value that was last loaded will be used.
If the dead-time register (DEADTM) is changed after PWMEN or OUTCTL
is set, an improper dead-time insertion could occur. However, the
dead-time can never be shorter than the specified value.
Because of the equals-comparator architecture of this PWM, the modulus
= 0 case is considered illegal. Therefore, the modulus register is not reset,
and a modulus value of 0 will result in waveforms inconsistent with the other
modulus waveforms. See 12.9.2 PWM Counter Modulo Registers.
When PWMEN is set, the PWM pins change from high impedance to outputs. At this time, assuming no
fault condition is present, the PWM pins will drive according to the PWM values, polarity, and dead-time.
See the timing diagram in Figure 12-32.
CPU CLOCK
PWMEN
DRIVE ACCORDING TO PWM
VALUE, POLARITY, AND DEAD-TIME
HI-Z IF OUTCTL = 0
PWM PINS
HI-Z IF OUTCTL = 0
Figure 12-32. PWMEN and PWM Pins
When the PWMEN bit is cleared, this will occur:
•
•
•
PWM pins will be three-stated unless OUTCTL = 1.
PWM counter is cleared and will not be clocked.
Internally, the PWM generator will force its outputs to 0 to avoid glitches when the PWMEN is set
again.
When PWMEN is cleared, these features remain active:
•
•
•
All fault circuitry
Manual PWM pin control via the PWMOUT register
Dead-time insertion when PWM pins change via the PWMOUT register
NOTE
The PWMF flag and pending CPU interrupts are NOT cleared when
PWMEN = 0.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
142
Freescale Semiconductor
PWM Operation in Wait Mode
12.8 PWM Operation in Wait Mode
When the microcontroller is put in low-power wait mode via the WAIT instruction, all clocks to the PWM
module will continue to run. If an interrupt is issued from the PWM module (via a reload or a fault), the
microcontroller will exit wait mode.
Clearing the PWMEN bit before entering wait mode will reduce power consumption in wait mode because
the counter, prescaler divider, and LDFQ divider will no longer be clocked. In addition, power will be
reduced because the PWMs will no longer toggle.
12.9 Control Logic Block
This subsection provides a description of the control logic block.
12.9.1 PWM Counter Registers
The PWM counter registers (PCNTH and PCNTL) display the 12-bit up/down or up-only counter. When
the high byte of the counter is read, the lower byte is latched. PCNTL will hold this latched value until it is
read. See Figure 12-33 and Figure 12-34.
Address:
$0026
Bit 7
0
6
0
5
0
4
0
3
2
1
Bit 0
Bit 8
Read:
Write:
Reset:
Bit 11
Bit 10
Bit 9
0
0
0
0
0
0
0
0
= Unimplemented
Figure 12-33. PWM Counter Register High (PCNTH)
Address:
$0027
Bit 7
Bit 7
6
5
4
3
2
1
Bit 0
Bit 0
Read:
Write:
Reset:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
0
0
0
0
0
0
0
0
= Unimplemented
Figure 12-34. PWM Counter Register Low (PCNTL)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
143
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.2 PWM Counter Modulo Registers
The PWM counter modulus registers (PMODH and PMODL) hold a 12-bit unsigned number that
determines the maximum count for the up/down or up-only counter. In center-aligned mode, the PWM
period will be twice the modulus (assuming no prescaler). In edge-aligned mode, the PWM period will
equal the modulus. See Figure 12-35 and Figure 12-36.
Address:
$0028
Bit 7
0
6
0
5
0
4
0
3
Bit 11
X
2
Bit 10
X
1
Bit 9
X
Bit 0
Bit 8
X
Read:
Write:
Reset:
0
0
0
0
= Unimplemented
X = Indeterminate
Figure 12-35. PWM Counter Modulo Register High (PMODH)
Address:
$0029
Bit 7
Bit 7
X
6
Bit 6
X
5
Bit 5
X
4
Bit 4
X
3
Bit 3
X
2
Bit 2
X
1
Bit 1
X
Bit 0
Bit 0
X
Read:
Write:
Reset:
X = Indeterminate
Figure 12-36. PWM Counter Modulo Register Low (PMODL)
To avoid erroneous PWM periods, this value is buffered and will not be used by the PWM generator until
the LDOK bit has been set and the next PWM load cycle begins.
NOTE
When reading this register, the value read is the buffer (not necessarily the
value the PWM generator is currently using).
Because of the equals-comparator architecture of this PWM, the
modulus = 0 case is considered illegal. Therefore, the modulus register is
not reset, and a modulus value of 0 will result in waveforms inconsistent
with the other modulus waveforms. If a modulus of 0 is loaded, the counter
will continually count down from $FFF. This operation will not be tested or
guaranteed (the user should consider it illegal). However, the dead-time
constraints and fault conditions will still be guaranteed.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
144
Freescale Semiconductor
Control Logic Block
12.9.3 PWMx Value Registers
Each of the six PWMs has a 16-bit PWM value register.
Bit 7
6
5
Bit 13
0
4
Bit 12
0
3
Bit 11
0
2
Bit 10
0
1
Bit 9
0
Bit 0
Read:
Write:
Reset:
Bit 15
Bit 14
Bit 8
0
0
0
Bold
= Buffered
Figure 12-37. PWMx Value Registers High (PVALxH)
Bit 7
6
5
Bit 5
0
4
Bit 4
0
3
Bit 3
0
2
Bit 2
0
1
Bit 1
0
Bit 0
Bit 0
0
Read:
Write:
Reset:
Bit 7
Bit 6
0
0
Bold
= Buffered
Figure 12-38. PWMx Value Registers Low (PVALxL)
The 16-bit signed value stored in this register determines the duty cycle of the PWM. The duty cycle is
defined as: (PWM value/modulus) x 100.
Writing a number less than or equal to 0 causes the PWM to be off for the entire PWM period. Writing a
number greater than or equal to the 12-bit modulus causes the PWM to be on for the entire PWM period.
If the complementary mode is selected, the PWM pairs share PWM value registers.
To avoid erroneous PWM pulses, this value is buffered and will not be used by the PWM generator until
the LDOK bit has been set and the next PWM load cycle begins.
NOTE
When reading these registers, the value read is the buffer (not necessarily
the value the PWM generator is currently using).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
145
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.4 PWM Control Register 1
PWM control register 1 (PCTL1) controls PWM enabling/disabling, the loading of new modulus, prescaler,
PWM values, and the PWM correction method. In addition, this register contains the software disable bits
to force the PWM outputs to their inactive states (according to the disable mapping register).
Address:
$0020
Bit 7
6
DISY
0
5
PWMINT
0
4
PWMF
0
3
ISENS1
0
2
ISENS0
0
1
LDOK
0
Bit 0
PWMEN
0
Read:
Write:
Reset:
DISX
0
Figure 12-39. PWM Control Register 1 (PCTL1)
DISX — Software Disable Bit for Bank X Bit
This read/write bit allows the user to disable one or more PWM pins in bank X. The pins that are
disabled are determined by the disable mapping write-once register.
1 = Disable PWM pins in bank X.
0 = Re-enable PWM pins at beginning of next PWM cycle.
DISY — Software Disable Bit for Bank Y Bit
This read/write bit allows the user to disable one or more PWM pins in bank Y. The pins that are
disabled are determined by the disable mapping write-once register.
1 = Disable PWM pins in bank Y.
0 = Re-enable PWM pins at beginning of next PWM cycle.
PWMINT — PWM Interrupt Enable Bit
This read/write bit allows the user to enable and disable PWM CPU interrupts. If set, a CPU interrupt
will be pending when the PWMF flag is set.
1 = Enable PWM CPU interrupts.
0 = Disable PWM CPU interrupts.
NOTE
When PWMINT is cleared, pending CPU interrupts are inhibited.
PWMF — PWM Reload Flag
This read/write bit is set at the beginning of every reload cycle regardless of the state of the LDOK bit.
This bit is cleared by reading PWM control register 1 with the PWMF flag set, then writing a logic 0 to
PWMF. If another reload occurs before the clearing sequence is complete, then writing logic 0 to
PWMF has no effect.
1 = New reload cycle began.
0 = New reload cycle has not begun.
NOTE
When PWMF is cleared, pending PWM CPU interrupts are cleared (not
including fault interrupts).
ISENS1 and ISENS0 — Current Sense Correction Bits
These read/write bits select the top/bottom correction scheme as shown in Table 12-7.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
146
Freescale Semiconductor
Control Logic Block
Table 12-7. Correction Methods
Current Correction Bits
ISENS1 and ISENS0
Correction Method
00
01
Bits IPOL1, IPOL2, and IPOL3 are used for correction.
Current sensing on pins IS1, IS2, and IS3 occurs during the
dead-time.
10
11
Current sensing on pins IS1, IS2, and IS3 occurs at the half
cycle in center-aligned mode and at the end of the cycle in
edge-aligned mode.
1. The polarity of the ISx pin is latched when both the top and bottom PWMs are off. At
the 0% and 100% duty cycle boundaries, there is no dead-time, so no new current
value is sensed.
2. Current is sensed even with 0% and 100% duty cycle.
NOTE
The ISENSx bits are not buffered. Changing the current sensing method
can affect the present PWM cycle.
LDOK— Load OK Bit
This read/write bit loads the prescaler bits of the PMCTL2 register and the entire PMMODH/L and
PWMVALH/L registers into a set of buffers. The buffered prescaler divisor, PWM counter modulus
value, and PWM pulse will take effect at the next PWM load. Set LDOK by reading it when it is logic 0
and then writing a logic 1 to it. LDOK is automatically cleared after the new values are loaded or can
be manually cleared before a reload by writing a 0 to it. Reset clears LDOK.
1 = Load prescaler, modulus, and PWM values.
0 = Do not load new modulus, prescaler, and PWM values.
NOTE
The user should initialize the PWM registers and set the LDOK bit before
enabling the PWM.
A PWM CPU interrupt request can still be generated when LDOK is 0.
PWMEN — PWM Module Enable Bit
This read/write bit enables and disables the PWM generator and the PWM pins. When PWMEN is
clear, the PWM generator is disabled and the PWM pins are in the high-impedance state (unless
OUTCTL = 1).
When the PWMEN bit is set, the PWM generator and PWM pins are activated.
For more information, see 12.7 Initialization and the PWMEN Bit.
1 = PWM generator and PWM pins enabled
0 = PWM generator and PWM pins disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
147
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.5 PWM Control Register 2
PWM control register 2 (PCTL2) controls the PWM load frequency, the PWM correction method, and the
PWM counter prescaler. For ease of software and to avoid erroneous PWM periods, some of these
register bits are buffered. The PWM generator will not use the prescaler value until the LDOK bit has been
set, and a new PWM cycle is starting. The correction bits are used at the beginning of each PWM cycle
(if the ISENSx bits are configured for software correction). The load frequency bits are not used until the
current load cycle is complete.
See Figure 12-40.
NOTE
The user should initialize this register before enabling the PWM.
Address:
$0021
Bit 7
6
LDFQ0
0
5
0
4
3
2
IPOL3
0
1
PRSC1
0
Bit 0
PRSC0
0
Read:
Write:
Reset:
LDFQ1
IPOL1
IPOL2
0
0
0
0
= Unimplemented
Bold
= Buffered
Figure 12-40. PWM Control Register 2 (PCTL2)
LDFQ1 and LDFQ0 — PWM Load Frequency Bits
These buffered read/write bits select the PWM CPU load frequency according to Table 12-8.
NOTE
When reading these bits, the value read is the buffer value (not necessarily
the value the PWM generator is currently using).
The LDFQx bits take effect when the current load cycle is complete
regardless of the state of the load okay bit, LDOK.
Table 12-8. PWM Reload Frequency
Reload Frequency Bits
PWM Reload Frequency
LDFQ1 and LDFQ0
00
01
10
11
Every PWM cycle
Every 2 PWM cycles
Every 4 PWM cycles
Every 8 PWM cycles
NOTE
Reading the LPFQx bit reads the buffered values and not necessarily the
values currently in effect.
IPOL1 — Top/Bottom Correction Bit for PWM Pair 1 (PWMs 1 and 2)
This buffered read/write bit selects which PWM value register is used if top/bottom correction is to be
achieved without current sensing.
1 = Use PWM value register 2.
0 = Use PWM value register 1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
148
Freescale Semiconductor
Control Logic Block
NOTE
When reading this bit, the value read is the buffer value (not necessarily the
value the output control block is currently using).
The IPOLx bits take effect at the beginning of the next load cycle,
regardless of the state of the load okay bit, LDOK.
IPOL2 — Top/Bottom Correction Bit for PWM Pair 2 (PWMs 3 and 4)
This buffered read/write bit selects which PWM value register is used if top/bottom correction is to be
achieved without current sensing.
1 = Use PWM value register 4.
0 = Use PWM value register 3.
NOTE
When reading this bit, the value read is the buffer value (not necessarily the
value the output control block is currently using).
IPOL3 — Top/Bottom Correction Bit for PWM Pair 3 (PWMs 5 and 6)
This buffered read/write bit selects which PWM value register is used if top/bottom correction is to be
achieved without current sensing.
1 = Use PWM value register 6.
0 = Use PWM value register 5.
NOTE
When reading this bit, the value read is the buffer value (not necessarily the
value the output control block is currently using).
PRSC1 and PRSC0 — PWM Prescaler Bits
These buffered read/write bits allow the PWM clock frequency to be modified as shown in Table 12-9.
NOTE
When reading these bits, the value read is the buffer value (not necessarily
the value the PWM generator is currently using).
Table 12-9. PWM Prescaler
Prescaler Bits
PWM Clock Frequency
PRSC1 and PRSC0
fOP
00
01
10
11
fOP/2
fOP/4
fOP/8
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
149
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.6 Dead-Time Write-Once Register
The dead-time write-once register (DEADTM) holds an 8-bit value which specifies the number of CPU
clock cycles to use for the dead-time when complementary PWM mode is selected. After this register is
written for the first time, it cannot be rewritten unless a reset occurs. Dead-time is not affected by changes
to the prescaler value.
Address:
$0036
Bit 7
6
Bit 6
1
5
Bit 5
1
4
Bit 4
1
3
Bit 3
1
2
Bit 2
1
1
Bit 1
1
Bit 0
Bit 0
1
Read:
Write:
Reset:
Bit 7
1
Figure 12-41. Dead-Time Write-Once Register (DEADTM)
12.9.7 PWM Disable Mapping Write-Once Register
The PWM disable mapping write-once register (DISMAP) holds an 8-bit value which determines which
PWM pins will be disabled if an external fault or software disable occurs. For a further description of
disable mapping, see 12.6 Fault Protection. After this register is written for the first time, it cannot be
rewritten unless a reset occurs.
Address:
$0037
Bit 7
6
Bit 6
1
5
Bit 5
1
4
Bit 4
1
3
Bit 3
1
2
Bit 2
1
1
Bit 1
1
Bit 0
Bit 0
1
Read:
Write:
Reset:
Bit 7
1
Figure 12-42. PWM Disable Mapping Write-Once Register (DISMAP)
12.9.8 Fault Control Register
The fault control register (FCR) controls the fault-protection circuitry.
Address: $0022
Bit 7
FINT4
0
6
FMODE4
0
5
FINT3
0
4
FMODE3
0
3
FINT2
0
2
FMODE2
0
1
FINT1
0
Bit 0
FMODE1
0
Read:
Write:
Reset:
Figure 12-43. Fault Control Register (FCR)
FINT4 — Fault 4 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault pin 4 to be enabled. The fault
protection circuitry is independent of this bit and will always be active. If a fault is detected, the PWM
pins will still be disabled according to the disable mapping register.
1 = Fault pin 4 will cause CPU interrupts.
0 = Fault pin 4 will not cause CPU interrupts.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
150
Freescale Semiconductor
Control Logic Block
FMODE4 —Fault Mode Selection for Fault Pin 4 Bit (automatic versus manual mode)
This read/write bit allows the user to select between automatic and manual mode faults. For further
descriptions of each mode, see 12.6 Fault Protection.
1 = Automatic mode
0 = Manual mode
FINT3 — Fault 3 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault pin 3 to be enabled. The fault
protection circuitry is independent of this bit and will always be active. If a fault is detected, the PWM
pins will still be disabled according to the disable mapping register.
1 = Fault pin 3 will cause CPU interrupts.
0 = Fault pin 3 will not cause CPU interrupts.
FMODE3 —Fault Mode Selection for Fault Pin 3 Bit (automatic versus manual mode)
This read/write bit allows the user to select between automatic and manual mode faults. For further
descriptions of each mode, see 12.6 Fault Protection.
1 = Automatic mode
0 = Manual mode
FINT2 — Fault 2 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault pin 2 to be enabled. The fault
protection circuitry is independent of this bit and will always be active. If a fault is detected, the PWM
pins will still be disabled according to the disable mapping register.
1 = Fault pin 2 will cause CPU interrupts.
0 = Fault pin 2 will not cause CPU interrupts.
FMODE2 —Fault Mode Selection for Fault Pin 2 Bit
(automatic versus manual mode)
This read/write bit allows the user to select between automatic and manual mode faults. For further
descriptions of each mode, see 12.6 Fault Protection.
1 = Automatic mode
0 = Manual mode
FINT1 — Fault 1 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault pin 1 to be enabled. The fault
protection circuitry is independent of this bit and will always be active. If a fault is detected, the PWM
pins will still be disabled according to the disable mapping register.
1 = Fault pin 1 will cause CPU interrupts.
0 = Fault pin 1 will not cause CPU interrupts.
FMODE1 —Fault Mode Selection for Fault Pin 1 Bit (automatic versus manual mode)
This read/write bit allows the user to select between automatic and manual mode faults. For further
descriptions of each mode, see 12.6 Fault Protection.
1 = Automatic mode
0 = Manual mode
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
151
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.9 Fault Status Register
The fault status register (FSR) is a read-only register that indicates the current fault status.
Address:
$0023
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
FPIN4
FFLAG4
FPIN3
FFLAG3
FPIN2
FFLAG2
FPIN1
FFLAG1
U
0
U
0
U
0
U
0
= Unimplemented
U = Unaffected
Figure 12-44. Fault Status Register (FSR)
FPIN4 — State of Fault Pin 4 Bit
This read-only bit allows the user to read the current state of fault
pin 4.
1 = Fault pin 4 is at logic 1.
0 = Fault pin 4 is at logic 0.
FFLAG4 — Fault Event Flag 4
The FFLAG4 event bit is set within two CPU cycles after a rising edge on fault pin 4. To clear the
FFLAG4 bit, the user must write a 1 to the FTACK4 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 4.
0 = No new fault on fault pin 4
FPIN3 — State of Fault Pin 3 Bit
This read-only bit allows the user to read the current state of fault
pin 3.
1 = Fault pin 3 is at logic 1.
0 = Fault pin 3 is at logic 0.
FFLAG3 — Fault Event Flag 3
The FFLAG3 event bit is set within two CPU cycles after a rising edge on fault pin 3. To clear the
FFLAG3 bit, the user must write a 1 to the FTACK3 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 3.
0 = No new fault on fault pin 3.
FPIN2 — State of Fault Pin 2 Bit
This read-only bit allows the user to read the current state of fault pin 2.
1 = Fault pin 2 is at logic 1.
0 = Fault pin 2 is at logic 0.
FFLAG2 — Fault Event Flag 2
The FFLAG2 event bit is set within two CPU cycles after a rising edge on fault pin 2. To clear the
FFLAG2 bit, the user must write a 1 to the FTACK2 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 2.
0 = No new fault on fault pin 2
FPIN1 — State of Fault Pin 1 Bit
This read-only bit allows the user to read the current state of fault pin 1.
1 = Fault pin 1 is at logic 1.
0 = Fault pin 1 is at logic 0.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
152
Freescale Semiconductor
Control Logic Block
FFLAG1 — Fault Event Flag 1
The FFLAG1 event bit is set within two CPU cycles after a rising edge on fault pin 1. To clear the
FFLAG1 bit, the user must write a 1 to the FTACK1 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 1.
0 = No new fault on fault pin 1.
12.9.10 Fault Acknowledge Register
The fault acknowledge register (FTACK) is used to acknowledge and clear the FFLAGs. In addition, it is
used to monitor the current sensing bits to test proper operation.
Address: $0024
Bit 7
0
6
5
4
DT5
3
2
DT3
1
Bit 0
DT1
Read:
Write:
Reset:
0
FTACK4
0
DT6
DT4
DT2
FTACK3
0
FTACK2
0
FTACK1
0
0
0
0
0
= Unimplemented
Figure 12-45. Fault Acknowledge Register (FTACK)
FTACK4 — Fault Acknowledge 4 Bit
The FTACK4 bit is used to acknowledge and clear FFLAG4. This bit will always read 0. Writing a 1 to
this bit will clear FFLAG4. Writing a 0 will have no effect.
FTACK3 — Fault Acknowledge 3 Bit
The FTACK3 bit is used to acknowledge and clear FFLAG3. This bit will always read 0. Writing a 1 to
this bit will clear FFLAG3. Writing a 0 will have no effect.
FTACK2 — Fault Acknowledge 2 Bit
The FTACK2 bit is used to acknowledge and clear FFLAG2. This bit will always read 0. Writing a 1 to
this bit will clear FFLAG2. Writing a 0 will have no effect.
FTACK1 — Fault Acknowledge 1 Bit
The FTACK1 bit is used to acknowledge and clear FFLAG1. This bit will always read 0. Writing a 1 to
this bit will clear FFLAG1. Writing a 0 will have no effect.
DT6 — Dead-Time 6 Bit
Current sensing pin IS3 is monitored immediately before dead-time ends due to the assertion of
PWM6.
DT5 — Dead-Time 5 Bit
Current sensing pin IS3 is monitored immediately before dead-time ends due to the assertion of
PWM5.
DT4 — Dead-Time 4 Bit
Current sensing pin IS2 is monitored immediately before dead-time ends due to the assertion of
PWM4.
DT3 — Dead-Time 3 Bit
Current sensing pin IS2 is monitored immediately before dead-time ends due to the assertion of
PWM3.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
153
Pulse-Width Modulator for Motor Control (PWMMC)
DT2 — Dead-Time 2 Bit
Current sensing pin IS1 is monitored immediately before dead-time ends due to the assertion of
PWM2.
DT1 — Dead-Time 1 Bit
Current sensing pin IS1 is monitored immediately before dead-time ends due to the assertion of
PWM1.
12.9.11 PWM Output Control Register
The PWM output control register (PWMOUT) is used to manually control the PWM pins.
Address: $0025
Bit 7
0
6
OUTCTL
0
5
OUT6
0
4
OUT5
0
3
OUT4
0
2
OUT3
0
1
OUT2
0
Bit 0
OUT1
0
Read:
Write:
Reset:
0
= Unimplemented
Figure 12-46. PWM Output Control Register (PWMOUT)
OUTCTL— Output Control Enable Bit
This read/write bit allows the user to manually control the PWM pins. When set, the PWM generator is
no longer the input to the dead-time and output circuitry. The OUTx bits determine the state of the
PWM pins. Setting the OUTCTL bit does not disable the PWM generator. The generator continues to
run, but is no longer the input to the PWM dead-time and output circuitry. When OUTCTL is cleared,
the outputs of the PWM generator immediately become the inputs to the dead-time and output circuitry.
1 = PWM outputs controlled manually
0 = PWM outputs determined by PWM generator
OUT6–OUT1— PWM Pin Output Control Bits
These read/write bits control the PWM pins according to Table 12-10.
Table 12-10. OUTx Bits
OUTx Bit
Complementary Mode
1 — PWM1 is active.
0 — PWM1 is inactive.
Independent Mode
1 — PWM1 is active.
0 — PWM1 is inactive.
OUT1
1 — PWM2 is complement of PWM 1.
0 — PWM2 is inactive.
1 — PWM2 is active.
0 — PWM2 is inactive.
OUT2
OUT3
OUT4
OUT5
OUT6
1 — PWM3 is active.
0 — PWM3 is inactive.
1 — PWM3 is active.
0 — PWM3 is inactive.
1 — PWM4 is complement of PWM 3.
0 — PWM4 is inactive.
1 — PWM4 is active.
0 — PWM4 is inactive.
1 — PWM5 is active.
0 — PWM5 is inactive.
1 — PWM5 is active.
0 — PWM5 is inactive.
1 — PWM 6 is complement of PWM 5.
0 — PWM6 is inactive.
1 — PWM6 is active.
0 — PWM6 is inactive.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
154
Freescale Semiconductor
PWM Glossary
12.10 PWM Glossary
CPU cycle — One internal bus cycle (1/fOP
)
PWM clock cycle (or period) — One tick of the PWM counter (1/fOP with no prescaler). See
Figure 12-47.
PWM cycle (or period)
•
Center-aligned mode: The time it takes the PWM counter to count up and count down (modulus *
2/fOP assuming no prescaler). See Figure 12-47.
•
Edge-aligned mode: The time it takes the PWM counter to count up (modulus/fOP). See Figure
12-47.
Center-Aligned Mode
PWM CLOCK CYCLE
PWM CYCLE (OR PERIOD)
Edge-Aligned Mode
PWM
CLOCK
CYCLE
PWM CYCLE (OR PERIOD)
Figure 12-47. PWM Clock Cycle and PWM Cycle Definitions
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
155
Pulse-Width Modulator for Motor Control (PWMMC)
PWM Load Frequency — Frequency at which new PWM parameters get loaded into the PWM. See
Figure 12-48.
LDFQ1:LDFQ0 = 01 — Reload Every Two Cycles
PWM LOAD CYCLE
(1/PWM LOAD FREQUENCY)
RELOAD NEW
MODULUS,
RELOAD NEW
MODULUS,
PRESCALER, &
PWM VALUES IF
LDOK = 1
PRESCALER, &
PWM VALUES IF
LDOK = 1
Figure 12-48. PWM Load Cycle/Frequency Definition
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
156
Freescale Semiconductor
Chapter 13
Serial Communications Interface Module (SCI)
13.1 Introduction
This section describes the serial communications interface module (SCI, version D), which allows
high-speed asynchronous communications with peripheral devices and other microcontroller units
(MCUs).
13.2 Features
Features of the SCI module include:
•
•
•
•
•
•
•
•
•
Full-duplex operation
Standard mark/space non-return-to-zero (NRZ) format
32 programmable baud rates
Programmable 8-bit or 9-bit character length
Separately enabled transmitter and receiver
Separate receiver and transmitter CPU interrupt requests
Separate receiver and transmitter
Programmable transmitter output polarity
Two receiver wakeup methods:
–
–
Idle line wakeup
Address mark wakeup
•
Interrupt-driven operation with eight interrupt flags:
–
–
–
–
–
–
–
–
Transmitter empty
Transmission complete
Receiver full
Idle receiver input
Receiver overrun
Noise error
Framing error
Parity error
•
•
•
Receiver framing error detection
Hardware parity checking
1/16 bit-time noise detection
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
157
INTERNAL BUS
M68HC08 CPU
PTA7–PTA0
CPU
REGISTERS
ARITHMETIC/LOGIC
UNIT
LOW-VOLTAGE INHIBIT
MODULE
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
COMPUTER OPERATING PROPERLY
MODULE
CONTROL AND STATUS REGISTERS — 112 BYTES
USER FLASH — 32,256 BYTES
TIMER INTERFACE
MODULE A
USER RAM — 768 BYTES
PTC6
PTC5
TIMER INTERFACE
MODULE B
PTC4
MONITOR ROM — 240 BYTES
PTC3
PTC2
SERIAL COMMUNICATIONS INTERFACE
MODULE
PTC1/ATD9(1)
PTC0/ATD8
USER FLASH VECTOR SPACE — 46 BYTES
OSC1
PTD6/IS3
CLOCK GENERATOR
MODULE
OSC2
SERIAL PERIPHERAL INTERFACE
MODULE(2)
PTD5/IS2
CGMXFC
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
POWER-ON RESET
MODULE
SYSTEM INTEGRATION
MODULE
RST
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
IRQ
MODULE
IRQ
SINGLE BREAK
MODULE
VDDA
(3)
VSSA
ANALOG-TO-DIGITAL CONVERTER
MODULE
(3)
VREFL
VREFH
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PWMGND
PULSE-WIDTH MODULATOR
MODULE
PWM6–PWM1
PTF1/SS(1)
PTF0/SPSCK(1)
VSS
VDD
POWER
VDDAD
VSSAD
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 13-1. Block Diagram Highlighting SCI Block and Pins
Functional Description
13.3 Functional Description
Figure 13-2 shows the structure of the SCI module. The SCI allows full-duplex, asynchronous, NRZ serial
communication among the MCU and remote devices, including other MCUs. The transmitter and receiver
of the SCI operate independently, although they use the same baud rate generator. During normal
operation, the CPU monitors the status of the SCI, writes the data to be transmitted, and processes
received data.
INTERNAL BUS
SCI DATA
REGISTER
SCI DATA
REGISTER
RECEIVE
SHIFT REGISTER
TRANSMIT
SHIFT REGISTER
PTF4/RxD
PTF5/TxD
TXINV
SCTIE
R8
T8
TCIE
SCRIE
ILIE
TE
SCTE
TC
RE
RWU
SBK
SCRF
IDLE
OR
NF
FE
PE
ORIE
NEIE
FEIE
PEIE
LOOPS
ENSCI
LOOPS
RECEIVE
CONTROL
FLAG
CONTROL
TRANSMIT
CONTROL
WAKEUP
CONTROL
M
BKF
RPF
ENSCI
WAKE
ILTY
PEN
PTY
PRE- BAUD RATE
SCALER GENERATOR
fOP
÷ 4
DATA SELECTION
CONTROL
÷ 16
Figure 13-2. SCI Module Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
159
Serial Communications Interface Module (SCI)
Addr.
Register Name
Bit 7
LOOPS
0
6
ENSCI
0
5
4
M
3
WAKE
0
2
ILTY
0
1
PEN
0
Bit 0
PTY
0
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
SCI Control Register 1
(SCC1)
See page 169.
TXINV
0
$0038
0
SCI Control Register 2
(SCC2)
See page 171.
SCTIE
TCIE
0
SCRIE
ILIE
TE
RE
0
RWU
0
SBK
0
$0039
$003A
$003B
$003C
$003D
$003E
0
R8
R
0
0
0
0
0
SCI Control Register 3
(SCC3)
See page 173.
T8
ORIE
NEIE
FEIE
PEIE
R
R
U
U
TC
R
0
0
0
OR
R
0
NF
R
0
FE
R
0
PE
R
Read: SCTE
SCRF
R
IDLE
R
SCI Status Register 1
(SCS1)
See page 174.
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
R
1
1
0
0
0
0
0
0
0
0
0
0
0
0
BKF
R
RPF
R
SCI Status Register 2
(SCS2)
See page 176.
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R7
T7
R6
T6
R5
T5
R4
T4
R3
T3
R2
T2
R1
T1
R0
T0
SCI Data Register
(SCDR)
See page 177.
Unaffected by reset
0
R
0
0
0
SCI Baud Rate Register
(SCBR)
See page 177.
SCP1
0
SCP0
R
SCR2
0
SCR1
0
SCR0
0
R
0
0
0
= Reserved
U = Unaffected
R
Figure 13-3. SCI I/O Register Summary
13.3.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 13-4.
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
POSSIBLE
PARITY
BIT
NEXT
START
BIT
START
BIT
STOP
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
9-BIT DATA FORMAT
BIT M IN SCC1 SET
POSSIBLE
PARITY
BIT
NEXT
START
BIT
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
STOP
BIT
Figure 13-4. SCI Data Formats
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
160
Freescale Semiconductor
Functional Description
13.3.2 Transmitter
Figure 13-5 shows the structure of the SCI transmitter.
INTERNAL BUS
PRE- BAUD
SCALER DIVIDER
÷ 16
÷ 4
SCI DATA REGISTER
SCP1
SCP0
SCR2
SCR1
SCR0
11-BIT
TRANSMIT
SHIFT REGISTER
H
8
7
6
5
4
3
2
1
0
L
PTF5/TxD
TXINV
M
PEN
PTY
PARITY
GENERATION
T8
TRANSMITTER CPU
INTERRUPT REQUEST
TRANSMITTER
CONTROL LOGIC
SCTE
SBK
SCTE
LOOPS
ENSCI
TE
SCTIE
SCTIE
TC
TC
TCIE
TCIE
Figure 13-5. SCI Transmitter
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
161
Serial Communications Interface Module (SCI)
13.3.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1
(SCC1) determines character length. When transmitting 9-bit data, bit T8 in SCI control register 3 (SCC3)
is the ninth bit (bit 8).
13.3.2.2 Character Transmission
During an SCI transmission, the transmit shift register shifts a character out to the PTF5/TxD pin. The SCI
data register (SCDR) is the write-only buffer between the internal data bus and the transmit shift register.
To initiate an SCI transmission:
1. Enable the SCI by writing a 1 to the enable SCI bit (ENSCI) in SCI control register 1 (SCC1).
2. Enable the transmitter by writing a 1 to the transmitter enable bit (TE) in SCI control register 2
(SCC2).
3. Clear the SCI transmitter empty bit by first reading SCI status register 1 (SCS1) and then writing
to the SCDR.
4. Repeat step 3 for each subsequent transmission.
At the start of a transmission, transmitter control logic automatically loads the transmit shift register with
a preamble of 1s. After the preamble shifts out, control logic transfers the SCDR data into the transmit
shift register. A 0 start bit automatically goes into the least significant bit (LSB) position of the transmit shift
register. A 1 stop bit goes into the most significant bit (MSB) position.
The SCI transmitter empty bit, SCTE, in SCS1 becomes set when the SCDR transfers a byte to the
transmit shift register. The SCTE bit indicates that the SCDR can accept new data from the internal data
bus. If the SCI transmit interrupt enable bit, SCTIE, in SCC2 is also set, the SCTE bit generates a
transmitter CPU interrupt request.
When the transmit shift register is not transmitting a character, the PTF5/TxD pin goes to the idle
condition, logic 1. If at any time software clears the ENSCI bit in SCI control register 1 (SCC1), the
transmitter and receiver relinquish control of the port E pins.
13.3.2.3 Break Characters
Writing a 1 to the send break bit, SBK, in SCC2 loads the transmit shift register with a break character. A
break character contains all 0s and has no start, stop, or parity bit. Break character length depends on
the M bit in SCC1. As long as SBK is at 1, transmitter logic continuously loads break characters into the
transmit shift register. After software clears the SBK bit, the shift register finishes transmitting the last
break character and then transmits at least one logic 1. The automatic logic 1 at the end of a break
character guarantees the recognition of the start bit of the next character.
The SCI recognizes a break character when a start bit is followed by eight or nine logic 0 data bits and a
logic 0 where the stop bit should be.
Receiving a break character has these effects on SCI registers:
•
•
•
•
•
•
Sets the framing error bit (FE) in SCS1
Sets the SCI receiver full bit (SCRF) in SCS1
Clears the SCI data register (SCDR)
Clears the R8 bit in SCC3
Sets the break flag bit (BKF) in SCS2
May set the overrun (OR), noise flag (NF), parity error (PE), or reception-in-progress flag (RPF) bits
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
162
Freescale Semiconductor
Functional Description
13.3.2.4 Idle Characters
An idle character contains all 1s and has no start, stop, or parity bit. Idle character length depends on the
M bit in SCC1. The preamble is a synchronizing idle character that begins every transmission.
If the TE bit is cleared during a transmission, the PTF5/TxD pin becomes idle after completion of the
transmission in progress. Clearing and then setting the TE bit during a transmission queues an idle
character to be sent after the character currently being transmitted.
NOTE
When a break sequence is followed immediately by an idle character, this
SCI design exhibits a condition in which the break character length is
reduced by one half bit time. In this instance, the break sequence will
consist of a valid start bit, eight or nine data bits (as defined by the M bit in
SCC1) of logic 0 and one half data bit length of logic 0 in the stop bit position
followed immediately by the idle character. To ensure a break character of
the proper length is transmitted, always queue up a byte of data to be
transmitted while the final break sequence is in progress.
When queueing an idle character, return the TE bit to 1 before the stop bit
of the current character shifts out to the PTF5/TxD pin. Setting TE after the
stop bit appears on PTF5/TxD causes data previously written to the SCDR
to be lost.
A good time to toggle the TE bit is when the SCTE bit becomes set and just
before writing the next byte to the SCDR.
13.3.2.5 Inversion of Transmitted Output
The transmit inversion bit (TXINV) in SCI control register 1 (SCC1) reverses the polarity of transmitted
data. All transmitted values, including idle, break, start, and stop bits, are inverted when TXINV is at 1.
See 13.7.1 SCI Control Register 1.
13.3.2.6 Transmitter Interrupts
These conditions can generate CPU interrupt requests from the SCI transmitter:
•
SCI transmitter empty (SCTE) — The SCTE bit in SCS1 indicates that the SCDR has transferred
a character to the transmit shift register. SCTE can generate a transmitter CPU interrupt request.
Setting the SCI transmit interrupt enable bit, SCTIE, in SCC2 enables the SCTE bit to generate
transmitter CPU interrupt requests.
•
Transmission complete (TC) — The TC bit in SCS1 indicates that the transmit shift register and the
SCDR are empty and that no break or idle character has been generated. The transmission
complete interrupt enable bit, TCIE, in SCC2 enables the TC bit to generate transmitter CPU
interrupt requests.
13.3.3 Receiver
Figure 13-6 shows the structure of the SCI receiver.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
163
Serial Communications Interface Module (SCI)
INTERNAL BUS
SCR2
SCR1
SCR0
SCP1
SCP0
SCI DATA REGISTER
PRE- BAUD
SCALER DIVIDER
÷ 4
÷ 16
11-BIT
RECEIVE SHIFT REGISTER
fOP
DATA
RECOVERY
H
8
7
6
5
4
3
2
1
0
L
PTF4/RxD
ALL 0s
BKF
RPF
M
RWU
SCRF
IDLE
WAKE
ILTY
WAKEUP
LOGIC
PEN
PTY
R8
PARITY
CHECKING
IDLE
ILIE
ILIE
SCRF
SCRIE
SCRIE
OR
OR
ORIE
ORIE
NF
NF
NEIE
NEIE
FE
FE
FEIE
FEIE
PE
PE
PEIE
PEIE
Figure 13-6. SCI Receiver Block Diagram
13.3.3.1 Character Length
The receiver can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1
(SCC1) determines character length. When receiving 9-bit data, bit R8 in SCI control register 2 (SCC2)
is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth bit (bit 7).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
164
Freescale Semiconductor
Functional Description
13.3.3.2 Character Reception
During an SCI reception, the receive shift register shifts characters in from the PTF4/RxD pin. The SCI
data register (SCDR) is the read-only buffer between the internal data bus and the receive shift register.
After a complete character shifts into the receive shift register, the data portion of the character transfers
to the SCDR. The SCI receiver full bit, SCRF, in SCI status register 1 (SCS1) becomes set, indicating that
the received byte can be read. If the SCI receive interrupt enable bit, SCRIE, in SCC2 is also set, the
SCRF bit generates a receiver CPU interrupt request.
13.3.3.3 Data Sampling
The receiver samples the PTF4/RxD pin at the RT clock rate. The RT clock is an internal signal with a
frequency 16 times the baud rate. To adjust for baud rate mismatch, the RT clock is resynchronized at
these times (see Figure 13-7):
•
•
After every start bit
After the receiver detects a data bit change from 1 to 0 (after the majority of data bit samples at
RT8, RT9, and RT10 return a valid 1 and the majority of the next RT8, RT9, and RT10 samples
return a valid 0)
START BIT
LSB
PTF4/RxD
SAMPLES
START BIT
QUALIFICATION
START BIT
VERIFICATION
DATA
SAMPLING
RT
CLOCK
RT CLOCK
STATE
RT CLOCK
RESET
Figure 13-7. Receiver Data Sampling
To locate the start bit, data recovery logic does an asynchronous search for a 0 preceded by three 1s.
When the falling edge of a possible start bit occurs, the RT clock begins to count to 16.
To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7.
Table 13-1 summarizes the results of the start bit verification samples.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
165
Serial Communications Interface Module (SCI)
Table 13-1. Start Bit Verification
RT3, RT5, and RT7
Samples
Start Bit
Verification
Noise Flag
000
001
010
011
100
101
110
111
Yes
Yes
Yes
No
0
1
1
0
1
0
0
0
Yes
No
No
No
If start bit verification is not successful, the RT clock is reset and a new search for a start bit begins.
To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and
RT10. Table 13-2 summarizes the results of the data bit samples.
Table 13-2. Data Bit Recovery
RT8, RT9, and RT10
Samples
Data Bit
Determination
Noise Flag
000
001
010
011
100
101
110
111
0
0
0
1
0
1
1
1
0
1
1
1
1
1
1
0
NOTE
The RT8, RT9, and RT10 samples do not affect start bit verification. If any
or all of the RT8, RT9, and RT10 start bit samples are 1s following a
successful start bit verification, the noise flag (NF) is set and the receiver
assumes that the bit is a start bit.
To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 13-3
summarizes the results of the stop bit samples.
Table 13-3. Stop Bit Recovery
RT8, RT9, and RT10
Samples
Framing
Error Flag
Noise Flag
000
001
010
011
100
101
110
111
1
1
1
0
1
0
0
0
0
1
1
1
1
1
1
0
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
166
Freescale Semiconductor
Functional Description
13.3.3.4 Framing Errors
If the data recovery logic does not detect a 1 where the stop bit should be in an incoming character, it sets
the framing error bit, FE, in SCS1. The FE flag is set at the same time that the SCRF bit is set. A break
character that has no stop bit also sets the FE bit.
13.3.3.5 Receiver Wakeup
So that the MCU can ignore transmissions intended only for other receivers in multiple-receiver systems,
the receiver can be put into a standby state. Setting the receiver wakeup bit, RWU, in SCC2 puts the
receiver into a standby state during which receiver interrupts are disabled.
Depending on the state of the WAKE bit in SCC1, either of two conditions on the PTF4/RxD pin can bring
the receiver out of the standby state:
•
Address mark — An address mark is a 1 in the most significant bit position of a received character.
When the WAKE bit is set, an address mark wakes the receiver from the standby state by clearing
the RWU bit. The address mark also sets the SCI receiver full bit, SCRF. Software can then
compare the character containing the address mark to the user-defined address of the receiver. If
they are the same, the receiver remains awake and processes the characters that follow. If they
are not the same, software can set the RWU bit and put the receiver back into the standby state.
•
Idle input line condition — When the WAKE bit is clear, an idle character on the PTF4/RxD pin
wakes the receiver from the standby state by clearing the RWU bit. The idle character that wakes
the receiver does not set the receiver idle bit, IDLE, or the SCI receiver full bit, SCRF. The idle line
type bit, ILTY, determines whether the receiver begins counting 1s as idle character bits after the
start bit or after the stop bit.
NOTE
Clearing the WAKE bit after the PTF4/RxD pin has been idle can cause the
receiver to wake up immediately.
13.3.3.6 Receiver Interrupts
These sources can generate CPU interrupt requests from the SCI receiver:
•
SCI receiver full (SCRF) — The SCRF bit in SCS1 indicates that the receive shift register has
transferred a character to the SCDR. SCRF can generate a receiver CPU interrupt request. Setting
the SCI receive interrupt enable bit, SCRIE, in SCC2 enables the SCRF bit to generate receiver
CPU interrupts.
•
Idle input (IDLE) — The IDLE bit in SCS1 indicates that 10 or 11 consecutive 1s shifted in from the
PTF4/RxD pin. The idle line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to generate
CPU interrupt requests.
13.3.3.7 Error Interrupts
These receiver error flags in SCS1 can generate CPU interrupt requests:
•
Receiver overrun (OR) — The OR bit indicates that the receive shift register shifted in a new
character before the previous character was read from the SCDR. The previous character remains
in the SCDR, and the new character is lost. The overrun interrupt enable bit, ORIE, in SCC3
enables OR to generate SCI error CPU interrupt requests.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
167
Serial Communications Interface Module (SCI)
•
•
•
Noise flag (NF) — The NF bit is set when the SCI detects noise on incoming data or break
characters, including start, data, and stop bits. The noise error interrupt enable bit, NEIE, in SCC3
enables NF to generate SCI error CPU interrupt requests.
Framing error (FE) — The FE bit in SCS1 is set when a 0 occurs where the receiver expects a stop
bit. The framing error interrupt enable bit, FEIE, in SCC3 enables FE to generate SCI error CPU
interrupt requests.
Parity error (PE) — The PE bit in SCS1 is set when the SCI detects a parity error in incoming data.
The parity error interrupt enable bit, PEIE, in SCC3 enables PE to generate SCI error CPU interrupt
requests.
13.4 Wait Mode
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
The SCI module remains active after the execution of a WAIT instruction. In wait mode the SCI module
registers are not accessible by the CPU. Any enabled CPU interrupt request from the SCI module can
bring the MCU out of wait mode.
If SCI module functions are not required during wait mode, reduce power consumption by disabling the
module before executing the WAIT instruction.
13.5 SCI During Break Module Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during
interrupts generated by the break module. The BCFE bit in the SIM break flag control register (SBFCR)
enables software to clear status bits during the break state.
To allow software to clear status bits during a break interrupt, write a 1 to the BCFE bit. If a status bit is
cleared during the break state, it remains cleared when the MCU exits the break state.
To protect status bits during the break state, write a 0 to the BCFE bit. With BCFE at 0 (its default state),
software can read and write I/O registers during the break state without affecting status bits. Some status
bits have a 2-step read/write clearing procedure. If software does the first step on such a bit before the
break, the bit cannot change during the break state as long as BCFE is at 0. After the break, doing the
second step clears the status bit.
13.6 I/O Signals
Port F shares two of its pins with the SCI module. The two SCI input/output (I/O) pins are:
•
•
PTF5/TxD — Transmit data
PTF4/RxD — Receive data
13.6.1 PTF5/TxD (Transmit Data)
The PTF5/TxD pin is the serial data output from the SCI transmitter. The SCI shares the PTF5/TxD pin
with port F. When the SCI is enabled, the PTF5/TxD pin is an output regardless of the state of the DDRF5
bit in data direction register F (DDRF).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
168
Freescale Semiconductor
I/O Registers
13.6.2 PTF4/RxD (Receive Data)
The PTF4/RxD pin is the serial data input to the SCI receiver. The SCI shares the PTF4/RxD pin with
port F. When the SCI is enabled, the PTF4/RxD pin is an input regardless of the state of the DDRF4 bit
in data direction register F (DDRF).
13.7 I/O Registers
These I/O registers control and monitor SCI operation:
•
•
•
•
•
•
•
SCI control register 1 (SCC1)
SCI control register 2 (SCC2)
SCI control register 3 (SCC3)
SCI status register 1 (SCS1)
SCI status register 2 (SCS2)
SCI data register (SCDR)
SCI baud rate register (SCBR)
13.7.1 SCI Control Register 1
SCI control register 1 (SCC1):
•
•
•
•
•
•
•
•
Enables loop-mode operation
Enables the SCI
Controls output polarity
Controls character length
Controls SCI wakeup method
Controls idle character detection
Enables parity function
Controls parity type
Address: $0038
Bit 7
LOOPS
0
6
ENSCI
0
5
TXINV
0
4
M
0
3
WAKE
0
2
ILTY
0
1
PEN
0
Bit 0
PTY
0
Read:
Write:
Reset:
Figure 13-8. SCI Control Register 1 (SCC1)
LOOPS — Loop Mode Select Bit
This read/write bit enables loop mode operation. In loop mode the PTF4/RxD pin is disconnected from
the SCI, and the transmitter output goes into the receiver input. Both the transmitter and the receiver
must be enabled to use loop mode. Reset clears the
LOOPS bit.
1 = Loop mode enabled
0 = Normal operation enabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
169
Serial Communications Interface Module (SCI)
ENSCI — Enable SCI Bit
This read/write bit enables the SCI and the SCI baud rate generator. Clearing ENSCI sets the SCTE
and TC bits in SCI status register 1 and disables transmitter interrupts. Reset clears the ENSCI bit.
1 = SCI enabled
0 = SCI disabled
TXINV — Transmit Inversion Bit
This read/write bit reverses the polarity of transmitted data. Reset clears the TXINV bit.
1 = Transmitter output inverted
0 = Transmitter output not inverted
NOTE
Setting the TXINV bit inverts all transmitted values, including idle, break,
start, and stop bits.
M — Mode (Character Length) Bit
This read/write bit determines whether SCI characters are eight or nine bits long. See Table 13-4. The
ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. Reset clears the
M bit.
1 = 9-bit SCI characters
0 = 8-bit SCI characters
WAKE — Wakeup Condition Bit
This read/write bit determines which condition wakes up the SCI: a 1 (address mark) in the most
significant bit (MSB) position of a received character or an idle condition on the PTF4/RxD pin. Reset
clears the WAKE bit.
1 = Address mark wakeup
0 = Idle line wakeup
ILTY — Idle Line Type Bit
This read/write bit determines when the SCI starts counting 1s as idle character bits. The counting
begins either after the start bit or after the stop bit. If the count begins after the start bit, then a string
of 1s preceding the stop bit may cause false recognition of an idle character. Beginning the count after
the stop bit avoids false idle character recognition, but requires properly synchronized transmissions.
Reset clears the ILTY bit.
1 = Idle character bit count begins after stop bit.
0 = Idle character bit count begins after start bit.
PEN — Parity Enable Bit
This read/write bit enables the SCI parity function. See Table 13-4. When enabled, the parity function
inserts a parity bit in the most significant bit position. See Figure 13-4. Reset clears the PEN bit.
1 = Parity function enabled
0 = Parity function disabled
PTY — Parity Bit
This read/write bit determines whether the SCI generates and checks for odd parity or even parity. See
Table 13-4. Reset clears the PTY bit.
1 = Odd parity
0 = Even parity
NOTE
Changing the PTY bit in the middle of a transmission or reception can
generate a parity error.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
170
Freescale Semiconductor
I/O Registers
Table 13-4. Character Format Selection
Control Bits
PEN:PTY
Character Format
Start
Bits
Data
Bits
Stop
Bits
Character
Length
M
Parity
0
1
0
0
1
1
0X
0X
10
11
10
11
1
1
1
1
1
1
8
9
7
7
8
8
None
None
Even
Odd
1
1
1
1
1
1
10 bits
11 bits
10 bits
10 bits
11 bits
11 bits
Even
Odd
13.7.2 SCI Control Register 2
SCI control register 2 (SCC2):
•
Enables these CPU interrupt requests:
–
–
–
–
Enables the SCTE bit to generate transmitter CPU interrupt requests
Enables the TC bit to generate transmitter CPU interrupt requests
Enables the SCRF bit to generate receiver CPU interrupt requests
Enables the IDLE bit to generate receiver CPU interrupt requests
•
•
•
•
Enables the transmitter
Enables the receiver
Enables SCI wakeup
Transmits SCI break characters
Address: $0039
Bit 7
SCTIE
0
6
TCIE
0
5
SCRIE
0
4
ILIE
0
3
TE
0
2
RE
0
1
RWU
0
Bit 0
SBK
0
Read:
Write:
Reset:
Figure 13-9. SCI Control Register 2 (SCC2)
SCTIE — SCI Transmit Interrupt Enable Bit
This read/write bit enables the SCTE bit to generate SCI transmitter CPU interrupt requests. Setting
the SCTIE bit in SCC3 enables SCTE CPU interrupt requests. Reset clears the SCTIE bit.
1 = SCTE enabled to generate CPU interrupt
0 = SCTE not enabled to generate CPU interrupt
TCIE — Transmission Complete Interrupt Enable Bit
This read/write bit enables the TC bit to generate SCI transmitter CPU interrupt requests. Reset clears
the TCIE bit.
1 = TC enabled to generate CPU interrupt requests
0 = TC not enabled to generate CPU interrupt requests
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
171
Serial Communications Interface Module (SCI)
SCRIE — SCI Receive Interrupt Enable Bit
This read/write bit enables the SCRF bit to generate SCI receiver CPU interrupt requests. Setting the
SCRIE bit in SCC3 enables the SCRF bit to generate CPU interrupt requests. Reset clears the SCRIE
bit.
1 = SCRF enabled to generate CPU interrupt
0 = SCRF not enabled to generate CPU interrupt
ILIE — Idle Line Interrupt Enable Bit
This read/write bit enables the IDLE bit to generate SCI receiver CPU interrupt requests. Reset clears
the ILIE bit.
1 = IDLE enabled to generate CPU interrupt requests
0 = IDLE not enabled to generate CPU interrupt requests
TE — Transmitter Enable Bit
Setting this read/write bit begins the transmission by sending a preamble of 10 or 11 1s from the
transmit shift register to the PTF5/TxD pin. If software clears the TE bit, the transmitter completes any
transmission in progress before the PTF5/TxD returns to the idle condition (logic 1). Clearing and then
setting TE during a transmission queues an idle character to be sent after the character currently being
transmitted. Reset clears the TE bit.
1 = Transmitter enabled
0 = Transmitter disabled
NOTE
Writing to the TE bit is not allowed when the enable SCI bit (ENSCI) is clear.
ENSCI is in SCI control register 1.
RE — Receiver Enable Bit
Setting this read/write bit enables the receiver. Clearing the RE bit disables the receiver but does not
affect receiver interrupt flag bits. Reset clears the RE bit.
1 = Receiver enabled
0 = Receiver disabled
NOTE
Writing to the RE bit is not allowed when the enable SCI bit (ENSCI) is
clear. ENSCI is in SCI control register 1.
RWU — Receiver Wakeup Bit
This read/write bit puts the receiver in a standby state during which receiver interrupts are disabled.
The WAKE bit in SCC1 determines whether an idle input or an address mark brings the receiver out
of the standby state and clears the RWU bit. Reset clears the RWU bit.
1 = Standby state
0 = Normal operation
SBK — Send Break Bit
Setting and then clearing this read/write bit transmits a break character followed by a 1. The 1 after the
break character guarantees recognition of a valid start bit. If SBK remains set, the transmitter
continuously transmits break characters with no 1s between them. Reset clears the SBK bit.
1 = Transmit break characters
0 = No break characters being transmitted
NOTE
Do not toggle the SBK bit immediately after setting the SCTE bit. Toggling
SBK too early causes the SCI to send a break character instead of a
preamble.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
172
Freescale Semiconductor
I/O Registers
13.7.3 SCI Control Register 3
SCI control register 3 (SCC3):
•
•
•
•
Stores the ninth SCI data bit received and the ninth SCI data bit to be transmitted
Enables SCI receiver full (SCRF)
Enables SCI transmitter empty (SCTE)
Enables the following interrupts:
–
–
–
–
Receiver overrun interrupts
Noise error interrupts
Framing error interrupts
Parity error interrupts
Address:
$003A
Bit 7
R8
R
6
5
0
4
0
3
2
NEIE
0
1
FEIE
0
Bit 0
PEIE
0
Read:
Write:
Reset:
T8
ORIE
R
0
R
0
U
U
0
R
= Reserved
U = Unaffected
Figure 13-10. SCI Control Register 3 (SCC3)
R8 — Received Bit 8
When the SCI is receiving 9-bit characters, R8 is the read-only ninth bit (bit 8) of the received character.
R8 is received at the same time that the SCDR receives the other eight bits.
When the SCI is receiving 8-bit characters, R8 is a copy of the eighth bit (bit 7). Reset has no effect on
the R8 bit.
T8 — Transmitted Bit 8
When the SCI is transmitting 9-bit characters, T8 is the read/write ninth bit (bit 8) of the transmitted
character. T8 is loaded into the transmit shift register at the same time that the SCDR is loaded into
the transmit shift register. Reset has no effect on the T8 bit.
ORIE — Receiver Overrun Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the receiver overrun bit, OR.
1 = SCI error CPU interrupt requests from OR bit enabled
0 = SCI error CPU interrupt requests from OR bit disabled
NEIE — Receiver Noise Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the noise error bit, NE.
Reset clears NEIE.
1 = SCI error CPU interrupt requests from NE bit enabled
0 = SCI error CPU interrupt requests from NE bit disabled
FEIE — Receiver Framing Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the framing error bit, FE.
Reset clears FEIE.
1 = SCI error CPU interrupt requests from FE bit enabled
0 = SCI error CPU interrupt requests from FE bit disabled
PEIE — Receiver Parity Error Interrupt Enable Bit
This read/write bit enables SCI receiver CPU interrupt requests generated by the parity error bit, PE.
See 13.7.4 SCI Status Register 1. Reset clears PEIE.
1 = SCI error CPU interrupt requests from PE bit enabled
0 = SCI error CPU interrupt requests from PE bit disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
173
Serial Communications Interface Module (SCI)
13.7.4 SCI Status Register 1
SCI status register 1 (SCS1) contains flags to signal these conditions:
•
•
•
•
•
•
•
•
Transfer of SCDR data to transmit shift register complete
Transmission complete
Transfer of receive shift register data to SCDR complete
Receiver input idle
Receiver overrun
Noisy data
Framing error
Parity error
Address: $003B
Bit 7
SCTE
R
6
5
SCRF
R
4
IDLE
R
3
OR
R
2
NF
R
1
FE
R
Bit 0
PE
R
Read:
Write:
Reset:
TC
R
1
1
0
0
0
0
0
0
R
= Reserved
Figure 13-11. SCI Status Register 1 (SCS1)
SCTE — SCI Transmitter Empty Bit
This clearable, read-only bit is set when the SCDR transfers a character to the transmit shift register.
SCTE can generate an SCI transmitter CPU interrupt request. When the SCTIE bit in SCC2 is set,
SCTE generates an SCI transmitter CPU interrupt request. In normal operation, clear the SCTE bit by
reading SCS1 with SCTE set and then writing to SCDR. Reset sets the SCTE bit.
1 = SCDR data transferred to transmit shift register
0 = SCDR data not transferred to transmit shift register
TC — Transmission Complete Bit
This read-only bit is set when the SCTE bit is set and no data, preamble, or break character is being
transmitted. TC generates an SCI transmitter CPU interrupt request if the TCIE bit in SCC2 is also set.
TC is cleared automatically when data, preamble, or break is queued and ready to be sent. There may
be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the
transmission actually starting. Reset sets the TC bit.
1 = No transmission in progress
0 = Transmission in progress
SCRF — SCI Receiver Full Bit
This clearable, read-only bit is set when the data in the receive shift register transfers to the SCI data
register. SCRF can generate an SCI receiver CPU interrupt request. When the SCRIE bit in SCC2 is
set, SCRF generates a CPU interrupt request. In normal operation, clear the SCRF bit by reading
SCS1 with SCRF set and then reading the SCDR. Reset clears SCRF.
1 = Received data available in SCDR
0 = Data not available in SCDR
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
174
Freescale Semiconductor
I/O Registers
IDLE — Receiver Idle Bit
This clearable, read-only bit is set when 10 or 11 consecutive 1s appear on the receiver input. IDLE
generates an SCI error CPU interrupt request if the ILIE bit in SCC2 is also set. Clear the IDLE bit by
reading SCS1 with IDLE set and then reading the SCDR. After the receiver is enabled, it must receive
a valid character that sets the SCRF bit before an idle condition can set the IDLE bit. Also, after the
IDLE bit has been cleared, a valid character must again set the SCRF bit before an idle condition can
set the IDLE bit. Reset clears the
IDLE bit.
1 = Receiver input idle
0 = Receiver input active or idle since the IDLE bit was cleared
OR — Receiver Overrun Bit
This clearable, read-only bit is set when software fails to read the SCDR before the receive shift
register receives the next character. The OR bit generates an SCI error CPU interrupt request if the
ORIE bit in SCC3 is also set. The data in the shift register is lost, but the data already in the SCDR is
not affected. Clear the OR bit by reading SCS1 with OR set and then reading the SCDR. Reset clears
the OR bit.
1 = Receive shift register full and SCRF = 1
0 = No receiver overrun
Software latency may allow an overrun to occur between reads of SCS1 and SCDR in the flag-clearing
sequence. Figure 13-12 shows the normal flag-clearing sequence and an example of an overrun
caused by a delayed flag-clearing sequence. The delayed read of SCDR does not clear the OR bit
because OR was not set when SCS1 was read. Byte 2 caused the overrun and is lost. The next
flag-clearing sequence reads byte 3 in the SCDR instead of byte 2.
NORMAL FLAG CLEARING SEQUENCE
BYTE 1
BYTE 2
BYTE 3
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCDR
BYTE 1
READ SCDR
BYTE 2
READ SCDR
BYTE 3
DELAYED FLAG CLEARING SEQUENCE
BYTE 1
BYTE 2
BYTE 3
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 1
READ SCDR
BYTE 1
READ SCDR
BYTE 3
Figure 13-12. Flag Clearing Sequence
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
175
Serial Communications Interface Module (SCI)
In applications that are subject to software latency or in which it is important to know which byte is lost
due to an overrun, the flag-clearing routine can check the OR bit in a second read of SCS1 after
reading the data register.
NF — Receiver Noise Flag Bit
This clearable, read-only bit is set when the SCI detects noise on the PTF4/RxD pin. NF generates an
NF CPU interrupt request if the NEIE bit in SCC3 is also set. Clear the NF bit by reading SCS1 and
then reading the SCDR. Reset clears the NF bit.
1 = Noise detected
0 = No noise detected
FE — Receiver Framing Error Bit
This clearable, read-only bit is set when a 0 is accepted as the stop bit. FE generates an SCI error CPU
interrupt request if the FEIE bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set and
then reading the SCDR. Reset clears the FE bit.
1 = Framing error detected
0 = No framing error detected
PE — Receiver Parity Error Bit
This clearable, read-only bit is set when the SCI detects a parity error in incoming data. PE generates
a PE CPU interrupt request if the PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with
PE set and then reading the SCDR. Reset clears the PE bit.
1 = Parity error detected
0 = No parity error detected
13.7.5 SCI Status Register 2
SCI status register 2 (SCS2) contains flags to signal these conditions:
•
•
Break character detected
Incoming data
Address:
$003C
Bit 7
0
6
5
0
4
0
3
0
2
0
1
BKF
R
Bit 0
RPF
R
Read:
Write:
Reset:
0
R
R
R
0
R
0
R
0
R
0
0
0
0
0
R
= Reserved
Figure 13-13. SCI Status Register 2 (SCS2)
BKF — Break Flag
This clearable, read-only bit is set when the SCI detects a break character on the PTF4/RxD pin. In
SCS1, the FE and SCRF bits are also set. In 9-bit character transmissions, the R8 bit in SCC3 is
cleared. BKF does not generate a CPU interrupt request. Clear BKF by reading SCS2 with BKF set
and then reading the SCDR. Once cleared, BKF can become set again only after logic 1s again appear
on the PTF4/RxD pin followed by another break character. Reset clears the BKF bit.
1 = Break character detected
0 = No break character detected
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
176
Freescale Semiconductor
I/O Registers
RPF —Reception-in-Progress Flag
This read-only bit is set when the receiver detects a logic 0 during the RT1 time period of the start bit
search. RPF does not generate an interrupt request. RPF is reset after the receiver detects false start
bits (usually from noise or a baud rate mismatch, or when the receiver detects an idle character. Polling
RPF before disabling the SCI module or entering stop mode can show whether a reception is in
progress.
1 = Reception in progress
0 = No reception in progress
13.7.6 SCI Data Register
The SCI data register (SCDR) is the buffer between the internal data bus and the receive and transmit
shift registers. Reset has no effect on data in the SCI data register.
Address:
$003D
Bit 7
R7
6
5
4
3
2
1
Bit 0
R0
Read:
Write:
Reset:
R6
T6
R5
T5
R4
T4
R3
T3
R2
T2
R1
T1
T7
T0
Unaffected by reset
Figure 13-14. SCI Data Register (SCDR)
R7/T7:R0/T0 — Receive/Transmit Data Bits
Reading address $003D accesses the read-only received data bits, R7:R0. Writing to address $003D
writes the data to be transmitted, T7:T0. Reset has no effect on the SCI data register.
13.7.7 SCI Baud Rate Register
The baud rate register (SCBR) selects the baud rate for both the receiver and the transmitter.
Address:
$003E
Bit 7
0
6
5
SCP1
0
4
SCP0
0
3
0
2
SCR2
0
1
SCR1
0
Bit 0
SCR0
0
Read:
Write:
Reset:
0
R
R
R
0
0
0
R
= Reserved
Figure 13-15. SCI Baud Rate Register (SCBR)
SCP1 and SCP0 — SCI Baud Rate Prescaler Bits
These read/write bits select the baud rate prescaler divisor as shown in Table 13-5. Reset clears SCP1
and SCP0.
Table 13-5. SCI Baud Rate Prescaling
SCP1:SCP0
Prescaler Divisor (PD)
00
01
10
11
1
3
4
13
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
177
Serial Communications Interface Module (SCI)
SCR2–SCR0 — SCI Baud Rate Select Bits
These read/write bits select the SCI baud rate divisor as shown in Table 13-6. Reset clears
SCR2–SCR0.
Table 13-6. SCI Baud Rate Selection
SCR2:SCR1:SCR0
Baud Rate Divisor (BD)
000
001
010
011
100
101
110
111
1
2
4
8
16
32
64
128
Use this formula to calculate the SCI baud rate:
f
OP
Baud rate = ------------------------------------
64 × PD × BD
where:
f
OP = internal operating frequency
PD = prescaler divisor
BD = baud rate divisor
Table 13-7 shows the SCI baud rates that can be generated with a 4.9152-MHz crystal with the CGM set
for an fOP of 7.3728 MHz and the CGM set for an fOP of 4.9152 MHz.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
178
Freescale Semiconductor
I/O Registers
Table 13-7. SCI Baud Rate Selection Examples
Baud Rate
(fOP = 7.3728 MHz)
Baud Rate
(fOP = 4.9152 MHz)
Prescaler
Divisor (PD)
Baud Rate
Divisor (BD)
SCP1:SCP0
SCR2:SCR1:SCR0
00
00
00
00
00
00
00
00
01
01
01
01
01
01
01
01
10
10
10
10
10
10
10
10
11
11
11
11
11
11
11
11
1
1
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
1
2
115,200
57,600
28,800
14,400
7200
76,800
38,400
19,200
9600
4800
2400
1200
600
1
4
1
8
1
16
32
64
128
1
1
3600
1
1800
1
900
3
38,400
19,200
9600
25,600
12,800
6400
3200
1600
800
3
2
3
4
3
8
4800
3
16
32
64
128
1
2400
3
1200
3
600
400
3
300
200
4
28,800
14,400
7200
19,200
9600
4800
2400
1200
600
4
2
4
4
4
8
3600
4
16
32
64
128
1
1800
4
900
4
450
300
4
225
150
13
13
13
13
13
13
13
13
8861.5
4430.7
2215.4
1107.7
553.8
276.9
138.5
69.2
5907.7
2953.8
1476.9
738.5
369.2
184.6
92.3
2
4
8
16
32
64
128
46.2
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
179
Serial Communications Interface Module (SCI)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
180
Freescale Semiconductor
Chapter 14
System Integration Module (SIM)
14.1 Introduction
This section describes the system integration module (SIM). Together with the central processor unit
(CPU), the SIM controls all microcontroller unit (MCU) activities.
A block diagram of the SIM is shown in Figure 14-1.
The SIM is a system state controller that coordinates CPU and exception timing. The SIM is responsible
for:
•
Bus clock generation and control for CPU and peripherals:
–
–
Wait/reset/break entry and recovery
Internal clock control
•
•
Master reset control, including power-on reset (POR) and computer operating properly (COP)
timeout
Interrupt control:
–
–
–
Acknowledge timing
Arbitration control timing
Vector address generation
•
•
CPU enable/disable timing
Modular architecture expandable to 128 interrupt sources
Table 14-1 shows the internal signal names used in this section.
Table 14-1. Signal Name Conventions
Signal Name
CGMXCLK
CGMVCLK
CGMOUT
IAB
Description
Buffered version of OSC1 from clock generator module (CGM)
Phase-locked loop (PLL) circuit output
PLL-based or OSC1-based clock output from CGM module (bus clock = CGMOUT divided by two)
Internal address bus
IDB
Internal data bus
PORRST
IRST
Signal from the power-on reset module to the SIM
Internal reset signal
R/W
Read/write signal
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
181
System Integration Module (SIM)
MODULE WAIT
WAIT
CONTROL
CPU WAIT (FROM CPU)
SIMOSCEN (TO CGM)
SIM
COUNTER
COP CLOCK
CGMXCLK (FROM CGM)
CGMOUT (FROM CGM)
÷ 2
CLOCK
CONTROL
CLOCK GENERATORS
INTERNAL CLOCKS
LVI (FROM LVI MODULE)
RESET
PIN LOGIC
POR CONTROL
RESET PIN CONTROL
MASTER
RESET
CONTROL
ILLEGAL OPCODE (FROM CPU)
ILLEGAL ADDRESS (FROM ADDRESS
MAP DECODERS)
SIM RESET STATUS REGISTER
COP (FROM COP MODULE)
RESET
INTERRUPT SOURCES
CPU INTERFACE
INTERRUPT CONTROL
AND PRIORITY DECODE
Figure 14-1. SIM Block Diagram
14.2 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and peripherals on the MCU. The
system clocks are generated from an incoming clock, CGMOUT, as shown in Figure 14-2. This clock
can come from either an external oscillator or from the on-chip phase-locked loop (PLL) circuit. See
Chapter 4 Clock Generator Module (CGM).
14.2.1 Bus Timing
In user mode, the internal bus frequency is either the crystal oscillator output (CGMXCLK) divided by four
or the PLL output (CGMVCLK) divided by four. See Chapter 4 Clock Generator Module (CGM).
14.2.2 Clock Startup from POR or LVI Reset
When the power-on reset (POR) module or the low-voltage inhibit (LVI) module generates a reset, the
clocks to the CPU and peripherals are inactive and held in an inactive phase until after the 4096
CGMXCLK cycle POR timeout has completed. The RST pin is driven low by the SIM during this entire
period. The internal bus (IBUS) clocks start upon completion of the timeout.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
182
Freescale Semiconductor
Reset and System Initialization
CGMXCLK
CGMOUT
OSC1
SIM COUNTER
CLOCK
SELECT
CIRCUIT
A
B
BUS CLOCK
÷ 2
÷ 2
GENERATORS
CGMVCLK
S*
*When S = 1,
CGMOUT = B
BCS
SIM
PLL
PTC2
MONITOR MODE
USER MODE
CGM
Figure 14-2. CGM Clock Signals
14.2.3 Clocks in Wait Mode
In wait mode, the CPU clocks are inactive. The SIM also produces two sets of clocks for other modules.
Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
14.3 Reset and System Initialization
The MCU has these reset sources:
•
•
•
•
•
•
Power-on reset module (POR)
External reset pin (RST)
Computer operating properly (COP) module
Low-voltage inhibit (LVI) module
Illegal opcode
Illegal address
All of these resets produce the vector $FFFE–FFFF ($FEFE–FEFF in monitor mode) and assert the
internal reset signal (IRST). IRST causes all registers to be returned to their default values and all
modules to be returned to their reset states.
An internal reset clears the SIM counter (see 14.4 SIM Counter), but an external reset does not. Each of
the resets sets a corresponding bit in the SIM reset status register (SRSR). See 14.7.2 SIM Reset Status
Register.
14.3.1 External Pin Reset
Pulling the asynchronous RST pin low halts all processing. The PIN bit of the SIM reset status register
(SRSR) is set as long as RST is held low for a minimum of 67 CGMXCLK cycles, assuming that neither
the POR nor the LVI was the source of the reset. See Table 14-2 for details. Figure 14-3 shows the relative
timing.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
183
System Integration Module (SIM)
Table 14-2. PIN Bit Set Timing
Reset Type
POR/LVI
Number of Cycles Required to Set PIN
4163 (4096 + 64 + 3)
67 (64 + 3)
All others
CGMOUT
RST
IAB
VECT H
VECT L
PC
Figure 14-3. External Reset Timing
14.3.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 CGMXCLK cycles to allow resetting of
external peripherals. The internal reset signal (IRST) continues to be asserted for an additional 32 cycles
(see Figure 14-5). An internal reset can be caused by an illegal address, illegal opcode, COP timeout,
LVI, or POR. (See Figure 14-4.)
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
LVI
INTERNAL RESET
POR
Figure 14-4. Sources of Internal Reset
NOTE
For LVI or POR resets, the SIM cycles through 4096 CGMXCLK cycles
during which the SIM forces the RST pin low. The internal reset signal then
follows the sequence from the falling edge of RST, as shown in Figure 14-5.
IRST
RST PULLED LOW BY MCU
32 CYCLES
RST
32 CYCLES
CGMXCLK
IAB
VECTOR HIGH
Figure 14-5. Internal Reset Timing
The COP reset is asynchronous to the bus clock.
The active reset feature allows the part to issue a reset to peripherals and other chips within a system
built around the MCU.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
184
Freescale Semiconductor
Reset and System Initialization
14.3.2.1 Power-On Reset (POR)
When power is first applied to the MCU, the power-on reset (POR) module generates a pulse to indicate
that power-on has occurred. The external reset pin (RST) is held low while the SIM counter counts out
4096 CGMXCLK cycles. Sixty-four CGMXCLK cycles later, the CPU and memories are released from
reset to allow the reset vector sequence to occur.
OSC1
PORRST
4096
CYCLES
32
CYCLES
32
CYCLES
CGMXCLK
CGMOUT
RST
IAB
$FFFE
$FFFF
Figure 14-6. POR Recovery
At power-on, these events occur:
•
•
•
•
A POR pulse is generated.
The internal reset signal is asserted.
The SIM enables CGMOUT.
Internal clocks to the CPU and modules are held inactive for 4096 CGMXCLK cycles to allow
stabilization of the oscillator.
•
•
The RST pin is driven low during the oscillator stabilization time.
The POR bit of the SIM reset status register (SRSR) is set and all other bits in the register are
cleared.
14.3.2.2 Computer Operating Properly (COP) Reset
An input to the SIM is reserved for the COP reset signal. The overflow of the COP counter causes an
internal reset and sets the COP bit in the SIM reset status register (SRSR). The SIM actively pulls down
the RST pin for all internal reset sources.
To prevent a COP module timeout, write any value to location $FFFF. Writing to location $FFFF clears
the COP counter and bits 12–4 of the SIM counter. The SIM counter output, which occurs at least every
213–24 CGMXCLK cycles, drives the COP counter. The COP should be serviced as soon as possible out
of reset to guarantee the maximum amount of time before the first timeout.
The COP module is disabled if the RST pin or the IRQ pin is held at VHI while the MCU is in monitor mode.
The COP module can be disabled only through combinational logic conditioned with the high voltage
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
185
System Integration Module (SIM)
signal on the RST or the IRQ pin. This prevents the COP from becoming disabled as a result of external
noise. During a break state, VHI on the RST pin disables the COP module.
14.3.2.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An illegal instruction sets the ILOP
bit in the SIM reset status register (SRSR) and causes a reset.
Because the MC68HC908MR32 has stop mode disabled, execution of the STOP instruction will cause
an illegal opcode reset.
14.3.2.4 Illegal Address Reset
An opcode fetch from addresses other than FLASH or RAM addresses generates an illegal address reset
(unimplemented locations within memory map). The SIM verifies that the CPU is fetching an opcode prior
to asserting the ILAD bit in the SIM reset status register (SRSR) and resetting the MCU. A data fetch from
an unmapped address does not generate a reset.
14.3.2.5 Forced Monitor Mode Entry Reset (MENRST)
The MENRST module monitors the reset vector fetches and will assert an internal reset if it detects that
the reset vectors are erased ($FF). When the MCU comes out of reset, it is forced into monitor mode.
14.3.2.6 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit (LVI) module asserts its output to the SIM when the VDD voltage falls to the VLVRX
voltage and remains at or below that level for at least nine consecutive CPU cycles (see 19.5 DC Electrical
Characteristics). The LVI bit in the SIM reset status register (SRSR) is set, and the external reset pin
(RST) is held low while the SIM counter counts out 4096 CGMXCLK cycles. Sixty-four CGMXCLK cycles
later, the CPU is released from reset to allow the reset vector sequence to occur. The SIM actively pulls
down the RST pin for all internal reset sources.
14.4 SIM Counter
The SIM counter is used by the power-on reset (POR) module to allow the oscillator time to stabilize
before enabling the internal bus (IBUS) clocks. The SIM counter also serves as a prescaler for the
computer operating properly (COP) module. The SIM counter overflow supplies the clock for the COP
module. The SIM counter is 13 bits long and is clocked by the falling edge of CGMXCLK.
14.4.1 SIM Counter During Power-On Reset
The power-on reset (POR) module detects power applied to the MCU. At power-on, the POR circuit
asserts the signal PORRST. Once the SIM is initialized, it enables the clock generation (CGM) module to
drive the bus clock state machine.
14.4.2 SIM Counter and Reset States
External reset has no effect on the SIM counter. The SIM counter is free-running after all reset states. For
counter control and internal reset recovery sequences, see 14.3.2 Active Resets from Internal Sources.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
186
Freescale Semiconductor
Exception Control
14.5 Exception Control
Normal, sequential program execution can be changed in three different ways:
1. Interrupts:
a. Maskable hardware CPU interrupts
b. Non-maskable software interrupt instruction (SWI)
2. Reset
3. Break interrupts
14.5.1 Interrupts
At the beginning of an interrupt, the CPU saves the CPU register contents on the stack and sets the
interrupt mask (I bit) to prevent additional interrupts. At the end of an interrupt, the return-from-interrupt
(RTI) instruction recovers the CPU register contents from the stack so that normal processing can
resume. Figure 14-7 shows interrupt entry timing. Figure 14-9 shows interrupt recovery timing.
MODULE
INTERRUPT
I BIT
START
ADDR
IAB
IDB
DUMMY
SP
SP – 1
SP – 2
SP – 3
SP – 4
VECT H
VECT L
DUMMY PC – 1[7:0] PC – 1[15:8]
X
A
CCR
V DATA H V DATA L OPCODE
R/W
Figure 14-7. Interrupt Entry
Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The
arbitration result is a constant that the CPU uses to determine which vector to fetch. Once an interrupt is
latched by the SIM, no other interrupt can take precedence, regardless of priority, until the latched
interrupt is serviced (or the I bit is cleared). See Figure 14-8.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
187
System Integration Module (SIM)
FROM RESET
YES
BREAK OR SWI
INTERRUPT?
NO
YES
I BIT SET?
NO
YES
INTERRUPT?
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
AS MANY INTERRUPTS AS EXIST ON CHIP
FETCH NEXT
INSTRUCTION
SWI
INSTRUCTION?
YES
YES
NO
RTI
INSTRUCTION?
UNSTACK CPU REGISTERS
EXECUTE INSTRUCTION
NO
Figure 14-8. Interrupt Processing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
188
Freescale Semiconductor
Exception Control
MODULE
INTERRUPT
I BIT
IAB
SP – 4
SP – 3
SP – 2
SP – 1
SP
PC
PC + 1
IDB
R/W
CCR
A
X
PC – 1[7:0] PC – 1[15:8] OPCODE OPERAND
Figure 14-9. Interrupt Recovery
14.5.1.1 Hardware Interrupts
A hardware interrupt does not stop the current instruction. Processing of a hardware interrupt begins after
completion of the current instruction. When the current instruction is complete, the SIM checks all pending
hardware interrupts. If interrupts are not masked (I bit clear in the condition code register), and if the
corresponding interrupt enable bit is set, the SIM proceeds with interrupt processing; otherwise, the next
instruction is fetched and executed.
If more than one interrupt is pending at the end of an instruction execution, the highest priority interrupt is
serviced first. Figure 14-10 demonstrates what happens when two interrupts are pending. If an interrupt
is pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the
load-accumulator-from- memory (LDA) instruction is executed.
CLI
LDA#$FF
BACKGROUND ROUTINE
INT1
INT2
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 14-10. Interrupt Recognition Example
The LDA opcode is prefetched by both the INT1 and INT2 RTI instructions. However, in the case of the
INT1 RTI prefetch, this is a redundant operation.
NOTE
To maintain compatibility with the M6805 Family, the H register is not
pushed on the stack during interrupt entry. If the interrupt service routine
modifies the H register or uses the indexed addressing mode, software
should save the H register and then restore it prior to exiting the routine.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
189
System Integration Module (SIM)
14.5.1.2 Software Interrupt (SWI) Instruction
The software interrupt (SWI) instruction is a non-maskable instruction that causes an interrupt regardless
of the state of the interrupt mask
(I bit) in the condition code register.
14.5.2 Reset
All reset sources always have equal and highest priority and cannot be arbitrated.
14.6 Low-Power Mode
Executing the WAIT instruction puts the MCU in a low power-consumption mode for standby situations.
The SIM holds the CPU in a non-clocked state. WAIT clears the interrupt mask (I) in the condition code
register, allowing interrupts to occur.
14.6.1 Wait Mode
In wait mode, the CPU clocks are inactive while the peripheral clocks continue to run. Figure 14-11 shows
the timing for wait mode entry.
A module that is active during wait mode can wake up the CPU with an interrupt if the interrupt is enabled.
Stacking for the interrupt begins one cycle after the WAIT instruction during which the interrupt occurred.
Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
Wait mode can also be exited by a reset. If the COP disable bit, COPD, in the configuration register is
logic 0, then the computer operating properly module (COP) is enabled and remains active in wait mode.
IAB
IDB
WAIT ADDR
WAIT ADDR + 1
SAME
SAME
PREVIOUS DATA
NEXT OPCODE
SAME
SAME
R/W
Note: Previous data can be operand data or the WAIT opcode, depending on the
last instruction.
Figure 14-11. Wait Mode Entry Timing
Figure 14-12 and Figure 14-13 show the timing for wait recovery.
IAB
IDB
$6E0B
$A6
$6E0C
$00FF
$00FE
$00FD
$00FC
$A6
$A6
$01
$0B
$6E
EXITSTOPWAIT
Note: EXITSTOPWAIT = RST pin OR CPU interrupt
Figure 14-12. Wait Recovery from Interrupt
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
190
Freescale Semiconductor
SIM Registers
32
CYCLES
32
CYCLES
IAB
$6E0B
$A6
RST VCT H RST VCT L
IDB $A6
RST
$A6
CGMXCLK
Figure 14-13. Wait Recovery from Internal Reset
14.6.2 Stop Mode
In stop mode, the SIM counter is reset and the system clocks are disabled. An interrupt request from a
module can cause an exit from stop mode. Stacking for interrupts begins after the selected stop recovery
time has elapsed. Reset or break also causes an exit from stop mode.
The SIM disables the clock generator module outputs (CGMOUT and CGMXCLK) in stop mode, stopping
the CPU and peripherals. Stop recovery time is hard wired at the normal delay of 4096 CGMXCLK cycles.
It is important to note that when using the PWM generator, its outputs will stop toggling when stop mode
is entered. The PWM module must be disabled before entering stop mode to prevent external inverter
failure.
14.7 SIM Registers
This subsection describes the SIM registers.
14.7.1 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from wait
mode.
Address:
$FE00
BIt 7
6
5
4
3
2
1
Bit 0
R
Read:
Write:
Reset:
SBSW
Note(1)
0
R
R
R
R
R
R
R
= Reserved
Note 1. Writing a logic 0 clears SBSW.
Figure 14-14. SIM Break Status Register (SBSR)
SBSW — SIM Break Stop/Wait
This status bit is useful in applications requiring a return to wait mode after exiting from a break
interrupt. Clear SBSW by writing a logic 0 to it. Reset clears SBSW.
1 = Wait mode was exited by break interrupt.
0 = Wait mode was not exited by break interrupt.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
191
System Integration Module (SIM)
SBSW can be read within the break state SWI routine. The user can modify the return address on the
stack by subtracting one from it.
14.7.2 SIM Reset Status Register
The SIM reset status register (SRSR) contains six flags that show the source of the last reset. Clear the
SIM reset status register by reading it. A power-on reset sets the POR bit and clears all other bits in the
register.
Address: $FE01
BIt 7
POR
R
6
5
COP
R
4
ILOP
R
3
ILAD
R
2
1
LVI
R
Bit 0
0
Read:
Write:
Reset:
PIN
MENRST
R
R
0
R
1
0
0
0
0
0
0
R
= Reserved
Figure 14-15. SIM Reset Status Register (SRSR)
POR — Power-On Reset Bit
1 = Last reset caused by POR circuit
0 = Read of SRSR
PIN — External Reset Bit
1 = Last reset caused by external reset pin (RST)
0 = POR or read of SRSR
COP — Computer Operating Properly Reset Bit
1 = Last reset caused by COP counter
0 = POR or read of SRSR
ILOP — Illegal Opcode Reset Bit
1 = Last reset caused by an illegal opcode
0 = POR or read of SRSR
ILAD — Illegal Address Reset Bit (opcode fetches only)
1 = Last reset caused by an opcode fetch from an illegal address
0 = POR or read of SRSR
MENRST — Forced Monitor Mode Entry Reset Bit
1 = Last reset caused by the MENRST circuit
0 = POR or read of SRSR
LVI — Low-Voltage Inhibit Reset Bit
1 = Last reset caused by the LVI circuit
0 = POR or read of SRSR
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
192
Freescale Semiconductor
SIM Registers
14.7.3 SIM Break Flag Control Register
The SIM break control register (SBFCR) contains a bit that enables software to clear status bits while the
MCU is in a break state.
Address:
$FE03
BIt 7
6
5
4
3
2
1
Bit 0
R
Read:
Write:
Reset:
BCFE
R
R
R
R
R
R
0
R
= Reserved
Figure 14-16. SIM Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing status registers while the MCU is
in a break state. To clear status bits during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
193
System Integration Module (SIM)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
194
Freescale Semiconductor
Chapter 15
Serial Peripheral Interface Module (SPI)
15.1 Introduction
The serial peripheral interface (SPI) module allows full-duplex, synchronous, serial communications with
peripheral devices.
15.2 Features
Features of the SPI module include:
•
•
•
•
•
•
•
Full-duplex operation
Master and slave modes
Double-buffered operation with separate transmit and receive registers
Four master mode frequencies (maximum = bus frequency ÷ 2)
Maximum slave mode frequency = bus frequency
Serial clock with programmable polarity and phase
Two separately enabled interrupts with central processor unit (CPU) service:
–
–
SPRF (SPI receiver full)
SPTE (SPI transmitter empty)
•
•
•
•
Mode fault error flag with CPU interrupt capability
Overflow error flag with CPU interrupt capability
Programmable wired-OR mode
I2C (inter-integrated circuit) compatibility
15.3 Pin Name Conventions
The generic names of the SPI input/output (I/O) pins are:
•
•
•
•
SS, slave select
SPSCK, SPI serial clock
MOSI, master out/slave in
MISO, master in/slave out
SPI pins are shared by parallel I/O ports or have alternate functions. The full name of an SPI pin reflects
the name of the shared port pin or the name of an alternate pin function. The generic pin names appear
in the text that follows. Table 15-1 shows the full names of the SPI I/O pins.
Table 15-1. Pin Name Conventions
Generic Pin Names:
MISO
MOSI
SPSCK
SS
Full Pin Names: PTF3/MISO
PTF2/MOSI PTF0/SPSCK
PTF1/SS
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
195
INTERNAL BUS
M68HC08 CPU
PTA7–PTA0
CPU
REGISTERS
ARITHMETIC/LOGIC
UNIT
LOW-VOLTAGE INHIBIT
MODULE
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
COMPUTER OPERATING PROPERLY
MODULE
CONTROL AND STATUS REGISTERS — 112 BYTES
USER FLASH — 32,256 BYTES
TIMER INTERFACE
MODULE A
USER RAM — 768 BYTES
PTC6
PTC5
TIMER INTERFACE
MODULE B
PTC4
MONITOR ROM — 240 BYTES
PTC3
PTC2
SERIAL COMMUNICATIONS INTERFACE
MODULE
PTC1/ATD9(1)
PTC0/ATD8
USER FLASH VECTOR SPACE — 46 BYTES
OSC1
PTD6/IS3
CLOCK GENERATOR
MODULE
OSC2
SERIAL PERIPHERAL INTERFACE
MODULE(2)
PTD5/IS2
CGMXFC
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
POWER-ON RESET
MODULE
SYSTEM INTEGRATION
MODULE
RST
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
IRQ
MODULE
IRQ
SINGLE BREAK
MODULE
VDDA
(3)
VSSA
ANALOG-TO-DIGITAL CONVERTER
MODULE
(3)
VREFL
VREFH
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PWMGND
PULSE-WIDTH MODULATOR
MODULE
PWM6–PWM1
PTF1/SS(1)
PTF0/SPSCK(1)
VSS
VDD
POWER
VDDAD
VSSAD
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 15-1. Block Diagram Highlighting SPI Block and Pins
Functional Description
15.4 Functional Description
Figure 15-2 shows the structure of the SPI module and Figure 15-3 shows the locations and contents of
the SPI I/O registers.
The SPI module allows full-duplex, synchronous, serial communication between the microcontroller unit
(MCU) and peripheral devices, including other MCUs. Software can poll the SPI status flags or SPI
operation can be interrupt-driven. All SPI interrupts can be serviced by the CPU.
INTERNAL BUS
TRANSMIT DATA REGISTER
CGMOUT ÷ 2
(FROM SIM)
SHIFT REGISTER
MISO
MOSI
7
6
5
4
3
2
1
0
÷ 2
÷ 8
CLOCK
DIVIDER
RECEIVE DATA REGISTER
÷ 32
÷ 128
PIN
CONTROL
LOGIC
CLOCK
SELECT
SPSCK
SS
SPMSTR
SPE
M
S
CLOCK
LOGIC
SPR1
SPR0
SPMSTR
CPHA
CPOL
SPWOM
TRANSMITTER CPU INTERRUPT REQUEST
RECEIVER/ERROR CPU INTERRUPT REQUEST
MODFEN
ERRIE
SPTIE
SPRIE
SPE
SPI
CONTROL
SPRF
SPTE
OVRF
MODF
Figure 15-2. SPI Module Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
197
Serial Peripheral Interface Module (SPI)
Addr.
Register Name
Bit 7
SPRIE
0
6
5
4
3
2
1
SPE
0
Bit 0
SPTIE
0
Read:
SPI Control Register
(SPCR) Write:
See page 211.
R
0
SPMSTR
CPOL
CPHA
SPWOM
0
$0044
Reset:
1
OVRF
R
0
MODF
R
1
SPTE
R
Read: SPRF
SPI Status and Control
See page 212.
ERRIE
MODFEN
SPR1
SPR0
$0045
$0046
Register (SPSCR) Write:
R
0
Reset:
Read:
0
0
0
1
0
0
0
R7
T7
R6
T6
R5
T5
R4
T4
R3
T3
R2
T2
R1
T1
R0
T0
SPI Data Register
(SPDR) Write:
See page 214.
Reset:
Unaffected by reset
R
= Reserved
Figure 15-3. SPI I/O Register Summary
15.4.1 Master Mode
The SPI operates in master mode when the SPI master bit, SPMSTR, is set.
NOTE
Configure the SPI modules as master or slave before enabling them.
Enable the master SPI before enabling the slave SPI. Disable the slave SPI
before disabling the master SPI. See 15.12.1 SPI Control Register.
Only a master SPI module can initiate transmissions. Software begins the transmission from a master SPI
module by writing to the SPI data register. If the shift register is empty, the byte immediately transfers to
the shift register, setting the SPI transmitter empty bit, SPTE. The byte begins shifting out on the MOSI
pin under the control of the serial clock. See Figure 15-4.
MASTER MCU
SLAVE MCU
MISO
MOSI
MISO
MOSI
SHIFT REGISTER
SHIFT REGISTER
SPSCK
SS
SPSCK
SS
BAUD RATE
GENERATOR
VDD
Figure 15-4. Full-Duplex Master-Slave Connections
The SPR1 and SPR0 bits control the baud rate generator and determine the speed of the shift register.
See 15.12.2 SPI Status and Control Register. Through the SPSCK pin, the baud-rate generator of the
master also controls the shift register of the slave peripheral.
As the byte shifts out on the MOSI pin of the master, another byte shifts in from the slave on the master’s
MISO pin. The transmission ends when the receiver full bit, SPRF, becomes set. At the same time that
SPRF becomes set, the byte from the slave transfers to the receive data register. In normal operation,
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
198
Freescale Semiconductor
Transmission Formats
SPRF signals the end of a transmission. Software clears SPRF by reading the SPI status and control
register with SPRF set and then reading the SPI data register. Writing to the SPI data register clears the
SPTE bit.
15.4.2 Slave Mode
The SPI operates in slave mode when the SPMSTR bit is clear. In slave mode the SPSCK pin is the input
for the serial clock from the master MCU. Before a data transmission occurs, the SS pin of the slave SPI
must be at logic 0. SS must remain low until the transmission is complete. See 15.6.2 Mode Fault Error.
In a slave SPI module, data enters the shift register under the control of the serial clock from the master
SPI module. After a byte enters the shift register of a slave SPI, it transfers to the receive data register,
and the SPRF bit is set. To prevent an overflow condition, slave software then must read the receive data
register before another full byte enters the shift register.
The maximum frequency of the SPSCK for an SPI configured as a slave is the bus clock speed (which is
twice as fast as the fastest master SPSCK clock that can be generated). The frequency of the SPSCK for
an SPI configured as a slave does not have to correspond to any SPI baud rate. The baud rate only
controls the speed of the SPSCK generated by an SPI configured as a master. Therefore, the frequency
of the SPSCK for an SPI configured as a slave can be any frequency less than or equal to the bus speed.
When the master SPI starts a transmission, the data in the slave shift register begins shifting out on the
MISO pin. The slave can load its shift register with a new byte for the next transmission by writing to its
transmit data register. The slave must write to its transmit data register at least one bus cycle before the
master starts the next transmission. Otherwise, the byte already in the slave shift register shifts out on the
MISO pin. Data written to the slave shift register during a transmission remains in a buffer until the end of
the transmission.
When the clock phase bit (CPHA) is set, the first edge of SPSCK starts a transmission. When CPHA is
clear, the falling edge of SS starts a transmission. See 15.5 Transmission Formats.
NOTE
If the write to the data register is late, the SPI transmits the data already in
the shift register from the previous transmission.
SPSCK must be in the proper idle state before the slave is enabled to
prevent SPSCK from appearing as a clock edge.
15.5 Transmission Formats
During an SPI transmission, data is simultaneously transmitted (shifted out serially) and received (shifted
in serially). A serial clock synchronizes shifting and sampling on the two serial data lines. A slave select
line allows selection of an individual slave SPI device; slave devices that are not selected do not interfere
with SPI bus activities. On a master SPI device, the slave select line can optionally be used to indicate
multiple-master bus contention.
15.5.1 Clock Phase and Polarity Controls
Software can select any of four combinations of serial clock (SPSCK) phase and polarity using two bits
in the SPI control register (SPCR). The clock polarity is specified by the CPOL control bit, which selects
an active high or low clock and has no significant effect on the transmission format.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
199
Serial Peripheral Interface Module (SPI)
The clock phase (CPHA) control bit selects one of two fundamentally different transmission formats. The
clock phase and polarity should be identical for the master SPI device and the communicating slave
device. In some cases, the phase and polarity are changed between transmissions to allow a master
device to communicate with peripheral slaves having different requirements.
NOTE
Before writing to the CPOL bit or the CPHA bit, disable the SPI by clearing
the SPI enable bit (SPE).
15.5.2 Transmission Format When CPHA = 0
Figure 15-5 shows an SPI transmission in which CPHA is logic 0. The figure should not be used as a
replacement for data sheet parametric information.Two waveforms are shown for SPSCK: one for
CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing
diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins
are directly connected between the master and the slave. The MISO signal is the output from the slave,
and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The
slave SPI drives its MISO output only when its slave select input (SS) is at logic 0, so that only the selected
slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS
pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. (See
15.6.2 Mode Fault Error.) When CPHA = 0, the first SPSCK edge is the MSB capture strobe. Therefore,
the slave must begin driving its data before the first SPSCK edge, and a falling edge on the SS pin is used
to start the slave data transmission. The slave’s SS pin must be toggled back to high and then low again
between each byte transmitted as shown in Figure 15-6.
SPSCK CYCLE #
FOR REFERENCE
1
2
3
4
5
6
7
8
SPSCK, CPOL = 0
SPSCK, CPOL = 1
MOSI
FROM MASTER
MSB
BIT 6
BIT 6
BIT 5
BIT 5
BIT 4
BIT 4
BIT 3
BIT 3
BIT 2
BIT 2
BIT 1
BIT 1
LSB
LSB
MISO
FROM SLAVE
MSB
SS, TO SLAVE
CAPTURE STROBE
Figure 15-5. Transmission Format (CPHA = 0)
MISO/MOSI
MASTER SS
BYTE 1
BYTE 2
BYTE 3
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 15-6. CPHA/SS Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
200
Freescale Semiconductor
Transmission Formats
When CPHA = 0 for a slave, the falling edge of SS indicates the beginning of the transmission. This
causes the SPI to leave its idle state and begin driving the MISO pin with the MSB of its data. Once the
transmission begins, no new data is allowed into the shift register from the transmit data register.
Therefore, the SPI data register of the slave must be loaded with transmit data before the falling edge of
SS. Any data written after the falling edge is stored in the transmit data register and transferred to the shift
register after the current transmission.
15.5.3 Transmission Format When CPHA = 1
Figure 15-7 shows an SPI transmission in which CPHA is logic 1. The figure should not be used as a
replacement for data sheet parametric information. Two waveforms are shown for SPSCK: one for
CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing
diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins
are directly connected between the master and the slave. The MISO signal is the output from the slave,
and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The
slave SPI drives its MISO output only when its slave select input (SS) is at logic 0, so that only the selected
slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS
pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. See
15.6.2 Mode Fault Error. When CPHA = 1, the master begins driving its MOSI pin on the first SPSCK
edge. Therefore, the slave uses the first SPSCK edge as a start transmission signal. The SS pin can
remain low between transmissions. This format may be preferable in systems having only one master and
only one slave driving the MISO data line.
When CPHA = 1 for a slave, the first edge of the SPSCK indicates the beginning of the transmission. This
causes the SPI to leave its idle state and begin driving the MISO pin with the MSB of its data. Once the
transmission begins, no new data is allowed into the shift register from the transmit data register.
Therefore, the SPI data register of the slave must be loaded with transmit data before the first edge of
SPSCK. Any data written after the first edge is stored in the transmit data register and transferred to the
shift register after the current transmission.
SPSCK CYCLE #
FOR REFERENCE
1
2
3
4
5
6
7
8
SPSCK, CPOL = 0
SPSCK, CPOL = 1
MOSI
FROM MASTER
MSB
MSB
BIT 6
BIT 6
BIT 5
BIT 5
BIT 4
BIT 4
BIT 3
BIT 3
BIT 2
BIT 2
BIT 1
BIT 1
LSB
MISO
FROM SLAVE
LSB
SS, TO SLAVE
CAPTURE STROBE
Figure 15-7. Transmission Format (CPHA = 1)
15.5.4 Transmission Initiation Latency
When the SPI is configured as a master (SPMSTR = 1), writing to the SPDR starts a transmission. CPHA
has no effect on the delay to the start of the transmission, but it does affect the initial state of the SPSCK
signal. When CPHA = 0, the SPSCK signal remains inactive for the first half of the first SPSCK cycle.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
201
Serial Peripheral Interface Module (SPI)
When CPHA = 1, the first SPSCK cycle begins with an edge on the SPSCK line from its inactive to its
active level. The SPI clock rate (selected by SPR1:SPR0) affects the delay from the write to SPDR and
the start of the SPI transmission. See Figure 15-8 The internal SPI clock in the master is a free-running
derivative of the internal MCU clock. To conserve power, it is enabled only when both the SPE and
SPMSTR bits are set. SPSCK edges occur halfway through the low time of the internal MCU clock. Since
the SPI clock is free-running, it is uncertain where the write to the SPDR occurs relative to the slower
SPSCK. This uncertainty causes the variation in the initiation delay shown in Figure 15-8. This delay is
no longer than a single SPI bit time. That is, the maximum delay is two MCU bus cycles for DIV2, eight
MCU bus cycles for DIV8, 32 MCU bus cycles for DIV32, and 128 MCU bus cycles for DIV128.
WRITE
TO SPDR
INITIATION DELAY
BUS
CLOCK
MOSI
MSB
BIT 6
BIT 5
SPSCK
CPHA = 1
SPSCK
CPHA = 0
SPSCK CYCLE
NUMBER
1
2
3
INITIATION DELAY FROM WRITE SPDR TO TRANSFER BEGIN
WRITE
TO SPDR
BUS
CLOCK
SPSCK = INTERNAL CLOCK ÷ 2;
2 POSSIBLE START POINTS
EARLIEST LATEST
WRITE
TO SPDR
BUS
CLOCK
EARLIEST
WRITE
TO SPDR
SPSCK = INTERNAL CLOCK ÷ 8;
8 POSSIBLE START POINTS
LATEST
LATEST
LATEST
BUS
CLOCK
EARLIEST
WRITE
TO SPDR
SPSCK = INTERNAL CLOCK ÷ 32;
32 POSSIBLE START POINTS
BUS
CLOCK
EARLIEST
SPSCK = INTERNAL CLOCK ÷ 128;
128 POSSIBLE START POINTS
Figure 15-8. Transmission Start Delay (Master)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
202
Freescale Semiconductor
Error Conditions
15.6 Error Conditions
These flags signal SPI error conditions:
•
Overflow (OVRF) — Failing to read the SPI data register before the next full byte enters the shift
register sets the OVRF bit. The new byte does not transfer to the receive data register, and the
unread byte still can be read. OVRF is in the SPI status and control register.
•
Mode fault error (MODF) — The MODF bit indicates that the voltage on the slave select pin (SS)
is inconsistent with the mode of the SPI. MODF is in the SPI status and control register.
15.6.1 Overflow Error
The overflow flag (OVRF) becomes set if the receive data register still has unread data from a previous
transmission when the capture strobe of bit 1 of the next transmission occurs. If an overflow occurs, all
data received after the overflow and before the OVRF bit is cleared does not transfer to the receive data
register and does not set the SPI receiver full bit (SPRF). The unread data that transferred to the receive
data register before the overflow occurred can still be read. Therefore, an overflow error always indicates
the loss of data. Clear the overflow flag by reading the SPI status and control register and then reading
the SPI data register.
OVRF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also
set. MODF and OVRF can generate a receiver/error CPU interrupt request. See Figure 15-11. It is not
possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request.
However, leaving MODFEN low prevents MODF from being set.
If the CPU SPRF interrupt is enabled and the OVRF interrupt is not, watch for an overflow condition.
Figure 15-9 shows how it is possible to miss an overflow. The first part of Figure 15-9 shows how it is
possible to read the SPSCR and SPDR to clear the SPRF without problems. However, as illustrated by
the second transmission example, the OVRF bit can be set in between the time that SPSCR and SPDR
are read.
BYTE 1
1
BYTE 2
4
BYTE 3
6
BYTE 4
8
SPRF
OVRF
READ
SPSCR
2
5
5
READ
SPDR
3
7
1
2
BYTE 1 SETS SPRF BIT.
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
6
7
BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST.
3
4
CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT,
BUT NOT OVRF BIT.
BYTE 2 SETS SPRF BIT.
8
BYTE 4 FAILS TO SET SPRF BIT BECAUSE
OVRF BIT IS NOT CLEARED. BYTE 4 IS LOST.
Figure 15-9. Missed Read of Overflow Condition
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
203
Serial Peripheral Interface Module (SPI)
In this case, an overflow can easily be missed. Since no more SPRF interrupts can be generated until this
OVRF is serviced, it is not obvious that bytes are being lost as more transmissions are completed. To
prevent this, either enable the OVRF interrupt or do another read of the SPSCR following the read of the
SPDR. This ensures that the OVRF was not set before the SPRF was cleared and that future
transmissions can set the SPRF bit. Figure 15-10 illustrates this process. Generally, to avoid this second
SPSCR read, enable the OVRF interrupt to the CPU by setting the ERRIE bit.
BYTE 1
1
BYTE 2
5
BYTE 3
7
BYTE 4
11
SPI RECEIVE
COMPLETE
SPRF
OVRF
READ
SPSCR
2
4
6
9
12
14
READ
SPDR
3
8
10
13
1
2
8
9
BYTE 1 SETS SPRF BIT.
CPU READS BYTE 2 IN SPDR,
CLEARING SPRF BIT.
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
3
4
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
10
CPU READS BYTE 2 SPDR,
CLEARING OVRF BIT.
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
11
12
13
BYTE 4 SETS SPRF BIT.
CPU READS SPSCR.
5
6
BYTE 2 SETS SPRF BIT.
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 4 IN SPDR,
CLEARING SPRF BIT.
7
BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST.
14
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
Figure 15-10. Clearing SPRF When OVRF Interrupt Is Not Enabled
15.6.2 Mode Fault Error
Setting the SPMSTR bit selects master mode and configures the SPSCK and MOSI pins as outputs and
the MISO pin as an input. Clearing SPMSTR selects slave mode and configures the SPSCK and MOSI
pins as inputs and the MISO pin as an output. The mode fault bit, MODF, becomes set any time the state
of the slave select pin, SS, is inconsistent with the mode selected by SPMSTR.
To prevent SPI pin contention and damage to the MCU, a mode fault error occurs if:
•
•
The SS pin of a slave SPI goes high during a transmission.
The SS pin of a master SPI goes low at any time.
For the MODF flag to be set, the mode fault error enable bit (MODFEN) must be set. Clearing the
MODFEN bit does not clear the MODF flag but does prevent MODF from being set again after MODF is
cleared.
MODF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also
set. The SPRF, MODF, and OVRF interrupts share the same CPU interrupt vector. MODF and OVRF can
generate a receiver/error CPU interrupt request. See Figure 15-11. It is not possible to enable MODF or
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
204
Freescale Semiconductor
Error Conditions
OVRF individually to generate a receiver/error CPU interrupt request. However, leaving MODFEN low
prevents MODF from being set.
In a master SPI with the mode fault enable bit (MODFEN) set, the mode fault flag (MODF) is set if SS
goes to logic 0. A mode fault in a master SPI causes these events to occur:
•
•
•
•
•
If ERRIE = 1, the SPI generates an SPI receiver/error CPU interrupt request.
The SPE bit is cleared.
The SPTE bit is set.
The SPI state counter is cleared.
The data direction register of the shared I/O port regains control of port drivers.
NOTE
To prevent bus contention with another master SPI after a mode fault error,
clear all SPI bits of the data direction register of the shared I/O port before
enabling the SPI.
When configured as a slave (SPMSTR = 0), the MODF flag is set if SS goes high during a transmission.
When CPHA = 0, a transmission begins when SS goes low and ends once the incoming SPSCK goes
back to its idle level following the shift of the eighth data bit. When CPHA = 1, the transmission begins
when the SPSCK leaves its idle level and SS is already low. The transmission continues until the SPSCK
returns to its idle level following the shift of the last data bit. See 15.5 Transmission Formats.
NOTE
Setting the MODF flag does not clear the SPMSTR bit. Reading SPMSTR
when MODF = 1 will indicate a mode fault error occurred in either master
mode or slave mode.
When CPHA = 0, a MODF occurs if a slave is selected (SS is at logic 0) and
later unselected (SS is at logic 1) even if no SPSCK is sent to that slave.
This happens because SS at logic 0 indicates the start of the transmission
(MISO driven out with the value of MSB) for CPHA = 0. When CPHA = 1, a
slave can be selected and then later unselected with no transmission
occurring. Therefore, MODF does not occur since a transmission was
never begun.
In a slave SPI (MSTR = 0), the MODF bit generates an SPI receiver/error CPU interrupt request if the
ERRIE bit is set. The MODF bit does not clear the SPE bit or reset the SPI in any way. Software can abort
the SPI transmission by clearing the SPE bit of the slave.
NOTE
A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a high
impedance state. Also, the slave SPI ignores all incoming SPSCK clocks,
even if it was already in the middle of a transmission.
To clear the MODF flag, read the SPSCR with the MODF bit set and then write to the SPCR register. This
entire clearing procedure must occur with no MODF condition existing or else the flag is not cleared.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
205
Serial Peripheral Interface Module (SPI)
15.7 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt requests as shown in Table 15-2.
Table 15-2. SPI Interrupts
Flag
Request
SPTE transmitter empty
SPRF receiver full
OVRF overflow
SPI transmitter CPU interrupt request (SPTIE = 1, SPE = 1)
SPI receiver CPU interrupt request (SPRIE = 1)
SPI receiver/error interrupt request (ERRIE = 1)
SPI receiver/error interrupt request (ERRIE = 1)
MODF mode fault
The SPI transmitter interrupt enable bit (SPTIE) enables the SPTE flag to generate transmitter CPU
interrupt requests, provided that the SPI is enabled (SPE = 1).
The SPI receiver interrupt enable bit (SPRIE) enables the SPRF bit to generate receiver CPU interrupt
requests, provided that the SPI is enabled (SPE = 1). (See Figure 15-11.)
SPTE
SPTIE
SPRF
SPE
SPI TRANSMITTER
CPU INTERRUPT REQUEST
SPRIE
SPI RECEIVER/ERROR
CPU INTERRUPT REQUEST
ERRIE
MODF
OVRF
Figure 15-11. SPI Interrupt Request Generation
The error interrupt enable bit (ERRIE) enables both the MODF and OVRF bits to generate a receiver/error
CPU interrupt request.
The mode fault enable bit (MODFEN) can prevent the MODF flag from being set so that only the OVRF
bit is enabled by the ERRIE bit to generate receiver/error CPU interrupt requests.
These sources in the SPI status and control register can generate CPU interrupt requests:
•
SPI receiver full bit (SPRF) — The SPRF bit becomes set every time a byte transfers from the shift
register to the receive data register. If the SPI receiver interrupt enable bit, SPRIE, is also set,
SPRF can generate either an SPI receiver/error or CPU interrupt.
•
SPI transmitter empty (SPTE) — The SPTE bit becomes set every time a byte transfers from the
transmit data register to the shift register. If the SPI transmit interrupt enable bit, SPTIE, is also set,
SPTE can generate either an SPTE or CPU interrupt request.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
206
Freescale Semiconductor
Resetting the SPI
15.8 Resetting the SPI
Any system reset completely resets the SPI. Partial resets occur whenever the SPI enable bit (SPE) is
low. Whenever SPE is low:
•
•
•
•
•
The SPTE flag is set.
Any transmission currently in progress is aborted.
The shift register is cleared.
The SPI state counter is cleared, making it ready for a new complete transmission.
All the SPI port logic is defaulted back to being general-purpose I/O.
These items are reset only by a system reset:
•
•
•
All control bits in the SPCR
All control bits in the SPSCR (MODFEN, ERRIE, SPR1, and SPR0)
The status flags SPRF, OVRF, and MODF
By not resetting the control bits when SPE is low, the user can clear SPE between transmissions without
having to set all control bits again when SPE is set back high for the next transmission.
By not resetting the SPRF, OVRF, and MODF flags, the user can still service these interrupts after the
SPI has been disabled. The user can disable the SPI by writing 0 to the SPE bit. The SPI can also be
disabled by a mode fault occurring in an SPI that was configured as a master with the MODFEN bit set.
15.9 Queuing Transmission Data
The double-buffered transmit data register allows a data byte to be queued and transmitted. For an SPI
configured as a master, a queued data byte is transmitted immediately after the previous transmission
has completed. The SPI transmitter empty flag (SPTE) indicates when the transmit data buffer is ready
to accept new data. Write to the transmit data register only when the SPTE bit is high. Figure 15-12
shows the timing associated with doing back-to-back transmissions with the SPI (SPSCK has
CPHA:CPOL = 1:0).
For a slave, the transmit data buffer allows back-to-back transmissions without the slave precisely timing
its writes between transmissions as in a system with a single data buffer. Also, if no new data is written
to the data buffer, the last value contained in the shift register is the next data word to be transmitted.
For an idle master or idle slave that has no data loaded into its transmit buffer, the SPTE is set again no
more than two bus cycles after the transmit buffer empties into the shift register. This allows the user to
queue up a 16-bit value to send. For an already active slave, the load of the shift register cannot occur
until the transmission is completed. This implies that a back-to-back write to the transmit data register is
not possible. The SPTE indicates when the next write can occur.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
207
Serial Peripheral Interface Module (SPI)
1
3
8
WRITE TO SPDR
SPTE
5
10
2
SPSCK
CPHA:CPOL = 1:0
MOSI
MSBBIT BIT BIT BIT BIT BIT LSBMSBBIT BIT BIT BIT BIT BIT LSBMSBBIT BIT BIT
3
6
BYTE 1
5
4
3
2
1
6
BYTE 2
5
4
2
1
6
BYTE 3
5
4
4
9
SPRF
READ SPSCR
READ SPDR
6
11
7
12
1
2
CPU WRITES BYTE 1 TO SPDR, CLEARING SPTE BIT.
7
8
CPU READS SPDR, CLEARING SPRF BIT.
CPU WRITES BYTE 3 TO SPDR, QUEUEING BYTE
3 AND CLEARING SPTE BIT.
BYTE 1 TRANSFERS FROM TRANSMIT DATA
REGISTER TO SHIFT REGISTER, SETTING SPTE BIT.
9
SECOND INCOMING BYTE TRANSFERS FROM SHIFT
REGISTER TO RECEIVE DATA REGISTER, SETTING
SPRF BIT.
CPU WRITES BYTE 2 TO SPDR, QUEUEING BYTE 2
AND CLEARING SPTE BIT.
3
4
10
FIRST INCOMING BYTE TRANSFERS FROM SHIFT
REGISTER TO RECEIVE DATA REGISTER, SETTING
SPRF BIT.
BYTE 3 TRANSFERS FROM TRANSMIT DATA
REGISTER TO SHIFT REGISTER, SETTING SPTE BIT.
11
12
CPU READS SPSCR WITH SPRF BIT SET.
CPU READS SPDR, CLEARING SPRF BIT.
5
6
BYTE 2 TRANSFERS FROM TRANSMIT DATA
REGISTER TO SHIFT REGISTER, SETTING SPTE BIT.
CPU READS SPSCR WITH SPRF BIT SET.
Figure 15-12. SPRF/SPTE CPU Interrupt Timing
15.10 Low-Power Mode
The WAIT instruction puts the MCU in a low power-consumption standby mode.
The SPI module remains active after the execution of a WAIT instruction. In wait mode the SPI module
registers are not accessible by the CPU. Any enabled CPU interrupt request from the SPI module can
bring the MCU out of wait mode.
If SPI module functions are not required during wait mode, reduce power consumption by disabling the
SPI module before executing the WAIT instruction.
To exit wait mode when an overflow condition occurs, enable the OVRF bit to generate CPU interrupt
requests by setting the error interrupt enable bit (ERRIE). See 15.7 Interrupts.
Since the SPTE bit cannot be cleared during a break with the BCFE bit cleared, a write to the transmit
data register in break mode does not initiate a transmission nor is this data transferred into the shift
register. Therefore, a write to the SPDR in break mode with the BCFE bit cleared has no effect.
15.11 I/O Signals
The SPI module has five I/O pins and shares four of them with a parallel I/O port. The pins are:
•
•
•
•
MISO — Data received
MOSI — Data transmitted
SPSCK — Serial clock
SS — Slave select
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
208
Freescale Semiconductor
I/O Signals
The SPI has limited inter-integrated circuit (I2C) capability (requiring software support) as a master in a
single-master environment. To communicate with I2C peripherals, MOSI becomes an open-drain output
when the SPWOM bit in the SPI control register is set. In I2C communication, the MOSI and MISO pins
are connected to a bidirectional pin from the I2C peripheral and through a pullup resistor to VDD
.
15.11.1 MISO (Master In/Slave Out)
MISO is one of the two SPI module pins that transmits serial data. In full duplex operation, the MISO pin
of the master SPI module is connected to the MISO pin of the slave SPI module. The master SPI
simultaneously receives data on its MISO pin and transmits data from its MOSI pin.
Slave output data on the MISO pin is enabled only when the SPI is configured as a slave. The SPI is
configured as a slave when its SPMSTR bit is logic 0 and its SS pin is at logic 0. To support a
multiple-slave system, a logic 1 on the SS pin puts the MISO pin in a high-impedance state.
When enabled, the SPI controls data direction of the MISO pin regardless of the state of the data direction
register of the shared
I/O port.
15.11.2 MOSI (Master Out/Slave In)
MOSI is one of the two SPI module pins that transmits serial data. In full-duplex operation, the MOSI pin
of the master SPI module is connected to the MOSI pin of the slave SPI module. The master SPI
simultaneously transmits data from its MOSI pin and receives data on its MISO pin.
When enabled, the SPI controls data direction of the MOSI pin regardless of the state of the data direction
register of the shared I/O port.
15.11.3 SPSCK (Serial Clock)
The serial clock synchronizes data transmission between master and slave devices. In a master MCU,
the SPSCK pin is the clock output. In a slave MCU, the SPSCK pin is the clock input. In full-duplex
operation, the master and slave MCUs exchange a byte of data in eight serial clock cycles.
When enabled, the SPI controls data direction of the SPSCK pin regardless of the state of the data
direction register of the shared I/O port.
15.11.4 SS (Slave Select)
The SS pin has various functions depending on the current state of the SPI. For an SPI configured as a
slave, the SS is used to select a slave. For CPHA = 0, the SS is used to define the start of a transmission.
See 15.5 Transmission Formats. Since it is used to indicate the start of a transmission, the SS must be
toggled high and low between each byte transmitted for the CPHA = 0 format. However, it can remain low
between transmissions for the CPHA = 1 format. See Figure 15-13.
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 15-13. CPHA/SS Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
209
Serial Peripheral Interface Module (SPI)
When an SPI is configured as a slave, the SS pin is always configured as an input. It cannot be used as
a general-purpose I/O regardless of the state of the MODFEN control bit. However, the MODFEN bit can
still prevent the state of the SS from creating a MODF error. See 15.12.2 SPI Status and Control Register.
NOTE
A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a
high-impedance state. The slave SPI ignores all incoming SPSCK clocks,
even if it was already in the middle of a transmission.
When an SPI is configured as a master, the SS input can be used in conjunction with the MODF flag to
prevent multiple masters from driving MOSI and SPSCK. (See 15.6.2 Mode Fault Error.) For the state of
the SS pin to set the MODF flag, the MODFEN bit in the SPSCK register must be set. If the MODFEN bit
is low for an SPI master, the SS pin can be used as a general-purpose I/O under the control of the data
direction register of the shared I/O port. With MODFEN high, it is an input-only pin to the SPI regardless
of the state of the data direction register of the shared I/O port.
The CPU can always read the state of the SS pin by configuring the appropriate pin as an input and
reading the port data register. See Table 15-3.
Table 15-3. SPI Configuration
SPE
SPMSTR
MODFEN
SPI Configuration
Not enabled
State of SS Logic
General-purpose I/O; SS ignored by SPI
Input-only to SPI
X(1)
0
0
1
1
1
X
X
0
Slave
1
Master without MODF
Master with MODF
General-purpose I/O; SS ignored by SPI
Input-only to SPI
1
1
1. X = don’t care
15.11.5 V (Clock Ground)
SS
VSS is the ground return for the serial clock pin, SPSCK, and the ground for the port output buffers. To
reduce the ground return path loop and minimize radio frequency (RF) emissions, connect the ground pin
of the slave to the VSS pin of the master.
15.12 I/O Registers
Three registers control and monitor SPI operation:
•
•
•
SPI control register, SPCR
SPI status and control register, SPSCR
SPI data register, SPDR
15.12.1 SPI Control Register
The SPI control register (SPCR):
•
•
•
•
•
•
Enables SPI module interrupt requests
Selects CPU interrupt requests or DMA service requests
Configures the SPI module as master or slave
Selects serial clock polarity and phase
Configures the SPSCK, MOSI, and MISO pins as open-drain outputs
Enables the SPI module
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
210
Freescale Semiconductor
I/O Registers
Address: $0044
Bit 7
6
5
SPMSTR
1
4
CPOL
0
3
CPHA
1
2
SPWOM
0
1
SPE
0
Bit 0
SPTIE
0
Read:
Write:
Reset:
SPRIE
R
0
0
R
= Reserved
Figure 15-14. SPI Control Register (SPCR)
SPRIE — SPI Receiver Interrupt Enable Bit
This read/write bit enables CPU interrupt requests generated by the SPRF bit. The SPRF bit is set
when a byte transfers from the shift register to the receive data register. Reset clears the SPRIE bit.
1 = SPRF CPU interrupt requests enabled
0 = SPRF CPU interrupt requests disabled
SPMSTR — SPI Master Bit
This read/write bit selects master mode operation or slave mode operation. Reset sets the SPMSTR
bit.
1 = Master mode
0 = Slave mode
CPOL — Clock Polarity Bit
This read/write bit determines the logic state of the SPSCK pin between transmissions. See Figure
15-5 and Figure 15-7. To transmit data between SPI modules, the SPI modules must have identical
CPOL values. Reset clears the CPOL bit.
CPHA — Clock Phase Bit
This read/write bit controls the timing relationship between the serial clock and SPI data. See Figure
15-5 and Figure 15-7. To transmit data between SPI modules, the SPI modules must have identical
CPHA bits. When CPHA = 0, the SS pin of the slave SPI module must be set to logic 1 between bytes.
See Figure 15-13. Reset sets the CPHA bit.
When CPHA = 0 for a slave, the falling edge of SS indicates the beginning of the transmission. This
causes the SPI to leave its idle state and begin driving the MISO pin with the MSB of its data, once the
transmission begins, no new data is allowed into the shift register from the data register. Therefore,
the slave data register must be loaded with the desired transmit data before the falling edge of SS. Any
data written after the falling edge is stored in the data register and transferred to the shift register at
the current transmission.
When CPHA = 1 for a slave, the first edge of the SPSCK indicates the beginning of the transmission.
The same applies when SS is high for a slave. The MISO pin is held in a high-impedance state, and
the incoming SPSCK is ignored. In certain cases, it may also cause the MODF flag to be set. See
15.6.2 Mode Fault Error. A logic 1 on the SS pin does not in any way affect the state of the SPI state
machine.
SPWOM — SPI Wired-OR Mode Bit
This read/write bit disables the pullup devices on pins SPSCK, MOSI, and MISO so that those pins
become open-drain outputs.
1 = Wired-OR SPSCK, MOSI, and MISO pins
0 = Normal push-pull SPSCK, MOSI, and MISO pins
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Serial Peripheral Interface Module (SPI)
SPE — SPI Enable Bit
This read/write bit enables the SPI module. Clearing SPE causes a partial reset of the SPI. See 15.8
Resetting the SPI. Reset clears the SPE bit.
1 = SPI module enabled
0 = SPI module disabled
SPTIE— SPI Transmit Interrupt Enable Bit
This read/write bit enables CPU interrupt requests generated by the SPTE bit. SPTE is set when a byte
transfers from the transmit data register to the shift register. Reset clears the SPTIE bit.
1 = SPTE CPU interrupt requests enabled
0 = SPTE CPU interrupt requests disabled
15.12.2 SPI Status and Control Register
The SPI status and control register (SPSCR) contains flags to signal these conditions:
•
•
•
•
Receive data register full
Failure to clear SPRF bit before next byte is received (overflow error)
Inconsistent logic level on SS pin (mode fault error)
Transmit data register empty
The SPI status and control register also contains bits that perform these functions:
•
•
•
Enable error interrupts
Enable mode fault error detection
Select master SPI baud rate
Address: $0045
Bit 7
SPRF
R
6
5
OVRF
R
4
MODF
R
3
SPTE
R
2
MODFEN
0
1
SPR1
0
Bit 0
SPR0
0
Read:
Write:
Reset:
ERRIE
0
0
0
0
1
R
= Reserved
Figure 15-15. SPI Status and Control Register (SPSCR)
SPRF — SPI Receiver Full Bit
This clearable, read-only flag is set each time a byte transfers from the shift register to the receive data
register. SPRF generates a CPU interrupt request if the SPRIE bit in the SPI control register is set also.
During an SPRF CPU interrupt (DMAS = 0), the CPU clears SPRF by reading the SPI status and
control register with SPRF set and then reading the SPI data register.
Reset clears the SPRF bit.
1 = Receive data register full
0 = Receive data register not full
ERRIE — Error Interrupt Enable Bit
This read/write bit enables the MODF and OVRF bits to generate CPU interrupt requests. Reset clears
the ERRIE bit.
1 = MODF and OVRF can generate CPU interrupt requests.
0 = MODF and OVRF cannot generate CPU interrupt requests.
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I/O Registers
OVRF — Overflow Bit
This clearable, read-only flag is set if software does not read the byte in the receive data register before
the next full byte enters the shift register. In an overflow condition, the byte already in the receive data
register is unaffected, and the byte that shifted in last is lost. Clear the OVRF bit by reading the SPI
status and control register with OVRF set and then reading the receive data register. Reset clears the
OVRF bit.
1 = Overflow
0 = No overflow
MODF — Mode Fault Bit
This clearable, read-only flag is set in a slave SPI if the SS pin goes high during a transmission with
the MODFEN bit set. In a master SPI, the MODF flag is set if the SS pin goes low at any time with the
MODFEN bit set. Clear the MODF bit by reading the SPI status and control register (SPSCR) with
MODF set and then writing to the SPI control register (SPCR). Reset clears the MODF bit.
1 = SS pin at inappropriate logic level
0 = SS pin at appropriate logic level
SPTE — SPI Transmitter Empty Bit
This clearable, read-only flag is set each time the transmit data register transfers a byte into the shift
register. SPTE generates an SPTE CPU interrupt request or an SPTE DMA service request if the
SPTIE bit in the SPI control register is set also.
NOTE
Do not write to the SPI data register unless the SPTE bit is high.
For an idle master of idle slave that has no data loaded into its transmit buffer, the SPTE will be set
again within two bus cycles since the transmit buffer empties into the shift register. This allows the user
to queue up a 16-bit value to send. For an already active slave, the load of the shift register cannot
occur until the transmission is completed. This implies that a back-to-back write to the transmit data
register is not possible. The SPTE indicates when the next write can occur.
Reset sets the SPTE bit.
1 = Transmit data register empty
0 = Transmit data register not empty
MODFEN — Mode Fault Enable Bit
This read/write bit, when set to 1, allows the MODF flag to be set. If the MODF flag is set, clearing the
MODFEN does not clear the MODF flag. If the SPI is enabled as a master and the MODFEN bit is low,
then the SS pin is available as a general-purpose I/O.
If the MODFEN bit is set, then this pin is not available as a general-purpose I/O. When the SPI is
enabled as a slave, the SS pin is not available as a general-purpose I/O regardless of the value of
MODFEN. See 15.11.4 SS (Slave Select).
If the MODFEN bit is low, the level of the SS pin does not affect the operation of an enabled SPI
configured as a master. For an enabled SPI configured as a slave, having MODFEN low only prevents
the MODF flag from being set. It does not affect any other part of SPI operation. See 15.6.2 Mode Fault
Error.
SPR1 and SPR0 — SPI Baud Rate Select Bits
In master mode, these read/write bits select one of four baud rates as shown in Table 15-4. SPR1 and
SPR0 have no effect in slave mode. Reset clears SPR1 and SPR0.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
213
Serial Peripheral Interface Module (SPI)
Table 15-4. SPI Master Baud Rate Selection
SPR1:SPR0
Baud Rate Divisor (BD)
00
01
10
11
2
8
32
128
Use this formula to calculate the SPI baud rate:
CGMOUT
Baud rate = --------------------------
2 × BD
where:
CGMOUT = base clock output of the clock generator module (CGM)
BD = baud rate divisor
15.12.3 SPI Data Register
The SPI data register consists of the read-only receive data register and the write-only transmit data
register. Writing to the SPI data register writes data into the transmit data register. Reading the SPI data
register reads data from the receive data register. The transmit data and receive data registers are
separate registers that can contain different values. See Figure 15-2.
Address: $0046
Bit 7
R7
6
5
4
3
2
1
Bit 0
R0
Read:
Write:
Reset:
R6
T6
R5
T5
R4
T4
R3
T3
R2
T2
R1
T1
T7
T0
Indeterminate after reset
Figure 15-16. SPI Data Register (SPDR)
R7:R0/T7:T0 — Receive/Transmit Data Bits
NOTE
Do not use read-modify-write instructions on the SPI data register since the
register read is not the same as the register written.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Chapter 16
Timer Interface A (TIMA)
16.1 Introduction
This section describes the timer interface module A (TIMA). The TIMA is a 4-channel timer that provides:
•
•
•
Timing reference with input capture
Output compare
Pulse-width modulator functions
Figure 16-2 is a block diagram of the TIMA.
16.2 Features
Features of the TIMA include:
•
Four input capture/output compare channels:
–
–
Rising-edge, falling-edge, or any-edge input capture trigger
Set, clear, or toggle output compare action
•
•
Buffered and unbuffered pulse-width modulator (PWM) signal generation
Programmable TIMA clock input:
–
–
7-frequency internal bus clock prescaler selection
External TIMA clock input (4-MHz maximum frequency)
•
•
•
Free-running or modulo up-count operation
Toggle any channel pin on overflow
TIMA counter stop and reset bits
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
215
INTERNAL BUS
M68HC08 CPU
PTA7–PTA0
CPU
REGISTERS
ARITHMETIC/LOGIC
UNIT
LOW-VOLTAGE INHIBIT
MODULE
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
COMPUTER OPERATING PROPERLY
MODULE
CONTROL AND STATUS REGISTERS — 112 BYTES
USER FLASH — 32,256 BYTES
TIMER INTERFACE
MODULE A
USER RAM — 768 BYTES
PTC6
PTC5
TIMER INTERFACE
MODULE B
PTC4
MONITOR ROM — 240 BYTES
PTC3
PTC2
SERIAL COMMUNICATIONS INTERFACE
MODULE
PTC1/ATD9(1)
PTC0/ATD8
USER FLASH VECTOR SPACE — 46 BYTES
OSC1
PTD6/IS3
CLOCK GENERATOR
MODULE
OSC2
SERIAL PERIPHERAL INTERFACE
MODULE(2)
PTD5/IS2
CGMXFC
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
POWER-ON RESET
MODULE
SYSTEM INTEGRATION
MODULE
RST
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
IRQ
MODULE
IRQ
SINGLE BREAK
MODULE
VDDA
(3)
VSSA
ANALOG-TO-DIGITAL CONVERTER
MODULE
(3)
VREFL
VREFH
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PWMGND
PULSE-WIDTH MODULATOR
MODULE
PWM6–PWM1
PTF1/SS(1)
PTF0/SPSCK(1)
VSS
VDD
POWER
VDDAD
VSSAD
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 16-1. Block Diagram Highlighting TIMA Block and Pins
Features
TCLK
PTE3/TCLKA
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
TSTOP
PS2
PS1
PS0
TRST
16-BIT COUNTER
INTER-
RUPT
LOGIC
TOF
TOIE
16-BIT COMPARATOR
TMODH:TMODL
ELS0B
ELS0A
CHANNEL 0
16-BIT COMPARATOR
TCH0H:TCH0L
TOV0
CH0MAX
PTE4
LOGIC
PTE4/TCH0A
CH0F
MS0B
INTER-
RUPT
LOGIC
16-BIT LATCH
CH0IE
MS0A
ELS1B ELS1A
CHANNEL 1
16-BIT COMPARATOR
TCH1H:TCH1L
TOV1
CH1MAX
PTE5
LOGIC
PTE5/TCH1A
CH1F
INTER-
RUPT
LOGIC
16-BIT LATCH
CH1IE
MS1A
ELS2B ELS2A
CHANNEL 2
16-BIT COMPARATOR
TCH2H:TCH2L
TOV2
CH2MAX
PTE6
LOGIC
PTE6/TCH2A
CH2F
MS2B
INTER-
RUPT
LOGIC
16-BIT LATCH
CH2IE
MS2A
ELS3B ELS3A
CHANNEL 3
16-BIT COMPARATOR
TCH3H:TCH3L
TOV3
CH3MAX
PTE7
LOGIC
PTE7/TCH3A
CH3F
INTER-
RUPT
LOGIC
16-BIT LATCH
CH3IE
MS3A
Figure 16-2. TIMA Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
217
Timer Interface A (TIMA)
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read: TOF
0
TRST
0
0
R
TIMA Status/Control Register
TOIE
TSTOP
PS2
PS1
PS0
$000E
(TASC) Write:
0
0
See page 226.
TIMA Counter Register High
See page 227.
Reset:
0
Bit 14
R
1
Bit 13
R
0
0
Bit 10
R
0
Bit 9
R
0
Bit 8
R
Read: Bit 15
Bit 12
R
Bit 11
R
$000F
$0010
$0011
$0012
$0013
$0014
$0015
$0016
$0017
$0018
$0019
(TACNTH) Write:
R
0
Reset:
0
0
0
0
0
0
0
Read: Bit 7
Bit 6
R
Bit 5
R
Bit 4
R
Bit 3
R
Bit 2
R
Bit 1
R
Bit 0
R
TIMA Counter Register Low
See page 227.
(TACNTL) Write:
R
0
Reset:
Read:
0
0
0
0
0
0
0
TIMA Counter Modulo
Bit 15
1
14
13
12
11
10
9
1
1
1
Bit 8
1
Register High (TAMODH) Write:
See page 228.
Reset:
1
1
1
1
1
Read:
TIMA Counter Modulo
Register Low (TAMODL) Write:
Bit 7
6
1
5
1
4
1
3
2
Bit 0
1
See page 228.
Reset:
1
1
ELS0B
0
1
ELS0A
0
Read: CH0F
TIMA Channel 0 Status/Control
See page 229.
CH0IE
0
MS0B
0
MS0A
0
TOV0 CH0MAX
Register (TASC0) Write:
0
0
Reset:
Read:
0
9
0
TIMA Channel 0 Register High
Bit 15
14
13
12
11
10
Bit 8
(TACH0H) Write:
See page 232.
Reset:
Read:
Indeterminate after reset
TIMA Channel 0 Register Low
Bit 7
6
5
4
3
2
1
Bit 0
(TACH0L) Write:
See page 232.
Reset:
Read: CH1F
Indeterminate after reset
0
R
0
TIMA Channel 1 Status/Control
See page 229.
CH1IE
MS1A
0
ELS1B
ELS1A
TOV1 CH1MAX
Register (TASC1) Write:
0
0
Reset:
Read:
0
0
0
0
9
0
TIMA Channel 1 Register High
Bit 15
14
13
12
11
10
Bit 8
(TACH1H) Write:
See page 232.
Reset:
Read:
Indeterminate after reset
TIMA Channel 1 Register Low
Bit 7
6
5
4
3
2
1
Bit 0
(TACH1L) Write:
See page 232.
Reset:
Read: CH2F
Indeterminate after reset
TIMA Channel 2 Status/Control
See page 229.
CH2IE
MS2B
0
MS2A
0
ELS2B
0
ELS2A
0
TOV2 CH2MAX
Register (TASC2) Write:
0
0
Reset:
0
0
0
= Reserved
R
Figure 16-3. TIM I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
218
Freescale Semiconductor
Functional Description
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
TIMA Channel 2 Register High
Bit 15
14
13
12
11
10
9
Bit 8
$001A
(TACH2H) Write:
See page 232.
Reset:
Read:
Indeterminate after reset
TIMA Channel 2 Register Low
Bit 7
6
5
4
3
2
1
Bit 0
$001B
$001C
$001D
$001E
(TACH2L) Write:
See page 232.
Reset:
Read: CH3F
Indeterminate after reset
0
R
0
TIMA Channel 3 Status/Control
See page 229.
CH3IE
MS3A
0
ELS3B
ELS3A
TOV3 CH3MAX
Register (TASC3) Write:
0
0
Reset:
Read:
0
0
0
0
9
0
TIMA Channel 3 Register High
Bit 15
14
13
12
11
10
Bit 8
(TACH3H) Write:
See page 232.
Reset:
Read:
Indeterminate after reset
TIMA Channel 3 Register Low
Bit 7
R
6
5
4
3
2
1
Bit 0
(TACH3L) Write:
See page 232.
Reset:
Indeterminate after reset
= Reserved
Figure 16-3. TIM I/O Register Summary (Continued)
16.3 Functional Description
Figure 16-2 shows the TIMA structure. The central component of the TIMA is the 16-bit TIMA counter that
can operate as a free-running counter or a modulo up-counter. The TIMA counter provides the timing
reference for the input capture and output compare functions. The TIMA counter modulo registers,
TAMODH–TAMODL, control the modulo value of the TIMA counter. Software can read the TIMA counter
value at any time without affecting the counting sequence.
The four TIMA channels are programmable independently as input capture or output compare channels.
16.3.1 TIMA Counter Prescaler
The TIMA clock source can be one of the seven prescaler outputs or the TIMA clock pin, PTE3/TCLKA.
The prescaler generates seven clock rates from the internal bus clock. The prescaler select bits, PS[2:0],
in the TIMA status and control register select the TIMA clock source.
16.3.2 Input Capture
An input capture function has three basic parts:
1. Edge select logic
2. Input capture latch
3. 16-bit counter
Two 8-bit registers, which make up the 16-bit input capture register, are used to latch the value of the
free-running counter after the corresponding input capture edge detector senses a defined transition. The
polarity of the active edge is programmable. The level transition which triggers the counter transfer is
defined by the corresponding input edge bits (ELSxB and ELSxA in TASC0–TASC3 control registers with
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
219
Timer Interface A (TIMA)
x referring to the active channel number). When an active edge occurs on the pin of an input capture
channel, the TIMA latches the contents of the TIMA counter into the TIMA channel registers,
TACHxH–TACHxL. Input captures can generate TIMA CPU interrupt requests. Software can determine
that an input capture event has occurred by enabling input capture interrupts or by polling the status flag
bit.
The free-running counter contents are transferred to the TIMA channel status and control register
(TACHxH–TACHxL, see 16.7.5 TIMA Channel Registers) on each proper signal transition regardless of
whether the TIMA channel flag (CH0F–CH3F in TASC0–TASC3 registers) is set or clear. When the status
flag is set, a CPU interrupt is generated if enabled. The value of the count latched or “captured” is the time
of the event. Because this value is stored in the input capture register two bus cycles after the actual event
occurs, user software can respond to this event at a later time and determine the actual time of the event.
However, this must be done prior to another input capture on the same pin; otherwise, the previous time
value will be lost.
By recording the times for successive edges on an incoming signal, software can determine the period
and/or pulse width of the signal. To measure a period, two successive edges of the same polarity are
captured. To measure a pulse width, two alternate polarity edges are captured. Software should track the
overflows at the 16-bit module counter to extend its range.
Another use for the input capture function is to establish a time reference. In this case, an input capture
function is used in conjunction with an output compare function. For example, to activate an output signal
a specified number of clock cycles after detecting an input event (edge), use the input capture function to
record the time at which the edge occurred. A number corresponding to the desired delay is added to this
captured value and stored to an output compare register (see
16.7.5 TIMA Channel Registers). Because both input captures and output compares are referenced to
the same 16-bit modulo counter, the delay can be controlled to the resolution of the counter independent
of software latencies.
Reset does not affect the contents of the input capture channel registers.
16.3.3 Output Compare
With the output compare function, the TIMA can generate a periodic pulse with a programmable polarity,
duration, and frequency. When the counter reaches the value in the registers of an output compare
channel, the TIMA can set, clear, or toggle the channel pin. Output compares can generate TIMA CPU
interrupt requests.
16.3.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare pulses as described in 16.3.3
Output Compare. The pulses are unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMA channel registers.
An unsynchronized write to the TIMA channel registers to change an output compare value could cause
incorrect operation for up to two counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new value prevents any compare during
that counter overflow period. Also, using a TIMA overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMA may pass the new value before it is
written.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
220
Freescale Semiconductor
Functional Description
Use this method to synchronize unbuffered changes in the output compare value on channel x:
•
When changing to a smaller value, enable channel x output compare interrupts and write the new
value in the output compare interrupt routine. The output compare interrupt occurs at the end of
the current output compare pulse. The interrupt routine has until the end of the counter overflow
period to write the new value.
•
When changing to a larger output compare value, enable TIMA overflow interrupts and write the
new value in the TIMA overflow interrupt routine. The TIMA overflow interrupt occurs at the end of
the current counter overflow period. Writing a larger value in an output compare interrupt routine
(at the end of the current pulse) could cause two output compares to occur in the same counter
overflow period.
16.3.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the
PTE4/TCH0A pin. The TIMA channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIMA channel 0 status and control register (TASC0) links channel 0 and
channel 1. The output compare value in the TIMA channel 0 registers initially controls the output on the
PTE4/TCH0A pin. Writing to the TIMA channel 1 registers enables the TIMA channel 1 registers to
synchronously control the output after the TIMA overflows. At each subsequent overflow, the TIMA
channel registers (0 or 1) that control the output are the ones written to last. TASC0 controls and monitors
the buffered output compare function, and TIMA channel 1 status and control register (TASC1) is unused.
While the MS0B bit is set, the channel 1 pin, PTE5/TCH1A, is available as a general-purpose I/O pin.
Channels 2 and 3 can be linked to form a buffered output compare channel whose output appears on the
PTE6/TCH2A pin. The TIMA channel registers of the linked pair alternately control the output.
Setting the MS2B bit in TIMA channel 2 status and control register (TASC2) links channel 2 and
channel 3. The output compare value in the TIMA channel 2 registers initially controls the output on the
PTE6/TCH2A pin. Writing to the TIMA channel 3 registers enables the TIMA channel 3 registers to
synchronously control the output after the TIMA overflows. At each subsequent overflow, the TIMA
channel registers (2 or 3) that control the output are the ones written to last. TASC2 controls and monitors
the buffered output compare function, and TIMA channel 3 status and control register (TASC3) is unused.
While the MS2B bit is set, the channel 3 pin, PTE7/TCH3A, is available as a general-purpose I/O pin.
NOTE
In buffered output compare operation, do not write new output compare
values to the currently active channel registers. User software should track
the currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered output compares.
16.3.4 Pulse-Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel, the TIMA can generate a PWM
signal. The value in the TIMA counter modulo registers determines the period of the PWM signal. The
channel pin toggles when the counter reaches the value in the TIMA counter modulo registers. The time
between overflows is the period of the PWM signal.
As Figure 16-4 shows, the output compare value in the TIMA channel registers determines the pulse width
of the PWM signal. The time between overflow and output compare is the pulse width. Program the TIMA
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
221
Timer Interface A (TIMA)
to clear the channel pin on output compare if the polarity of the PWM pulse is 1 (ELSxA = 0). Program the
TIMA to set the pin if the polarity of the PWM pulse is 0 (ELSxA = 1).
The value in the TIMA counter modulo registers and the selected prescaler output determines the
frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMA counter modulo registers produces a PWM period of 256 times the internal bus
clock period if the prescaler select value is $000 (see 16.7.1 TIMA Status and Control Register).
The value in the TIMA channel registers determines the pulse width of the PWM output. The pulse width
of an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIMA channel registers
produces a duty cycle of 128/256 or 50 percent.
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
POLARITY = 1
(ELSxA = 0)
TCHx
TCHx
PULSE
WIDTH
POLARITY = 0
(ELSxA = 1)
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 16-4. PWM Period and Pulse Width
16.3.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as described in 16.3.4 Pulse-Width
Modulation (PWM). The pulses are unbuffered because changing the pulse width requires writing the new
pulse width value over the value currently in the TIMA channel registers.
An unsynchronized write to the TIMA channel registers to change a pulse width value could cause
incorrect operation for up to two PWM periods. For example, writing a new value before the counter
reaches the old value but after the counter reaches the new value prevents any compare during that PWM
period. Also, using a TIMA overflow interrupt routine to write a new, smaller pulse width value may cause
the compare to be missed. The TIMA may pass the new value before it is written to the TIMA channel
registers.
Use this method to synchronize unbuffered changes in the PWM pulse width on channel x:
•
When changing to a shorter pulse width, enable channel x output compare interrupts and write the
new value in the output compare interrupt routine. The output compare interrupt occurs at the end
of the current pulse. The interrupt routine has until the end of the PWM period to write the new
value.
•
When changing to a longer pulse width, enable TIMA overflow interrupts and write the new value
in the TIMA overflow interrupt routine. The TIMA overflow interrupt occurs at the end of the current
PWM period. Writing a larger value in an output compare interrupt routine (at the end of the current
pulse) could cause two output compares to occur in the same PWM period.
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Functional Description
duty cycle generation and removes the ability of the channel to self-correct
in the event of software error or noise. Toggling on output compare also can
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
16.3.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the
PTE4/TCH0A pin. The TIMA channel registers of the linked pair alternately control the pulse width of the
output.
Setting the MS0B bit in TIMA channel 0 status and control register (TASC0) links channel 0 and
channel 1. The TIMA channel 0 registers initially control the pulse width on the PTE4/TCH0A pin. Writing
to the TIMA channel 1 registers enables the TIMA channel 1 registers to synchronously control the pulse
width at the beginning of the next PWM period. At each subsequent overflow, the TIMA channel registers
(0 or 1) that control the pulse width are the ones written to last. TASC0 controls and monitors the buffered
PWM function, and TIMA channel 1 status and control register (TASC1) is unused. While the MS0B bit is
set, the channel 1 pin, PTE5/TCH1A, is available as a general-purpose
I/O pin.
Channels 2 and 3 can be linked to form a buffered PWM channel whose output appears on the
PTE6/TCH2A pin. The TIMA channel registers of the linked pair alternately control the pulse width of the
output.
Setting the MS2B bit in TIMA channel 2 status and control register (TASC2) links channel 2 and
channel 3. The TIMA channel 2 registers initially control the pulse width on the PTE6/TCH2A pin. Writing
to the TIMA channel 3 registers enables the TIMA channel 3 registers to synchronously control the pulse
width at the beginning of the next PWM period. At each subsequent overflow, the TIMA channel registers
(2 or 3) that control the pulse width are written to last. TASC2 controls and monitors the buffered PWM
function, and TIMA channel 3 status and control register (TASC3) is unused. While the MS2B bit is set,
the channel 3 pin, PTE7/TCH3A, is available as a general-purpose
I/O pin.
NOTE
In buffered PWM signal generation, do not write new pulse width values to
the currently active channel registers. User software should track the
currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered PWM signals.
16.3.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered PWM signals, use this initialization
procedure:
1. In the TIMA status and control register (TASC):
a. Stop the TIMA counter by setting the TIMA stop bit, TSTOP.
b. Reset the TIMA counter and prescaler by setting the TIMA reset bit, TRST.
2. In the TIMA counter modulo registers (TAMODH–TAMODL), write the value for the required PWM
period.
3. In the TIMA channel x registers (TACHxH–TACHxL), write the value for the required pulse width.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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223
Timer Interface A (TIMA)
4. In TIMA channel x status and control register (TSCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or 1:0 (for buffered output compare
or PWM signals) to the mode select bits, MSxB–MSxA. (See Table 16-2.)
b. Write 1 to the toggle-on-overflow bit, TOVx.
c. Write 1:0 (polarity 1 — to clear output on compare) or 1:1 (polarity 0 — to set output on
compare) to the edge/level select bits, ELSxB–ELSxA. The output action on compare must
force the output to the complement of the pulse width level. (See Table 16-2.)
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
duty cycle generation and removes the ability of the channel to self-correct
in the event of software error or noise. Toggling on output compare can also
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
5. In the TIMA status control register (TASC), clear the TIMA stop bit, TSTOP.
Setting MS0B links channels 0 and 1 and configures them for buffered PWM operation. The TIMA
channel 0 registers (TACH0H–TACH0L) initially control the buffered PWM output. TIMA status control
register 0 (TASC0) controls and monitors the PWM signal from the linked channels. MS0B takes priority
over MS0A.
Setting MS2B links channels 2 and 3 and configures them for buffered PWM operation. The TIMA
channel 2 registers (TACH2H–TACH2L) initially control the buffered PWM output. TIMA status control
register 2 (TASC2) controls and monitors the PWM signal from the linked channels. MS2B takes priority
over MS2A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIMA overflows. Subsequent output
compares try to force the output to a state it is already in and have no effect. The result is a 0 percent duty
cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the TOVx bit generates a 100
percent duty cycle output. (See 16.7.4 TIMA Channel Status and Control Registers.)
16.4 Interrupts
These TIMA sources can generate interrupt requests:
•
TIMA overflow flag (TOF) — The timer overflow flag (TOF) bit is set when the TIMA counter
reaches the modulo value programmed in the TIMA counter modulo registers. The TIMA overflow
interrupt enable bit, TOIE, enables TIMA overflow interrupt requests. TOF and TOIE are in the
TIMA status and control registers.
•
TIMA channel flags (CH3F–CH0F) — The CHxF bit is set when an input capture or output compare
occurs on channel x. Channel x TIMA CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE.
16.5 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
I/O Signals
The TIMA remains active after the execution of a WAIT instruction. In wait mode, the TIMA registers are
not accessible by the CPU. Any enabled CPU interrupt request from the TIMA can bring the MCU out of
wait mode.
If TIMA functions are not required during wait mode, reduce power consumption by stopping the TIMA
before executing the WAIT instruction.
16.6 I/O Signals
Port E shares five of its pins with the TIMA:
•
•
PTE3/TCLKA is an external clock input to the TIMA prescaler.
The four TIMA channel I/O pins are PTE4/TCH0A, PTE5/TCH1A, PTE6/TCH2A, and
PTE7/TCH3A.
16.6.1 TIMA Clock Pin (PTE3/TCLKA)
PTE3/TCLKA is an external clock input that can be the clock source for the TIMA counter instead of the
prescaled internal bus clock. Select the PTE3/TCLKA input by writing logic 1s to the three prescaler select
bits, PS[2:0]. See 16.7.1 TIMA Status and Control Register.
The maximum TCLK frequency is the least: 4 MHz or bus frequency ÷ 2.
PTE3/TCLKA is available as a general-purpose I/O pin when not used as the TIMA clock input. When the
PTE3/TCLKA pin is the TIMA clock input, it is an input regardless of the state of the DDRE3 bit in data
direction register E.
16.6.2 TIMA Channel I/O Pins (PTE4/TCH0A–PTE7/TCH3A)
Each channel I/O pin is programmable independently as an input capture pin or an output compare pin.
PTE2/TCH0 and PTE4/TCH2 can be configured as buffered output compare or buffered PWM pins.
16.7 I/O Registers
These input/output (I/O) registers control and monitor TIMA operation:
•
•
•
•
•
TIMA status and control register (TASC)
TIMA control registers (TACNTH–TACNTL)
TIMA counter modulo registers (TAMODH–TAMODL)
TIMA channel status and control registers (TASC0, TASC1, TASC2, and TASC3)
TIMA channel registers (TACH0H–TACH0L, TACH1H–TACH1L, TACH2H–TACH2L, and
TACH3H–TACH3L)
16.7.1 TIMA Status and Control Register
The TIMA status and control register:
•
•
•
•
•
Enables TIMA overflow interrupts
Flags TIMA overflows
Stops the TIMA counter
Resets the TIMA counter
Prescales the TIMA counter clock
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
225
Timer Interface A (TIMA)
Address: $000E
Bit 7
TOF
0
6
5
TSTOP
1
4
0
3
0
2
PS2
0
1
PS1
0
Bit 0
PS0
0
Read:
Write:
Reset:
TOIE
TRST
0
R
0
0
0
R
= Reserved
Figure 16-5. TIMA Status and Control Register (TASC)
TOF — TIMA Overflow Flag
This read/write flag is set when the TIMA counter reaches the modulo value programmed in the TIMA
counter modulo registers. Clear TOF by reading the TIMA status and control register when TOF is set
and then writing a logic 0 to TOF. If another TIMA overflow occurs before the clearing sequence is
complete, then writing logic 0 to TOF has no effect. Therefore, a TOF interrupt request
cannot be lost due to inadvertent clearing of TOF. Reset clears the TOF bit. Writing a logic 1 to TOF
has no effect.
1 = TIMA counter has reached modulo value.
0 = TIMA counter has not reached modulo value.
TOIE — TIMA Overflow Interrupt Enable Bit
This read/write bit enables TIMA overflow interrupts when the TOF bit becomes set. Reset clears the
TOIE bit.
1 = TIMA overflow interrupts enabled
0 = TIMA overflow interrupts disabled
TSTOP — TIMA Stop Bit
This read/write bit stops the TIMA counter. Counting resumes when TSTOP is cleared. Reset sets the
TSTOP bit, stopping the TIMA counter until software clears the TSTOP bit.
1 = TIMA counter stopped
0 = TIMA counter active
NOTE
Do not set the TSTOP bit before entering wait mode if the TIMA is required
to exit wait mode. Also when the TSTOP bit is set and the timer is
configured for input capture operation, input captures are inhibited until the
TSTOP bit is cleared.
TRST — TIMA Reset Bit
Setting this write-only bit resets the TIMA counter and the TIMA prescaler. Setting TRST has no effect
on any other registers. Counting resumes from $0000. TRST is cleared automatically after the TIMA
counter is reset and always reads as logic 0. Reset clears the TRST bit.
1 = Prescaler and TIMA counter cleared
0 = No effect
NOTE
Setting the TSTOP and TRST bits simultaneously stops the TIMA counter
at a value of $0000.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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I/O Registers
PS[2:0] — Prescaler Select Bits
These read/write bits select either the PTE3/TCLKA pin or one of the seven prescaler outputs as the
input to the TIMA counter as Table 16-1 shows. Reset clears the PS[2:0] bits.
Table 16-1. Prescaler Selection
PS[2:0]
000
TIMA Clock Source
Internal bus clock ÷1
Internal bus clock ÷ 2
Internal bus clock ÷ 4
Internal bus clock ÷ 8
Internal bus clock ÷ 16
Internal bus clock ÷ 32
Internal bus clock ÷ 64
PTE3/TCLKA
001
010
011
100
101
110
111
16.7.2 TIMA Counter Registers
The two read-only TIMA counter registers contain the high and low bytes of the value in the TIMA counter.
Reading the high byte (TACNTH) latches the contents of the low byte (TACNTL) into a buffer. Subsequent
reads of TACNTH do not affect the latched TACNTL value until TACNTL is read. Reset clears the TIMA
counter registers. Setting the TIMA reset bit (TRST) also clears the TIMA counter registers.
NOTE
If TACNTH is read during a break interrupt, be sure to unlatch TACNTL by
reading TACNTL before exiting the break interrupt. Otherwise, TACNTL
retains the value latched during the break.
Register Name and Address:
Bit 7
TACNTH — $000F
6
Bit 14
R
5
Bit 13
R
4
3
Bit 11
R
2
Bit 10
R
1
Bit 9
R
Bit 0
Bit 8
R
Read:
Write:
Reset:
Bit 15
Bit 12
R
0
R
0
0
0
0
0
0
0
Register Name and Address:
Bit 7
TACNTL — $0010
6
5
Bit 5
R
4
3
Bit 3
R
2
Bit 2
R
1
Bit 1
R
Bit 0
Bit 0
R
Read:
Write:
Reset:
Bit 7
R
Bit 6
Bit 4
R
R
0
0
0
0
0
0
0
0
R
= Reserved
Figure 16-6. TIMA Counter Registers (TACNTH and TACNTL)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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227
Timer Interface A (TIMA)
16.7.3 TIMA Counter Modulo Registers
The read/write TIMA modulo registers contain the modulo value for the TIMA counter. When the TIMA
counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIMA counter resumes
counting from $0000 at the next timer clock. Writing to the high byte (TAMODH) inhibits the TOF bit and
overflow interrupts until the low byte (TAMODL) is written. Reset sets the TIMA counter modulo registers.
Register Name and Address:
Bit 7
TAMODH — $0011
6
Bit 14
1
5
Bit 13
1
4
Bit 12
1
3
Bit 11
1
2
Bit 10
1
1
Bit 9
1
Bit 0
Bit 8
1
Read:
Bit 15
Write:
Reset:
1
Register Name and Address:
Bit 7
TAMODL — $0012
6
Bit 6
1
5
Bit 5
1
4
3
Bit 3
1
2
Bit 2
1
1
Bit 1
1
Bit 0
Bit 0
1
Read:
Bit 7
Write:
Bit 4
1
Reset:
1
Figure 16-7. TIMA Counter Modulo Registers
(TAMODH and TAMODL)
NOTE
Reset the TIMA counter before writing to the TIMA counter modulo registers.
16.7.4 TIMA Channel Status and Control Registers
Each of the TIMA channel status and control registers:
•
•
•
•
•
•
•
•
Flags input captures and output compares
Enables input capture and output compare interrupts
Selects input capture, output compare, or PWM operation
Selects high, low, or toggling output on output compare
Selects rising edge, falling edge, or any edge as the active input capture trigger
Selects output toggling on TIMA overflow
Selects 0 percent and 100 percent PWM duty cycle
Selects buffered or unbuffered output compare/PWM operation
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
I/O Registers
Register Name and Address:
Bit 7
TASC0 — $0013
5
6
CH0IE
0
4
3
ELS0B
0
2
ELS0A
0
1
TOV0
0
Bit 0
CH0MAX
0
Read:
Write:
Reset:
CH0F
MS0B
0
MS0A
0
0
0
Register Name and Address:
Bit 7
TASC1 — $0016
6
CH1IE
0
5
0
4
3
ELS1B
0
2
ELS1A
0
1
TOV1
0
Bit 0
CH1MAX
0
Read:
Write:
Reset:
CH1F
MS1A
0
0
0
R
0
Register Name and Address:
Bit 7
TASC2 — $0019
5
6
CH2IE
0
4
3
ELS2B
0
2
ELS2A
0
1
TOV2
0
Bit 0
CH2MAX
0
Read:
Write:
Reset:
CH2F
MS2B
0
MS2A
0
0
0
Register Name and Address:
Bit 7
TASC3 — $001C
6
5
0
4
3
ELS3B
0
2
ELS3A
0
1
TOV3
0
Bit 0
CH3MAX
0
Read:
Write:
Reset:
CH3F
CH3IE
MS3A
0
0
0
R
0
0
R
= Reserved
Figure 16-8. TIMA Channel Status
and Control Registers (TASC0–TASC3)
CHxF — Channel x Flag Bit
When channel x is an input capture channel, this read/write bit is set when an active edge occurs on
the channel x pin. When channel x is an output compare channel, CHxF is set when the value in the
TIMA counter registers matches the value in the TIMA channel x registers.
When CHxIE = 1, clear CHxF by reading TIMA channel x status and control register with CHxF set,
and then writing a 0 to CHxF. If another interrupt request occurs before the clearing sequence is
complete, then writing 0 to CHxF has no effect. Therefore, an interrupt request cannot be lost due to
inadvertent clearing of CHxF.
Reset clears the CHxF bit. Writing a 1 to CHxF has no effect.
1 = Input capture or output compare on channel x
0 = No input capture or output compare on channel x
CHxIE — Channel x Interrupt Enable Bit
This read/write bit enables TIMA CPU interrupts on channel x.
Reset clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
229
Timer Interface A (TIMA)
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation. MSxB exists only in the TIMA
channel 0 and TIMA channel 2 status and control registers.
Setting MS0B disables the channel 1 status and control register and reverts TCH1A pin to
general-purpose I/O.
Setting MS2B disables the channel 3 status and control register and reverts TCH3A pin to
general-purpose I/O.
Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture operation or unbuffered output
compare/PWM operation. See Table 16-2.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level of the TCHxA pin once PWM,
input capture, or output compare operation is enabled. See Table 16-2. Reset clears the MSxA bit.
1 = Initial output level low
0 = Initial output level high
NOTE
Before changing a channel function by writing to the MSxB or MSxA bit, set
the TSTOP and TRST bits in the TIMA status and control register (TASC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits control the active edge-sensing logic
on channel x.
When channel x is an output compare channel, ELSxB and ELSxA control the channel x output
behavior when an output compare occurs.
When ELSxB and ELSxA are both clear, channel x is not connected to port E, and pin PTEx/TCHxA
is available as a general-purpose I/O pin. However, channel x is at a state determined by these bits
and becomes transparent to the respective pin when PWM, input capture, or output compare mode is
enabled. Table 16-2 shows how ELSxB and ELSxA work. Reset clears the ELSxB and ELSxA bits.
NOTE
Before enabling a TIMA channel register for input capture operation, make
sure that the PTEx/TACHx pin is stable for at least two bus clocks.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
I/O Registers
Table 16-2. Mode, Edge, and Level Selection
MSxB:MSxA
ELSxB:ELSxA
Mode
Configuration
Pin under port control; initialize timer output level high
X0
X1
00
00
00
01
01
01
01
1X
1X
1X
00
00
01
10
11
00
01
10
11
01
10
11
Output preset
Pin under port control; initialize timer output level low
Capture on rising edge only
Capture on falling edge only
Capture on rising or falling edge
Software compare only
Input capture
Output
compare
or PWM
Toggle output on compare
Clear output on compare
Set output on compare
Toggle output on compare
Clear output on compare
Buffered
output compare
or buffered PWM
Set output on compare
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit controls the behavior of the channel
x output when the TIMA counter overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIMA counter overflow.
0 = Channel x pin does not toggle on TIMA counter overflow.
NOTE
When TOVx is set, a TIMA counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx is 1 and clear output on compare is selected, setting the CHxMAX bit forces the duty
cycle of buffered and unbuffered PWM signals to 100 percent. As Figure 16-9 shows, CHxMAX bit
takes effect in the cycle after it is set or cleared. The output stays at 100 percent duty cycle level until
the cycle after CHxMAX is cleared.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PTEx/TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
TOVx
Figure 16-9. CHxMAX Latency
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
231
Timer Interface A (TIMA)
16.7.5 TIMA Channel Registers
These read/write registers contain the captured TIMA counter value of the input capture function or the
output compare value of the output compare function. The state of the TIMA channel registers after reset
is unknown.
In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the TIMA channel x registers
(TACHxH) inhibits input captures until the low byte (TACHxL) is read.
In output compare mode (MSxB:MSxA ≠ 0:0), writing to the high byte of the TIMA channel x registers
(TACHxH) inhibits output compares until the low byte (TACHxL) is written.
Register Name and Address:
Bit 7
TACH0H — $0014
6
5
4
3
2
1
Bit 0
Bit 8
Read:
Bit 15
Write:
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Reset:
Indeterminate after reset
Register Name and Address:
Bit 7
TACH0L — $0015
6
5
4
3
2
1
Bit 0
Bit 0
Read:
Bit 7
Write:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Reset:
Indeterminate after reset
Register Name and Address: TACH1H — $0017
Bit 7
6
5
4
3
2
1
Bit 0
Bit 8
Read:
Write:
Reset:
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Indeterminate after reset
Register Name and Address:
Bit 7
TACH1L — $0018
6
5
4
3
2
1
Bit 0
Bit 0
Read:
Bit 7
Write:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Reset:
Indeterminate after reset
Register Name and Address:
Bit 7
TACH2H — $001A
6
5
4
3
2
1
Bit 0
Bit 8
Read:
Bit 15
Write:
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Reset:
Indeterminate after reset
Figure 16-10. TIMA Channel Registers
(TACH0H/L–TACH3H/L)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
232
Freescale Semiconductor
I/O Registers
Register Name and Address:
Bit 7
TACH2L — $001B
6
5
4
3
2
1
Bit 0
Bit 0
Read:
Bit 7
Write:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Reset:
Indeterminate after reset
Register Name and Address:
Bit 7
TACH3H — $001D
6
5
4
3
2
1
Bit 0
Bit 8
Read:
Bit 15
Write:
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Reset:
Indeterminate after reset
Register Name and Address:
Bit 7
TACH3L — $001E
6
5
4
3
2
1
Bit 0
Bit 0
Read:
Bit 7
Write:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Reset:
Indeterminate after reset
Figure 16-10. TIMA Channel Registers
(TACH0H/L–TACH3H/L) (Continued)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
233
Timer Interface A (TIMA)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Chapter 17
Timer Interface B (TIMB)
17.1 Introduction
This section describes the timer interface module B (TIMB). The TIMB is a 2-channel timer that provides:
•
•
•
Timing reference with input capture
Output compare
Pulse-width modulation functions
Figure 17-2 is a block diagram of the TIMB.
NOTE
The TIMB module is not available in the 56-pin shrink dual in-line package
(SDIP).
17.2 Features
Features of the TIMB include:
•
Two input capture/output compare channels:
–
–
Rising-edge, falling-edge, or any-edge input capture trigger
Set, clear, or toggle output compare action
•
•
Buffered and unbuffered pulse-width modulation (PWM) signal generation
Programmable TIMB clock input:
–
–
7-frequency internal bus clock prescaler selection
External TIMB clock input (4-MHz maximum frequency)
•
•
•
Free-running or modulo up-count operation
Toggle any channel pin on overflow
TIMB counter stop and reset bits
17.3 Functional Description
Figure 17-2 shows the TIMB structure. The central component of the TIMB is the 16-bit TIMB counter that
can operate as a free-running counter or a modulo up-counter. The TIMB counter provides the timing
reference for the input capture and output compare functions. The TIMB counter modulo registers,
TBMODH–TBMODL, control the modulo value of the TIMB counter. Software can read the TIMB counter
value at any time without affecting the counting sequence.
The two TIMB channels are programmable independently as input capture or output compare channels.
NOTE
The TIMB module is not available in the 56-pin SDIP.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
235
INTERNAL BUS
M68HC08 CPU
PTA7–PTA0
CPU
REGISTERS
ARITHMETIC/LOGIC
UNIT
LOW-VOLTAGE INHIBIT
MODULE
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
COMPUTER OPERATING PROPERLY
MODULE
CONTROL AND STATUS REGISTERS — 112 BYTES
USER FLASH — 32,256 BYTES
TIMER INTERFACE
MODULE A
USER RAM — 768 BYTES
PTC6
PTC5
TIMER INTERFACE
MODULE B
PTC4
MONITOR ROM — 240 BYTES
PTC3
PTC2
SERIAL COMMUNICATIONS INTERFACE
MODULE
PTC1/ATD9(1)
PTC0/ATD8
USER FLASH VECTOR SPACE — 46 BYTES
OSC1
PTD6/IS3
CLOCK GENERATOR
MODULE
OSC2
SERIAL PERIPHERAL INTERFACE
MODULE(2)
PTD5/IS2
CGMXFC
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
POWER-ON RESET
MODULE
SYSTEM INTEGRATION
MODULE
RST
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
IRQ
MODULE
IRQ
SINGLE BREAK
MODULE
VDDA
(3)
VSSA
ANALOG-TO-DIGITAL CONVERTER
MODULE
(3)
VREFL
VREFH
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PWMGND
PULSE-WIDTH MODULATOR
MODULE
PWM6–PWM1
PTF1/SS(1)
PTF0/SPSCK(1)
VSS
VDD
POWER
VDDAD
VSSAD
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 17-1. Block Diagram Highlighting TIMB Block and Pins
Functional Description
TCLK
PTE0/TCLKB
INTERNAL
BUS CLOCK
PRESCALER SELECT
PRESCALER
TSTOP
TRST
PS2
PS1
PS0
16-BIT COUNTER
INTER-
RUPT
LOGIC
TOF
TOIE
16-BIT COMPARATOR
TMODH:TMODL
ELS0B
ELS0A
CHANNEL 0
16-BIT COMPARATOR
TCH0H:TCH0L
TOV0
CH0MAX
PTE1
LOGIC
PTE1/TCH0B
CH0F
MS0B
INTER-
RUPT
LOGIC
16-BIT LATCH
CH0IE
MS0A
ELS1B ELS1A
CHANNEL 1
16-BIT COMPARATOR
TCH1H:TCH1L
TOV1
CH1MAX
PTE2
LOGIC
PTE2/TCH1B
CH1F
INTER-
RUPT
LOGIC
16-BIT LATCH
CH1IE
MS1A
Figure 17-2. TIMB Block Diagram
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read: TOF
0
TRST
0
0
R
TIMB Status/Control Register
TOIE
TSTOP
PS2
PS1
PS0
$0051
(TBSC) Write:
0
0
See page 244.
TIMB Counter Register High
See page 246.
Reset:
0
Bit 14
R
1
Bit 13
R
0
0
Bit 10
R
0
Bit 9
R
0
Bit 8
R
Read: Bit 15
Bit 12
R
Bit 11
R
$0052
$0053
$0054
$0055
(TBCNTH) Write:
R
0
Reset:
0
0
0
0
0
0
0
Read: Bit 7
Bit 6
R
Bit 5
R
Bit 4
R
Bit 3
R
Bit 2
R
Bit 1
R
Bit 0
R
TIMB Counter Register Low
See page 246.
(TBCNTL) Write:
R
0
Reset:
Read:
0
0
0
0
0
0
0
TIMB Counter Modulo Register
Bit 15
1
Bit 14
1
Bit 13
1
Bit 12
1
Bit 11
1
Bit 10
1
Bit 9
1
Bit 8
1
High (TBMODH) Write:
See page 246.
Reset:
Read:
TIMB Counter Modulo Register
Bit 7
Bit 6
Bit 5
1
Bit 4
1
Bit 3
1
Bit 2
1
Bit 1
1
Bit 0
1
Low (TBMODL) Write:
See page 246.
Reset:
1
1
R
= Reserved
Figure 17-3. TIMB I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
237
Timer Interface B (TIMB)
Addr.
Register Name
Bit 7
6
5
4
3
ELS0B
0
2
ELS0A
0
1
Bit 0
Read: CH0F
TIMB Channel 0 Status/Control
CH0IE
0
MS0B
0
MS0A
0
TOV0 CH0MAX
$0056
Register Write:
0
0
(TBSC0) See page 247.
Reset:
Read:
0
0
TIMB Channel 0 Register High
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
$0057
$0058
$0059
$005A
$005B
(TBCH0H) Write:
See page 250.
Reset:
Read:
Indeterminate after reset
Bit 4 Bit 3
Indeterminate after reset
TIMB Channel 0 Register Low
Bit 7
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
(TBCH0L) Write:
See page 250.
Reset:
Read: CH1F
0
R
0
TIMB Channel 1 Status/Control
(TBSC1) See page 247.
CH1IE
0
MS1A
0
ELS1B
0
ELS1A
0
TOV1 CH1MAX
Register Write:
0
0
Reset:
Read:
0
0
TIMB Channel 1 Register High
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
(TBCH1H) Write:
See page 250.
Reset:
Read:
Indeterminate after reset
Bit 4 Bit 3
Indeterminate after reset
TIMB Channel 1 Register Low
Bit 7
R
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
(TBCH1L) Write:
See page 250.
Reset:
= Reserved
Figure 17-3. TIMB I/O Register Summary (Continued)
17.3.1 TIMB Counter Prescaler
The TIMB clock source can be one of the seven prescaler outputs or the TIMB clock pin, PTE0/TCLKB.
The prescaler generates seven clock rates from the internal bus clock. The prescaler select bits, PS[2:0],
in the TIMB status and control register select the TIMB clock source.
17.3.2 Input Capture
An input capture function has three basic parts:
1. Edge select logic
2. Input capture latch
3. 16-bit counter
Two 8-bit registers, which make up the 16-bit input capture register, are used to latch the value of the
free-running counter after the corresponding input capture edge detector senses a defined transition. The
polarity of the active edge is programmable. The level transition which triggers the counter transfer is
defined by the corresponding input edge bits (ELSxB and ELSxA in TBSC0–TBSC1 control registers with
x referring to the active channel number). When an active edge occurs on the pin of an input capture
channel, the TIMB latches the contents of the TIMB counter into the TIMB channel registers,
TCHxH–TCHxL. Input captures can generate TIMB CPU interrupt requests. Software can determine that
an input capture event has occurred by enabling input capture interrupts or by polling the status flag bit.
The free-running counter contents are transferred to the TIMB channel status and control register
(TBCHxH–TBCHxL, see 17.7.5 TIMB Channel Registers) on each proper signal transition regardless of
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
238
Freescale Semiconductor
Functional Description
whether the TIMB channel flag (CH0F–CH1F in TBSC0–TBSC1 registers) is set or clear. When the status
flag is set, a CPU interrupt is generated if enabled. The value of the count latched or “captured” is the time
of the event. Because this value is stored in the input capture register two bus cycles after the actual event
occurs, user software can respond to this event at a later time and determine the actual time of the event.
However, this must be done prior to another input capture on the same pin; otherwise, the previous time
value will be lost.
By recording the times for successive edges on an incoming signal, software can determine the period
and/or pulse width of the signal. To measure a period, two successive edges of the same polarity are
captured. To measure a pulse width, two alternate polarity edges are captured. Software should track the
overflows at the 16-bit module counter to extend its range.
Another use for the input capture function is to establish a time reference. In this case, an input capture
function is used in conjunction with an output compare function. For example, to activate an output signal
a specified number of clock cycles after detecting an input event (edge), use the input capture function to
record the time at which the edge occurred. A number corresponding to the desired delay is added to this
captured value and stored to an output compare register (see 17.7.5 TIMB Channel Registers). Because
both input captures and output compares are referenced to the same 16-bit modulo counter, the delay
can be controlled to the resolution of the counter independent of software latencies.
Reset does not affect the contents of the input capture channel register (TBCHxH–TBCHxL).
17.3.3 Output Compare
With the output compare function, the TIMB can generate a periodic pulse with a programmable polarity,
duration, and frequency. When the counter reaches the value in the registers of an output compare
channel, the TIMB can set, clear, or toggle the channel pin. Output compares can generate TIMB CPU
interrupt requests.
17.3.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare pulses as described in 17.3.3
Output Compare. The pulses are unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMB channel registers.
An unsynchronized write to the TIMB channel registers to change an output compare value could cause
incorrect operation for up to two counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new value prevents any compare during
that counter overflow period. Also, using a TIMB overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMB may pass the new value before it is
written.
Use this method to synchronize unbuffered changes in the output compare value on channel x:
•
When changing to a smaller value, enable channel x output compare interrupts and write the new
value in the output compare interrupt routine. The output compare interrupt occurs at the end of
the current output compare pulse. The interrupt routine has until the end of the counter overflow
period to write the new value.
•
When changing to a larger output compare value, enable TIMB overflow interrupts and write the
new value in the TIMB overflow interrupt routine. The TIMB overflow interrupt occurs at the end of
the current counter overflow period. Writing a larger value in an output compare interrupt routine
(at the end of the current pulse) could cause two output compares to occur in the same counter
overflow period.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
239
Timer Interface B (TIMB)
17.3.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the
PTE1/TCH0B pin. The TIMB channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIMB channel 0 status and control register (TBSC0) links channel 0 and channel
1. The output compare value in the TIMB channel 0 registers initially controls the output on the
PTE1/TCH0B pin. Writing to the TIMB channel 1 registers enables the TIMB channel 1 registers to
synchronously control the output after the TIMB overflows. At each subsequent overflow, the TIMB
channel registers (0 or 1) that control the output are the ones written to last. TSC0 controls and monitors
the buffered output compare function, and TIMB channel 1 status and control register (TBSC1) is unused.
While the MS0B bit is set, the channel 1 pin, PTE2/TCH1B, is available as a general-purpose I/O pin.
NOTE
In buffered output compare operation, do not write new output compare
values to the currently active channel registers. User software should track
the currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered output compares.
17.3.4 Pulse-Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel, the TIMB can generate a PWM
signal. The value in the TIMB counter modulo registers determines the period of the PWM signal. The
channel pin toggles when the counter reaches the value in the TIMB counter modulo registers. The time
between overflows is the period of the PWM signal.
As Figure 17-4 shows, the output compare value in the TIMB channel registers determines the pulse width
of the PWM signal. The time between overflow and output compare is the pulse width. Program the TIMB
to clear the channel pin on output compare if the polarity of the PWM pulse is 1 (ELSxA = 0). Program the
TIMB to set the pin if the polarity of the PWM pulse is 0 (ELSxA = 1).
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
POLARITY = 1
(ELSxA = 0)
TCHx
TCHx
PULSE
WIDTH
POLARITY = 0
(ELSxA = 1)
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 17-4. PWM Period and Pulse Width
The value in the TIMB counter modulo registers and the selected prescaler output determines the
frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMB counter modulo registers produces a PWM period of 256 times the internal bus
clock period if the prescaler select value is $000 (see 17.7.1 TIMB Status and Control Register).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
240
Freescale Semiconductor
Functional Description
The value in the TIMB channel registers determines the pulse width of the PWM output. The pulse width
of an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIMB channel registers
produces a duty cycle of 128/256 or 50 percent.
17.3.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as described in 17.3.4 Pulse-Width
Modulation (PWM). The pulses are unbuffered because changing the pulse width requires writing the new
pulse width value over the value currently in the TIMB channel registers.
An unsynchronized write to the TIMB channel registers to change a pulse width value could cause
incorrect operation for up to two PWM periods. For example, writing a new value before the counter
reaches the old value but after the counter reaches the new value prevents any compare during that PWM
period. Also, using a TIMB overflow interrupt routine to write a new, smaller pulse width value may cause
the compare to be missed. The TIMB may pass the new value before it is written to the TIMB channel
registers.
Use this method to synchronize unbuffered changes in the PWM pulse width on channel x:
•
When changing to a shorter pulse width, enable channel x output compare interrupts and write the
new value in the output compare interrupt routine. The output compare interrupt occurs at the end
of the current pulse. The interrupt routine has until the end of the PWM period to write the new
value.
•
When changing to a longer pulse width, enable TIMB overflow interrupts and write the new value
in the TIMB overflow interrupt routine. The TIMB overflow interrupt occurs at the end of the current
PWM period. Writing a larger value in an output compare interrupt routine (at the end of the current
pulse) could cause two output compares to occur in the same PWM period.
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
duty cycle generation and removes the ability of the channel to self-correct
in the event of software error or noise. Toggling on output compare also can
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
17.3.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the
PTE1/TCH0B pin. The TIMB channel registers of the linked pair alternately control the pulse width of the
output.
Setting the MS0B bit in TIMB channel 0 status and control register (TBSC0) links channel 0 and channel
1. The TIMB channel 0 registers initially control the pulse width on the PTE1/TCH0B pin. Writing to the
TIMB channel 1 registers enables the TIMB channel 1 registers to synchronously control the pulse width
at the beginning of the next PWM period. At each subsequent overflow, the TIMB channel registers
(0 or 1) that control the pulse width are the ones written to last. TBSC0 controls and monitors the buffered
PWM function, and TIMB channel 1 status and control register (TBSC1) is unused. While the MS0B bit is
set, the channel 1 pin, PTE2/TCH1B, is available as a general-purpose I/O pin.
NOTE
In buffered PWM signal generation, do not write new pulse width values to
the currently active channel registers. User software should track the
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
241
Timer Interface B (TIMB)
currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered PWM signals.
17.3.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered PWM signals, use this initialization
procedure:
1. In the TIMB status and control register (TBSC):
a. Stop the TIMB counter by setting the TIMB stop bit, TSTOP.
b. Reset the TIMB counter and prescaler by setting the TIMB reset bit, TRST.
2. In the TIMB counter modulo registers (TBMODH–TBMODL), write the value for the required PWM
period.
3. In the TIMB channel x registers (TBCHxH–TBCHxL), write the value for the required pulse width.
4. In TIMB channel x status and control register (TBSCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or 1:0 (for buffered output compare
or PWM signals) to the mode select bits, MSxB–MSxA. (See Table 17-2.)
b. Write 1 to the toggle-on-overflow bit, TOVx.
c. Write 1:0 (polarity 1 — to clear output on compare) or 1:1 (polarity 0 — to set output on
compare) to the edge/level select bits, ELSxB–ELSxA. The output action on compare must
force the output to the complement of the pulse width level. (See Table 17-2.)
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
duty cycle generation and removes the ability of the channel to self-correct
in the event of software error or noise. Toggling on output compare can also
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
5. In the TIMB status control register (TBSC), clear the TIMB stop bit, TSTOP.
Setting MS0B links channels 0 and 1 and configures them for buffered PWM operation. The TIMB channel
0 registers (TBCH0H–TBCH0L) initially control the buffered PWM output. TIMB status control register 0
(TBSC0) controls and monitors the PWM signal from the linked channels. MS0B takes priority over MS0A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIMB overflows. Subsequent output
compares try to force the output to a state it is already in and have no effect. The result is a 0 percent duty
cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the TOVx bit generates a
100 percent duty cycle output. (See 17.7.4 TIMB Channel Status and Control Registers.)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
242
Freescale Semiconductor
Interrupts
17.4 Interrupts
These TIMB sources can generate interrupt requests:
•
TIMB overflow flag (TOF) — The timer overflow flag (TOF) bit is set when the TIMB counter
reaches the modulo value programmed in the TIMB counter modulo registers. The TIMB overflow
interrupt enable bit, TOIE, enables TIMB overflow interrupt requests. TOF and TOIE are in the
TIMB status and control registers.
•
TIMB channel flags (CH1F–CH0F) — The CHxF bit is set when an input capture or output compare
occurs on channel x. Channel x TIMB CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE.
17.5 Wait Mode
The WAIT instruction puts the MCU in low-power standby mode.
The TIMB remains active after the execution of a WAIT instruction. In wait mode, the TIMB registers are
not accessible by the CPU. Any enabled CPU interrupt request from the TIMB can bring the MCU out of
wait mode.
If TIMB functions are not required during wait mode, reduce power consumption by stopping the TIMB
before executing the WAIT instruction.
17.6 I/O Signals
Port E shares three of its pins with the TIMB:
•
•
PTE0/TCLKB is an external clock input to the TIMB prescaler.
The two TIMB channel I/O pins are PTE1/TCH0B and PTE2/TCH1B.
17.6.1 TIMB Clock Pin (PTE0/TCLKB)
PTE0/TCLKB is an external clock input that can be the clock source for the TIMB counter instead of the
prescaled internal bus clock. Select the PTE0/TCLKB input by writing 1s to the three prescaler select bits,
PS[2:0]. See 17.7.1 TIMB Status and Control Register.
The maximum TCLK frequency is the least: 4 MHz or bus frequency ÷ 2.
PTE0/TCLKB is available as a general-purpose I/O pin or ADC channel when not used as the TIMB clock
input. When the PTE0/TCLKB pin is the TIMB clock input, it is an input regardless of the state of the
DDRE0 bit in data direction register E.
17.6.2 TIMB Channel I/O Pins (PTE1/TCH0B–PTE2/TCH1B)
Each channel I/O pin is programmable independently as an input capture pin or an output compare pin.
PTE1/TCH0B and PTE2/TCH1B can be configured as buffered output compare or buffered PWM pins.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
243
Timer Interface B (TIMB)
17.7 I/O Registers
These input/output (I/O) registers control and monitor TIMB operation:
•
•
•
•
•
TIMB status and control register (TBSC)
TIMB control registers (TBCNTH–TBCNTL)
TIMB counter modulo registers (TBMODH–TBMODL)
TIMB channel status and control registers (TBSC0 and TBSC1)
TIMB channel registers (TBCH0H–TBCH0L and TBCH1H–TBCH1L)
17.7.1 TIMB Status and Control Register
The TIMB status and control register:
•
•
•
•
•
Enables TIMB overflow interrupts
Flags TIMB overflows
Stops the TIMB counter
Resets the TIMB counter
Prescales the TIMB counter clock
Address:
$0051
Bit 7
TOF
0
6
5
TSTOP
1
4
0
3
0
2
PS2
0
1
PS1
0
Bit 0
PS0
0
Read:
Write:
Reset:
TOIE
TRST
0
R
0
0
0
R
= Reserved
Figure 17-5. TIMB Status and Control Register (TBSC)
TOF — TIMB Overflow Flag
This read/write flag is set when the TIMB counter reaches the modulo value programmed in the TIMB
counter modulo registers. Clear TOF by reading the TIMB status and control register when TOF is set
and then writing a logic 0 to TOF. If another TIMB overflow occurs before the clearing sequence is
complete, then writing logic 0 to TOF has no effect. Therefore, a TOF interrupt request cannot be lost
due to inadvertent clearing of TOF. Reset clears the TOF bit. Writing a logic 1 to TOF has no effect.
1 = TIMB counter has reached modulo value.
0 = TIMB counter has not reached modulo value.
TOIE — TIMB Overflow Interrupt Enable Bit
This read/write bit enables TIMB overflow interrupts when the TOF bit becomes set. Reset clears the
TOIE bit.
1 = TIMB overflow interrupts enabled
0 = TIMB overflow interrupts disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
244
Freescale Semiconductor
I/O Registers
TSTOP — TIMB Stop Bit
This read/write bit stops the TIMB counter. Counting resumes when TSTOP is cleared. Reset sets the
TSTOP bit, stopping the TIMB counter until software clears the TSTOP bit.
1 = TIMB counter stopped
0 = TIMB counter active
NOTE
Do not set the TSTOP bit before entering wait mode if the TIMB is required
to exit wait mode. Also, when the TSTOP bit is set and the timer is
configured for input capture operation, input captures are inhibited until
TSTOP is cleared.
TRST — TIMB Reset Bit
Setting this write-only bit resets the TIMB counter and the TIMB prescaler. Setting TRST has no effect
on any other registers. Counting resumes from $0000. TRST is cleared automatically after the TIMB
counter is reset and always reads as logic 0. Reset clears the TRST bit.
1 = Prescaler and TIMB counter cleared
0 = No effect
NOTE
Setting the TSTOP and TRST bits simultaneously stops the TIMB counter
at a value of $0000.
PS[2:0] — Prescaler Select Bits
These read/write bits select either the PTE0/TCLKB pin or one of the seven prescaler outputs as the
input to the TIMB counter as Table 17-1 shows. Reset clears the PS[2:0] bits.
Table 17-1. Prescaler Selection
PS[2:0]
000
TIMB Clock Source
Internal bus clock ÷1
Internal bus clock ÷ 2
Internal bus clock ÷ 4
Internal bus clock ÷ 8
Internal bus clock ÷ 16
Internal bus clock ÷ 32
Internal bus clock ÷ 64
PTE0/TCLKB
001
010
011
100
101
110
111
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
245
Timer Interface B (TIMB)
17.7.2 TIMB Counter Registers
The two read-only TIMB counter registers contain the high and low bytes of the value in the TIMB counter.
Reading the high byte (TBCNTH) latches the contents of the low byte (TBCNTL) into a buffer. Subsequent
reads of TBCNTH do not affect the latched TBCNTL value until TBCNTL is read. Reset clears the TIMB
counter registers. Setting the TIMB reset bit (TRST) also clears the TIMB counter registers.
NOTE
If TBCNTH is read during a break interrupt, be sure to unlatch TBCNTL by
reading TBCNTL before exiting the break interrupt. Otherwise, TBCNTL
retains the value latched during the break.
Register Name and Address:
Bit 7
TBCNTH — $0052
6
Bit 14
R
5
Bit 13
R
4
3
Bit 11
R
2
Bit 10
R
1
Bit 9
R
Bit 0
Bit 8
R
Read:
Write:
Reset:
Bit 15
Bit 12
R
0
R
0
0
0
0
0
0
0
Register Name and Address:
Bit 7
TBCNTL — $0053
6
5
Bit 5
R
4
3
Bit 3
R
2
Bit 2
R
1
Bit 1
R
Bit 0
Bit 0
R
Read:
Write:
Reset:
Bit 7
R
Bit 6
Bit 4
R
R
0
0
0
0
0
0
0
0
R
= Reserved
Figure 17-6. TIMB Counter Registers (TBCNTH and TBCNTL)
17.7.3 TIMB Counter Modulo Registers
The read/write TIMB modulo registers contain the modulo value for the TIMB counter. When the TIMB
counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIMB counter resumes
counting from $0000 at the next timer clock. Writing to the high byte (TBMODH) inhibits the TOF bit and
overflow interrupts until the low byte (TBMODL) is written. Reset sets the TIMB counter modulo registers.
Register Name and Address:
Bit 7
TBMODH — $0054
6
Bit 14
1
5
Bit 13
1
4
Bit 12
1
3
Bit 11
1
2
Bit 10
1
1
Bit 9
1
Bit 0
Bit 8
1
Read:
Bit 15
Write:
Reset:
1
Register Name and Address:
Bit 7
TBMODL — $0055
6
Bit 6
1
5
Bit 5
1
4
3
Bit 3
1
2
Bit 2
1
1
Bit 1
1
Bit 0
Bit 0
1
Read:
Bit 7
Write:
Bit 4
1
Reset:
1
Figure 17-7. TIMB Counter Modulo Registers (TBMODH and TBMODL)
NOTE
Reset the TIMB counter before writing to the TIMB counter modulo registers.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
246
Freescale Semiconductor
I/O Registers
17.7.4 TIMB Channel Status and Control Registers
Each of the TIMB channel status and control registers:
•
•
•
•
•
•
•
•
Flags input captures and output compares
Enables input capture and output compare interrupts
Selects input capture, output compare, or PWM operation
Selects high, low, or toggling output on output compare
Selects rising edge, falling edge, or any edge as the active input capture trigger
Selects output toggling on TIMB overflow
Selects 0 percent and 100 percent PWM duty cycle
Selects buffered or unbuffered output compare/PWM operation
Register Name and Address:
Bit 7
TBSC0 — $0056
5
6
CH0IE
0
4
3
ELS0B
0
2
ELS0A
0
1
TOV0
0
Bit 0
CH0MAX
0
Read:
Write:
Reset:
CH0F
MS0B
0
MS0A
0
0
0
Register Name and Address:
Bit 7
TBSC1 — $0059
6
5
0
4
3
ELS1B
0
2
ELS1A
0
1
TOV1
0
Bit 0
CH1MAX
0
Read:
Write:
Reset:
CH1F
CH1IE
MS1A
0
0
0
R
0
0
R
= Reserved
Figure 17-8. TIMB Channel Status and Control Registers (TBSC0–TBSC1)
CHxF — Channel x Flag
When channel x is an input capture channel, this read/write bit is set when an active edge occurs on
the channel x pin. When channel x is an output compare channel, CHxF is set when the value in the
TIMB counter registers matches the value in the TIMB channel x registers.
When CHxIE = 1, clear CHxF by reading TIMB channel x status and control register with CHxF set,
and then writing a 0 to CHxF. If another interrupt request occurs before the clearing sequence is
complete, then writing 0 to CHxF has no effect. Therefore, an interrupt request cannot be lost due to
inadvertent clearing of CHxF.
Reset clears the CHxF bit. Writing a 1 to CHxF has no effect.
1 = Input capture or output compare on channel x
0 = No input capture or output compare on channel x
CHxIE — Channel x Interrupt Enable Bit
This read/write bit enables TIMB CPU interrupts on channel x.
Reset clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
247
Timer Interface B (TIMB)
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation. MSxB exists only in the TIMB
channel 0.
Setting MS0B disables the channel 1 status and control register and reverts TCH1B to
general-purpose I/O.
Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture operation or unbuffered output
compare/PWM operation. See Table 17-2.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level of the TCHx pin once PWM, input
capture, or output compare operation is enabled. See Table 17-2. Reset clears the MSxA bit.
1 = Initial output level low
0 = Initial output level high
NOTE
Before changing a channel function by writing to the MSxB or MSxA bit, set
the TSTOP and TRST bits in the TIMB status and control register (TBSC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits control the active edge-sensing logic
on channel x.
When channel x is an output compare channel, ELSxB and ELSxA control the channel x output
behavior when an output compare occurs.
When ELSxB and ELSxA are both clear, channel x is not connected to port E, and pin PTEx/TCHxB
is available as a general-purpose I/O pin. However, channel x is at a state determined by these bits
and becomes transparent to the respective pin when PWM, input capture, or output compare mode is
enabled. Table 17-2 shows how ELSxB and ELSxA work. Reset clears the ELSxB and ELSxA bits.
NOTE
Before enabling a TIMB channel register for input capture operation, make
sure that the PTEx/TBCHx pin is stable for at least two bus clocks.
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit controls the behavior of the channel
x output when the TIMB counter overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIMB counter overflow.
0 = Channel x pin does not toggle on TIMB counter overflow.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
248
Freescale Semiconductor
I/O Registers
Table 17-2. Mode, Edge, and Level Selection
MSxB:MSxA
ELSxB:ELSxA
Mode
Configuration
Pin under port control; initialize timer output level high
X0
X1
00
00
00
01
01
01
01
1X
1X
00
00
01
10
11
00
01
10
11
01
10
Output preset
Pin under port control; initialize timer output level low
Capture on rising edge only
Capture on falling edge only
Capture on rising or falling edge
Softare compare only
Input capture
Toggle output on compare
Clear output on compare
Output compare
or PWM
Set output on compare
Buffered output
compare
or buffered
PWM
Toggle output on compare
Clear output on compare
1X
11
Set output on compare
NOTE
When TOVx is set, a TIMB counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx is 1 and clear output on compare is selected, setting the CHxMAX bit forces the duty
cycle of buffered and unbuffered PWM signals to 100 percent. As Figure 17-9 shows, CHxMAX bit
takes effect in the cycle after it is set or cleared. The output stays at 100 percent duty cycle level until
the cycle after CHxMAX is cleared.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PTEx/TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
TOVx
Figure 17-9. CHxMAX Latency
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
249
Timer Interface B (TIMB)
17.7.5 TIMB Channel Registers
These read/write registers contain the captured TIMB counter value of the input capture function or the
output compare value of the output compare function. The state of the TIMB channel registers after reset
is unknown.
In input capture mode (MSxB–MSxA = 0:0), reading the high byte of the TIMB channel x registers
(TBCHxH) inhibits input captures until the low byte (TBCHxL) is read.
In output compare mode (MSxB–MSxA ≠ 0:0), writing to the high byte of the TIMB channel x registers
(TBCHxH) inhibits output compares until the low byte (TBCHxL) is written.
Register Name and Address:
Bit 7
TBCH0H — $0057
6
5
4
3
2
1
Bit 0
Bit 8
Read:
Bit 15
Write:
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Reset:
Indeterminate after reset
TBCH0L — $0058
Register Name and Address:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 0
Read:
Bit 7
Write:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Reset:
Indeterminate after reset
TBCH1H — $005A
Register Name and Address:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 8
Read:
Bit 15
Write:
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Reset:
Indeterminate after reset
TBCH1L — $005B
Register Name and Address:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 0
Read:
Bit 7
Write:
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Reset:
Indeterminate after reset
Figure 17-10. TIMB Channel Registers (TBCH0H/L–TBCH1H/L)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
250
Freescale Semiconductor
Chapter 18
Development Support
18.1 Introduction
This section describes the break module, the monitor read-only memory (MON), and the monitor mode
entry methods.
18.2 Break Module (BRK)
The break module (BRK) can generate a break interrupt that stops normal program flow at a defined
address to enter a background program. Features include:
•
•
•
•
Accessible input/output (I/O) registers during the break interrupt
Central processor unit (CPU) generated break interrupts
Software-generated break interrupts
Computer operating properly (COP) disabling during break interrupts
18.2.1 Functional Description
When the internal address bus matches the value written in the break address registers, the break module
issues a breakpoint signal to the CPU. The CPU then loads the instruction register with a software
interrupt instruction (SWI) after completion of the current CPU instruction. The program counter vectors
to $FFFC and $FFFD ($FEFC and $FEFD in monitor mode).
These events can cause a break interrupt to occur:
•
A CPU-generated address (the address in the program counter) matches the contents of the break
address registers.
•
Software writes a logic 1 to the BRKA bit in the break status and control register.
When a CPU-generated address matches the contents of the break address registers, the break interrupt
begins after the CPU completes its current instruction. A return-from-interrupt instruction (RTI) in the
break routine ends the break interrupt and returns the microcontroller unit (MCU) to normal operation.
Figure 18-1 shows the structure of the break module.
18.2.1.1 Flag Protection During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during
the break state.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
251
Development Support
IAB15–IAB8
BREAK ADDRESS REGISTER HIGH
8-BIT COMPARATOR
IAB15–IAB0
CONTROL
BREAK
8-BIT COMPARATOR
BREAK ADDRESS REGISTER LOW
IAB7–IAB0
Figure 18-1. Break Module Block Diagram
Addr.
Register Name
Bit 7
6
5
4
3
2
1
BW
0
Bit 0
Read:
SIM Break Status Register
R
R
R
R
R
R
R
$FE00
(SBSR) Write:
See page 255.
Reset:
Read:
SIM Break Flag Control
BCFE
0
R
R
R
R
R
R
R
$FE03
$FE0C
$FE0D
$FE0E
Register (SBFCR) Write:
See page 255.
Reset:
Read:
Break Address Register High
Bit 15
0
14
13
0
12
0
11
0
10
0
9
0
1
Bit 8
0
(BRKH) Write:
See page 254.
Reset:
Read:
0
Break Address Register Low
Bit 7
0
6
0
5
4
3
2
Bit 0
(BRKL) Write:
See page 254.
Reset:
Read:
0
0
0
0
0
0
0
0
0
0
0
0
Break Status and Control
BRKE
0
BRKA
Register (BRKSCR) Write:
See page 254.
Reset:
0
0
0
0
0
0
0
Note: Writing a 0 clears BW.
= Unimplemented
R
= Reserved
Figure 18-2. I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
252
Freescale Semiconductor
Break Module (BRK)
18.2.1.2 CPU During Break Interrupts
The CPU starts a break interrupt by:
•
•
Loading the instruction register with the SWI instruction
Loading the program counter with $FFFC and $FFFD ($FEFC and $FEFD in monitor mode)
The break interrupt begins after completion of the CPU instruction in progress. If the break address
register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately.
18.2.1.3 TIM1 and TIM2 During Break Interrupts
A break interrupt stops the timer counters.
18.2.1.4 COP During Break Interrupts
The COP is disabled during a break interrupt when VTST is present on the RST pin.
18.2.2 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes.
18.2.2.1 Wait Mode
If enabled, the break module is active in wait mode. In the break routine, the user can subtract one from
the return address on the stack if SBSW is set. Clear the BW bit by writing logic 0 to it.
18.2.2.2 Stop Mode
The break module is inactive in stop mode. The STOP instruction does not affect break module register
states.
18.2.3 Break Module Registers
These registers control and monitor operation of the break module:
•
•
•
•
•
Break status and control register (BRKSCR)
Break address register high (BRKH)
Break address register low (BRKL)
SIM break status register (SBSR)
SIM break flag control register (SBFCR)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
253
Development Support
18.2.3.1 Break Status and Control Register
The break status and control register (BRKSCR) contains break module enable and status bits.
Address: $FE0E
Bit 7
BRKE
0
6
BRKA
0
5
0
4
0
3
0
2
0
1
0
Bit 0
0
Read:
Write:
Reset:
0
0
0
0
0
0
= Unimplemented
Figure 18-3. Break Status and Control Register (BRKSCR)
BRKE — Break Enable Bit
This read/write bit enables breaks on break address register matches. Clear BRKE by writing a logic
0 to bit 7. Reset clears the BRKE bit.
1 = Breaks enabled on 16-bit address match
0 = Breaks disabled on 16-bit address match
BRKA — Break Active Bit
This read/write status and control bit is set when a break address match occurs. Writing a logic 1 to
BRKA generates a break interrupt. Clear BRKA by writing a logic 0 to it before exiting the break routine.
Reset clears the BRKA bit.
1 = When read, break address match
0 = When read, no break address match
18.2.3.2 Break Address Registers
The break address registers (BRKH and BRKL) contain the high and low bytes of the desired breakpoint
address. Reset clears the break address registers.
Address: $FE0C
Bit 7
Bit 15
0
6
14
0
5
13
0
4
12
0
3
11
0
2
10
0
1
9
0
Bit 0
Bit 8
0
Read:
Write:
Reset:
Figure 18-4. Break Address Register High (BRKH)
Address: $FE0D
Bit 7
6
6
0
5
5
0
4
4
0
3
3
0
2
2
0
1
1
0
Bit 0
Bit 0
0
Read:
Bit 7
Write:
Reset:
0
Figure 18-5. Break Address Register Low (BRKL)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
254
Freescale Semiconductor
Monitor ROM (MON)
18.2.3.3 Break Status Register
The break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode.
The flag is useful in applications requiring a return to wait mode after exiting from a break interrupt.
Address:
$FE00
Bit 7
6
5
4
3
2
1
BW
0
Bit 0
R
Read:
Write:
Reset:
R
R
R
R
R
R
Figure 18-6. SIM Break Status Register (SBSR)
BW — Break Wait Bit
This read/write bit is set when a break interrupt causes an exit from wait mode. Clear BW by writing a
logic 0 to it. Reset clears BW.
1 = Break interrupt during wait mode
0 = No break interrupt during wait mode
BW can be read within the break interrupt routine. The user can modify the return address on the stack
by subtracting 1 from it.
18.2.3.4 Break Flag Control Register
The break flag control register (SBFCR) contains a bit that enables software to clear status bits while the
MCU is in a break state.
Address:
$FE03
Bit 7
6
5
4
3
2
1
Bit 0
R
Read:
Write:
Reset:
BCFE
R
R
R
R
R
R
0
R
= Reserved
Figure 18-7. SIM Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing status registers while the MCU is
in a break state. To clear status bits during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
18.3 Monitor ROM (MON)
The monitor ROM (MON) allows complete testing of the microcontroller unit (MCU) through a single-wire
interface with a host computer. Monitor mode entry can be achieved without the use of VTST as long as
vector addresses $FFFE and $FFFF are blank, thus reducing the hardware requirements for in-circuit
programming.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
255
Development Support
Features include:
•
•
•
•
•
•
Normal user-mode pin functionality
One pin dedicated to serial communication between monitor ROM and host computer
Standard mark/space non-return-to-zero (NRZ) communication with host computer
4800 baud–28.8 Kbaud communication with host computer
Execution of code in random-access memory (RAM) or ROM
FLASH programming
18.3.1 Functional Description
The monitor ROM receives and executes commands from a host computer. Figure 18-8 shows a sample
circuit used to enter monitor mode and communicate with a host computer via a standard RS-232
interface.
Simple monitor commands can access any memory address. In monitor mode, the MCU can execute
host-computer code in RAM while all MCU pins retain normal operating mode functions. All
communication between the host computer and the MCU is through the PTA0 pin. A level-shifting and
multiplexing interface is required between PTA0 and the host computer. PTA0 is used in a wired-OR
configuration and requires a pullup resistor.
18.3.1.1 Entering Monitor Mode
There are two methods for entering monitor:
•
The first is the traditional M68HC08 method where VDD + VHI is applied to IRQ1 and the mode pins
are configured appropriately.
•
A second method, intended for in-circuit programming applications, will force entry into monitor
mode without requiring high voltage on the IRQ1 pin when the reset vector locations of the FLASH
are erased ($FF).
NOTE
For both methods, holding the PTC2 pin low when entering monitor mode
causes a bypass of a divide-by-two stage at the oscillator. The CGMOUT
frequency is equal to the CGMXCLK frequency, and the OSC1 input
directly generates internal bus clocks. In this case, the OSC1 signal must
have a 50 percent duty cycle at maximum bus frequency.
Table 18-1 is a summary of the differences between user mode and monitor mode.
Table 18-1. Mode Differences
Functions
Modes
Rest
Vector High
Reset
Vector Low
Break
Vector High
Break
Vector Low
SWI
Vector High
SWI
Vector Low
COP
User
Enabled
$FFFE
$FEFE
$FFFF
$FEFF
$FFFC
$FEFC
$FFFD
$FEFD
$FFFC
$FEFC
$FFFD
$FEFD
Disabled(1)
Monitor
1. If the high voltage (VDD + VHI) is removed from the IRQ1 pin or the RST pin, the SIM asserts its COP enable output. The
COP is a mask option enabled or disabled by the COPD bit in the configuration register.
18.3.1.2 Normal Monitor Mode
Table 18-2 shows the pin conditions for entering monitor mode.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
256
Freescale Semiconductor
Monitor ROM (MON)
VDD
10 kΩ
MC68HC908MR16/
MC68HC908MR32
S1
RST
0.1 µF
VHI
10 kΩ
IRQ
VDDA
VDDA
1
20
MC145407
0.1 µF
+
+
+
+
VDDAD
10 µF
10 µF
10 µF
10 µF
VDDAD
3
4
18
17
0.1 µF
VREFH
VDD
VREFH
2
19
0.1 µF
CGMXFC
0.02 µF
10 MΩ
DB-25
2
5
6
16
15
3
7
OSC1
OSC2
X1
4.9152 MHz
20 pF
VDD
VREFL
VSSAD
VSSA
20 pF
1
2
6
4
14
3
MC74HC125
PWMGND
VSS
5
VDD
VDD
0.1 µF
VDD
7
VDD
10 kΩ
10 kΩ
PTA0
PTA7
PTC2
A
B
S3
VDD
VDD
10 kΩ
10 kΩ
S2 Position A — Bus clock = CGMXCLK ÷ 4 or CGMVCLK ÷ 4
S2 Position B — Bus clock = CGMXCLK ÷ 2
S3 Position A — Parallel communication
A
PTC3
PTC4
S2
B
S3 Position B — Serial communication
Figure 18-8. Monitor Mode Circuit
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
257
Table 18-2. Monitor Mode Signal Requirements and Options
For Serial
Communication(2)
External
Clock(1)
RESET
(S1)
$FFFE
/$FFFF
PTC2
(S2)
Bus
Frequency
IRQ
PLL PTC3 PTC4
CGMOUT
COP
Comment
Baud
PTA7
(S3)
PTA0
Rate(3) (4)
X
GND
VDD
X
X
X
X
1
X
0
X
0
X
0
0
Disabled
Disabled
X
1
X
0
0
No operation until reset goes high
9600
PTC3 and PTC2 voltages only required if
IRQ = VTST; PTC2 determines frequency
4.9152
MHz
4.9152
MHz
2.4576
MHz
VTST
or
VTST
OFF
X
1
1
0
1
DNA
9600
DNA
divider
VDD
PTC3 and PTC2 voltages only required if
IRQ = VTST; PTC2 determines frequency
9.8304
MHz
4.9152
MHz
2.4576
MHz
VTST
or
VTST
X
OFF
OFF
OFF
1
X
X
0
X
X
1
X
X
Disabled
Disabled
Enabled
X
divider
1
0
1
9600
DNA
$FFFF
Blank
9.8304
MHz
4.9152
MHz
2.4576
MHz
VDD
VDD
VDD
External frequency always divided by 4
X
$FFFF
Blank
Enters user mode — will encounter an
illegal address reset
VTST
X
X
—
—
—
—
X
X
X
X
—
—
or
GND
VDD
VDD
Non-$FF
Programmed
or
VTST
OFF
X
X
X
Enabled
Enters user mode
or
GND
1. External clock is derived by a 32.768 kHz crystal or a 4.9152/9.8304 MHz off-chip oscillator.
2. DNA = does not apply, X = don’t care
3. PAT0 = 1 if serial communication; PTA0 = X if parallel communication
4. PTA7 = 0 → serial, PTA7 = 1 → parallel communication for security code entry
Monitor ROM (MON)
Enter monitor mode by either:
•
•
Executing a software interrupt instruction (SWI) or
Applying a logic 0 and then a logic 1 to the RST pin
Once out of reset, the MCU waits for the host to send eight security bytes. After receiving the security
bytes, the MCU sends a break signal (10 consecutive logic 0s) to the host computer, indicating that it is
ready to receive a command. The break signal also provides a timing reference to allow the host to
determine the necessary baud rate.
Monitor mode uses alternate vectors for reset and SWI. The alternate vectors are in the $FE page instead
of the $FF page and allow code execution from the internal monitor firmware instead of user code. The
computer operating properly (COP) module is disabled in monitor mode as long as VHI is applied to either
the IRQ pin or the RST pin. (See Chapter 14 System Integration Module (SIM) for more information on
modes of operation.)
18.3.1.3 Forced Monitor Mode
If the voltage applied to the IRQ1 is less than VDD + VHI the MCU will come out of reset in user mode. The
MENRST module is monitoring the reset vector fetches and will assert an internal reset if it detects that
the reset vectors are erased ($FF). When the MCU comes out of reset, it is forced into monitor mode
without requiring high voltage on the IRQ1 pin.
The COP module is disabled in forced monitor mode. Any reset other than a POR reset will automatically
force the MCU to come back to the forced monitor mode.
18.3.1.4 Data Format
Communication with the monitor ROM is in standard non-return-to-zero (NRZ) mark/space data format.
(See Figure 18-9 and Figure 18-10.)
NEXT
START
BIT
START
BIT
STOP
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
Figure 18-9. Monitor Data Format
NEXT
START
BIT
START
BIT
STOP
BIT
$A5
BIT 0
BIT 1
BIT 1
BIT 2
BIT 2
BIT 3
BIT 3
BIT 4
BIT 4
BIT 5
BIT 5
BIT 6
BIT 6
BIT 7
BIT 7
STOP
BIT
START
BIT
NEXT
START
BIT
BREAK
BIT 0
Figure 18-10. Sample Monitor Waveforms
The data transmit and receive rate can be anywhere from 4800 baud to 28.8 Kbaud. Transmit and receive
baud rates must be identical.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
259
Development Support
18.3.1.5 Echoing
As shown in Figure 18-11, the monitor ROM immediately echoes each received byte back to the PTA0
pin for error checking.
SENT TO
MONITOR
READ
READ
ADDR. HIGH ADDR. HIGH ADDR. LOW ADDR. LOW
DATA
ECHO
RESULT
Figure 18-11. Read Transaction
Any result of a command appears after the echo of the last byte of the command.
18.3.1.6 Break Signal
A start bit followed by nine low bits is a break signal. See Figure 18-12. When the monitor receives a break
signal, it drives the PTA0 pin high for the duration of two bits before echoing the break signal.
MISSING STOP BIT
2--STOP-BIT DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Figure 18-12. Break Transaction
18.3.1.7 Commands
The monitor ROM uses these commands (see Table 18-3–Table 18-8):
•
•
•
•
•
•
READ, read memory
WRITE, write memory
IREAD, indexed read
IWRITE, indexed write
READSP, read stack pointer
RUN, run user program
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
260
Freescale Semiconductor
Monitor ROM (MON)
Table 18-3. READ (Read Memory) Command
Description
Operand
Read byte from memory
2-byte address in high-byte:low-byte order
Returns contents of specified address
$4A
Data Returned
Opcode
Command Sequence
SENT TO MONITOR
ADDRESS ADDRESS ADDRESS
HIGH HIGH LOW
ADDRESS
LOW
READ
READ
DATA
ECHO
RETURN
Table 18-4. WRITE (Write Memory) Command
Description
Operand
Write byte to memory
2-byte address in high-byte:low-byte order; low byte followed by data byte
Data Returned
Opcode
None
$49
Command Sequence
FROM HOST
ADDRESS ADDRESS ADDRESS ADDRESS
LOW
DATA
DATA
WRITE
ECHO
WRITE
HIGH
HIGH
LOW
Table 18-5. IREAD (Indexed Read) Command
Description
Operand
Read next 2 bytes in memory from last address accessed
2-byte address in high byte:low byte order
Data Returned
Opcode
Returns contents of next two addresses
$1A
Command Sequence
FROM HOST
IREAD
IREAD
DATA
DATA
ECHO
RETURN
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
261
Development Support
Table 18-6. IWRITE (Indexed Write) Command
Description
Write to last address accessed + 1
Operand
Data Returned
Opcode
Single data byte
None
$19
Command Sequence
FROM HOST
DATA
DATA
IWRITE
IWRITE
ECHO
A sequence of IREAD or IWRITE commands can access a block of memory sequentially over the full
64-Kbyte memory map.
Table 18-7. READSP (Read Stack Pointer) Command
Description
Operand
Reads stack pointer
None
Data Returned
Opcode
Returns incremented stack pointer value (SP + 1) in high-byte:low-byte order
$0C
Command Sequence
FROM HOST
SP
HIGH
SP
LOW
READSP
READSP
ECHO
RETURN
Table 18-8. RUN (Run User Program) Command
Description
Operand
Executes PULH and RTI instructions
None
Data Returned
Opcode
None
$28
Command Sequence
FROM HOST
RUN
RUN
ECHO
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
262
Freescale Semiconductor
Monitor ROM (MON)
18.3.1.8 Baud Rate
With a 4.9152-MHz crystal and the PTC2 pin at logic 1 during reset, data is transferred between the
monitor and host at 4800 baud. If the PTC2 pin is at logic 0 during reset, the monitor baud rate is 9600.
See Table 18-9.
Table 18-9. Monitor Baud Rate Selection
VCO Frequency Multiplier (N)
1
2
3
4
5
6
Monitor baud rate
4800
9600
14,400
19,200
24,000
28,800
18.3.2 Security
A security feature discourages unauthorized reading of FLASH locations while in monitor mode. The host
can bypass the security feature at monitor mode entry by sending eight security bytes that match the
bytes at locations $FFF6–$FFFD. Locations $FFF6–$FFFD contain user-defined data.
NOTE
Do not leave locations $FFF6–$FFFD blank. For security reasons, program
locations $FFF6–$FFFD even if they are not used for vectors.
During monitor mode entry, the MCU waits after the power-on reset for the host to send the eight security
bytes on pin PTA0. If the received bytes match those at locations $FFF6–$FFFD, the host bypasses the
security feature and can read all FLASH locations and execute code from FLASH. Security remains
bypassed until a power-on reset occurs. If the reset was not a power-on reset, security remains bypassed
and security code entry is not required. (See Figure 18-13.)
Upon power-on reset, if the received bytes of the security code do not match the data at locations
$FFF6–$FFFD, the host fails to bypass the security feature. The MCU remains in monitor mode, but
reading a FLASH location returns an invalid value and trying to execute code from FLASH causes an
illegal address reset. After receiving the eight security bytes from the host, the MCU transmits a break
character, signifying that it is ready to receive a command.
NOTE
The MCU does not transmit a break character until after the host sends the
eight security bytes.
To determine whether the security code entered is correct, check to see if bit 6 of RAM address $60 is
set. If it is, then the correct security code has been entered and FLASH can be accessed.
If the security sequence fails, the device can be reset (via power-pin reset only) and brought up in monitor
mode to attempt another entry. After failing the security sequence, the FLASH mode can also be bulk
erased by executing an erase routine that was downloaded into internal RAM. The bulk erase operation
clears the security code locations so that all eight security bytes become $FF.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
263
Development Support
VDD
RST
PA7
4096 + 32 CGMXCLK CYCLES
24 BUS CYCLES
256 BUS CYCLES (MINIMUM)
FROM HOST
PA0
1
1
3
1
3
2
1
FROM MCU
NOTES:
1 = Echo delay, 2 bit times
2 = Data return delay, 2 bit times
3 = Wait 1 bit time before sending next byte.
Figure 18-13. Monitor Mode Entry Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
264
Freescale Semiconductor
Chapter 19
Electrical Specifications
19.1 Introduction
This section contains electrical and timing specifications.
19.2 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the microcontroller unit (MCU) can be exposed without
permanently damaging it.
NOTE
This device is not guaranteed to operate properly at the maximum ratings. For guaranteed operating
conditions, refer to 19.5 DC Electrical Characteristics.
Characteristic(1)
Symbol
Value
Unit
VDD
Supply voltage
Input voltage
–0.3 to +6.0
V
VSS –0.3 to
VDD +0.3
VIn
VHI
V
VDD + 4 maximum
Input high voltage
V
Maximum current per pin excluding VDD and VSS
I
25
–55 to +150
100
mA
°C
TSTG
IMVSS
IMVDD
Storage temperature
Maximum current out of VSS
Maximum current into VDD
mA
mA
100
1. Voltages referenced to VSS
.
NOTE
This device contains circuitry to protect the inputs against damage due to
high static voltages or electric fields; however, it is advised that normal
precautions be taken to avoid application of any voltage higher than
maximum-rated voltages to this high-impedance circuit. For proper
operation, it is recommended that VIn and VOut be constrained to the range
VSS ≤ (VIn or VOut) ≤ VDD. Reliability of operation is enhanced if unused
inputs are connected to an appropriate logic voltage level (for example,
either VSS or VDD).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
265
Electrical Specifications
19.3 Functional Operating Range
Characteristic
Symbol
Value
Unit
°C
Operating temperature range(1)
MC68HC908MR24CFU
MC68HC908MR24VFU
TA
–40 to 85
–40 to 105
VDD
Operating voltage range
5.0 10%
V
1. See Freescale representative for temperature availability.
C = Extended temperature range (–40°C to +85°C)
V = Automotive temperature range (–40°C to +105°C)
19.4 Thermal Characteristics
Characteristic
Symbol
Value
76
Unit
°C/W
W
Thermal resistance,
64-pin QFP
θJA
PI/O
PD
I/O pin power dissipation
Power dissipation(1)
User determined
PD = (IDD x VDD) + PI/O
=
W
K/(TJ + 273°C)
PD x (TA + 273°C)
+ PD2 x θJA
Constant(2)
K
W/°C
TJ
TA + (PD x θJA)
Average junction temperature
°C
°C
TJM
Maximum junction temperature
125
1. Power dissipation is a function of temperature.
2. K is a constant unique to the device. K can be determined for a known TA and measured PD. With this value of K, PD and
TJ can be determined for any value of TA.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
266
Freescale Semiconductor
DC Electrical Characteristics
19.5 DC Electrical Characteristics
Characteristic(1)
Typ(2)
Symbol
Min
Max
Unit
Output high voltage
(ILoad = –2.0 mA) all I/O pins
VOH
VDD –0.8
—
—
V
Output low voltage
(ILoad = 1.6 mA) all I/O pins
VOL
IOH
—
—
—
0.4
—
V
PWM pin output source current
(VOH = VDD –0.8 V)
–7
mA
PWM pin output sink current (VOL = 0.8 V)
IOL
VIH
VIL
20
0.7 x VDD
VSS
—
—
—
—
mA
V
VDD
Input high voltage, all ports, IRQs, RESET, OSC1
Input low voltage, all ports, IRQs, RESET, OSC1
VDD supply current
0.3 x VDD
V
Run(3)
Wait(4)
Stop(5)
—
—
—
—
—
—
30
12
700
mA
mA
µA
IDD
IIL
IIn
I/O ports high-impedance leakage current
Input current (input only pins)
—
—
—
—
10
1
µA
µA
COut
CIn
Capacitance
Ports (as input or output)
—
—
—
—
12
8
pF
Low-voltage inhibit reset(6)
VLVR1
VLVH1
4.0
40
4.35
90
4.65
150
V
Low-voltage reset/recover hysteresis
mV
Low-voltage inhibit reset recovery
VREC1
4.04
4.5
4.75
V
(VREC1 = VLVR1 + VLVH1
)
VLVR2
VLVH2
Low-voltage inhibit reset
3.85
150
4.15
210
4.45
250
V
Low-voltage reset/recover hysteresis
Low-voltage inhibit reset recovery
(VREC2 = VLVR2 + VLVH2
mV
VREC2
4.0
4.4
4.6
V
)
POR re-arm voltage(7)
POR rise time ramp rate(8)
POR reset voltage(9)
VPOR
RPOR
0
0.035
0
—
—
100
—
mV
V/ms
V
VPORRST
VHi
700
—
800
8.0
VDD + 2.5
Monitor mode entry voltage (on IRQ)
V
1. VDD = 5.0 Vdc 10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted.
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using external square wave clock source (fOSC = 8.2 MHz). All inputs 0.2 V from rail; no dc
loads; less than 100 pF on all outputs. CL = 20 pF on OSC2; all ports configured as inputs; OSC2 capacitance linearly
affects run IDD; measured with all modules enabled
4. Wait IDD measured using external square wave clock source (fOSC = 8.2 MHz); all inputs 0.2 V from rail; no dc loads; less
than 100 pF on all outputs. CL = 20 pF on OSC2; all ports configured as inputs; OSC2 capacitance linearly affects wait IDD
;
measured with PLL and LVI enabled.
5. Stop IDD measured with PLL and LVI disengaged, OCS1 grounded, no port pins sourcing current. It is measured through
combination of VDD, VDDAD, and VDDA
.
6. The low-voltage inhibit reset is software selectable. Refer to Chapter 9 Low-Voltage Inhibit (LVI).
7. Maximum is highest voltage that POR is guaranteed.
8. If minimum VDD is not reached before the internal POR is released, RST must be driven low externally until minimum VDD
is reached.
9. Maximum is highest voltage that POR is possible.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
267
Electrical Specifications
19.6 FLASH Memory Characteristics
Characteristic
RAM data retention voltage
Symbol
Min
1.3
1
Typ
—
Max
—
Unit
V
VRDR
FLASH program bus clock frequency
FLASH read bus clock frequency
—
—
—
MHz
Hz
(1)
0
—
8 M
fRead
FLASH page erase time
<1 K cycles
>1 K cycles
tErase
0.9
3.6
1
4
1.1
5.5
ms
tMErase
tNVS
FLASH mass erase time
4
10
5
—
—
—
—
—
—
—
—
—
—
—
—
40
—
ms
µs
µs
µs
µs
µs
µs
FLASH PGM/ERASE to HVEN setup time
FLASH high-voltage hold time
FLASH high-voltage hold time (mass erase)
FLASH program hold time
tNVH
tNVHL
tPGS
100
5
tPROG
FLASH program time
30
1
(2)
FLASH return to read time
tRCV
(3)
FLASH cumulative program HV period
—
10 k
15
—
4
ms
tHV
FLASH endurance(4)
—
—
100 k
100
—
—
Cycles
Years
FLASH data retention time(5)
1. fRead is defined as the frequency range for which the FLASH memory can be read.
2. tRCV is defined as the time it needs before the FLASH can be read after turning off the high voltage charge pump, by
clearing HVEN to 0.
3. tHV is defined as the cumulative high voltage programming time to the same row before next erase.
t
HV must satisfy this condition: tNVS + tNVH + tPGS + (tPROG x 32) ≤ tHV maximum.
4. Typical endurance was evaluated for this product family. For additional information on how Freescale defines Typical
Endurance, please refer to Engineering Bulletin EB619.
5. Typical data retention values are based on intrinsic capability of the technology measured at high temperature and de-rated
to 25°C using the Arrhenius equation. For additional information on how Freescale defines Typical Data Retention, please
refer to Engineering Bulletin EB618.
19.7 Control Timing
Characteristic(1)
Symbol
Min
Max
Unit
Frequency of operation(2)
Crystal option
External clock option(3)
1
dc(4)
fOSC
8
32.8
MHz
fOP
tIRL
Internal operating frequency
—
8.2
—
MHz
ns
RESET input pulse width low(5)
50
1. VDD = 5.0 Vdc 10%, VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VDD, unless otherwise noted
2. See 19.8 Serial Peripheral Interface Characteristics for more information.
3. No more than 10% duty cycle deviation from 50%.
4. Some modules may require a minimum frequency greater than dc for proper operation; see appropriate table for this
information.
5. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse width to cause a reset.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
268
Freescale Semiconductor
Serial Peripheral Interface Characteristics
19.8 Serial Peripheral Interface Characteristics
Diagram
Number(1)
Characteristic(2)
Symbol
Min
Max
Unit
Operating frequency
Master
Slave
fOP(M)
fOP(S)
f
OP/2
f
OP/128
dc
MHz
f
OP
Cycle time
Master
Slave
tCYC(M)
tCYC(S)
tCYC
1
2
1
128
—
tLead(S)
tLag(S)
2
3
Enable lead time
Enable lag time
15
15
—
—
ns
ns
Clock (SPCK) high time
Master
Slave
tSCKH(M)
tSCKH(S)
4
5
100
50
—
—
ns
ns
Clock (SPCK) low time
Master
Slave
tSCKL(M)
tSCKL(S)
100
50
—
—
Data setup time (inputs)
Master
Slave
tSU(M)
tSU(S)
45
5
—
—
6
7
ns
ns
Data hold time (inputs)
Master
Slave
tH(M)
tH(S)
0
15
—
—
Access time, slave(3)
CPHA = 0
CHPA = 1
tA(CP0)
tA(CP1)
0
0
40
20
8
9
ns
ns
ns
Disable time, slave(4)
tDIS(S)
—
25
Data valid time after enable edge
Master
Slave(5)
tV(M)
tV(S)
10
—
—
10
40
1. VDD = 5.0 Vdc 10%, all timing is shown with respect to 20% VDD and 70% VDD, unless otherwise noted; assumes 100 pF
load on all SPI pins
2. Numbers refer to dimensions in Figure 19-1 and Figure 19-2.
3. Time to data active from high-impedance state
4. Hold time to high-impedance state
5. With 100 pF on all SPI pins
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
269
Electrical Specifications
SS
INPUT
SS PIN OF MASTER HELD HIGH
1
5
4
SPCK, CPOL = 0
OUTPUT
NOTE
4
5
SPCK, CPOL = 1
OUTPUT
NOTE
6
7
MISO
INPUT
MSB IN
BITS 6–1
BITS 6–1
LSB IN
10
11
MASTER MSB OUT
10
11
MOSI
OUTPUT
MASTER LSB OUT
Note: This first clock edge is generated internally, but is not seen at the SCK pin.
a) SPI Master Timing (CPHA = 0)
SS
INPUT
SS PIN OF MASTER HELD HIGH
1
SPCK, CPOL = 0
OUTPUT
5
NOTE
NOTE
4
SPCK, CPOL = 1
OUTPUT
5
4
6
7
LSB IN
11
MISO
INPUT
MSB IN
BITS 6–1
BITS 6–1
10
MOSI
OUTPUT
11
10
MASTER MSB OUT
MASTER LSB OUT
Note: This last clock edge is generated internally, but is not seen at the SCK pin.
b) SPI Master Timing (CPHA = 1)
Figure 19-1. SPI Master Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
270
Freescale Semiconductor
Serial Peripheral Interface Characteristics
SS
INPUT
3
1
SPCK, CPOL = 0
INPUT
11
4
4
5
2
SPCK, CPOL = 1
INPUT
9
8
MISO
INPUT
SLAVE MSB OUT
BITS 6–1
BITS 6–1
SLAVE LSB OUT
11
NOTE
11
6
7
10
MOSI
OUTPUT
MSB IN
LSB IN
Note: Not defined, but normally MSB of character just received
a) SPI Slave Timing (CPHA = 0)
SS
INPUT
1
SPCK, CPOL = 0
INPUT
5
4
5
2
3
SPCK, CPOL = 1
INPUT
4
10
9
8
MISO
INPUT
NOTE
SLAVE MSB OUT
BITS 6–1
BITS 6–1
SLAVE LSB OUT
11
6
7
10
MOSI
OUTPUT
MSB IN
LSB IN
Note: Not defined, but normally LSB of character previously transmitted
b) SPI Slave Timing (CPHA = 1)
Figure 19-2. SPI Slave Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
271
Electrical Specifications
19.9 TImer Interface Module Characteristics
Characteristic
Symbol
tTIH, TIL
tTCH, TCL
Min
125
Max
—
Unit
ns
t
Input capture pulse width
Input clock pulse width
t
(1/fOP) + 5
—
ns
19.10 Clock Generation Module Component Specifications
Characteristic
Symbol
Min
Typ
Max
Notes
Consult crystal
manufacturing data
CL
Crystal load capacitance
—
—
—
Consult crystal
manufacturing data
C1
C2
2 * CL
2 * CL
Crystal fixed capacitance
Crystal tuning capacitance
—
—
—
—
Consult crystal
manufacturing data
RB
RS
Feedback bias resistor
Series resistor
—
0
22 MΩ
330 kΩ
—
1 MΩ
Not required
CFACT
(VDDA/fXCLK
*
CF
Filter capacitor
—
—
—
)
CBYP must provide low ac
impedance from
f = fXCLK/100 to 100*fVCLK, so
series resistance must be
considered
CBYP
Bypass capacitor
—
0.1 µF
19.11 CGM Operating Conditions
Characteristic
Crystal reference frequency
Range nominal multiplier
Symbol
Min
1
Typ
Max
8
Unit
MHz
MHz
fXCLK
—
fNOM
fVRS
—
4.9152
—
VCO center-of-range frequency
VCO frequency multiplier
4.9152
—
—
—
—
32.8
15
MHz
—
N
L
1
1
VCO center of range multiplier
VCO operating frequency
15
—
fVCLK
fVRSMIN
fVRSMAX
—
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
272
Freescale Semiconductor
CGM Acquisition/Lock Time Specifications
19.12 CGM Acquisition/Lock Time Specifications
Description
Filter capacitor multiply factor
Acquisition mode time factor
Tracking mode time factor
Symbol
Min
—
Typ
Max
—
Notes
F/sV
V
CFACT
0.0154
0.1135
0.0174
KACQ
KTRK
—
—
—
—
V
(8*VDDA)/
(fXCLK*KACQ)
If CF chosen
correctly
tACQ
Manual mode time to stable
—
—
—
—
(4*VDDA)/
(fXCLK*KTRK
If CF chosen
correctly
tAL
Manual stable to lock time
Manual acquisition time
)
tLock
tACQ+tAL
—
0
—
Tracking mode entry frequency
tolerance
∆
—
—
3.6%
TRK
Acquisition mode entry frequency
tolerance
∆
7.2%
6.3%
ACQ
∆
Lock entry frequency tolerance
Lock exit frequency tolerance
0
—
—
0.9%
1.8%
Lock
∆
0.9%
UNL
Reference cycles per acquisition mode
measurement
nACQ
nTRK
—
—
32
—
—
Reference cycles per tracking mode
measurement
128
(8*VDDA)/
(fXCLK*KACQ)
If CF chosen
correctly
tACQ
nACQ/fXCLK
Automatic mode time to stable
—
—
(4*VDDA)/
(fXCLK*KTRK
If CF chosen
correctly
tAL
nTRK/fXCLK
—
Automatic stable to lock time
Automatic lock time
)
tLock
tACQ+tAL
—
(fXCLK
*(0.025%)
*(N/4)
)
PLL jitter (deviation of average bus
frequency over 2 ms)
N = VCO
freq. mult.
fJ
0
—
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
273
Electrical Specifications
19.13 Analog-to-Digital Converter (ADC) Characteristics
Characteristic
Symbol
Min
Typ
Max
Unit
Notes
VDDAD should be tied to
VDDAD
Supply voltage
4.5
—
5.5
V
the same potential as
VDD via separate traces
VADIN
BAD
VDDAD
VADIN <= VDDAD
Input voltages
0
10
—
—
—
—
—
—
—
—
V
Bits
Resolution
10
4
AAD
Absolute accuracy
ADC internal clock
Conversion range
Power-up time
—
LSB
Includes quantization
fADIC
RAD
tAIC = 1/fADIC
500 k
VSSAD
1.048 M
VDDAD
Hz
V
tADPU
tADC
tADS
MAD
ZADI
FADI
CADI
IVREF
tAIC cycles
tAIC cycles
tAIC cycles
16
16
5
—
17
—
Conversion time
Sample time
Monotonicity
Guaranteed
VADIN = VSSAD
ADIN = VDDAD
Zero input reading
Full-scale reading
Input capacitance
VREFH/VREFL current
000
3FC
—
—
—
003
3FF
30
Hex
Hex
pF
V
—
Not tested
—
1.6
—
mA
Absolute accuracy
(8-bit truncation mode)
AAD
—
—
—
—
—
1
LSB
LSB
Includes quantization
Quantization error
(8-bit truncation mode)
+ 7/8
– 1/8
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
274
Freescale Semiconductor
Chapter 20
Ordering Information and Mechanical Specifications
20.1 Introduction
This section provides ordering information for the MC68HC908MR16 and MC68HC908MR32 along with
the dimensions for:
•
•
64-lead plastic quad flat pack (QFP)
56-pin shrink dual in-line package (SDIP)
The following figures show the latest package drawings at the time of this publication. To make sure that
you have the latest package specifications, contact your local Freescale Sales Office.
20.2 Order Numbers
Table 20-1. Order Numbers
Operating
Temperature Range
MC Order Number(1)
68HC908MR16CFU
68HC908MR16VFU
–40°C to +85°C
–40°C to +105°C
68HC908MR16CB
68HC908MR16VB
–40°C to +85°C
–40°C to +105°C
68HC908MR32CFU
68HC908MR32VFU
–40°C to +85°C
–40°C to +105°C
68HC908MR32CB
68HC908MR32VB
–40°C to +85°C
–40°C to +105°C
1. FU = quad flat pack
B = shrink dual in-line package
M C 6 8 H C 9 0 8 M R 3 2 X X X
PACKAGE DESIGNATOR
FAMILY
TEMPERATURE RANGE
Figure 20-1. Device Numbering System
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
275
Ordering Information and Mechanical Specifications
20.3 64-Pin Plastic Quad Flat Pack (QFP)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
276
Freescale Semiconductor
56-Pin Shrink Dual In-Line Package (SDIP)
20.4 56-Pin Shrink Dual In-Line Package (SDIP)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
277
Ordering Information and Mechanical Specifications
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
278
Freescale Semiconductor
Appendix A
MC68HC908MR16
The information contained in this document pertains to the MC68HC908MR16 with the exception of that
shown in Figure A-1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
279
MC68HC908MR16
$0000
↓
I/O REGISTERS — 96 BYTES
RAM — 768 BYTES
$005F
$0060
↓
$035F
$0360
↓
UNIMPLEMENTED — 31,904 BYTES
FLASH — 16,128 BYTES
$7FFF
$8000
↓
$BEFF
$BF00
↓
$FDFF
UNIMPLEMENTED — 16,128 BYTES
$FE00
$FE01
$FE02
$FE03
$FE04
$FE05
$FE06
$FE07
$FE08
$FE09
$FE0A
$FE0B
$FE0C
$FE0D
$FE0E
$FE0F
SIM BREAK STATUS REGISTER (SBSR)
SIM RESET STATUS REGISTER (SRSR)
RESERVED
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
RESERVED
RESERVED
RESERVED
RESERVED
FLASH CONTROL REGISTER (FLCR)
UNIMPLEMENTED
UNIMPLEMENTED
UNIMPLEMENTED
SIM BREAK ADDRESS REGISTER HIGH (BRKH)
SIM BREAK ADDRESS REGISTER LOW (BRKL)
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
LVI STATUS AND CONTROL REGISTER (LVISCR)
$FE10
↓
$FEFF
MONITOR ROM — 240 BYTES
$FF00
↓
$FF7D
UNIMPLEMENTED — 126 BYTES
FLASH BLOCK PROTECT REGISTER (FLBPR)
UNIMPLEMENTED — 83 BYTES
$FF7E
$FF7F
↓
$FFD1
$FFD2
↓
$FFFF
VECTORS — 46 BYTES
Figure A-1. MC68HC908MR16 Memory Map
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
280
Freescale Semiconductor
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MC68HC908MR32
Rev. 6.1, 07/2005
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