C8051F02X [SILICON]
8K ISP FLASH MCU Family; 8K ISP功能的Flash MCU系列
| 型号： | C8051F02X |
| 厂家： | 
SILICON |
| 描述： | 8K ISP FLASH MCU Family |
| 文件： | 总272页 (文件大小：3832K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
C8051F020/1/2/3
8K ISP FLASH MCU Family
ANALOG PERIPHERALS
HIGH SPEED 8051 µC CORE
-
SAR ADC
-
Pipelined Instruction Architecture; Executes 70% of
Instruction Set in 1 or 2 System Clocks
Up to 25 MIPS Throughput with 25 MHz Clock
22 Vectored Interrupt Sources
•
•
•
•
•
12-Bit (C8051F020/1)
-
-
10-Bit (C8051F022/3)
± 1 LSB INL
MEMORY
Programmable Throughput up to 100 ksps
-
-
4352 Bytes Internal Data RAM (4k + 256)
Up to 8 External Inputs; Programmable as Single-Ended or
Differential
64k Bytes FLASH; In-System programmable in 512-byte
Sectors
•
•
•
Programmable Amplifier Gain: 16, 8, 4, 2, 1, 0.5
Data-Dependent Windowed Interrupt Generator
Built-in Temperature Sensor (± 3°C)
-
External 64k Byte Data Memory Interface (programma-
ble multiplexed or non-multiplexed modes)
DIGITAL PERIPHERALS
-
-
8-bit ADC
-
-
8 Byte-Wide Port I/O (C8051F020/2); 5V tolerant
4 Byte-Wide Port I/O (C8051F021/3); 5V tolerant
•
•
•
Programmable Throughput up to 500 ksps
8 External Inputs
-
-
Hardware SMBus™ (I2C™ Compatible), SPI™, and
Two UART Serial Ports Available Concurrently
Programmable 16-bit Counter/Timer Array with
5 Capture/Compare Modules
Programmable Amplifier Gain: 4, 2, 1, 0.5
Two 12-bit DACs
•
Can Synchronize Outputs to Timers for Jitter-Free Wave-
form Generation
-
-
-
Two Analog Comparators
-
-
5 General Purpose 16-bit Counter/Timers
Voltage Reference
Dedicated Watch-Dog Timer; Bi-directional Reset Pin
Precision VDD Monitor/Brown-Out Detector
CLOCK SOURCES
ON-CHIP JTAG DEBUG & BOUNDARY SCAN
-
-
-
Internal Programmable Oscillator: 2-to-16 MHz
External Oscillator: Crystal, RC, C, or Clock
Real-Time Clock Mode using Timer 3 or PCA
-
-
-
On-Chip Debug Circuitry Facilitates Full- Speed, Non-
Intrusive In-Circuit/In-System Debugging
Provides Breakpoints, Single-Stepping, Watchpoints,
Stack Monitor; Inspect/Modify Memory and Registers
Superior Performance to Emulation Systems Using ICE-
Chips, Target Pods, and Sockets
SUPPLY VOLTAGE .......................... 2.7V TO 3.6V
-
-
Typical Operating Current: 10 mA @ 20 MHz
Multiple Power Saving Sleep and Shutdown Modes
100-Pin TQFP and 64-Pin TQFP Packages Available
Temperature Range: -40°C to +85°C
-
-
IEEE1149.1 Compliant Boundary Scan
Low-Cost, Complete Development Kit
ANALOG PERIPHERALS
DIGITAL I/O
TEMP
UART0
Port 0
SENSOR
UART1
Port 1
SMBus
10/12-bit
10A0kDspCs
PGA
Port 2
SPI Bus
PCA
VREF
Port 3
Timer 0
Timer 1
Timer 2
Timer 3
Timer 4
8-bit
Port 4
Port 5
Port 6
PGA
500ksps
ADC
12-Bit
DAC
+
-
+
-
12-Bit
DAC
Port 7
64 pin 100 pin
VOLTAGE
COMPARATORS
HIGH-SPEED CONTROLLER CORE
8051 CPU
64KB
ISP FLASH
DEBUG
4352 B
SRAM
CLOCK
CIRCUIT
JTAG
(25MIPS)
22
SANITY
INTERRUPTS
CIRCUITRY
CONTROL
Preliminary Rev. 1.4 12/03
Copyright © 2003 by Silicon Laboratories
C8051F020/1/2/3-DS14
This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
C8051F020/1/2/3
Notes
2
Rev. 1.4
C8051F020/1/2/3
TABLE OF CONTENTS
1. SYSTEM OVERVIEW .........................................................................................................17
1.1. CIP-51™ Microcontroller Core ......................................................................................22
1.1.1. Fully 8051 Compatible ..........................................................................................22
1.1.2. Improved Throughput............................................................................................22
1.1.3. Additional Features................................................................................................23
1.2. On-Chip Memory ............................................................................................................24
1.3. JTAG Debug and Boundary Scan ...................................................................................25
1.4. Programmable Digital I/O and Crossbar.........................................................................26
1.5. Programmable Counter Array .........................................................................................27
1.6. Serial Ports.......................................................................................................................27
1.7. 12-Bit Analog to Digital Converter.................................................................................28
1.8. 8-Bit Analog to Digital Converter...................................................................................29
1.9. Comparators and DACs...................................................................................................30
2. ABSOLUTE MAXIMUM RATINGS..................................................................................31
3. GLOBAL DC ELECTRICAL CHARACTERISTICS ......................................................32
4. PINOUT AND PACKAGE DEFINITIONS........................................................................33
5. ADC0 (12-BIT ADC, C8051F020/1 ONLY) ........................................................................43
5.1. Analog Multiplexer and PGA..........................................................................................43
5.2. ADC Modes of Operation ...............................................................................................44
5.2.1. Starting a Conversion.............................................................................................44
5.2.2. Tracking Modes .....................................................................................................45
5.2.3. Settling Time Requirements ..................................................................................46
5.3. ADC0 Programmable Window Detector.........................................................................53
6. ADC0 (10-BIT ADC, C8051F022/3 ONLY) ........................................................................59
6.1. Analog Multiplexer and PGA..........................................................................................59
6.2. ADC Modes of Operation ...............................................................................................60
6.2.1. Starting a Conversion.............................................................................................60
6.2.2. Tracking Modes .....................................................................................................61
6.2.3. Settling Time Requirements ..................................................................................62
6.3. ADC0 Programmable Window Detector.........................................................................69
7. ADC1 (8-BIT ADC) ...............................................................................................................75
7.1. Analog Multiplexer and PGA..........................................................................................75
7.2. ADC1 Modes of Operation .............................................................................................76
7.2.1. Starting a Conversion.............................................................................................76
7.2.2. Tracking Modes .....................................................................................................76
7.2.3. Settling Time Requirements ..................................................................................78
8. DACS, 12-BIT VOLTAGE MODE......................................................................................83
8.1. DAC Output Scheduling..................................................................................................83
8.1.1. Update Output On-Demand...................................................................................84
8.1.2. Update Output Based on Timer Overflow.............................................................84
8.2. DAC Output Scaling/Justification...................................................................................84
9. VOLTAGE REFERENCE (C8051F020/2)..........................................................................91
Rev. 1.4
3
C8051F020/1/2/3
10. VOLTAGE REFERENCE (C8051F021/3)..........................................................................93
11. COMPARATORS..................................................................................................................95
12. CIP-51 MICROCONTROLLER........................................................................................101
12.1.Instruction Set................................................................................................................102
12.1.1. Instruction and CPU Timing................................................................................102
12.1.2. MOVX Instruction and Program Memory...........................................................102
12.2.Memory Organization ...................................................................................................107
12.2.1. Program Memory.................................................................................................107
12.2.2. Data Memory .......................................................................................................108
12.2.3. General Purpose Registers...................................................................................108
12.2.4. Bit Addressable Locations...................................................................................108
12.2.5. Stack .................................................................................................................108
12.2.6. Special Function Registers...................................................................................109
12.2.7. Register Descriptions...........................................................................................113
12.3.Interrupt Handler ...........................................................................................................116
12.3.1. MCU Interrupt Sources and Vectors ...................................................................116
12.3.2. External Interrupts ...............................................................................................116
12.3.3. Interrupt Priorities................................................................................................118
12.3.4. Interrupt Latency..................................................................................................118
12.3.5. Interrupt Register Descriptions............................................................................119
12.4.Power Management Modes...........................................................................................125
12.4.1. Idle Mode.............................................................................................................125
12.4.2. Stop Mode............................................................................................................125
13. RESET SOURCES ..............................................................................................................127
13.1.Power-on Reset..............................................................................................................128
13.2.Power-fail Reset ............................................................................................................128
13.3.External Reset................................................................................................................129
13.4.Software Forced Reset...................................................................................................129
13.5.Missing Clock Detector Reset.......................................................................................129
13.6.Comparator0 Reset........................................................................................................129
13.7.External CNVSTR Pin Reset.........................................................................................129
13.8.Watchdog Timer Reset..................................................................................................129
13.8.1. Enable/Reset WDT ..............................................................................................130
13.8.2. Disable WDT .......................................................................................................130
13.8.3. Disable WDT Lockout.........................................................................................130
13.8.4. Setting WDT Interval...........................................................................................130
14. OSCILLATORS...................................................................................................................135
14.1.External Crystal Example..............................................................................................138
14.2.External RC Example....................................................................................................138
14.3.External Capacitor Example..........................................................................................138
15. FLASH MEMORY..............................................................................................................139
15.1.Programming The FLASH Memory .............................................................................139
15.2.Non-volatile Data Storage.............................................................................................140
15.3.Security Options............................................................................................................140
16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP XRAM.......................145
4
Rev. 1.4
C8051F020/1/2/3
16.1.Accessing XRAM..........................................................................................................145
16.1.1. 16-Bit MOVX Example.......................................................................................145
16.1.2. 8-Bit MOVX Example.........................................................................................145
16.2.Configuring the External Memory Interface .................................................................146
16.3.Port Selection and Configuration ..................................................................................146
16.4.Multiplexed and Non-multiplexed Selection.................................................................148
16.4.1. Multiplexed Configuration ..................................................................................148
16.4.2. Non-multiplexed Configuration...........................................................................149
16.5.Memory Mode Selection...............................................................................................150
16.5.1. Internal XRAM Only...........................................................................................150
16.5.2. Split Mode without Bank Select ..........................................................................150
16.5.3. Split Mode with Bank Select ...............................................................................151
16.5.4. External Only.......................................................................................................151
16.6.Timing .......................................................................................................................151
16.6.1. Non-multiplexed Mode........................................................................................153
16.6.1.1.16-bit MOVX: EMI0CF[4:2] = ‘101’, ‘110’, or ‘111’................................153
16.6.1.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘101’ or ‘111’............154
16.6.1.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘110’...............................155
16.6.2. Multiplexed Mode................................................................................................156
16.6.2.1.16-bit MOVX: EMI0CF[4:2] = ‘001’, ‘010’, or ‘011’................................156
16.6.2.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘001’ or ‘011’............157
16.6.2.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘010’...............................158
17. PORT INPUT/OUTPUT .....................................................................................................161
17.1.Ports 0 through 3 and the Priority Crossbar Decoder....................................................163
17.1.1. Crossbar Pin Assignment and Allocation ............................................................163
17.1.2. Configuring the Output Modes of the Port Pins ..................................................164
17.1.3. Configuring Port Pins as Digital Inputs...............................................................165
17.1.4. External Interrupts (IE6 and IE7) ........................................................................165
17.1.5. Weak Pull-ups......................................................................................................165
17.1.6. Configuring Port 1 Pins as Analog Inputs (AIN1.[7:0])......................................165
17.1.7. External Memory Interface Pin Assignments......................................................166
17.1.8. Crossbar Pin Assignment Example......................................................................168
17.2.Ports 4 through 7 (C8051F020/2 only)..........................................................................177
17.2.1. Configuring Ports which are not Pinned Out.......................................................177
17.2.2. Configuring the Output Modes of the Port Pins ..................................................177
17.2.3. Configuring Port Pins as Digital Inputs...............................................................178
17.2.4. Weak Pull-ups......................................................................................................178
17.2.5. External Memory Interface..................................................................................178
18. SYSTEM MANAGEMENT BUS / I2C BUS (SMBUS0) .................................................183
18.1.Supporting Documents..................................................................................................184
18.2.SMBus Protocol.............................................................................................................185
18.2.1. Arbitration............................................................................................................185
18.2.2. Clock Low Extension...........................................................................................185
18.2.3. SCL Low Timeout ...............................................................................................186
18.2.4. SCL High (SMBus Free) Timeout.......................................................................186
Rev. 1.4
5
C8051F020/1/2/3
18.3.SMBus Transfer Modes.................................................................................................187
18.3.1. Master Transmitter Mode ....................................................................................187
18.3.2. Master Receiver Mode.........................................................................................187
18.3.3. Slave Transmitter Mode.......................................................................................188
18.3.4. Slave Receiver Mode...........................................................................................188
18.4.SMBus Special Function Registers ...............................................................................189
18.4.1. Control Register...................................................................................................189
18.4.2. Clock Rate Register .............................................................................................192
18.4.3. Data Register........................................................................................................193
18.4.4. Address Register..................................................................................................193
18.4.5. Status Register .....................................................................................................194
19. SERIAL PERIPHERAL INTERFACE BUS (SPI0) ........................................................197
19.1.Signal Descriptions........................................................................................................198
19.1.1. Master Out, Slave In (MOSI) ..............................................................................198
19.1.2. Master In, Slave Out (MISO) ..............................................................................198
19.1.3. Serial Clock (SCK) ..............................................................................................198
19.1.4. Slave Select (NSS)...............................................................................................198
19.2.SPI0 Operation ..............................................................................................................199
19.3.Serial Clock Timing ......................................................................................................200
19.4.SPI Special Function Registers .....................................................................................201
20. UART0 ..................................................................................................................................205
20.1.UART0 Operational Modes ..........................................................................................206
20.1.1. Mode 0: Synchronous Mode................................................................................206
20.1.2. Mode 1: 8-Bit UART, Variable Baud Rate .........................................................207
20.1.3. Mode 2: 9-Bit UART, Fixed Baud Rate..............................................................208
20.1.4. Mode 3: 9-Bit UART, Variable Baud Rate .........................................................209
20.2.Multiprocessor Communications...................................................................................210
20.3.Frame and Transmission Error Detection......................................................................211
21. UART1 ..................................................................................................................................215
21.1.UART1 Operational Modes ..........................................................................................216
21.1.1. Mode 0: Synchronous Mode................................................................................216
21.1.2. Mode 1: 8-Bit UART, Variable Baud Rate .........................................................217
21.1.3. Mode 2: 9-Bit UART, Fixed Baud Rate..............................................................218
21.1.4. Mode 3: 9-Bit UART, Variable Baud Rate .........................................................219
21.2.Multiprocessor Communications...................................................................................220
21.3.Frame and Transmission Error Detection......................................................................221
22. TIMERS................................................................................................................................225
22.1.Timer 0 and Timer 1......................................................................................................227
22.1.1. Mode 0: 13-bit Counter/Timer.............................................................................227
22.1.2. Mode 1: 16-bit Counter/Timer.............................................................................228
22.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload.................................................229
22.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only) ...........................................230
22.2.Timer 2 .......................................................................................................................234
22.2.1. Mode 0: 16-bit Counter/Timer with Capture.......................................................235
22.2.2. Mode 1: 16-bit Counter/Timer with Auto-Reload...............................................236
6
Rev. 1.4
C8051F020/1/2/3
22.2.3. Mode 2: Baud Rate Generator .............................................................................237
22.3.Timer 3 .......................................................................................................................240
22.4.Timer 4 .......................................................................................................................243
22.4.1. Mode 0: 16-bit Counter/Timer with Capture.......................................................244
22.4.2. Mode 1: 16-bit Counter/Timer with Auto-Reload...............................................245
22.4.3. Mode 2: Baud Rate Generator .............................................................................246
23. PROGRAMMABLE COUNTER ARRAY .......................................................................249
23.1.PCA Counter/Timer.......................................................................................................250
23.2.Capture/Compare Modules............................................................................................252
23.2.1. Edge-triggered Capture Mode .............................................................................253
23.2.2. Software Timer (Compare) Mode........................................................................254
23.2.3. High Speed Output Mode ....................................................................................255
23.2.4. Frequency Output Mode ......................................................................................256
23.2.5. 8-Bit Pulse Width Modulator Mode ....................................................................257
23.2.6. 16-Bit Pulse Width Modulator Mode ..................................................................258
23.3.Register Descriptions for PCA0 ....................................................................................259
24. JTAG (IEEE 1149.1)............................................................................................................265
24.1.Boundary Scan...............................................................................................................266
24.1.1. EXTEST Instruction ............................................................................................267
24.1.2. SAMPLE Instruction ...........................................................................................267
24.1.3. BYPASS Instruction............................................................................................267
24.1.4. IDCODE Instruction............................................................................................267
24.2.Flash Programming Commands ....................................................................................268
24.3.Debug Support...............................................................................................................271
Rev. 1.4
7
C8051F020/1/2/3
Notes
8
Rev. 1.4
C8051F020/1/2/3
LIST OF FIGURES AND TABLES
1. SYSTEM OVERVIEW .........................................................................................................17
Table 1.1. Product Selection Guide......................................................................................17
Figure 1.1. C8051F020 Block Diagram.................................................................................18
Figure 1.2. C8051F021 Block Diagram.................................................................................19
Figure 1.3. C8051F022 Block Diagram.................................................................................20
Figure 1.4. C8051F023 Block Diagram.................................................................................21
Figure 1.5. Comparison of Peak MCU Execution Speeds.....................................................22
Figure 1.6. On-Board Clock and Reset..................................................................................23
Figure 1.7. On-Chip Memory Map........................................................................................24
Figure 1.8. Development/In-System Debug Diagram ...........................................................25
Figure 1.9. Digital Crossbar Diagram....................................................................................26
Figure 1.10. PCA Block Diagram............................................................................................27
Figure 1.11. 12-Bit ADC Block Diagram................................................................................28
Figure 1.12. 8-Bit ADC Diagram ............................................................................................29
Figure 1.13. Comparator and DAC Diagram...........................................................................30
2. ABSOLUTE MAXIMUM RATINGS..................................................................................31
Table 2.1. Absolute Maximum Ratings*..............................................................................31
3. GLOBAL DC ELECTRICAL CHARACTERISTICS ......................................................32
Table 3.1. Global DC Electrical Characteristics...................................................................32
4. PINOUT AND PACKAGE DEFINITIONS........................................................................33
Table 4.1. Pin Definitions.....................................................................................................33
Figure 4.1. TQFP-100 Pinout Diagram..................................................................................38
Figure 4.2. TQFP-100 Package Drawing...............................................................................39
Figure 4.3. TQFP-64 Pinout Diagram....................................................................................40
Figure 4.4. TQFP-64 Package Drawing.................................................................................41
5. ADC0 (12-BIT ADC, C8051F020/1 ONLY) ........................................................................43
Figure 5.1. 12-Bit ADC0 Functional Block Diagram............................................................43
Figure 5.2. Temperature Sensor Transfer Function...............................................................44
Figure 5.3. 12-Bit ADC Track and Conversion Example Timing.........................................45
Figure 5.4. ADC0 Equivalent Input Circuits .........................................................................46
Figure 5.5. AMX0CF: AMUX0 Configuration Register (C8051F020/1).............................47
Figure 5.6. AMX0SL: AMUX0 Channel Select Register (C8051F020/1)............................48
Figure 5.7. ADC0CF: ADC0 Configuration Register (C8051F020/1)..................................49
Figure 5.8. ADC0CN: ADC0 Control Register (C8051F020/1) ...........................................50
Figure 5.9. ADC0H: ADC0 Data Word MSB Register (C8051F020/1)...............................51
Figure 5.10. ADC0L: ADC0 Data Word LSB Register (C8051F020/1).................................51
Figure 5.11. ADC0 Data Word Example (C8051F020/1).......................................................52
Figure 5.12. ADC0GTH: ADC0 Greater-Than Data High Byte Register (C8051F020/1) .....53
Figure 5.13. ADC0GTL: ADC0 Greater-Than Data Low Byte Register (C8051F020/1) ......53
Figure 5.14. ADC0LTH: ADC0 Less-Than Data High Byte Register (C8051F020/1) ..........53
Figure 5.15. ADC0LTL: ADC0 Less-Than Data Low Byte Register (C8051F020/1) ...........53
Figure 5.16. 12-Bit ADC0 Window Interrupt Example: Right Justified Single-Ended Data .54
Rev. 1.4
9
C8051F020/1/2/3
Figure 5.17. 12-Bit ADC0 Window Interrupt Example: Right Justified Differential Data.....55
Figure 5.18. 12-Bit ADC0 Window Interrupt Example: Left Justified Single-Ended Data....56
Figure 5.19. 12-Bit ADC0 Window Interrupt Example: Left Justified Differential Data.......57
Table 5.1. 12-Bit ADC0 Electrical Characteristics (C8051F020/1).....................................58
6. ADC0 (10-BIT ADC, C8051F022/3 ONLY) ........................................................................59
Figure 6.1. 10-Bit ADC0 Functional Block Diagram............................................................59
Figure 6.2. Temperature Sensor Transfer Function...............................................................60
Figure 6.3. 10-Bit ADC Track and Conversion Example Timing.........................................61
Figure 6.4. ADC0 Equivalent Input Circuits .........................................................................62
Figure 6.5. AMX0CF: AMUX0 Configuration Register (C8051F022/3).............................63
Figure 6.6. AMX0SL: AMUX0 Channel Select Register (C8051F022/3)............................64
Figure 6.7. ADC0CF: ADC0 Configuration Register (C8051F022/3)..................................65
Figure 6.8. ADC0CN: ADC0 Control Register (C8051F022/3) ...........................................66
Figure 6.9. ADC0H: ADC0 Data Word MSB Register (C8051F022/3)...............................67
Figure 6.10. ADC0L: ADC0 Data Word LSB Register (C8051F022/3).................................67
Figure 6.11. ADC0 Data Word Example (C8051F022/3).......................................................68
Figure 6.12. ADC0GTH: ADC0 Greater-Than Data High Byte Register (C8051F022/3) .....69
Figure 6.13. ADC0GTL: ADC0 Greater-Than Data Low Byte Register (C8051F022/3) ......69
Figure 6.14. ADC0LTH: ADC0 Less-Than Data High Byte Register (C8051F022/3) ..........69
Figure 6.15. ADC0LTL: ADC0 Less-Than Data Low Byte Register (C8051F022/3) ...........69
Figure 6.16. 10-Bit ADC0 Window Interrupt Example: Right Justified Single-Ended Data .70
Figure 6.17. 10-Bit ADC0 Window Interrupt Example: Right Justified Differential Data.....71
Figure 6.18. 10-Bit ADC0 Window Interrupt Example: Left Justified Single-Ended Data....72
Figure 6.19. 10-Bit ADC0 Window Interrupt Example: Left Justified Differential Data.......73
Table 6.1. 10-Bit ADC0 Electrical Characteristics (C8051F022/3).....................................74
7. ADC1 (8-BIT ADC) ...............................................................................................................75
Figure 7.1. ADC1 Functional Block Diagram.......................................................................75
Figure 7.2. ADC1 Track and Conversion Example Timing..................................................77
Figure 7.3. ADC1 Equivalent Input Circuit...........................................................................78
Figure 7.4. ADC1CF: ADC1 Configuration Register (C8051F020/1/2/3)............................79
Figure 7.5. AMX1SL: AMUX1 Channel Select Register (C8051F020/1/2/3) .....................79
Figure 7.6. ADC1CN: ADC1 Control Register (C8051F020/1/2/3).....................................80
Figure 7.7. ADC1: ADC1 Data Word Register.....................................................................81
Figure 7.8. ADC1 Data Word Example.................................................................................81
Table 7.1. ADC1 Electrical Characteristics..........................................................................82
8. DACS, 12-BIT VOLTAGE MODE......................................................................................83
Figure 8.1. DAC Functional Block Diagram.........................................................................83
Figure 8.2. DAC0H: DAC0 High Byte Register ...................................................................85
Figure 8.3. DAC0L: DAC0 Low Byte Register ....................................................................85
Figure 8.4. DAC0CN: DAC0 Control Register.....................................................................86
Figure 8.5. DAC1H: DAC1 High Byte Register ...................................................................87
Figure 8.6. DAC1L: DAC1 Low Byte Register ....................................................................87
Figure 8.7. DAC1CN: DAC1 Control Register.....................................................................88
Table 8.1. DAC Electrical Characteristics............................................................................89
9. VOLTAGE REFERENCE (C8051F020/2)..........................................................................91
10
Rev. 1.4
C8051F020/1/2/3
Figure 9.1. Voltage Reference Functional Block Diagram....................................................91
Figure 9.2. REF0CN: Reference Control Register ................................................................92
Table 9.1. Voltage Reference Electrical Characteristics......................................................92
10. VOLTAGE REFERENCE (C8051F021/3)..........................................................................93
Figure 10.1. Voltage Reference Functional Block Diagram ...................................................93
Figure 10.2. REF0CN: Reference Control Register ................................................................94
Table 10.1. Voltage Reference Electrical Characteristics......................................................94
11. COMPARATORS..................................................................................................................95
Figure 11.1. Comparator Functional Block Diagram ..............................................................95
Figure 11.2. Comparator Hysteresis Plot.................................................................................96
Figure 11.3. CPT0CN: Comparator0 Control Register ...........................................................97
Figure 11.4. CPT1CN: Comparator1 Control Register ...........................................................98
Table 11.1. Comparator Electrical Characteristics.................................................................99
12. CIP-51 MICROCONTROLLER........................................................................................101
Figure 12.1. CIP-51 Block Diagram......................................................................................101
Table 12.1. CIP-51 Instruction Set Summary.......................................................................103
Figure 12.2. Memory Map.....................................................................................................107
Table 12.2. Special Function Register (SFR) Memory Map................................................109
Table 12.3. Special Function Registers ................................................................................109
Figure 12.3. SP: Stack Pointer...............................................................................................113
Figure 12.4. DPL: Data Pointer Low Byte ............................................................................113
Figure 12.5. DPH: Data Pointer High Byte ...........................................................................113
Figure 12.6. PSW: Program Status Word..............................................................................114
Figure 12.7. ACC: Accumulator............................................................................................115
Figure 12.8. B: B Register .....................................................................................................115
Table 12.4. Interrupt Summary.............................................................................................117
Figure 12.9. IE: Interrupt Enable...........................................................................................119
Figure 12.10. IP: Interrupt Priority ........................................................................................120
Figure 12.11. EIE1: Extended Interrupt Enable 1 .................................................................121
Figure 12.12. EIE2: Extended Interrupt Enable 2 .................................................................122
Figure 12.13. EIP1: Extended Interrupt Priority 1.................................................................123
Figure 12.14. EIP2: Extended Interrupt Priority 2.................................................................124
Figure 12.15. PCON: Power Control.....................................................................................126
13. RESET SOURCES ..............................................................................................................127
Figure 13.1. Reset Sources ....................................................................................................127
Figure 13.2. Reset Timing .....................................................................................................128
Figure 13.3. WDTCN: Watchdog Timer Control Register ...................................................131
Figure 13.4. RSTSRC: Reset Source Register.......................................................................132
Table 13.1. Reset Electrical Characteristics.........................................................................133
14. OSCILLATORS...................................................................................................................135
Figure 14.1. Oscillator Diagram ............................................................................................135
Figure 14.2. OSCICN: Internal Oscillator Control Register .................................................136
Table 14.1. Internal Oscillator Electrical Characteristics.....................................................136
Figure 14.3. OSCXCN: External Oscillator Control Register...............................................137
15. FLASH MEMORY..............................................................................................................139
Rev. 1.4
11
C8051F020/1/2/3
Table 15.1. FLASH Electrical Characteristics .....................................................................140
Figure 15.1. FLASH Program Memory Map and Security Bytes .........................................141
Figure 15.2. FLACL: FLASH Access Limit .........................................................................142
Figure 15.3. FLSCL: FLASH Memory Control ....................................................................143
Figure 15.4. PSCTL: Program Store Read/Write Control.....................................................144
16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP XRAM.......................145
Figure 16.1. EMI0CN: External Memory Interface Control .................................................147
Figure 16.2. EMI0CF: External Memory Configuration.......................................................147
Figure 16.3. Multiplexed Configuration Example.................................................................148
Figure 16.4. Non-multiplexed Configuration Example.........................................................149
Figure 16.5. EMIF Operating Modes.....................................................................................150
Figure 16.6. EMI0TC: External Memory Timing Control ....................................................152
Figure 16.7. Non-multiplexed 16-bit MOVX Timing ...........................................................153
Figure 16.8. Non-multiplexed 8-bit MOVX without Bank Select Timing............................154
Figure 16.9. Non-multiplexed 8-bit MOVX with Bank Select Timing.................................155
Figure 16.10. Multiplexed 16-bit MOVX Timing.................................................................156
Figure 16.11. Multiplexed 8-bit MOVX without Bank Select Timing .................................157
Figure 16.12. Multiplexed 8-bit MOVX with Bank Select Timing.......................................158
Table 16.1. AC Parameters for External Memory Interface.................................................159
17. PORT INPUT/OUTPUT .....................................................................................................161
Figure 17.1. Port I/O Cell Block Diagram.............................................................................161
Table 17.1. Port I/O DC Electrical Characteristics ..............................................................161
Figure 17.2. Lower Port I/O Functional Block Diagram.......................................................162
Figure 17.3. Priority Crossbar Decode Table ........................................................................163
Figure 17.4. Priority Crossbar Decode Table ........................................................................166
Figure 17.5. Priority Crossbar Decode Table ........................................................................167
Figure 17.6. Crossbar Example: ............................................................................................169
Figure 17.7. XBR0: Port I/O Crossbar Register 0 .................................................................170
Figure 17.8. XBR1: Port I/O Crossbar Register 1 .................................................................171
Figure 17.9. XBR2: Port I/O Crossbar Register 2 .................................................................172
Figure 17.10. P0: Port0 Data Register ...................................................................................173
Figure 17.11. P0MDOUT: Port0 Output Mode Register.......................................................173
Figure 17.12. P1: Port1 Data Register ...................................................................................174
Figure 17.13. P1MDIN: Port1 Input Mode Register .............................................................174
Figure 17.14. P1MDOUT: Port1 Output Mode Register.......................................................175
Figure 17.15. P2: Port2 Data Register ...................................................................................175
Figure 17.16. P2MDOUT: Port2 Output Mode Register.......................................................175
Figure 17.17. P3: Port3 Data Register ...................................................................................176
Figure 17.18. P3MDOUT: Port3 Output Mode Register.......................................................176
Figure 17.19. P3IF: Port3 Interrupt Flag Register.................................................................177
Figure 17.20. P74OUT: Ports 7 - 4 Output Mode Register ...................................................179
Figure 17.21. P4: Port4 Data Register ...................................................................................180
Figure 17.22. P5: Port5 Data Register ...................................................................................180
Figure 17.23. P6: Port6 Data Register ...................................................................................181
Figure 17.24. P7: Port7 Data Register ...................................................................................181
12
Rev. 1.4
C8051F020/1/2/3
18. SYSTEM MANAGEMENT BUS / I2C BUS (SMBUS0) .................................................183
Figure 18.1. SMBus0 Block Diagram ...................................................................................183
Figure 18.2. Typical SMBus Configuration ..........................................................................184
Figure 18.3. SMBus Transaction ...........................................................................................185
Figure 18.4. Typical Master Transmitter Sequence...............................................................187
Figure 18.5. Typical Master Receiver Sequence ...................................................................187
Figure 18.6. Typical Slave Transmitter Sequence.................................................................188
Figure 18.7. Typical Slave Receiver Sequence .....................................................................188
Figure 18.8. SMB0CN: SMBus0 Control Register ...............................................................191
Figure 18.9. SMB0CR: SMBus0 Clock Rate Register..........................................................192
Figure 18.10. SMB0DAT: SMBus0 Data Register ...............................................................193
Figure 18.11. SMB0ADR: SMBus0 Address Register..........................................................193
Figure 18.12. SMB0STA: SMBus0 Status Register..............................................................194
Table 18.1. SMB0STA Status Codes and States..................................................................195
19. SERIAL PERIPHERAL INTERFACE BUS (SPI0) ........................................................197
Figure 19.1. SPI Block Diagram............................................................................................197
Figure 19.2. Typical SPI Interconnection..............................................................................198
Figure 19.3. Full Duplex Operation.......................................................................................199
Figure 19.4. Data/Clock Timing Diagram.............................................................................200
Figure 19.5. SPI0CFG: SPI0 Configuration Register............................................................201
Figure 19.6. SPI0CN: SPI0 Control Register ........................................................................202
Figure 19.7. SPI0CKR: SPI0 Clock Rate Register................................................................203
Figure 19.8. SPI0DAT: SPI0 Data Register ..........................................................................203
20. UART0 ..................................................................................................................................205
Figure 20.1. UART0 Block Diagram.....................................................................................205
Table 20.1. UART0 Modes ..................................................................................................206
Figure 20.2. UART0 Mode 0 Interconnect............................................................................206
Figure 20.3. UART0 Mode 0 Timing Diagram.....................................................................206
Figure 20.4. UART0 Mode 1 Timing Diagram.....................................................................207
Figure 20.5. UART Modes 2 and 3 Timing Diagram............................................................208
Figure 20.6. UART Modes 1, 2, and 3 Interconnect Diagram ..............................................209
Figure 20.7. UART Multi-Processor Mode Interconnect Diagram.......................................210
Table 20.2. Oscillator Frequencies for Standard Baud Rates...............................................212
Figure 20.8. SCON0: UART0 Control Register....................................................................213
Figure 20.9. SBUF0: UART0 Data Buffer Register..............................................................214
Figure 20.10. SADDR0: UART0 Slave Address Register ....................................................214
Figure 20.11. SADEN0: UART0 Slave Address Enable Register ........................................214
21. UART1 ..................................................................................................................................215
Figure 21.1. UART1 Block Diagram.....................................................................................215
Table 21.1. UART1 Modes ..................................................................................................216
Figure 21.2. UART1 Mode 0 Interconnect............................................................................216
Figure 21.3. UART1 Mode 0 Timing Diagram.....................................................................216
Figure 21.4. UART1 Mode 1 Timing Diagram.....................................................................217
Figure 21.5. UART Modes 2 and 3 Timing Diagram............................................................218
Figure 21.6. UART Modes 1, 2, and 3 Interconnect Diagram ..............................................219
Rev. 1.4
13
C8051F020/1/2/3
Figure 21.7. UART Multi-Processor Mode Interconnect Diagram.......................................220
Table 21.2. Oscillator Frequencies for Standard Baud Rates...............................................222
Figure 21.8. SCON1: UART1 Control Register....................................................................223
Figure 21.9. SBUF1: UART1 Data Buffer Register..............................................................224
Figure 21.10. SADDR1: UART1 Slave Address Register ....................................................224
Figure 21.11. SADEN1: UART1 Slave Address Enable Register ........................................224
22. TIMERS................................................................................................................................225
Figure 22.1. CKCON: Clock Control Register......................................................................226
Figure 22.2. T0 Mode 0 Block Diagram................................................................................228
Figure 22.3. T0 Mode 2 (8-bit Auto-Reload) Block Diagram...............................................229
Figure 22.4. T0 Mode 3 (Two 8-bit Timers) Block Diagram................................................230
Figure 22.5. TCON: Timer Control Register.........................................................................231
Figure 22.6. TMOD: Timer Mode Register...........................................................................232
Figure 22.7. TL0: Timer 0 Low Byte ....................................................................................233
Figure 22.8. TL1: Timer 1 Low Byte ....................................................................................233
Figure 22.9. TH0 Timer 0 High Byte ....................................................................................233
Figure 22.10. TH1: Timer 1 High Byte .................................................................................233
Figure 22.11. T2 Mode 0 Block Diagram..............................................................................235
Figure 22.12. T2 Mode 1 Block Diagram..............................................................................236
Figure 22.13. T2 Mode 2 Block Diagram..............................................................................237
Figure 22.14. T2CON: Timer 2 Control Register..................................................................238
Figure 22.15. RCAP2L: Timer 2 Capture Register Low Byte ..............................................239
Figure 22.16. RCAP2H: Timer 2 Capture Register High Byte .............................................239
Figure 22.17. TL2: Timer 2 Low Byte ..................................................................................239
Figure 22.18. TH2 Timer 2 High Byte ..................................................................................239
Figure 22.19. Timer 3 Block Diagram...................................................................................240
Figure 22.20. TMR3CN: Timer 3 Control Register ..............................................................241
Figure 22.21. TMR3RLL: Timer 3 Reload Register Low Byte ............................................241
Figure 22.22. TMR3RLH: Timer 3 Reload Register High Byte ...........................................242
Figure 22.23. TMR3L: Timer 3 Low Byte ............................................................................242
Figure 22.24. TMR3H: Timer 3 High Byte...........................................................................242
Figure 22.25. T4 Mode 0 Block Diagram..............................................................................244
Figure 22.26. T4 Mode 1 Block Diagram..............................................................................245
Figure 22.27. T4 Mode 2 Block Diagram..............................................................................246
Figure 22.28. T4CON: Timer 4 Control Register..................................................................247
Figure 22.29. RCAP4L: Timer 4 Capture Register Low Byte ..............................................248
Figure 22.30. RCAP4H: Timer 4 Capture Register High Byte .............................................248
Figure 22.31. TL4: Timer 4 Low Byte ..................................................................................248
Figure 22.32. TH4 Timer 4 High Byte ..................................................................................248
23. PROGRAMMABLE COUNTER ARRAY .......................................................................249
Figure 23.1. PCA Block Diagram..........................................................................................249
Figure 23.2. PCA Counter/Timer Block Diagram.................................................................250
Table 23.1. PCA Timebase Input Options............................................................................250
Figure 23.3. PCA Interrupt Block Diagram...........................................................................252
Table 23.2. PCA0CPM Register Settings for PCA Capture/Compare Modules..................252
14
Rev. 1.4
C8051F020/1/2/3
Figure 23.4. PCA Capture Mode Diagram ............................................................................253
Figure 23.5. PCA Software Timer Mode Diagram................................................................254
Figure 23.6. PCA High Speed Output Mode Diagram..........................................................255
Figure 23.7. PCA Frequency Output Mode...........................................................................256
Figure 23.8. PCA 8-Bit PWM Mode Diagram ......................................................................257
Figure 23.9. PCA 16-Bit PWM Mode ...................................................................................258
Figure 23.10. PCA0CN: PCA Control Register ....................................................................259
Figure 23.11. PCA0MD: PCA0 Mode Register ....................................................................260
Figure 23.12. PCA0CPMn: PCA0 Capture/Compare Mode Registers .................................261
Figure 23.13. PCA0L: PCA0 Counter/Timer Low Byte .......................................................262
Figure 23.14. PCA0H: PCA0 Counter/Timer High Byte ......................................................262
Figure 23.15. PCA0CPLn: PCA0 Capture Module Low Byte..............................................263
Figure 23.16. PCA0CPHn: PCA0 Capture Module High Byte.............................................263
24. JTAG (IEEE 1149.1)............................................................................................................265
Figure 24.1. IR: JTAG Instruction Register ..........................................................................265
Table 24.1. Boundary Data Register Bit Definitions............................................................266
Figure 24.2. DEVICEID: JTAG Device ID Register ............................................................267
Figure 24.3. FLASHCON: JTAG Flash Control Register.....................................................269
Figure 24.4. FLASHADR: JTAG Flash Address Register....................................................270
Figure 24.5. FLASHDAT: JTAG Flash Data Register..........................................................270
Rev. 1.4
15
C8051F020/1/2/3
Notes
16
Rev. 1.4
C8051F020/1/2/3
1.
SYSTEM OVERVIEW
The C8051F020/1/2/3 devices are fully integrated mixed-signal System-on-a-Chip MCUs with 64 digital I/O pins
(C8051F020/2) or 32 digital I/O pins (C8051F021/3). Highlighted features are listed below; refer to Table 1.1 for
specific product feature selection.
•
•
•
•
•
•
•
•
•
•
•
•
High-Speed pipelined 8051-compatible CIP-51 microcontroller core (up to 25 MIPS)
In-system, full-speed, non-intrusive debug interface (on-chip)
True 12-bit (C8051F020/1) or 10-bit (C8051F022/3) 100 ksps 8-channel ADC with PGA and analog multiplexer
True 8-bit ADC 500 ksps 8-channel ADC with PGA and analog multiplexer
Two 12-bit DACs with programmable update scheduling
64k bytes of in-system programmable FLASH memory
4352 (4096 + 256) bytes of on-chip RAM
External Data Memory Interface with 64k byte address space
2
SPI, SMBus/I C, and (2) UART serial interfaces implemented in hardware
Five general purpose 16-bit Timers
Programmable Counter/Timer Array with five capture/compare modules
On-chip Watchdog Timer, VDD Monitor, and Temperature Sensor
With on-chip VDD monitor, Watchdog Timer, and clock oscillator, the C8051F020/1/2/3 devices are truly stand-
alone System-on-a-Chip solutions. All analog and digital peripherals are enabled/disabled and configured by user
firmware. The FLASH memory can be reprogrammed even in-circuit, providing non-volatile data storage, and also
allowing field upgrades of the 8051 firmware.
On-board JTAG debug circuitry allows non-intrusive (uses no on-chip resources), full speed, in-circuit debugging
using the production MCU installed in the final application. This debug system supports inspection and modification
of memory and registers, setting breakpoints, watchpoints, single stepping, run and halt commands. All analog and
digital peripherals are fully functional while debugging using JTAG.
Each MCU is specified for 2.7 V-to-3.6 V operation over the industrial temperature range (-45° C to +85° C). The
Port I/Os, /RST, and JTAG pins are tolerant for input signals up to 5 V. The C8051F020/2 are available in a 100-pin
TQFP package (see block diagrams in Figure 1.1 and Figure 1.3). The C8051F021/3 are available in a 64-pin TQFP
package (see block diagrams in Figure 1.2 and Figure 1.4).
Table 1.1. Product Selection Guide
C8051F020 25 64k 4352
C8051F021 25 64k 4352
C8051F022 25 64k 4352
C8051F023 25 64k 4352
3
3
3
3
3
3
3
3
3
3
3
3
2
2
2
2
5
5
5
5
3
3
3
3
64
32
64
32
8
8
-
-
-
8
8
8
8
3
3
3
3
3
3
3
3
12
12
12
12
2
2
2
2
2
2
2
2
100TQFP
64TQFP
100TQFP
64TQFP
8
8
-
Rev. 1.4
17
C8051F020/1/2/3
Figure 1.1. C8051F020 Block Diagram
VDD
VDD
VDD
DGND
DGND
DGND
Port I/O
Config.
Digital Power
Analog Power
P0.0
P0.7
UART0
UART1
SMBus
SPI Bus
PCA
P0
8
0
5
1
Drv
AV+
AV+
AGND
C
R
O
S
S
B
A
R
P1.0/AIN1.0
P1.7/AIN1.7
P1
AGND
Drv
TCK
TMS
TDI
TDO
Boundary Scan
Debug HW
JTAG
Logic
Timers 0,
1, 2, 4
P2.0
P2.7
P2
SFR Bus
Drv
Reset
/RST
Timer 3/
RTC
VDD
64kbyte
FLASH
P3.0
P3.7
WDT
MONEN
P3
Monitor
P0, P1,
P2, P3
Latches
C
o
r
Drv
External
Oscillator
Circuit
XTAL1
XTAL2
256 byte
RAM
Crossbar
Config.
System
Clock
Internal
4kbyte
RAM
VREF1
P4.0
Oscillator
A
M
U
X
e
ADC
8:1
Prog
Gain
500ksps
(8-Bit)
VREF
VREF
VREFD
External Data Memory Bus
DAC1
DAC1
(12-Bit)
C
T
L
P4 Latch
Bus Control
P4
P4.4
P4.5/ALE
P4.6/RD
P4.7/WR
DRV
DAC0
DAC0
(12-Bit)
VREF0
P5.0/A8
P5 Latch
P6 Latch
P5
AIN0.0
AIN0.1
AIN0.2
AIN0.3
AIN0.4
AIN0.5
AIN0.6
AIN0.7
A
d
d
r
DRV
P5.7/A15
P6.0/A0
Address Bus
Data Bus
A
M
U
X
ADC
P6
Prog
Gain
100ksps
(12-Bit)
DRV
P6.7/A7
P7.0/D0
P7.7/D7
D
a
t
P7 Latch
TEMP
SENSOR
P7
DRV
CP0+
CP0-
CP1+
CP1-
CP0
a
CP1
18
Rev. 1.4
C8051F020/1/2/3
Figure 1.2. C8051F021 Block Diagram
VDD
VDD
VDD
DGND
DGND
DGND
Port I/O
Config.
Digital Power
Analog Power
P0.0
P0.7
UART0
UART1
SMBus
SPI Bus
PCA
P0
8
0
5
1
Drv
AV+
C
R
O
S
S
B
A
R
AGND
P1.0/AIN1.0
P1.7/AIN1.7
P1
Drv
TCK
TMS
TDI
TDO
Boundary Scan
Debug HW
JTAG
Logic
Timers 0,
1, 2, 4
P2.0
P2.7
P2
SFR Bus
Drv
Reset
/RST
Timer 3/
RTC
VDD
64kbyte
FLASH
P3.0
P3.7
WDT
MONEN
P3
Monitor
P0, P1,
P2, P3
Latches
C
o
r
Drv
External
Oscillator
Circuit
XTAL1
XTAL2
256 byte
RAM
Crossbar
Config.
System
Clock
Internal
4kbyte
RAM
A
M
U
X
ADC
Oscillator
8:1
Prog
Gain
e
500ksps
(8-Bit)
VREF
DAC1
VREF
AV+
VREFA
External Data Memory Bus
DAC1
(12-Bit)
C
T
L
P4 Latch
Bus Control
P4
DRV
DAC0
DAC0
(12-Bit)
VREFA
P5 Latch
P6 Latch
P5
AIN0.0
AIN0.1
AIN0.2
AIN0.3
AIN0.4
AIN0.5
AIN0.6
AIN0.7
A
d
d
r
DRV
Address Bus
Data Bus
ADC
A
M
U
X
P6
Prog
Gain
100ksps
(12-Bit)
DRV
D
a
t
P7 Latch
TEMP
SENSOR
P7
DRV
CP0+
CP0-
CP1+
CP1-
CP0
a
CP1
Rev. 1.4
19
C8051F020/1/2/3
Figure 1.3. C8051F022 Block Diagram
VDD
VDD
VDD
DGND
DGND
DGND
Port I/O
Config.
Digital Power
Analog Power
P0.0
P0.7
UART0
UART1
SMBus
SPI Bus
PCA
P0
8
0
5
1
Drv
AV+
AV+
AGND
C
R
O
S
S
B
A
R
P1.0/AIN1.0
P1.7/AIN1.7
P1
AGND
Drv
TCK
TMS
TDI
TDO
Boundary Scan
Debug HW
JTAG
Logic
Timers 0,
1, 2, 4
P2.0
P2.7
P2
SFR Bus
Drv
Reset
/RST
Timer 3/
RTC
VDD
64kbyte
FLASH
P3.0
P3.7
WDT
MONEN
P3
Monitor
P0, P1,
P2, P3
Latches
C
o
r
Drv
External
Oscillator
Circuit
XTAL1
XTAL2
256 byte
RAM
Crossbar
Config.
System
Clock
Internal
4kbyte
RAM
VREF1
P4.0
Oscillator
A
M
U
X
e
ADC
8:1
Prog
Gain
500ksps
(8-Bit)
VREF
VREF
VREFD
External Data Memory Bus
DAC1
DAC1
(12-Bit)
C
T
L
P4 Latch
Bus Control
P4
P4.4
P4.5/ALE
P4.6/RD
P4.7/WR
DRV
DAC0
DAC0
(12-Bit)
VREF0
P5.0/A8
P5 Latch
P6 Latch
P5
AIN0.0
AIN0.1
AIN0.2
AIN0.3
AIN0.4
AIN0.5
AIN0.6
AIN0.7
A
d
d
r
DRV
P5.7/A15
P6.0/A0
Address Bus
Data Bus
A
M
U
X
ADC
P6
Prog
Gain
100ksps
(10-Bit)
DRV
P6.7/A7
P7.0/D0
P7.7/D7
D
a
t
P7 Latch
TEMP
SENSOR
P7
DRV
CP0+
CP0-
CP1+
CP1-
CP0
a
CP1
20
Rev. 1.4
C8051F020/1/2/3
Figure 1.4. C8051F023 Block Diagram
VDD
VDD
VDD
DGND
DGND
DGND
Port I/O
Config.
Digital Power
Analog Power
P0.0
P0.7
UART0
UART1
SMBus
SPI Bus
PCA
P0
8
0
5
1
Drv
AV+
C
R
O
S
S
B
A
R
AGND
P1.0/AIN1.0
P1.7/AIN1.7
P1
Drv
TCK
TMS
TDI
TDO
Boundary Scan
Debug HW
JTAG
Logic
Timers 0,
1, 2, 4
P2.0
P2.7
P2
SFR Bus
Drv
Reset
/RST
Timer 3/
RTC
VDD
64kbyte
FLASH
P3.0
P3.7
WDT
MONEN
P3
Monitor
P0, P1,
P2, P3
Latches
C
o
r
Drv
External
Oscillator
Circuit
XTAL1
XTAL2
256 byte
RAM
Crossbar
Config.
System
Clock
Internal
4kbyte
RAM
A
M
U
X
ADC
Oscillator
8:1
Prog
Gain
e
500ksps
(8-Bit)
VREF
DAC1
VREF
AV+
VREFA
External Data Memory Bus
DAC1
(12-Bit)
C
T
L
P4 Latch
Bus Control
P4
DRV
DAC0
DAC0
(12-Bit)
VREFA
P5 Latch
P6 Latch
P5
AIN0.0
AIN0.1
AIN0.2
AIN0.3
AIN0.4
AIN0.5
AIN0.6
AIN0.7
A
d
d
r
DRV
Address Bus
Data Bus
ADC
A
M
U
X
P6
Prog
Gain
100ksps
(10-Bit)
DRV
D
a
t
P7 Latch
TEMP
SENSOR
P7
DRV
CP0+
CP0-
CP1+
CP1-
CP0
a
CP1
Rev. 1.4
21
C8051F020/1/2/3
1.1. CIP-51™ Microcontroller Core
1.1.1. Fully 8051 Compatible
The C8051F020 family utilizes Silicon Labs' proprietary CIP-51 microcontroller core. The CIP-51 is fully compati-
ble with the MCS-51™ instruction set; standard 803x/805x assemblers and compilers can be used to develop soft-
ware. The core has all the peripherals included with a standard 8052, including five 16-bit counter/timers, two full-
duplex UARTs, 256 bytes of internal RAM, 128 byte Special Function Register (SFR) address space, and 8/4 byte-
wide I/O Ports.
1.1.2. Improved Throughput
The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the standard 8051
architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system clock cycles to exe-
cute with a maximum system clock of 12-to-24 MHz. By contrast, the CIP-51 core executes 70% of its instructions in
one or two system clock cycles, with only four instructions taking more than four system clock cycles.
The CIP-51 has a total of 109 instructions. The table below shows the total number of instructions that require each
execution time.
Clocks to Execute
1
2
2/3
5
3
3/4
7
4
3
4/5
1
5
2
8
1
Number of Instructions
26
50
14
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. Figure 1.5 shows a com-
parison of peak throughputs of various 8-bit microcontroller cores with their maximum system clocks.
Figure 1.5. Comparison of Peak MCU Execution Speeds
25
20
15
10
5
Silicon Labs Microchip
Philips
80C51
ADuC812
8051
CIP-51
PIC17C75x
(25MHz clk) (33MHz clk) (33MHz clk) (16MHz clk)
22
Rev. 1.4
C8051F020/1/2/3
1.1.3. Additional Features
The C8051F020 MCU family includes several key enhancements to the CIP-51 core and peripherals to improve over-
all performance and ease of use in end applications.
The extended interrupt handler provides 22 interrupt sources into the CIP-51 (as opposed to 7 for the standard 8051),
allowing the numerous analog and digital peripherals to interrupt the controller. An interrupt driven system requires
less intervention by the MCU, giving it more effective throughput. The extra interrupt sources are very useful when
building multi-tasking, real-time systems.
There are up to seven reset sources for the MCU: an on-board VDD monitor, a Watchdog Timer, a missing clock
detector, a voltage level detection from Comparator0, a forced software reset, the CNVSTR input pin, and the /RST
pin. The /RST pin is bi-directional, accommodating an external reset, or allowing the internally generated POR to be
output on the /RST pin. Each reset source except for the VDD monitor and Reset Input pin may be disabled by the
user in software; the VDD monitor is enabled/disabled via the MONEN pin. The Watchdog Timer may be perma-
nently enabled in software after a power-on reset during MCU initialization.
The MCU has an internal, stand alone clock generator which is used by default as the system clock after any reset. If
desired, the clock source may be switched on the fly to the external oscillator, which can use a crystal, ceramic reso-
nator, capacitor, RC, or external clock source to generate the system clock. This can be extremely useful in low power
applications, allowing the MCU to run from a slow (power saving) external crystal source, while periodically switch-
ing to the fast (up to 16 MHz) internal oscillator as needed.
Figure 1.6. On-Board Clock and Reset
VDD
CNVSTR
(Port
I/O)
Crossbar
Supply
Monitor
(CNVSTR
reset
Supply
Reset
+
enable)
/RST
-
(wired-OR)
Timeout
Comparator0
CP0+
CP0-
+
-
(CP0
reset
enable)
Reset
Funnel
Missing
Clock
Detector
(one-
shot)
WDT
EN
EN
PRE
Internal
Clock
Generator
System
Clock
Software Reset
System Reset
CIP-51
XTAL1
XTAL2
OSC
Microcontroller
Core
Clock Select
Extended Interrupt
Handler
Rev. 1.4
23
C8051F020/1/2/3
1.2. On-Chip Memory
The CIP-51 has a standard 8051 program and data address configuration. It includes 256 bytes of data RAM, with the
upper 128 bytes dual-mapped. Indirect addressing accesses the upper 128 bytes of general purpose RAM, and direct
addressing accesses the 128 byte SFR address space. The lower 128 bytes of RAM are accessible via direct and indi-
rect addressing. The first 32 bytes are addressable as four banks of general purpose registers, and the next 16 bytes
can be byte addressable or bit addressable.
The CIP-51 in the C8051F020/1/2/3 MCUs additionally has an on-chip 4k byte RAM block and an external memory
interface (EMIF) for accessing off-chip data memory. The on-chip 4k byte block can be addressed over the entire 64k
external data memory address range (overlapping 4k boundaries). External data memory address space can be
mapped to on-chip memory only, off-chip memory only, or a combination of the two (addresses up to 4k directed to
on-chip, above 4k directed to EMIF). The EMIF is also configurable for multiplexed or non-multiplexed address/data
lines.
The MCU’s program memory consists of 64k bytes of FLASH. This memory may be reprogrammed in-system in
512 byte sectors, and requires no special off-chip programming voltage. The 512 bytes from addresses 0xFE00 to
0xFFFF are reserved for factory use. There is also a single 128 byte sector at address 0x10000 to 0x1007F, which
may be useful as a small table for software constants. See Figure 1.7 for the MCU system memory map.
Figure 1.7. On-Chip Memory Map
DATA MEMORY (RAM)
PROGRAM/DATA MEMORY
(FLASH)
INTERNAL DATA ADDRESS SPACE
0xFF
0x1007F
Scrachpad Memory
(DATA only)
Upper 128 RAM
(Indirect Addressing
Only)
Special Function
Register's
0x10000
0xFFFF
0xFE00
0xFDFF
(Direct Addressing Only)
0x80
0x7F
RESERVED
(Direct and Indirect
Addressing)
Lower 128 RAM
(Direct and Indirect
Addressing)
0x30
0x2F
FLASH
Bit Addressable
0x20
(In-System
Programmable in 512
Byte Sectors)
0x1F
General Purpose
Registers
0x00
EXTERNAL DATA ADDRESS SPACE
0x0000
0xFFFF
Off-chip XRAM space
0x1000
0x0FFF
XRAM - 4096 Bytes
(accessable using MOVX
instruction)
0x0000
24
Rev. 1.4
C8051F020/1/2/3
1.3. JTAG Debug and Boundary Scan
The C8051F020 family has on-chip JTAG boundary scan and debug circuitry that provides non-intrusive, full speed,
in-circuit debugging using the production part installed in the end application, via the four-pin JTAG interface. The
JTAG port is fully compliant to IEEE 1149.1, providing full boundary scan for test and manufacturing purposes.
Silicon Labs' debugging system supports inspection and modification of memory and registers, breakpoints, watch-
points, a stack monitor, and single stepping. No additional target RAM, program memory, timers, or communications
channels are required. All the digital and analog peripherals are functional and work correctly while debugging. All
the peripherals (except for the ADC and SMBus) are stalled when the MCU is halted, during single stepping, or at a
breakpoint in order to keep them synchronized.
The C8051F020DK development kit provides all the hardware and software necessary to develop application code
and perform in-circuit debugging with the C8051F020/1/2/3 MCUs. The kit includes software with a developer's stu-
dio and debugger, an integrated 8051 assembler, and an RS-232 to JTAG serial adapter. It also has a target application
board with the associated MCU installed, plus the RS-232 and JTAG cables, and wall-mount power supply. The
Development Kit requires a Windows 95/98/NT/ME/2000 computer with one available RS-232 serial port. As shown
in Figure 1.8, the PC is connected via RS-232 to the Serial Adapter. A six-inch ribbon cable connects the Serial
Adapter to the user's application board, picking up the four JTAG pins and VDD and GND. The Serial Adapter takes
its power from the application board; it requires roughly 20 mA at 2.7-3.6 V. For applications where there is not suf-
ficient power available from the target system, the provided power supply can be connected directly to the Serial
Adapter.
Silicon Labs’ debug environment is a vastly superior configuration for developing and debugging embedded applica-
tions compared to standard MCU emulators, which use on-board "ICE Chips" and target cables and require the MCU
in the application board to be socketed. Silicon Labs' debug environment both increases ease of use and preserves the
performance of the precision analog peripherals.
Figure 1.8. Development/In-System Debug Diagram
Silicon Labs Integrated
Development Environment
WINDOWS 95/98/NT/ME/2000
RS-232
Serial
Adapter
JTAG (x4), VDD, GND
TARGET PCB
VDD GND
C8051
F020
Rev. 1.4
25
C8051F020/1/2/3
1.4. Programmable Digital I/O and Crossbar
The standard 8051 Ports (0, 1, 2, and 3) are available on the MCUs. The C8051F020/2 have 4 additional ports (4, 5,
6, and 7) for a total of 64 general-purpose port I/O. The Port I/O behave like the standard 8051 with a few enhance-
ments.
Each Port I/O pin can be configured as either a push-pull or open-drain output. Also, the "weak pull-ups" which are
normally fixed on an 8051 can be globally disabled, providing additional power saving capabilities for low-power
applications.
Perhaps the most unique enhancement is the Digital Crossbar. This is essentially a large digital switching network
that allows mapping of internal digital system resources to Port I/O pins on P0, P1, P2, and P3. (See Figure 1.9)
Unlike microcontrollers with standard multiplexed digital I/O, all combinations of functions are supported.
The on-chip counter/timers, serial buses, HW interrupts, ADC Start of Conversion input, comparator outputs, and
other digital signals in the controller can be configured to appear on the Port I/O pins specified in the Crossbar Con-
trol registers. This allows the user to select the exact mix of general purpose Port I/O and digital resources needed for
the particular application.
Figure 1.9. Digital Crossbar Diagram
XBR0, XBR1,
XBR2, P1MDIN
Registers
P0MDOUT, P1MDOUT,
P2MDOUT, P3MDOUT
Registers
2
4
Highest
Priority
UART0
SPI
External
Pins
2
2
6
SMBus
UART1
PCA
Priority
Decoder
P0.0
Highest
Priority
P0
I/O
8
8
8
8
Cells
P0.7
2
Comptr.
Outputs
Digital
P1.0
P1.7
P1
I/O
Crossbar
Cells
T0, T1,
T2, T2EX,
T4,T4EX
/INT0,
8
P2.0
P2.7
/INT1
P2
I/O
Cells
Lowest
Priority
/SYSCLK
CNVSTR
P3.0
P3.7
P3
I/O
8
Lowest
Priority
Cells
P0
(P0.0-P0.7)
8
P1
P2
P3
(P1.0-P1.7)
8
To External
Memory
Interface
(EMIF)
To
Port
ADC1
Input
Latches
(P2.0-P2.7)
8
(P3.0-P3.7)
26
Rev. 1.4
C8051F020/1/2/3
1.5. Programmable Counter Array
The C8051F020 MCU family includes an on-board Programmable Counter/Timer Array (PCA) in addition to the five
16-bit general purpose counter/timers. The PCA consists of a dedicated 16-bit counter/timer time base with 5 pro-
grammable capture/compare modules. The timebase is clocked from one of six sources: the system clock divided by
12, the system clock divided by 4, Timer 0 overflow, an External Clock Input (ECI pin), the system clock, or the
external oscillator source divided by 8.
Each capture/compare module can be configured to operate in one of six modes: Edge-Triggered Capture, Software
Timer, High Speed Output, Frequency Output, 8-Bit Pulse Width Modulator, or 16-Bit Pulse Width Modulator. The
PCA Capture/Compare Module I/O and External Clock Input are routed to the MCU Port I/O via the Digital Cross-
bar.
Figure 1.10. PCA Block Diagram
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
PCA
16-Bit Counter/Timer
CLOCK
MUX
ECI
SYSCLK
External Clock/8
Capture/Compare
Module 0
Capture/Compare
Module 1
Capture/Compare
Module 2
Capture/Compare
Module 3
Capture/Compare
Module 4
Crossbar
Port I/O
1.6. Serial Ports
2
The C8051F020 MCU Family includes two Enhanced Full-Duplex UARTs, SPI Bus, and SMBus/I C. Each of the
serial buses is fully implemented in hardware and makes extensive use of the CIP-51's interrupts, thus requiring very
little intervention by the CPU. The serial buses do not "share" resources such as timers, interrupts, or Port I/O, so any
or all of the serial buses may be used together with any other.
Rev. 1.4
27
C8051F020/1/2/3
1.7. 12-Bit Analog to Digital Converter
The C8051F020/1 has an on-chip 12-bit SAR ADC (ADC0) with a 9-channel input multiplexer and programmable
gain amplifier. With a maximum throughput of 100 ksps, the ADC offers true 12-bit accuracy with an INL of ±1LSB.
C8051F022/3 devices include a 10-bit SAR ADC with similar specifications and configuration options. The ADC0
voltage reference is selected between the DAC0 output and an external VREF pin. On C8051F020/2 devices, ADC0
has its own dedicated VREF0 input pin; on C8051F021/3 devices, the ADC0 shares the VREFA input pin with the 8-
bit ADC1. The on-chip 15 ppm/°C voltage reference may generate the voltage reference for other system components
or the on-chip ADCs via the VREF output pin.
The ADC is under full control of the CIP-51 microcontroller via its associated Special Function Registers. One input
channel is tied to an internal temperature sensor, while the other eight channels are available externally. Each pair of
the eight external input channels can be configured as either two single-ended inputs or a single differential input.
The system controller can also put the ADC into shutdown mode to save power.
A programmable gain amplifier follows the analog multiplexer. The gain can be set in software from 0.5 to 16 in
powers of 2. The gain stage can be especially useful when different ADC input channels have widely varied input
voltage signals, or when it is necessary to "zoom in" on a signal with a large DC offset (in differential mode, a DAC
could be used to provide the DC offset).
Conversions can be started in four ways; a software command, an overflow of Timer 2, an overflow of Timer 3, or an
external signal input. This flexibility allows the start of conversion to be triggered by software events, external HW
signals, or a periodic timer overflow signal. Conversion completions are indicated by a status bit and an interrupt (if
enabled). The resulting 10 or 12-bit data word is latched into two SFRs upon completion of a conversion. The data
can be right or left justified in these registers under software control.
Window Compare registers for the ADC data can be configured to interrupt the controller when ADC data is within
or outside of a specified range. The ADC can monitor a key voltage continuously in background mode, but not inter-
rupt the controller unless the converted data is within the specified window.
Figure 1.11. 12-Bit ADC Block Diagram
Analog Multiplexer
Window
Configuration, Control, and Data
Registers
Window Compare
Logic
Compare
Interrupt
+
AIN0.0
AIN0.1
AIN0.2
AIN0.3
AIN0.4
AIN0.5
AIN0.6
AIN0.7
-
Programmable Gain
Amplifier
+
-
9-to-1
AMUX
(SE or
DIFF)
AV+
12-Bit
SAR
ADC
+
12
ADC Data
Registers
+
-
X
-
+
Conversion
-
Complete
Interrupt
TEMP
SENSOR
Write to AD0BUSY
External VREF
Pin
Start
VREF
Timer 3 Overflow
CNVSTR
Conversion
AGND
DAC0 Output
Timer 2 Overflow
28
Rev. 1.4
C8051F020/1/2/3
1.8. 8-Bit Analog to Digital Converter
The C8051F020/1/2/3 has an on-board 8-bit SAR ADC (ADC1) with an 8-channel input multiplexer and programma-
ble gain amplifier. This ADC features a 500 ksps maximum throughput and true 8-bit accuracy with an INL of
±1LSB. Eight input pins are available for measurement. The ADC is under full control of the CIP-51 microcontroller
via the Special Function Registers. The ADC1 voltage reference is selected between the analog power supply (AV+)
and an external VREF pin. On C8051F020/2 devices, ADC1 has its own dedicated VREF1 input pin; on
C8051F021/3 devices, ADC1 shares the VREFA input pin with the 12/10-bit ADC0. User software may put ADC1
into shutdown mode to save power.
A programmable gain amplifier follows the analog multiplexer. The gain stage can be especially useful when differ-
ent ADC input channels have widely varied input voltage signals, or when it is necessary to "zoom in" on a signal
with a large DC offset (in differential mode, a DAC could be used to provide the DC offset). The PGA gain can be set
in software to 0.5, 1, 2, or 4.
A flexible conversion scheduling system allows ADC1 conversions to be initiated by software commands, timer
overflows, or an external input signal. ADC1 conversions may also be synchronized with ADC0 software-com-
manded conversions. Conversion completions are indicated by a status bit and an interrupt (if enabled), and the
resulting 8-bit data word is latched into an SFR upon completion.
Figure 1.12. 8-Bit ADC Diagram
Analog Multiplexer
Configuration, Control, and Data Registers
AIN1.0
AIN1.1
Programmable Gain
AIN1.2
AIN1.3
AIN1.4
AIN1.5
AIN1.6
AIN1.7
Amplifier
Conversion
Complete
Interrupt
AV+
8-Bit
SAR
8-to-1
8
AMUX
+
-
ADC Data
Register
X
ADC
Write to AD1BUSY
Timer 3 Overflow
CNVSTR Input
External VREF
Pin
VREF
Start Conversion
AV+
Timer 2 Overflow
Write to AD0BUSY
(synchronized with
ADC0)
Rev. 1.4
29
C8051F020/1/2/3
1.9. Comparators and DACs
Each C8051F020/1/2/3 MCU has two 12-bit DACs and two comparators on chip. The MCU data and control inter-
face to each comparator and DAC is via the Special Function Registers. The MCU can place any DAC or comparator
in low power shutdown mode.
The comparators have software programmable hysteresis. Each comparator can generate an interrupt on its rising
edge, falling edge, or both; these interrupts are capable of waking up the MCU from sleep mode. The comparators'
output state can also be polled in software. The comparator outputs can be programmed to appear on the Port I/O pins
via the Crossbar.
The DACs are voltage output mode, and include a flexible output scheduling mechanism. This scheduling mecha-
nism allows DAC output updates to be forced by a software write or a Timer 2, 3, or 4 overflow. The DAC voltage
reference is supplied via the dedicated VREFD input pin on C8051F020/2 devices or via the internal voltage refer-
ence on C8051F021/3 devices. The DACs are especially useful as references for the comparators or offsets for the
differential inputs of the ADC.
Figure 1.13. Comparator and DAC Diagram
CP0
(Port I/O)
CROSSBAR
CP1
(Port I/O)
CP0+
+
CP0
-
CP0-
CP0
CP1
CP1+
CP1-
+
CP1
SFR's
-
CIP-51
and
(Data
and
Interrupt
Handler
Cntrl)
REF
DAC0
DAC0
DAC1
REF
DAC1
30
Rev. 1.4
C8051F020/1/2/3
2.
ABSOLUTE MAXIMUM RATINGS
*
Table 2.1. Absolute Maximum Ratings
PARAMETER
Ambient temperature under bias
Storage Temperature
CONDITIONS
MIN
-55
-65
TYP
MAX UNITS
125
150
°C
°C
Voltage on any Pin (except VDD and Port I/O) with
respect to DGND
VDD +
0.3
-0.3
V
Voltage on any Port I/O Pin or /RST with respect to
DGND
Voltage on VDD with respect to DGND
-0.3
-0.3
5.8
4.2
V
V
Maximum Total current through VDD, AV+, DGND,
and AGND
800
mA
Maximum output current sunk by any Port pin
Maximum output current sunk by any other I/O pin
Maximum output current sourced by any Port pin
Maximum output current sourced by any other I/O pin
*
100
50
100
50
mA
mA
mA
mA
Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This
is a stress rating only and functional operation of the devices at those or any other conditions above those indicated
in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended
periods may affect device reliability.
Rev. 1.4
31
C8051F020/1/2/3
3.
GLOBAL DC ELECTRICAL CHARACTERISTICS
Table 1.1. Global DC Electrical Characteristics
-40°C to +85°C, 25 MHz System Clock unless otherwise specified.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
†
Analog Supply Voltage
3.0
3.6
V
2.7
Analog Supply Current
AV+=2.7 V, Internal REF, ADC,
DAC, Comparators all active
1.7
mA
Analog Supply Current with
analog sub-systems inactive
AV+=2.7 V, Internal REF, ADC,
DAC, Comparators all disabled,
oscillator disabled, VDD Monitor
disabled
0.2
µA
Analog-to-Digital Supply Delta
(|VDD - AV+|)
0.5
3.6
V
V
Digital Supply Voltage
2.7
3.0
Digital Supply Current with
CPU active
VDD=2.7 V, Clock=25 MHz
VDD=2.7 V, Clock=1 MHz
VDD=2.7 V, Clock=32 kHz
10
0.5
20
mA
mA
µA
Digital Supply Current with
CPU inactive (not accessing
FLASH)
VDD=2.7 V, Clock=25 MHz
VDD=2.7 V, Clock=1 MHz
VDD=2.7 V, Clock=32 kHz
5
0.2
10
mA
mA
µA
Digital Supply Current (shut-
down)
VDD=2.7 V, Oscillator not running,
VDD Monitor disabled
0.2
1.5
µA
V
Digital Supply RAM Data
Retention Voltage
Specified Operating Tempera-
ture Range
-40
+85
25
°C
SYSCLK (system clock fre-
quency)
‡
MHz
0
Tsysl (SYSCLK low time)
18
18
ns
ns
Tsysh (SYSCLK high time)
†
Analog Supply AV+ must be greater than 1 V for VDD monitor to operate.
SYSCLK must be at least 32 kHz to enable debugging.
‡
32
Rev. 1.4
C8051F020/1/2/3
4.
PINOUT AND PACKAGE DEFINITIONS
Table 4.1. Pin Definitions
Pin Numbers
Name
F020
F022
F021
F023
Type Description
VDD
37, 64, 24, 41,
90 57
Digital Supply Voltage. Must be tied to +2.7 to +3.6 V.
DGND
38, 63, 25, 40,
Digital Ground. Must be tied to Ground.
89
56
AV+
AGND
TMS
TCK
TDI
11, 14
6
Analog Supply Voltage. Must be tied to +2.7 to +3.6 V.
Analog Ground. Must be tied to Ground.
10, 13
5
1
2
3
58
59
60
D In JTAG Test Mode Select with internal pull-up.
D In JTAG Test Clock with internal pull-up.
D In JTAG Test Data Input with internal pull-up. TDI is latched on the
rising edge of TCK.
TDO
/RST
4
5
61
62
D Out JTAG Test Data Output with internal pull-up. Data is shifted out on
TDO on the falling edge of TCK. TDO output is a tri-state driver.
D I/O Device Reset. Open-drain output of internal VDD monitor. Is driven
low when VDD is <2.7 V and MONEN is high. An external source
can initiate a system reset by driving this pin low.
XTAL1
26
17
A In Crystal Input. This pin is the return for the internal oscillator circuit
for a crystal or ceramic resonator. For a precision internal clock,
connect a crystal or ceramic resonator from XTAL1 to XTAL2. If
overdriven by an external CMOS clock, this becomes the system
clock.
XTAL2
27
28
18
19
A Out Crystal Output. This pin is the excitation driver for a crystal or
ceramic resonator.
MONEN
D In VDD Monitor Enable. When tied high, this pin enables the internal
VDD monitor, which forces a system reset when VDD is < 2.7 V.
When tied low, the internal VDD monitor is disabled.
VREF
12
7
8
A I/O Bandgap Voltage Reference Output (all devices).
DAC Voltage Reference Input (F021/3 only).
VREFA
VREF0
VREF1
VREFD
A In ADC0 and ADC1 Voltage Reference Input.
A In ADC0 Voltage Reference Input.
A In ADC1 Voltage Reference Input.
A In DAC Voltage Reference Input.
16
17
15
Rev. 1.4
33
C8051F020/1/2/3
Table 4.1. Pin Definitions
Pin Numbers
Name
F020
F022
18
F021
F023
9
Type Description
AIN0.0
AIN0.1
AIN0.2
AIN0.3
AIN0.4
AIN0.5
AIN0.6
AIN0.7
A In ADC0 Input Channel 0 (See ADC0 Specification for complete
description).
19
20
21
22
23
24
25
10
11
12
13
14
15
16
A In ADC0 Input Channel 1 (See ADC0 Specification for complete
description).
A In ADC0 Input Channel 2 (See ADC0 Specification for complete
description).
A In ADC0 Input Channel 3 (See ADC0 Specification for complete
description).
A In ADC0 Input Channel 4 (See ADC0 Specification for complete
description).
A In ADC0 Input Channel 5 (See ADC0 Specification for complete
description).
A In ADC0 Input Channel 6 (See ADC0 Specification for complete
description).
A In ADC0 Input Channel 7 (See ADC0 Specification for complete
description).
CP0+
CP0-
9
8
4
3
A In Comparator 0 Non-Inverting Input.
A In Comparator 0 Inverting Input.
A In Comparator 1 Non-Inverting Input.
A In Comparator 1 Inverting Input.
CP1+
CP1-
7
2
6
1
DAC0
100
64
A Out Digital to Analog Converter 0 Voltage Output. (See DAC Specifica-
tion for complete description).
DAC1
99
63
A Out Digital to Analog Converter 1 Voltage Output. (See DAC Specifica-
tion for complete description).
P0.0
P0.1
62
61
60
59
58
57
55
54
53
52
51
50
D I/O Port 0.0. See Port Input/Output section for complete description.
D I/O Port 0.1. See Port Input/Output section for complete description.
D I/O Port 0.2. See Port Input/Output section for complete description.
D I/O Port 0.3. See Port Input/Output section for complete description.
D I/O Port 0.4. See Port Input/Output section for complete description.
P0.2
P0.3
P0.4
ALE/P0.5
D I/O ALE Strobe for External Memory Address bus (multiplexed mode)
Port 0.5
See Port Input/Output section for complete description.
34
Rev. 1.4
C8051F020/1/2/3
Table 4.1. Pin Definitions
Pin Numbers
Name
F020
F022
56
F021
F023
49
Type Description
/RD/P0.6
D I/O /RD Strobe for External Memory Address bus
Port 0.6
See Port Input/Output section for complete description.
/WR/P0.7
55
36
48
29
D I/O /WR Strobe for External Memory Address bus
Port 0.7
See Port Input/Output section for complete description.
AIN1.0/A8/P1.0
A In ADC1 Input Channel 0 (See ADC1 Specification for complete
D I/O description).
Bit 8 External Memory Address bus (Non-multiplexed mode)
Port 1.0
See Port Input/Output section for complete description.
AIN1.1/A9/P1.1
AIN1.2/A10/P1.2
AIN1.3/A11/P1.3
AIN1.4/A12/P1.4
AIN1.5/A13/P1.5
AIN1.6/A14/P1.6
AIN1.7/A15/P1.7
A8m/A0/P2.0
35
34
33
32
31
30
29
46
28
27
26
23
22
21
20
37
A In Port 1.1. See Port Input/Output section for complete description.
D I/O
A In Port 1.2. See Port Input/Output section for complete description.
D I/O
A In Port 1.3. See Port Input/Output section for complete description.
D I/O
A In Port 1.4. See Port Input/Output section for complete description.
D I/O
A In Port 1.5. See Port Input/Output section for complete description.
D I/O
A In Port 1.6. See Port Input/Output section for complete description.
D I/O
A In Port 1.7. See Port Input/Output section for complete description.
D I/O
D I/O Bit 8 External Memory Address bus (Multiplexed mode)
Bit 0 External Memory Address bus (Non-multiplexed mode)
Port 2.0
See Port Input/Output section for complete description.
A9m/A1/P2.1
A10m/A2/P2.2
A11m/A3/P2.3
A12m/A4/P2.4
A13m/A5/P2.5
45
44
43
42
41
36
35
34
33
32
D I/O Port 2.1. See Port Input/Output section for complete description.
D I/O Port 2.2. See Port Input/Output section for complete description.
D I/O Port 2.3. See Port Input/Output section for complete description.
D I/O Port 2.4. See Port Input/Output section for complete description.
D I/O Port 2.5. See Port Input/Output section for complete description.
Rev. 1.4
35
C8051F020/1/2/3
Table 4.1. Pin Definitions
Pin Numbers
Name
F020
F022
40
F021
F023
31
Type Description
A14m/A6/P2.6
A15m/A7/P2.7
AD0/D0/P3.0
D I/O Port 2.6. See Port Input/Output section for complete description.
D I/O Port 2.7. See Port Input/Output section for complete description.
39
30
54
47
D I/O Bit 0 External Memory Address/Data bus (Multiplexed mode)
Bit 0 External Memory Data bus (Non-multiplexed mode)
Port 3.0
See Port Input/Output section for complete description.
AD1/D1/P3.1
AD2/D2/P3.2
AD3/D3/P3.3
AD4/D4/P3.4
AD5/D5/P3.5
AD6/D6/P3.6/IE6
AD7/D7/P3.7/IE7
P4.0
53
52
51
50
49
48
47
98
97
96
95
94
93
46
45
44
43
42
39
38
D I/O Port 3.1. See Port Input/Output section for complete description.
D I/O Port 3.2. See Port Input/Output section for complete description.
D I/O Port 3.3. See Port Input/Output section for complete description.
D I/O Port 3.4. See Port Input/Output section for complete description.
D I/O Port 3.5. See Port Input/Output section for complete description.
D I/O Port 3.6. See Port Input/Output section for complete description.
D I/O Port 3.7. See Port Input/Output section for complete description.
D I/O Port 4.0. See Port Input/Output section for complete description.
D I/O Port 4.1. See Port Input/Output section for complete description.
D I/O Port 4.2. See Port Input/Output section for complete description.
D I/O Port 4.3. See Port Input/Output section for complete description.
D I/O Port 4.4. See Port Input/Output section for complete description.
P4.1
P4.2
P4.3
P4.4
ALE/P4.5
D I/O ALE Strobe for External Memory Address bus (multiplexed mode)
Port 4.5
See Port Input/Output section for complete description.
/RD/P4.6
/WR/P4.7
A8/P5.0
92
91
88
D I/O /RD Strobe for External Memory Address bus
Port 4.6
See Port Input/Output section for complete description.
D I/O /WR Strobe for External Memory Address bus
Port 4.7
See Port Input/Output section for complete description.
D I/O Bit 8 External Memory Address bus (Non-multiplexed mode)
Port 5.0
See Port Input/Output section for complete description.
A9/P5.1
87
86
D I/O Port 5.1. See Port Input/Output section for complete description.
D I/O Port 5.2. See Port Input/Output section for complete description.
A10/P5.2
36
Rev. 1.4
C8051F020/1/2/3
Table 4.1. Pin Definitions
Pin Numbers
Name
F020
F022
85
F021
F023
Type Description
A11/P5.3
A12/P5.4
D I/O Port 5.3. See Port Input/Output section for complete description.
D I/O Port 5.4. See Port Input/Output section for complete description.
D I/O Port 5.5. See Port Input/Output section for complete description.
D I/O Port 5.6. See Port Input/Output section for complete description.
D I/O Port 5.7. See Port Input/Output section for complete description.
84
A13/P5.5
83
A14/P5.6
82
A15/P5.7
81
A8m/A0/P6.0
80
D I/O Bit 8 External Memory Address bus (Multiplexed mode)
Bit 0 External Memory Address bus (Non-multiplexed mode)
Port 6.0
See Port Input/Output section for complete description.
A9m/A1/P6.1
A10m/A2/P6.2
A11m/A3/P6.3
A12m/A4/P6.4
A13m/A5/P6.5
A14m/A6/P6.6
A15m/A7/P6.7
AD0/D0/P7.0
79
78
77
76
75
74
73
72
D I/O Port 6.1. See Port Input/Output section for complete description.
D I/O Port 6.2. See Port Input/Output section for complete description.
D I/O Port 6.3. See Port Input/Output section for complete description.
D I/O Port 6.4. See Port Input/Output section for complete description.
D I/O Port 6.5. See Port Input/Output section for complete description.
D I/O Port 6.6. See Port Input/Output section for complete description.
D I/O Port 6.7. See Port Input/Output section for complete description.
D I/O Bit 0 External Memory Address/Data bus (Multiplexed mode)
Bit 0 External Memory Data bus (Non-multiplexed mode)
Port 7.0
See Port Input/Output section for complete description.
AD1/D1/P7.1
AD2/D2/P7.2
AD3/D3/P7.3
AD4/D4/P7.4
AD5/D5/P7.5
AD6/D6/P7.6
AD7/D7/P7.7
71
70
69
68
67
66
65
D I/O Port 7.1. See Port Input/Output section for complete description.
D I/O Port 7.2. See Port Input/Output section for complete description.
D I/O Port 7.3. See Port Input/Output section for complete description.
D I/O Port 7.4. See Port Input/Output section for complete description.
D I/O Port 7.5. See Port Input/Output section for complete description.
D I/O Port 7.6. See Port Input/Output section for complete description.
D I/O Port 7.7. See Port Input/Output section for complete description.
Rev. 1.4
37
C8051F020/1/2/3
Figure 4.1. TQFP-100 Pinout Diagram
TMS
TCK
TDI
TDO
/RST
CP1-
CP1+
CP0-
CP0+
AGND 10
AV+ 11
VREF 12
AGND 13
AV+ 14
VREFD 15
VREF0 16
VREF1 17
AIN0.0 18
AIN0.1 19
AIN0.2 20
AIN0.3 21
AIN0.4 22
AIN0.5 23
AIN0.6 24
AIN0.7 25
1
2
3
4
5
6
7
8
9
75 A13m/A5/P6.5
74 A14m/A6/P6.6
73 A15m/A7/P6.7
72 AD0/D0/P7.0
71 AD1/D1/P7.1
70 AD2/D2/P7.2
69 AD3/D3/P7.3
68 AD4/D4/P7.4
67 AD5/D5/P7.5
66 AD6/D6/P7.6
65 AD7/D7/P7.7
64 VDD
63 DGND
62 P0.0
61 P0.1
60 P0.2
59 P0.3
58 P0.4
C8051F020
C8051F022
57 ALE/P0.5
56 /RD/P0.6
55 /WR/P0.7
54 AD0/D0/P3.0
53 AD1/D1/P3.1
52 AD2/D2/P3.2
51 AD3/D3/P3.3
38
Rev. 1.4
C8051F020/1/2/3
Figure 4.2. TQFP-100 Package Drawing
D
MIN NOM MAX
(mm) (mm) (mm)
D1
A
-
-
-
1.20
0.15
A1 0.05
A2 0.95 1.00 1.05
b
D
0.17 0.22 0.27
-
-
-
-
-
16.00
14.00
0.50
-
-
-
-
-
D1
e
E1
E
E
16.00
14.00
E1
100
PIN 1
DESIGNATOR
1
e
A2
A
b
A1
Rev. 1.4
39
C8051F020/1/2/3
Figure 4.3. TQFP-64 Pinout Diagram
CP1-
CP1+
CP0-
1
2
3
4
5
6
7
8
9
48 /WR/P0.7
47 AD0/D0/P3.0
46 AD1/D1/P3.1
45 AD2/D2/P3.2
44 AD3/D3/P3.3
43 AD4/D4/P3.4
42 AD5/D5/P3.5
41 VDD
CP0+
AGND
AV+
VREF
VREFA
AIN0.0
C8051F021
C8051F023
40 DGND
AIN0.1 10
AIN0.2 11
AIN0.3 12
AIN0.4 13
AIN0.5 14
AIN0.6 15
AIN0.7 16
39 AD6/D6/P3.6/IE6
38 AD7/D7/P3.7/IE7
37 A8m/A0/P2.0
36 A9m/A1/P2.1
35 A10m/A2/P2.2
34 A11m/A3/P2.3
33 A12m/A4/P2.4
40
Rev. 1.4
C8051F020/1/2/3
Figure 4.4. TQFP-64 Package Drawing
D
D1
MIN NOM MAX
(mm) (mm) (mm)
A
-
-
-
-
1.20
0.15
1.05
A1 0.05
A2 0.95
E1
E
b 0.17 0.22 0.27
D
D1
e
-
-
-
-
-
12.00
10.00
0.50
-
-
-
-
-
64
PIN 1
DESIGNATOR
1
e
A2
E
12.00
10.00
A
E1
b
A1
Rev. 1.4
41
C8051F020/1/2/3
Notes
42
Rev. 1.4
C8051F020/1
5.
ADC0 (12-BIT ADC, C8051F020/1 ONLY)
The ADC0 subsystem for the C8051F020/1 consists of a 9-channel, configurable analog multiplexer (AMUX0), a
programmable gain amplifier (PGA0), and a 100 ksps, 12-bit successive-approximation-register ADC with integrated
track-and-hold and Programmable Window Detector (see block diagram in Figure 5.1). The AMUX0, PGA0, Data
Conversion Modes, and Window Detector are all configurable under software control via the Special Function Regis-
ters shown in Figure 5.1. The voltage reference used by ADC0 is selected as described in Section “9. VOLTAGE
REFERENCE (C8051F020/2)” on page 91 for C8051F020/2 devices, or Section “10. VOLTAGE REFERENCE
(C8051F021/3)” on page 93 for C8051F021/3 devices. The ADC0 subsystem (ADC0, track-and-hold and PGA0) is
enabled only when the AD0EN bit in the ADC0 Control register (ADC0CN) is set to logic 1. The ADC0 subsystem is
in low power shutdown when this bit is logic 0.
Figure 5.1. 12-Bit ADC0 Functional Block Diagram
ADC0GTH
ADC0GTL
ADC0LTH
ADC0LTL
24
Comb.
Logic
AD0WINT
12
AV+
+
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AD0EN
AV+
-
+
-
9-to-1
AMUX
(SE or
DIFF)
12-Bit
SAR
ADC
+
+
12
X
-
-
+
AGND
-
TEMP
SENSOR
00
01
10
11
AD0BUSY (W)
Timer 3 Overflow
CNVSTR
Start Conversion
AGND
Timer 2 Overflow
AMX0SL
AMX0CF
ADC0CF
ADC0CN
5.1. Analog Multiplexer and PGA
Eight of the AMUX channels are available for external measurements while the ninth channel is internally connected
to an on-chip temperature sensor (temperature transfer function is shown in Figure 5.2). AMUX input pairs can be
programmed to operate in either differential or single-ended mode. This allows the user to select the best measure-
ment technique for each input channel, and even accommodates mode changes "on-the-fly". The AMUX defaults to
all single-ended inputs upon reset. There are two registers associated with the AMUX: the Channel Selection register
AMX0SL (Figure 5.6), and the Configuration register AMX0CF (Figure 5.7). The table in Figure 5.6 shows AMUX
functionality by channel, for each possible configuration. The PGA amplifies the AMUX output signal by an amount
determined by the states of the AMP0GN2-0 bits in the ADC0 Configuration register, ADC0CF (Figure 5.7). The
PGA can be software-programmed for gains of 0.5, 2, 4, 8 or 16. Gain defaults to unity on reset.
Rev. 1.4
43
C8051F020/1
The Temperature Sensor transfer function is shown in Figure 5.2. The output voltage (V
) is the PGA input when
TEMP
the Temperature Sensor is selected by bits AMX0AD3-0 in register AMX0SL; this voltage will be amplified by the
PGA according to the user-programmed PGA settings.
Figure 5.2. Temperature Sensor Transfer Function
(Volts)
1.000
0.900
0.800
VTEMP = 0.00286(TEMPC) + 0.776
0.700
for PGA Gain = 1
0.600
0.500
(Celsius)
-50
0
50
100
5.2. ADC Modes of Operation
ADC0 has a maximum conversion speed of 100 ksps. The ADC0 conversion clock is derived from the system clock
divided by the value held in the ADCSC bits of register ADC0CF.
5.2.1. Starting a Conversion
A conversion can be initiated in one of four ways, depending on the programmed states of the ADC0 Start of Conver-
sion Mode bits (AD0CM1, AD0CM0) in ADC0CN. Conversions may be initiated by:
1. Writing a ‘1’ to the AD0BUSY bit of ADC0CN;
2. A Timer 3 overflow (i.e. timed continuous conversions);
3. A rising edge detected on the external ADC convert start signal, CNVSTR;
4. A Timer 2 overflow (i.e. timed continuous conversions).
The AD0BUSY bit is set to logic 1 during conversion and restored to logic 0 when conversion is complete. The fall-
ing edge of AD0BUSY triggers an interrupt (when enabled) and sets the AD0INT interrupt flag (ADC0CN.5). Con-
verted data is available in the ADC0 data word MSB and LSB registers, ADC0H, ADC0L. Converted data can be
either left or right justified in the ADC0H:ADC0L register pair (see example in Figure 5.11) depending on the pro-
grammed state of the AD0LJST bit in the ADC0CN register.
When initiating conversions by writing a ‘1’ to AD0BUSY, the AD0INT bit should be polled to determine when a
conversion has completed (ADC0 interrupts may also be used). The recommended polling procedure is shown below.
Step 1. Write a ‘0’ to AD0INT;
Step 2. Write a ‘1’ to AD0BUSY;
Step 3. Poll AD0INT for ‘1’;
Step 4. Process ADC0 data.
44
Rev. 1.4
C8051F020/1
5.2.2. Tracking Modes
The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode. In its default state, the ADC0 input is
continuously tracked when a conversion is not in progress. When the AD0TM bit is logic 1, ADC0 operates in low-
power track-and-hold mode. In this mode, each conversion is preceded by a tracking period of 3 SAR clocks (after
the start-of-conversion signal). When the CNVSTR signal is used to initiate conversions in low-power tracking mode,
ADC0 tracks only when CNVSTR is low; conversion begins on the rising edge of CNVSTR (see Figure 5.3). Track-
ing can also be disabled (shutdown) when the entire chip is in low power standby or sleep modes. Low-power track-
and-hold mode is also useful when AMUX or PGA settings are frequently changed, to ensure that settling time
requirements are met (see Section “5.2.3. Settling Time Requirements” on page 46).
Figure 5.3. 12-Bit ADC Track and Conversion Example Timing
A. ADC Timing for External Trigger Source
CNVSTR
(AD0STM[1:0]=10
)
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
SAR Clocks
Low Power
or Convert
ADC0TM=1
ADC0TM=0
Track
Convert
Convert
Low Power Mode
Track
Track Or Convert
B. ADC Timing for Internal Trigger Sources
Timer 2, Timer 3 Overflow;
Write '1' to AD0BUSY
(AD0STM[1:0]=00, 01, 11)
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19
SAR Clocks
ADC0TM=1
Low Power
or Convert
Track
Convert
Low Power Mode
Track
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
SAR Clocks
ADC0TM=0
Track or
Convert
Convert
Rev. 1.4
45
C8051F020/1
5.2.3. Settling Time Requirements
When the ADC0 input configuration is changed (i.e., a different MUX or PGA selection is made), a minimum settling
(or tracking) time is required before an accurate conversion can be performed. This settling time is determined by the
ADC0 MUX resistance, the ADC0 sampling capacitance, any external source resistance, and the accuracy required
for the conversion. Figure 5.4 shows the equivalent ADC0 input circuits for both Differential and Single-ended
modes. Notice that the equivalent time constant for both input circuits is the same. The required settling time for a
given settling accuracy (SA) may be approximated by Equation 5.1. When measuring the Temperature Sensor output,
R
reduces to R
. Note that in low-power tracking mode, three SAR clocks are used for tracking at the start of
TOTAL
MUX
every conversion. For most applications, these three SAR clocks will meet the tracking requirements. See Table 5.1
on page 58 for absolute minimum settling/tracking time requirements.
Equation 5.1. ADC0 Settling Time Requirements
2n
SA
------
t = ln
× RTOTALCSAMPLE
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required settling time in seconds
R
is the sum of the ADC0 MUX resistance and any external source resistance.
TOTAL
n is the ADC resolution in bits (12).
Figure 5.4. ADC0 Equivalent Input Circuits
Differential Mode
Single-Ended Mode
MUX Select
MUX Select
AIN0.x
AIN0.x
RMUX = 5k
RMUX = 5k
CSAMPLE = 10pF
CSAMPLE = 10pF
RCInput= RMUX * CSAMPLE
RCInput= RMUX * CSAMPLE
CSAMPLE = 10pF
AIN0.y
RMUX = 5k
MUX Select
46
Rev. 1.4
C8051F020/1
Figure 5.5. AMX0CF: AMUX0 Configuration Register (C8051F020/1)
R/W
-
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
-
Bit4
R/W
R/W
R/W
R/W
Reset Value
AIN67IC AIN45IC AIN23IC AIN01IC 00000000
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xBA
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bit3:
Bit2:
Bit1:
Bit0:
AIN67IC: AIN6, AIN7 Input Pair Configuration Bit
0: AIN6 and AIN7 are independent single-ended inputs
1: AIN6, AIN7 are (respectively) +, - differential input pair
AIN45IC: AIN4, AIN5 Input Pair Configuration Bit
0: AIN4 and AIN5 are independent single-ended inputs
1: AIN4, AIN5 are (respectively) +, - differential input pair
AIN23IC: AIN2, AIN3 Input Pair Configuration Bit
0: AIN2 and AIN3 are independent single-ended inputs
1: AIN2, AIN3 are (respectively) +, - differential input pair
AIN01IC: AIN0, AIN1 Input Pair Configuration Bit
0: AIN0 and AIN1 are independent single-ended inputs
1: AIN0, AIN1 are (respectively) +, - differential input pair
NOTE:
The ADC0 Data Word is in 2’s complement format for channels configured as differential.
Rev. 1.4
47
C8051F020/1
Figure 5.6. AMX0SL: AMUX0 Channel Select Register (C8051F020/1)
R/W
-
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
-
Bit4
R/W
R/W
R/W
R/W
Reset Value
AMX0AD3 AMX0AD2 AMX0AD1 AMX0AD0 00000000
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xBB
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bits3-0: AMX0AD3-0: AMX0 Address Bits
0000-1111b: ADC Inputs selected per chart below
AMX0AD3-0
0000
0001
0010
0011
0100
0101
0110
0111
1xxx
TEMP
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN6
AIN6
AIN6
AIN6
AIN6
AIN6
AIN6
AIN7
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
+(AIN0)
-(AIN1)
AIN2
AIN3
AIN4
AIN4
AIN4
AIN5
AIN5
AIN5
AIN7
AIN7
AIN7
AIN7
AIN7
AIN7
AIN7
+(AIN2)
-(AIN3)
+(AIN2)
-(AIN3)
AIN0
AIN1
AIN1
AIN1
AIN1
AIN1
AIN1
AIN1
+(AIN0)
-(AIN1)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
AIN0
AIN2
AIN2
AIN3
AIN3
+(AIN0)
-(AIN1)
+(AIN2)
-(AIN3)
+(AIN2)
-(AIN3)
AIN0
+(AIN0)
-(AIN1)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
AIN0
AIN2
AIN2
AIN3
AIN3
AIN4
AIN4
AIN4
AIN4
AIN5
AIN5
AIN5
AIN5
+(AIN0)
-(AIN1)
+(AIN2)
-(AIN3)
+(AIN2)
-(AIN3)
AIN0
+(AIN0)
-(AIN1)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
AIN0
AIN2
AIN2
AIN3
AIN3
+(AIN0)
-(AIN1)
+(AIN2)
-(AIN3)
AIN0
+(AIN0)
-(AIN1)
+(AIN2)
-(AIN3)
+(AIN4)
-(AIN5)
+(AIN6)
-(AIN7)
TEMP
SENSOR
48
Rev. 1.4
C8051F020/1
Figure 5.7. ADC0CF: ADC0 Configuration Register (C8051F020/1)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
AD0SC4 AD0SC3 AD0SC2 AD0SC1 AD0SC0 AMP0GN2 AMP0GN1 AMP0GN0 11111000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xBC
Bits7-3: AD0SC4-0: ADC0 SAR Conversion Clock Period Bits
SAR Conversion clock is derived from system clock by the following equation, where AD0SC refers
to the 5-bit value held in AD0SC4-0, and CLK refers to the desired ADC0 SAR clock. See
SAR0
Table 5.1 on page 58 for SAR clock setting requirements.
SYSCLK
AD0SC = ---------------------- – 1
CLKSAR0
Bits2-0: AMP0GN2-0: ADC0 Internal Amplifier Gain (PGA)
000: Gain = 1
001: Gain = 2
010: Gain = 4
011: Gain = 8
10x: Gain = 16
11x: Gain = 0.5
Rev. 1.4
49
C8051F020/1
Figure 5.8. ADC0CN: ADC0 Control Register (C8051F020/1)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
AD0EN AD0TM AD0INT AD0BUSY AD0CM1 AD0CM0 AD0WINT AD0LJST 00000000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
(bit addressable)
0xE8
Bit7:
AD0EN: ADC0 Enable Bit.
0: ADC0 Disabled. ADC0 is in low-power shutdown.
1: ADC0 Enabled. ADC0 is active and ready for data conversions.
AD0TM: ADC Track Mode Bit
Bit6:
Bit5:
0: When the ADC is enabled, tracking is continuous unless a conversion is in process
1: Tracking Defined by ADSTM1-0 bits
AD0INT: ADC0 Conversion Complete Interrupt Flag.
This flag must be cleared by software.
0: ADC0 has not completed a data conversion since the last time this flag was cleared.
1: ADC0 has completed a data conversion.
Bit4:
AD0BUSY: ADC0 Busy Bit.
Read:
0: ADC0 Conversion is complete or a conversion is not currently in progress. AD0INT is set to
logic 1 on the falling edge of AD0BUSY.
1: ADC0 Conversion is in progress.
Write:
0: No Effect.
1: Initiates ADC0 Conversion if AD0STM1-0 = 00b
AD0CM1-0: ADC0 Start of Conversion Mode Select.
If AD0TM = 0:
Bit3-2:
00: ADC0 conversion initiated on every write of ‘1’ to AD0BUSY.
01: ADC0 conversion initiated on overflow of Timer 3.
10: ADC0 conversion initiated on rising edge of external CNVSTR.
11: ADC0 conversion initiated on overflow of Timer 2.
If AD0TM = 1:
00: Tracking starts with the write of ‘1’ to AD0BUSY and lasts for 3 SAR clocks, followed by con-
version.
01: Tracking started by the overflow of Timer 3 and last for 3 SAR clocks, followed by conversion.
10: ADC0 tracks only when CNVSTR input is logic low; conversion starts on rising CNVSTR edge.
11: Tracking started by the overflow of Timer 2 and last for 3 SAR clocks, followed by conversion.
AD0WINT: ADC0 Window Compare Interrupt Flag.
This bit must be cleared by software.
Bit1:
Bit0:
0: ADC0 Window Comparison Data match has not occurred since this flag was last cleared.
1: ADC0 Window Comparison Data match has occurred.
AD0LJST: ADC0 Left Justify Select.
0: Data in ADC0H:ADC0L registers are right-justified.
1: Data in ADC0H:ADC0L registers are left-justified.
50
Rev. 1.4
C8051F020/1
Figure 5.9. ADC0H: ADC0 Data Word MSB Register (C8051F020/1)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xBF
Bits7-0: ADC0 Data Word High-Order Bits.
For AD0LJST = 0: Bits 7-4 are the sign extension of Bit3. Bits 3-0 are the upper 4 bits of the 12-bit
ADC0 Data Word.
For AD0LJST = 1: Bits 7-0 are the most-significant bits of the 12-bit ADC0 Data Word.
Figure 5.10. ADC0L: ADC0 Data Word LSB Register (C8051F020/1)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xBE
Bits7-0: ADC0 Data Word Low-Order Bits.
For AD0LJST = 0: Bits 7-0 are the lower 8 bits of the 12-bit ADC0 Data Word.
For AD0LJST = 1: Bits 7-4 are the lower 4 bits of the 12-bit ADC0 Data Word. Bits3-0 will always
read ‘0’.
Rev. 1.4
51
C8051F020/1
Figure 5.11. ADC0 Data Word Example (C8051F020/1)
12-bit ADC0 Data Word appears in the ADC0 Data Word Registers as follows:
ADC0H[3:0]:ADC0L[7:0], if AD0LJST = 0
(ADC0H[7:4] will be sign-extension of ADC0H.3 for a differential reading, otherwise =
0000b).
ADC0H[7:0]:ADC0L[7:4], if AD0LJST = 1
(ADC0L[3:0] = 0000b).
Example: ADC0 Data Word Conversion Map, AIN0 Input in Single-Ended Mode
(AMX0CF = 0x00, AMX0SL = 0x00)
ADC0H:ADC0L
ADC0H:ADC0L
AIN0-AGND (Volts)
(AD0LJST = 0)
(AD0LJST = 1)
VREF * (4095/4096)
VREF / 2
VREF * (2047/4096)
0
0x0FFF
0x0800
0x07FF
0x0000
0xFFF0
0x8000
0x7FF0
0x0000
Example: ADC0 Data Word Conversion Map, AIN0-AIN1 Differential Input Pair
(AMX0CF = 0x01, AMX0SL = 0x00)
ADC0H:ADC0L
ADC0H:ADC0L
AIN0-AGND (Volts)
(AD0LJST = 0)
(AD0LJST = 1)
VREF * (2047/2048)
VREF / 2
VREF * (1/2048)
0
-VREF * (1/2048)
-VREF / 2
0x07FF
0x0400
0x0001
0x7FF0
0x4000
0x0010
0x0000
0xFFF0
0xC000
0x8000
0x0000
0xFFFF (-1d)
0xFC00 (-1024d)
0xF800 (-2048d)
-VREF
For AD0LJST = 0:
Gain
---------------
n
Code = Vin ×
× 2 ; ‘n’ = 12 for Single-Ended; ‘n’=11 for Differential.
VREF
52
Rev. 1.4
C8051F020/1
5.3. ADC0 Programmable Window Detector
The ADC0 Programmable Window Detector continuously compares the ADC0 output to user-programmed limits,
and notifies the system when an out-of-bound condition is detected. This is especially effective in an interrupt-driven
system, saving code space and CPU bandwidth while delivering faster system response times. The window detector
interrupt flag (AD0WINT in ADC0CN) can also be used in polled mode. The high and low bytes of the reference
words are loaded into the ADC0 Greater-Than and ADC0 Less-Than registers (ADC0GTH, ADC0GTL, ADC0LTH,
and ADC0LTL). Reference comparisons are shown starting on page 54. Notice that the window detector flag can be
asserted when the measured data is inside or outside the user-programmed limits, depending on the programming of
the ADC0GTx and ADC0LTx registers.
Figure 5.12. ADC0GTH: ADC0 Greater-Than Data High Byte Register (C8051F020/1)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
11111111
SFR Address:
0xC5
Bits7-0: High byte of ADC0 Greater-Than Data Word.
Figure 5.13. ADC0GTL: ADC0 Greater-Than Data Low Byte Register (C8051F020/1)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
11111111
SFR Address:
0xC4
Bits7-0: Low byte of ADC0 Greater-Than Data Word.
Figure 5.14. ADC0LTH: ADC0 Less-Than Data High Byte Register (C8051F020/1)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xC7
Bits7-0: High byte of ADC0 Less-Than Data Word.
Figure 5.15. ADC0LTL: ADC0 Less-Than Data Low Byte Register (C8051F020/1)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xC6
Bits7-0: Low byte of ADC0 Less-Than Data Word.
Rev. 1.4
53
C8051F020/1
Figure 5.16. 12-Bit ADC0 Window Interrupt Example: Right Justified Single-Ended Data
Input Voltage
(AD0 - AGND)
Input Voltage
(AD0 - AGND)
ADC Data
Word
0x0FFF
ADC Data
Word
0x0FFF
REF x (4095/4096)
REF x (4095/4096)
AD0WINT
AD0WINT=1
not affected
0x0201
0x0201
REF x (512/4096)
REF x (256/4096)
0x0200
0x01FF
ADC0LTH:ADC0LTL
AD0WINT=1
REF x (512/4096)
REF x (256/4096)
0x0200
0x01FF
ADC0GTH:ADC0GTL
AD0WINT
not affected
0x0101
0x0100
0x0101
0x0100
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0x00FF
0x00FF
AD0WINT=1
AD0WINT
not affected
0x0000
0x0000
0
0
Given:
Given:
AMX0SL = 0x00, AMX0CF = 0x00
AD0LJST = ‘0’,
AMX0SL = 0x00, AMX0CF = 0x00,
AD0LJST = ‘0’,
ADC0LTH:ADC0LTL = 0x0200,
ADC0GTH:ADC0GTL = 0x0100.
An ADC0 End of Conversion will cause an ADC0
Window Compare Interrupt (AD0WINT = ‘1’) if
the resulting ADC0 Data Word is < 0x0200 and
> 0x0100.
ADC0LTH:ADC0LTL = 0x0100,
ADC0GTH:ADC0GTL = 0x0200.
An ADC0 End of Conversion will cause an ADC0
Window Compare Interrupt (AD0WINT = ‘1’) if
the resulting ADC0 Data Word is > 0x0200 or
< 0x0100.
54
Rev. 1.4
C8051F020/1
Figure 5.17. 12-Bit ADC0 Window Interrupt Example: Right Justified Differential Data
Input Voltage
(AD0 - AD1)
Input Voltage
(AD0 - AD1)
ADC Data
Word
0x07FF
ADC Data
Word
0x07FF
REF x (2047/2048)
REF x (2047/2048)
AD0WINT
AD0WINT=1
not affected
0x0101
0x0101
REF x (256/2048)
REF x (-1/2048)
0x0100
0x00FF
ADC0LTH:ADC0LTL
AD0WINT=1
REF x (256/2048)
REF x (-1/2048)
0x0100
0x00FF
ADC0GTH:ADC0GTL
AD0WINT
not affected
0x0000
0xFFFF
0x0000
0xFFFF
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
AD0WINT=1
0xFFFE
0xFFFE
AD0WINT
not affected
0xF800
0xF800
-REF
-REF
Given:
Given:
AMX0SL = 0x00, AMX0CF = 0x01,
AD0LJST = ‘0’,
AMX0SL = 0x00, AMX0CF = 0x01,
AD0LJST = ‘0’,
ADC0LTH:ADC0LTL = 0x0100,
ADC0GTH:ADC0GTL = 0xFFFF.
An ADC0 End of Conversion will cause an ADC0
Window Compare Interrupt (AD0WINT = ‘1’) if
the resulting ADC0 Data Word is < 0x0100 and
> 0xFFFF. (In two’s-complement math,
0xFFFF = -1.)
ADC0LTH:ADC0LTL = 0xFFFF,
ADC0GTH:ADC0GTL = 0x0100.
An ADC0 End of Conversion will cause an ADC0
Window Compare Interrupt (AD0WINT = ‘1’) if
the resulting ADC0 Data Word is < 0xFFFF or
> 0x0100. (In two’s-complement math,
0xFFFF = -1.)
Rev. 1.4
55
C8051F020/1
Figure 5.18. 12-Bit ADC0 Window Interrupt Example: Left Justified Single-Ended Data
Input Voltage
(AD0 - AGND)
Input Voltage
(AD0 - AGND)
ADC Data
Word
0xFFF0
ADC Data
Word
0xFFF0
REF x (4095/4096)
REF x (4095/4096)
AD0WINT
AD0WINT=1
not affected
0x2010
0x2010
REF x (512/4096)
REF x (256/4096)
0x2000
0x1FF0
ADC0LTH:ADC0LTL
AD0WINT=1
REF x (512/4096)
REF x (256/4096)
0x2000
0x1FF0
ADC0GTH:ADC0GTL
AD0WINT
not affected
0x1010
0x1000
0x1010
0x1000
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
AD0WINT=1
0x0FF0
0x0FF0
AD0WINT
not affected
0x0000
0x0000
0
0
Given:
Given:
AMX0SL = 0x00, AMX0CF = 0x00,
AD0LJST = ‘1’,
AMX0SL = 0x00, AMX0CF = 0x00,
AD0LJST = ‘1’
ADC0LTH:ADC0LTL = 0x2000,
ADC0GTH:ADC0GTL = 0x1000.
An ADC0 End of Conversion will cause an ADC0
Window Compare Interrupt (AD0WINT = ‘1’) if
the resulting ADC0 Data Word is < 0x2000 and
> 0x1000.
ADC0LTH:ADC0LTL = 0x1000,
ADC0GTH:ADC0GTL = 0x2000.
An ADC0 End of Conversion will cause an ADC0
Window Compare Interrupt (AD0WINT = ‘1’) if
the resulting ADC0 Data Word is < 0x1000 or
> 0x2000.
56
Rev. 1.4
C8051F020/1
Figure 5.19. 12-Bit ADC0 Window Interrupt Example: Left Justified Differential Data
Input Voltage
(AD0 - AD1)
Input Voltage
(AD0 - AD1)
ADC Data
Word
0x7FF0
ADC Data
Word
0x7FF0
REF x (2047/2048)
REF x (2047/2048)
AD0WINT
AD0WINT=1
not affected
0x1010
0x1010
REF x (256/2048)
REF x (-1/2048)
0x1000
0x0FF0
ADC0LTH:ADC0LTL
AD0WINT=1
REF x (256/2048)
REF x (-1/2048)
0x1000
0x0FF0
ADC0GTH:ADC0GTL
AD0WINT
not affected
0x0000
0xFFF0
0x0000
0xFFF0
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0xFFE0
0xFFE0
AD0WINT=1
AD0WINT
not affected
0x8000
0x8000
-REF
-REF
Given:
Given:
AMX0SL = 0x00, AMX0CF = 0x01,
AD0LJST = ‘1’,
AMX0SL = 0x00, AMX0CF = 0x01,
AD0LJST = ‘1’,
ADC0LTH:ADC0LTL = 0x1000,
ADC0GTH:ADC0GTL = 0xFFF0.
ADC0LTH:ADC0LTL = 0xFFF0,
ADC0GTH:ADC0GTL = 0x1000.
An ADC0 End of Conversion will cause an ADC0
Window Compare Interrupt (AD0WINT = ‘1’) if
the resulting ADC0 Data Word is < 0x1000 and
> 0xFFF0. (Two’s-complement math.)
An ADC0 End of Conversion will cause an ADC0
Window Compare Interrupt (AD0WINT = ‘1’) if
the resulting ADC0 Data Word is < 0xFFF0 or
> 0x1000. (Two’s-complement math.)
Rev. 1.4
57
C8051F020/1
Table 5.1. 12-Bit ADC0 Electrical Characteristics (C8051F020/1)
VDD = 3.0V, AV+ = 3.0V, VREF = 2.40V (REFBE=0), PGA Gain = 1, -40°C to +85°C unless otherwise specified
PARAMETER
DC ACCURACY
CONDITIONS
MIN
TYP MAX
UNITS
Resolution
12
±1
bits
LSB
LSB
LSB
LSB
Integral Nonlinearity
Differential Nonlinearity
Offset Error
Full Scale Error
Offset Temperature Coefficient
Guaranteed Monotonic
Differential mode
±1
-3±1
-7±3
±0.25
ppm/°C
DYNAMIC PERFORMANCE (10 kHz sine-wave input, 0 to 1 dB below Full Scale, 100 ksps
Signal-to-Noise Plus Distortion
Total Harmonic Distortion
Spurious-Free Dynamic Range
CONVERSION RATE
SAR Clock Frequency
Conversion Time in SAR Clocks
Track/Hold Acquisition Time
Throughput Rate
66
dB
dB
th
-75
80
Up to the 5 harmonic
dB
2.5
MHz
clocks
µs
16
1.5
100
ksps
ANALOG INPUTS
Input Voltage Range
*Common-mode Voltage Range
Input Capacitance
Single-ended operation
Differential operation
0
VREF
AV+
V
V
pF
AGND
10
TEMPERATURE SENSOR
Nonlinearity
Absolute Accuracy
Gain
Offset
POWER SPECIFICATIONS
Power Supply Current (AV+ sup-
plied to ADC)
-1.0
+1.0
900
°C
°C
mV/°C
V
±3
2.86
0.776
PGA Gain = 1
PGA Gain = 1, Temp = 0°C
Operating Mode, 100 ksps
450
µA
Power Supply Rejection
±0.3
mV/V
58
Rev. 1.4
C8051F022/3
6.
ADC0 (10-BIT ADC, C8051F022/3 ONLY)
The ADC0 subsystem for the C8051F022/3 consists of a 9-channel, configurable analog multiplexer (AMUX0), a
programmable gain amplifier (PGA0), and a 100 ksps, 10-bit successive-approximation-register ADC with integrated
track-and-hold and Programmable Window Detector (see block diagram in Figure 6.1). The AMUX0, PGA0, Data
Conversion Modes, and Window Detector are all configurable under software control via the Special Function Regis-
ters shown in Figure 6.1. The voltage reference used by ADC0 is selected as described in Section “9. VOLTAGE
REFERENCE (C8051F020/2)” on page 91 for C8051F020/2 devices, or Section “10. VOLTAGE REFERENCE
(C8051F021/3)” on page 93 for C8051F021/3 devices. The ADC0 subsystem (ADC0, track-and-hold and PGA0) is
enabled only when the AD0EN bit in the ADC0 Control register (ADC0CN) is set to logic 1. The ADC0 subsystem is
in low power shutdown when this bit is logic 0.
Figure 6.1. 10-Bit ADC0 Functional Block Diagram
ADC0GTH
ADC0GTL
ADC0LTH
ADC0LTL
20
Comb.
Logic
AD0WINT
10
AV+
+
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AD0EN
AV+
-
+
-
9-to-1
AMUX
(SE or
DIFF)
10-Bit
SAR
ADC
+
+
10
X
-
-
+
AGND
-
TEMP
SENSOR
00
01
10
11
AD0BUSY (W)
Timer 3 Overflow
CNVSTR
Start Conversion
AGND
Timer 2 Overflow
AMX0SL
AMX0CF
ADC0CF
ADC0CN
6.1. Analog Multiplexer and PGA
Eight of the AMUX channels are available for external measurements while the ninth channel is internally connected
to an on-chip temperature sensor (temperature transfer function is shown in Figure 6.2). AMUX input pairs can be
programmed to operate in either differential or single-ended mode. This allows the user to select the best measure-
ment technique for each input channel, and even accommodates mode changes "on-the-fly". The AMUX defaults to
all single-ended inputs upon reset. There are two registers associated with the AMUX: the Channel Selection register
AMX0SL (Figure 6.6), and the Configuration register AMX0CF (Figure 6.7). The table in Figure 6.6 shows AMUX
functionality by channel, for each possible configuration. The PGA amplifies the AMUX output signal by an amount
determined by the states of the AMP0GN2-0 bits in the ADC0 Configuration register, ADC0CF (Figure 6.7). The
PGA can be software-programmed for gains of 0.5, 2, 4, 8 or 16. Gain defaults to unity on reset.
Rev. 1.4
59
C8051F022/3
The Temperature Sensor transfer function is shown in Figure 6.2. The output voltage (V
) is the PGA input when
TEMP
the Temperature Sensor is selected by bits AMX0AD3-0 in register AMX0SL; this voltage will be amplified by the
PGA according to the user-programmed PGA settings.
Figure 6.2. Temperature Sensor Transfer Function
(Volts)
1.000
0.900
0.800
VTEMP = 0.00286(TEMPC) + 0.776
0.700
for PGA Gain = 1
0.600
0.500
(Celsius)
-50
0
50
100
6.2. ADC Modes of Operation
ADC0 has a maximum conversion speed of 100 ksps. The ADC0 conversion clock is derived from the system clock
divided by the value held in the ADCSC bits of register ADC0CF.
6.2.1. Starting a Conversion
A conversion can be initiated in one of four ways, depending on the programmed states of the ADC0 Start of Conver-
sion Mode bits (AD0CM1, AD0CM0) in ADC0CN. Conversions may be initiated by:
1. Writing a ‘1’ to the AD0BUSY bit of ADC0CN;
2. A Timer 3 overflow (i.e. timed continuous conversions);
3. A rising edge detected on the external ADC convert start signal, CNVSTR;
4. A Timer 2 overflow (i.e. timed continuous conversions).
The AD0BUSY bit is set to logic 1 during conversion and restored to logic 0 when conversion is complete. The fall-
ing edge of AD0BUSY triggers an interrupt (when enabled) and sets the AD0INT interrupt flag (ADC0CN.5). Con-
verted data is available in the ADC0 data word MSB and LSB registers, ADC0H, ADC0L. Converted data can be
either left or right justified in the ADC0H:ADC0L register pair (see example in Figure 6.11) depending on the pro-
grammed state of the AD0LJST bit in the ADC0CN register.
When initiating conversions by writing a ‘1’ to AD0BUSY, the AD0INT bit should be polled to determine when a
conversion has completed (ADC0 interrupts may also be used). The recommended polling procedure is shown below.
Step 1. Write a ‘0’ to AD0INT;
Step 2. Write a ‘1’ to AD0BUSY;
Step 3. Poll AD0INT for ‘1’;
Step 4. Process ADC0 data.
60
Rev. 1.4
C8051F022/3
6.2.2. Tracking Modes
The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode. In its default state, the ADC0 input is
continuously tracked when a conversion is not in progress. When the AD0TM bit is logic 1, ADC0 operates in low-
power track-and-hold mode. In this mode, each conversion is preceded by a tracking period of 3 SAR clocks (after
the start-of-conversion signal). When the CNVSTR signal is used to initiate conversions in low-power tracking mode,
ADC0 tracks only when CNVSTR is low; conversion begins on the rising edge of CNVSTR (see Figure 6.3). Track-
ing can also be disabled (shutdown) when the entire chip is in low power standby or sleep modes. Low-power track-
and-hold mode is also useful when AMUX or PGA settings are frequently changed, to ensure that settling time
requirements are met (see Section “6.2.3. Settling Time Requirements” on page 62).
Figure 6.3. 10-Bit ADC Track and Conversion Example Timing
A. ADC Timing for External Trigger Source
CNVSTR
(AD0STM[1:0]=10
)
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
SAR Clocks
Low Power
or Convert
ADC0TM=1
ADC0TM=0
Track
Convert
Convert
Low Power Mode
Track
Track Or Convert
B. ADC Timing for Internal Trigger Sources
Timer 2, Timer 3 Overflow;
Write '1' to AD0BUSY
(AD0STM[1:0]=00, 01, 11)
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19
SAR Clocks
ADC0TM=1
Low Power
or Convert
Track
Convert
Low Power Mode
Track
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
SAR Clocks
ADC0TM=0
Track or
Convert
Convert
Rev. 1.4
61
C8051F022/3
6.2.3. Settling Time Requirements
When the ADC0 input configuration is changed (i.e., a different MUX or PGA selection is made), a minimum settling
(or tracking) time is required before an accurate conversion can be performed. This settling time is determined by the
ADC0 MUX resistance, the ADC0 sampling capacitance, any external source resistance, and the accuracy required
for the conversion. Figure 6.4 shows the equivalent ADC0 input circuits for both Differential and Single-ended
modes. Notice that the equivalent time constant for both input circuits is the same. The required settling time for a
given settling accuracy (SA) may be approximated by Equation 6.1. When measuring the Temperature Sensor output,
R
reduces to R
. Note that in low-power tracking mode, three SAR clocks are used for tracking at the start of
TOTAL
MUX
every conversion. For most applications, these three SAR clocks will meet the settling time requirements. See
Table 6.1 on page 74 for minimum settling/tracking time requirements.
Equation 6.1. ADC0 Settling Time Requirements
2n
SA
------
t = ln
× RTOTALCSAMPLE
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required settling time in seconds
R
is the sum of the ADC0 MUX resistance and any external source resistance.
TOTAL
n is the ADC resolution in bits (10).
Figure 6.4. ADC0 Equivalent Input Circuits
Differential Mode
Single-Ended Mode
MUX Select
MUX Select
AIN0.x
AIN0.x
RMUX = 5k
RMUX = 5k
CSAMPLE = 10pF
CSAMPLE = 10pF
RCInput= RMUX * CSAMPLE
RCInput= RMUX * CSAMPLE
CSAMPLE = 10pF
AIN0.y
RMUX = 5k
MUX Select
62
Rev. 1.4
C8051F022/3
Figure 6.5. AMX0CF: AMUX0 Configuration Register (C8051F022/3)
R/W
-
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
-
Bit4
R/W
R/W
R/W
R/W
Reset Value
AIN67IC AIN45IC AIN23IC AIN01IC 00000000
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xBA
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bit3:
Bit2:
Bit1:
Bit0:
AIN67IC: AIN6, AIN7 Input Pair Configuration Bit
0: AIN6 and AIN7 are independent single-ended inputs
1: AIN6, AIN7 are (respectively) +, - differential input pair
AIN45IC: AIN4, AIN5 Input Pair Configuration Bit
0: AIN4 and AIN5 are independent single-ended inputs
1: AIN4, AIN5 are (respectively) +, - differential input pair
AIN23IC: AIN2, AIN3 Input Pair Configuration Bit
0: AIN2 and AIN3 are independent single-ended inputs
1: AIN2, AIN3 are (respectively) +, - differential input pair
AIN01IC: AIN0, AIN1 Input Pair Configuration Bit
0: AIN0 and AIN1 are independent single-ended inputs
1: AIN0, AIN1 are (respectively) +, - differential input pair
NOTE:
The ADC0 Data Word is in 2’s complement format for channels configured as differential.
Rev. 1.4
63
C8051F022/3
Figure 6.6. AMX0SL: AMUX0 Channel Select Register (C8051F022/3)
R/W
-
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
-
Bit4
R/W
R/W
R/W
R/W
Reset Value
AMX0AD3 AMX0AD2 AMX0AD1 AMX0AD0 00000000
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xBB
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bits3-0: AMX0AD3-0: AMX0 Address Bits
0000-1111b: ADC Inputs selected per chart below
AMX0AD3-0
0000
0001
0010
0011
0100
0101
0110
0111
1xxx
TEMP
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN6
AIN6
AIN6
AIN6
AIN6
AIN6
AIN6
AIN7
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
TEMP
SENSOR
+(AIN0)
-(AIN1)
AIN2
AIN3
AIN4
AIN4
AIN4
AIN5
AIN5
AIN5
AIN7
AIN7
AIN7
AIN7
AIN7
AIN7
AIN7
+(AIN2)
-(AIN3)
+(AIN2)
-(AIN3)
AIN0
AIN1
AIN1
AIN1
AIN1
AIN1
AIN1
AIN1
+(AIN0)
-(AIN1)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
AIN0
AIN2
AIN2
AIN3
AIN3
+(AIN0)
-(AIN1)
+(AIN2)
-(AIN3)
+(AIN2)
-(AIN3)
AIN0
+(AIN0)
-(AIN1)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
+(AIN6)
-(AIN7)
AIN0
AIN2
AIN2
AIN3
AIN3
AIN4
AIN4
AIN4
AIN4
AIN5
AIN5
AIN5
AIN5
+(AIN0)
-(AIN1)
+(AIN2)
-(AIN3)
+(AIN2)
-(AIN3)
AIN0
+(AIN0)
-(AIN1)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
+(AIN4)
-(AIN5)
AIN0
AIN2
AIN2
AIN3
AIN3
+(AIN0)
-(AIN1)
+(AIN2)
-(AIN3)
AIN0
+(AIN0)
-(AIN1)
+(AIN2)
-(AIN3)
+(AIN4)
-(AIN5)
+(AIN6)
-(AIN7)
TEMP
SENSOR
64
Rev. 1.4
C8051F022/3
Figure 6.7. ADC0CF: ADC0 Configuration Register (C8051F022/3)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
AD0SC4 AD0SC3 AD0SC2 AD0SC1 AD0SC0 AMP0GN2 AMP0GN1 AMP0GN0 11111000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xBC
Bits7-3: AD0SC4-0: ADC0 SAR Conversion Clock Period Bits
SAR Conversion clock is derived from system clock by the following equation, where AD0SC refers
to the 5-bit value held in AD0SC4-0, and CLK refers to the desired ADC0 SAR clock. See
SAR0
Table 6.1 on page 74 for SAR clock setting requirements.
SYSCLK
AD0SC = ---------------------- – 1
CLKSAR0
Bits2-0: AMP0GN2-0: ADC0 Internal Amplifier Gain (PGA)
000: Gain = 1
001: Gain = 2
010: Gain = 4
011: Gain = 8
10x: Gain = 16
11x: Gain = 0.5
Rev. 1.4
65
C8051F022/3
Figure 6.8. ADC0CN: ADC0 Control Register (C8051F022/3)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
AD0EN AD0TM AD0INT AD0BUSY AD0CM1 AD0CM0 AD0WINT AD0LJST 00000000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
(bit addressable)
0xE8
Bit7:
AD0EN: ADC0 Enable Bit.
0: ADC0 Disabled. ADC0 is in low-power shutdown.
1: ADC0 Enabled. ADC0 is active and ready for data conversions.
AD0TM: ADC Track Mode Bit
Bit6:
Bit5:
0: When the ADC is enabled, tracking is continuous unless a conversion is in process
1: Tracking Defined by ADSTM1-0 bits
AD0INT: ADC0 Conversion Complete Interrupt Flag.
This flag must be cleared by software.
0: ADC0 has not completed a data conversion since the last time this flag was cleared.
1: ADC0 has completed a data conversion.
Bit4:
AD0BUSY: ADC0 Busy Bit.
Read:
0: ADC0 Conversion is complete or a conversion is not currently in progress. AD0INT is set to
logic 1 on the falling edge of AD0BUSY.
1: ADC0 Conversion is in progress.
Write:
0: No Effect.
1: Initiates ADC0 Conversion if AD0STM1-0 = 00b
AD0CM1-0: ADC0 Start of Conversion Mode Select.
If AD0TM = 0:
Bit3-2:
00: ADC0 conversion initiated on every write of ‘1’ to AD0BUSY.
01: ADC0 conversion initiated on overflow of Timer 3.
10: ADC0 conversion initiated on rising edge of external CNVSTR.
11: ADC0 conversion initiated on overflow of Timer 2.
If AD0TM = 1:
00: Tracking starts with the write of ‘1’ to AD0BUSY and lasts for 3 SAR clocks, followed by con-
version.
01: Tracking started by the overflow of Timer 3 and last for 3 SAR clocks, followed by conversion.
10: ADC0 tracks only when CNVSTR input is logic low; conversion starts on rising CNVSTR edge.
11: Tracking started by the overflow of Timer 2 and last for 3 SAR clocks, followed by conversion.
AD0WINT: ADC0 Window Compare Interrupt Flag.
This bit must be cleared by software.
Bit1:
Bit0:
0: ADC0 Window Comparison Data match has not occurred since this flag was last cleared.
1: ADC0 Window Comparison Data match has occurred.
AD0LJST: ADC0 Left Justify Select.
0: Data in ADC0H:ADC0L registers are right-justified.
1: Data in ADC0H:ADC0L registers are left-justified.
66
Rev. 1.4
C8051F022/3
Figure 6.9. ADC0H: ADC0 Data Word MSB Register (C8051F022/3)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xBF
Bits7-0: ADC Data Word High-Order Bits.
For ADLJST = 0: Bits 7-2 are the sign extension of Bit1. Bits 1-0 are the upper 2 bits of the 10-bit
ADC Data Word.
For ADLJST = 1: Bits 7-0 are the most-significant bits of the 10-bit ADC Data Word.
Figure 6.10. ADC0L: ADC0 Data Word LSB Register (C8051F022/3)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xBE
Bits7-0: ADC Data Word Low-Order Bits.
For ADLJST = 0: Bits 7-0 are the lower 8 bits of the 10-bit ADC Data Word.
For ADLJST = 1: Bits 7-6 are the lower 2 bits of the 10-bit ADC Data Word. Bits 5-0 will always
read ‘0’.
Rev. 1.4
67
C8051F022/3
Figure 6.11. ADC0 Data Word Example (C8051F022/3)
10-bit ADC Data Word appears in the ADC Data Word Registers as follows:
ADC0H[1:0]:ADC0L[7:0], if ADLJST = 0
(ADC0H[7:2] will be sign-extension of ADC0H.1 for a differential reading, otherwise =
000000b).
ADC0H[7:0]:ADC0L[7:6], if ADLJST = 1
(ADC0L[5:0] = 000000b).
Example: ADC Data Word Conversion Map, AIN0 Input in Single-Ended Mode
(AMX0CF = 0x00, AMX0SL = 0x00)
ADC0H:ADC0L
ADC0H:ADC0L
AIN0-AGND (Volts)
(ADLJST = 0)
(ADLJST = 1)
VREF * (1023/1024)
VREF / 2
VREF * (511/1024)
0
0x03FF
0x0200
0x01FF
0x0000
0xFFC0
0x8000
0x7FC0
0x0000
Example: ADC Data Word Conversion Map, AIN0-AIN1 Differential Input Pair
(AMX0CF = 0x01, AMX0SL = 0x00)
ADC0H:ADC0L
ADC0H:ADC0L
AIN0-AGND (Volts)
(ADLJST = 0)
(ADLJST = 1)
VREF * (511/512)
VREF / 2
VREF * (1/512)
0
-VREF * (1/512)
-VREF / 2
0x01FF
0x0100
0x0001
0x7FC0
0x4000
0x0040
0x0000
0xFFC0
0xC000
0x8000
0x0000
0xFFFF (-1)
0xFF00 (-256)
0xFE00 (-512)
-VREF
ADLJST = 0:
Gain
---------------
n
Code = Vin ×
× 2 ; ‘n’ = 10 for Single-Ended; ‘n’=9 for Differential.
VREF
68
Rev. 1.4
C8051F022/3
6.3. ADC0 Programmable Window Detector
The ADC0 Programmable Window Detector continuously compares the ADC0 output to user-programmed limits,
and notifies the system when an out-of-bound condition is detected. This is especially effective in an interrupt-driven
system, saving code space and CPU bandwidth while delivering faster system response times. The window detector
interrupt flag (AD0WINT in ADC0CN) can also be used in polled mode. The high and low bytes of the reference
words are loaded into the ADC0 Greater-Than and ADC0 Less-Than registers (ADC0GTH, ADC0GTL, ADC0LTH,
and ADC0LTL). Reference comparisons are shown starting on page 70. Notice that the window detector flag can be
asserted when the measured data is inside or outside the user-programmed limits, depending on the programming of
the ADC0GTx and ADC0LTx registers.
Figure 6.12. ADC0GTH: ADC0 Greater-Than Data High Byte Register (C8051F022/3)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
11111111
SFR Address:
0xC5
Bits7-0: High byte of ADC0 Greater-Than Data Word.
Figure 6.13. ADC0GTL: ADC0 Greater-Than Data Low Byte Register (C8051F022/3)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
11111111
SFR Address:
0xC4
Bits7-0: Low byte of ADC0 Greater-Than Data Word.
Figure 6.14. ADC0LTH: ADC0 Less-Than Data High Byte Register (C8051F022/3)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xC7
Bits7-0: High byte of ADC0 Less-Than Data Word.
Figure 6.15. ADC0LTL: ADC0 Less-Than Data Low Byte Register (C8051F022/3)
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xC6
Bits7-0: Low byte of ADC0 Less-Than Data Word.
Rev. 1.4
69
C8051F022/3
Figure 6.16. 10-Bit ADC0 Window Interrupt Example: Right Justified Single-Ended Data
Input Voltage
(AD0 - AGND)
Input Voltage
(AD0 - AGND)
ADC Data
Word
0x03FF
ADC Data
Word
0x03FF
REF x (1023/1024)
REF x (1023/1024)
ADWINT
ADWINT=1
not affected
0x0201
0x0201
REF x (512/1024)
REF x (256/1024)
0x0200
0x01FF
ADC0LTH:ADC0LTL
ADWINT=1
REF x (512/1024)
REF x (256/1024)
0x0200
0x01FF
ADC0GTH:ADC0GTL
ADWINT
not affected
0x0101
0x0100
0x0101
0x0100
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0x00FF
0x00FF
ADWINT=1
ADWINT
not affected
0x0000
0x0000
0
0
Given:
Given:
AMX0SL = 0x00, AMX0CF = 0x00, ADLJST = 0,
ADC0LTH:ADC0LTL = 0x0200,
AMX0SL = 0x00, AMX0CF = 0x00, ADLJST = 0,
ADC0LTH:ADC0LTL = 0x0100,
ADC0GTH:ADC0GTL = 0x0100.
ADC0GTH:ADC0GTL = 0x0200.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x0200 and
> 0x0100.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is > 0x0200 or < 0x0100.
70
Rev. 1.4
C8051F022/3
Figure 6.17. 10-Bit ADC0 Window Interrupt Example: Right Justified Differential Data
Input Voltage
(AD0 - AD1)
Input Voltage
(AD0 - AD1)
ADC Data
Word
0x01FF
ADC Data
Word
0x01FF
REF x (511/512)
REF x (511/512)
ADWINT
ADWINT=1
not affected
0x0101
0x0101
REF x (256/512)
REF x (-1/512)
0x0100
0x00FF
ADC0LTH:ADC0LTL
ADWINT=1
REF x (256/512)
REF x (-1/512)
0x0100
0x00FF
ADC0GTH:ADC0GTL
ADWINT
not affected
0x0000
0xFFFF
0x0000
0xFFFF
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
ADWINT=1
0xFFFE
0xFFFE
ADWINT
not affected
0xFE00
0xFE00
-REF
-REF
Given:
Given:
AMX0SL = 0x00, AMX0CF = 0x01, ADLJST = 0,
ADC0LTH:ADC0LTL = 0x0100,
AMX0SL = 0x00, AMX0CF = 0x01, ADLJST = 0,
ADC0LTH:ADC0LTL = 0xFFFF,
ADC0GTH:ADC0GTL = 0xFFFF.
ADC0GTH:ADC0GTL = 0x0100.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x0100 and
> 0xFFFF. (In two’s-complement math,
0xFFFF = -1.)
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0xFFFF or
> 0x0100. (In two’s-complement math,
0xFFFF = -1.)
Rev. 1.4
71
C8051F022/3
Figure 6.18. 10-Bit ADC0 Window Interrupt Example: Left Justified Single-Ended Data
Input Voltage
(AD0 - AGND)
Input Voltage
(AD0 - AGND)
ADC Data
Word
0xFFC0
ADC Data
Word
0xFFC0
REF x (1023/1024)
REF x (1023/1024)
ADWINT
ADWINT=1
not affected
0x8040
0x8040
REF x (512/1024)
REF x (256/1024)
0x8000
0x7FC0
ADC0LTH:ADC0LTL
ADWINT=1
REF x (512/1024)
REF x (256/1024)
0x8000
0x7FC0
ADC0GTH:ADC0GTL
ADWINT
not affected
0x4040
0x4000
0x4040
0x4000
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
ADWINT=1
0x3FC0
0x3FC0
ADWINT
not affected
0x0000
0x0000
0
0
Given:
Given:
AMX0SL = 0x00, AMX0CF = 0x00, ADLJST = 1,
ADC0LTH:ADC0LTL = 0x8000,
AMX0SL = 0x00, AMX0CF = 0x00, ADLJST = 1,
ADC0LTH:ADC0LTL = 0x4000,
ADC0GTH:ADC0GTL = 0x4000.
ADC0GTH:ADC0GTL = 0x8000.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x8000 and
> 0x4000.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x4000 or > 0x8000.
72
Rev. 1.4
C8051F022/3
Figure 6.19. 10-Bit ADC0 Window Interrupt Example: Left Justified Differential Data
Input Voltage
(AD0 - AD1)
Input Voltage
(AD0 - AD1)
ADC Data
Word
0x7FC0
ADC Data
Word
0x7FC0
REF x (511/512)
REF x (511/512)
ADWINT
ADWINT=1
not affected
0x2040
0x2040
REF x (128/512)
REF x (-1/512)
0x2000
0x1FC0
ADC0LTH:ADC0LTL
ADWINT=1
REF x (128/512)
REF x (-1/512)
0x2000
0x1FC0
ADC0GTH:ADC0GTL
ADWINT
not affected
0x0000
0xFFC0
0x0000
0xFFC0
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0xFF80
0xFF80
ADWINT=1
ADWINT
not affected
0x8000
0x8000
-REF
-REF
Given:
Given:
AMX0SL = 0x00, AMX0CF = 0x01, ADLJST = 1,
ADC0LTH:ADC0LTL = 0x2000,
AMX0SL = 0x00, AMX0CF = 0x01, ADLJST = 1,
ADC0LTH:ADC0LTL = 0xFFC0,
ADC0GTH:ADC0GTL = 0xFFC0.
ADC0GTH:ADC0GTL = 0x2000.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x2000 and
> 0xFFC0. (Two’s-complement math.)
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0xFFC0 or
> 0x2000. (Two’s-complement math.)
Rev. 1.4
73
C8051F022/3
Table 6.1. 10-Bit ADC0 Electrical Characteristics (C8051F022/3)
VDD = 3.0V, AV+ = 3.0V, VREF = 2.40V (REFBE=0), PGA Gain = 1, -40°C to +85°C unless otherwise specified
PARAMETER
DC ACCURACY
CONDITIONS
MIN
TYP
MAX
UNITS
Resolution
10
bits
LSB
LSB
LSB
LSB
Integral Nonlinearity
Differential Nonlinearity
Offset Error
Full Scale Error
Offset Temperature Coefficient
±1
±1
Guaranteed Monotonic
Differential mode
±0.5
-1.5±0.5
±0.25
ppm/°C
DYNAMIC PERFORMANCE (10 kHz sine-wave input, 0 to 1 dB below Full Scale, 100 ksps
Signal-to-Noise Plus Distortion
Total Harmonic Distortion
Spurious-Free Dynamic Range
CONVERSION RATE
SAR Clock Frequency
Conversion Time in SAR Clocks
Track/Hold Acquisition Time
Throughput Rate
59
dB
dB
th
-70
80
Up to the 5 harmonic
dB
2.5
MHz
clocks
µs
16
1.5
100
ksps
ANALOG INPUTS
Input Voltage Range
*Common-mode Voltage Range
Input Capacitance
Single-ended operation
Differential operation
0
VREF
AV+
V
V
pF
AGND
10
TEMPERATURE SENSOR
Nonlinearity
Absolute Accuracy
Gain
Offset
POWER SPECIFICATIONS
Power Supply Current (AV+ sup-
plied to ADC)
-1.0
+1.0
900
°C
°C
mV/°C
V
±3
2.86
0.776
PGA Gain = 1
PGA Gain = 1, Temp = 0°C
Operating Mode, 100 ksps
450
µA
Power Supply Rejection
±0.3
mV/V
74
Rev. 1.4
C8051F020/1/2/3
7.
ADC1 (8-BIT ADC)
The ADC1 subsystem for the C8051F020/1/2/3 consists of an 8-channel, configurable analog multiplexer (AMUX1),
a programmable gain amplifier (PGA1), and a 500 ksps, 8-bit successive-approximation-register ADC with inte-
grated track-and-hold (see block diagram in Figure 7.1). The AMUX1, PGA1, and Data Conversion Modes, are all
configurable under software control via the Special Function Registers shown in Figure 7.1. The ADC1 subsystem
(8-bit ADC, track-and-hold and PGA) is enabled only when the AD1EN bit in the ADC1 Control register (ADC1CN)
is set to logic 1. The ADC1 subsystem is in low power shutdown when this bit is logic 0. The voltage reference used
by ADC1 is selected as described in Section “9. VOLTAGE REFERENCE (C8051F020/2)” on page 91 for
C8051F020/2 devices, or Section “10. VOLTAGE REFERENCE (C8051F021/3)” on page 93 for C8051F021/3
devices.
Figure 7.1. ADC1 Functional Block Diagram
AV+
AD1EN
AIN1.0 (P1.0)
AV+
AIN1.1 (P1.1)
AIN1.2 (P1.2)
AIN1.3 (P1.3)
AIN1.4 (P1.4)
AIN1.5 (P1.5)
AIN1.6 (P1.6)
AIN1.7 (P1.7)
8-Bit
SAR
+
-
8
8-to-1
X
AMUX
ADC
AGND
000
001
010
011
1xx
Write to AD1BUSY
Timer 3 Overflow
CNVSTR
Start Conversion
Timer 2 Overflow
Write to AD0BUSY
(synchronized with
ADC0)
ADC1CF
AMX1SL
ADC1CN
7.1. Analog Multiplexer and PGA
Eight ADC1 channels are available for measurement, as selected by the AMX1SL register (see Figure 7.5). The PGA
amplifies the ADC1 output signal by an amount determined by the states of the AMP1GN2-0 bits in the ADC1 Con-
figuration register, ADC1CF (Figure 7.4). The PGA can be software-programmed for gains of 0.5, 1, 2, or 4. Gain
defaults to 0.5 on reset.
Important Note: AIN1 pins also function as Port 1 I/O pins, and must be configured as analog inputs when used as
ADC1 inputs. To configure an AIN1 pin for analog input, set to ‘0’ the corresponding bit in register P1MDIN. Port 1
pins selected as analog inputs are skipped by the Digital I/O Crossbar. See Section “17.1.6. Configuring Port 1 Pins
as Analog Inputs (AIN1.[7:0])” on page 165 for more information on configuring the AIN1 pins.
Rev. 1.4
75
C8051F020/1/2/3
7.2. ADC1 Modes of Operation
ADC1 has a maximum conversion speed of 500 ksps. The ADC1 conversion clock (SAR1 clock) is a divided version
of the system clock, determined by the AD1SC bits in the ADC1CF register (system clock divided by (AD1SC + 1)
for 0 ≤ AD1SC ≤ 31). The maximum ADC1 conversion clock is 6 MHz.
7.2.1. Starting a Conversion
A conversion can be initiated in one of five ways, depending on the programmed states of the ADC1 Start of Conver-
sion Mode bits (AD1CM2-0) in register ADC1CN. Conversions may be initiated by:
1. Writing a ‘1’ to the AD1BUSY bit of ADC1CN;
2. A Timer 3 overflow (i.e. timed continuous conversions);
3. A rising edge detected on the external ADC convert start signal, CNVSTR;
4. A Timer 2 overflow (i.e. timed continuous conversions);
5. Writing a ‘1’ to the AD0BUSY of register ADC0CN (initiate conversion of ADC1 and ADC0 with a
single software command).
During conversion, the AD1BUSY bit is set to logic 1 and restored to 0 when conversion is complete. The falling
edge of AD1BUSY triggers an interrupt (when enabled) and sets the interrupt flag in ADC1CN. Converted data is
available in the ADC1 data word, ADC1.
When a conversion is initiated by writing a ‘1’ to AD1BUSY, it is recommended to poll AD1INT to determine when
the conversion is complete. The recommended procedure is:
Step 1. Write a ‘0’ to AD1INT;
Step 2. Write a ‘1’ to AD1BUSY;
Step 3. Poll AD1INT for ‘1’;
Step 4. Process ADC1 data.
7.2.2. Tracking Modes
The AD1TM bit in register ADC1CN controls the ADC1 track-and-hold mode. In its default state, the ADC1 input is
continuously tracked, except when a conversion is in progress. When the AD1TM bit is logic 1, ADC1 operates in
low-power track-and-hold mode. In this mode, each conversion is preceded by a tracking period of 3 SAR clocks
(after the start-of-conversion signal). When the CNVSTR signal is used to initiate conversions in low-power tracking
mode, ADC1 tracks only when CNVSTR is low; conversion begins on the rising edge of CNVSTR (see Figure 7.2).
Tracking can also be disabled (shutdown) when the entire chip is in low power standby or sleep modes. Low-power
Track-and-Hold mode is also useful when AMUX or PGA settings are frequently changed, due to the settling time
requirements described in Section “7.2.3. Settling Time Requirements” on page 78.
76
Rev. 1.4
C8051F020/1/2/3
Figure 7.2. ADC1 Track and Conversion Example Timing
A. ADC Timing for External Trigger Source
CNVSTR
(AD1CM[2:0]=010)
1
2
3
4
5
6
7
8
9
SAR1 Clocks
AD1TM=1
Low Power
or Convert
Track
Convert
Convert
Low Power Mode
Track
AD1TM=0
Track or Convert
B. ADC Timing for Internal Trigger Source
Write '1' to AD1BUSY,
Timer 3 Overflow,
Timer 2 Overflow,
Write '1' to AD0BUSY
(AD1CM[2:0]=000, 001, 011, 1xx)
1
2
3
4
5
6
7
8
9
10 11 12
SAR1 Clocks
AD1TM=1
Low Power
or Convert
Track
Convert
Low Power Mode
Track
1
2
3
4
5
6
7
8
9
SAR1 Clocks
AD1TM=0
Track or
Convert
Convert
Rev. 1.4
77
C8051F020/1/2/3
7.2.3. Settling Time Requirements
When the ADC1 input configuration is changed (i.e., a different MUX or PGA selection), a minimum settling (or
tracking) time is required before an accurate conversion can be performed. This settling time is determined by the
ADC1 MUX resistance, the ADC1 sampling capacitance, any external source resistance, and the accuracy required
for the conversion. Figure 7.3 shows the equivalent ADC1 input circuit. The required ADC1 settling time for a given
settling accuracy (SA) may be approximated by Equation 7.1. Note that in low-power tracking mode, three SAR1
clocks are used for tracking at the start of every conversion. For most applications, these three SAR1 clocks will meet
the tracking requirements. See Table 7.1 for absolute minimum settling time requirements.
Equation 7.1. ADC1 Settling Time Requirements
2n
SA
------
t = ln
× RTOTALCSAMPLE
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required tracking time in seconds
R
is the sum of the ADC1 MUX resistance and any external source resistance.
TOTAL
n is the ADC resolution in bits (8).
Figure 7.3. ADC1 Equivalent Input Circuit
MUX Select
AIN1.x
RMUX = 5k
CSAMPLE = 10pF
RCInput= RMUX * CSAMPLE
78
Rev. 1.4
C8051F020/1/2/3
Figure 7.4. ADC1CF: ADC1 Configuration Register (C8051F020/1/2/3)
R/W
R/W
R/W
R/W
R/W
R/W
-
Bit2
R/W
R/W
Reset Value
AD1SC4 AD1SC3 AD1SC2 AD1SC1 AD1SC0
AMP1GN1 AMP1GN0 11111000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit1
Bit0
SFR Address:
0xAB
Bits7-3: AD1SC4-0: ADC1 SAR Conversion Clock Period Bits
SAR Conversion clock is derived from system clock by the following equation, where AD1SC refers
to the 5-bit value held in AD1SC4-0. SAR conversion clock requirements are given in Table 7.1.
SYSCLK
AD1SC = ---------------------- – 1
CLKSAR1
Bit2:
UNUSED. Read = 0b. Write = don’t care.
Bits1-0: AMP1GN1-0: ADC1 Internal Amplifier Gain (PGA)
00: Gain = 0.5
01: Gain = 1
10: Gain = 2
11: Gain = 4
Figure 7.5. AMX1SL: AMUX1 Channel Select Register (C8051F020/1/2/3)
R/W
-
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
-
Bit4
R/W
-
Bit3
R/W
R/W
R/W
Reset Value
AMX1AD2 AMX1AD1 AMX1AD0 00000000
Bit2
Bit1
Bit0
SFR Address:
0xAC
Bits7-3: UNUSED. Read = 00000b; Write = don’t care
Bits2-0: AMX1AD2-0: AMX1 Address Bits
000-111b: ADC1 Inputs selected as follows:
000: AIN1.0 selected
001: AIN1.1 selected
010: AIN1.2 selected
011: AIN1.3 selected
100: AIN1.4 selected
101: AIN1.5 selected
110: AIN1.6 selected
111: AIN1.7 selected
Rev. 1.4
79
C8051F020/1/2/3
Figure 7.6. ADC1CN: ADC1 Control Register (C8051F020/1/2/3)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
AD1CM0
Bit1
R/W
-
Bit0
Reset Value
00000000
SFR Address:
0xAA
AD1EN AD1TM AD1INT AD1BUSY AD1CM2 AD1CM1
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit7:
AD1EN: ADC1 Enable Bit.
0: ADC1 Disabled. ADC1 is in low-power shutdown.
1: ADC1 Enabled. ADC1 is active and ready for data conversions.
AD1TM: ADC1 Track Mode Bit.
Bit6:
Bit5:
Bit4:
0: Normal Track Mode: When ADC1 is enabled, tracking is continuous unless a conversion is in pro-
cess.
1: Low-power Track Mode: Tracking Defined by AD1STM2-0 bits (see below).
AD1INT: ADC1 Conversion Complete Interrupt Flag.
This flag must be cleared by software.
0: ADC1 has not completed a data conversion since the last time this flag was cleared.
1: ADC1 has completed a data conversion.
AD1BUSY: ADC1 Busy Bit.
Read:
0: ADC1 Conversion is complete or a conversion is not currently in progress. AD1INT is set to logic
1 on the falling edge of AD1BUSY.
1: ADC1 Conversion is in progress.
Write:
0: No Effect.
1: Initiates ADC1 Conversion if AD1STM2-0 = 000b
AD1CM2-0: ADC1 Start of Conversion Mode Select.
AD1TM = 0:
Bit3-1:
000: ADC1 conversion initiated on every write of ‘1’ to AD1BUSY.
001: ADC1 conversion initiated on overflow of Timer 3.
010: ADC1 conversion initiated on rising edge of external CNVSTR.
011: ADC1 conversion initiated on overflow of Timer 2.
1xx: ADC1 conversion initiated on write of ‘1’ to AD0BUSY (synchronized with ADC0 software-
commanded conversions).
AD1TM = 1:
000: Tracking initiated on write of ‘1’ to AD1BUSY and lasts 3 SAR1 clocks, followed by conver-
sion.
001: Tracking initiated on overflow of Timer 3 and lasts 3 SAR1 clocks, followed by conversion.
010: ADC1 tracks only when CNVSTR input is logic low; conversion starts on rising CNVSTR edge.
011: Tracking initiated on overflow of Timer 2 and lasts 3 SAR1 clocks, followed by conversion.
1xx: Tracking initiated on write of ‘1’ to AD0BUSY and lasts 3 SAR1 clocks, followed by conver-
sion.
Bit0:
UNUSED. Read = 0b. Write = don’t care.
80
Rev. 1.4
C8051F020/1/2/3
Figure 7.7. ADC1: ADC1 Data Word Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x9C
Bits7-0: ADC1 Data Word.
Figure 7.8. ADC1 Data Word Example
8-bit ADC Data Word appears in the ADC1 Data Word Register as follows:
Example: ADC1 Data Word Conversion Map, AIN1.0 Input
(AMX1SL = 0x00)
AIN1.0-AGND
ADC1
(Volts)
VREF * (255/256)
VREF / 2
VREF * (127/256)
0
0xFF
0x80
0x7F
0x00
Gain
---------------
Code = Vin ×
× 256
VREF
Rev. 1.4
81
C8051F020/1/2/3
Table 7.1. ADC1 Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, VREF1 = 2.40 V (REFBE=0), PGA1 = 1, -40°C to +85°C unless otherwise specified
PARAMETER
DC ACCURACY
CONDITIONS
MIN
TYP MAX
UNITS
Resolution
8
bits
LSB
LSB
LSB
LSB
Integral Nonlinearity
Differential Nonlinearity
Offset Error
Full Scale Error
Offset Temperature Coefficient
±1
±1
Guaranteed Monotonic
Differential mode
0.5±0.3
-1±0.2
TBD
ppm/°C
DYNAMIC PERFORMANCE (10 kHz sine-wave input, 0 to 1 dB below Full Scale, 500 ksps
Signal-to-Noise Plus Distortion
Total Harmonic Distortion
Spurious-Free Dynamic Range
CONVERSION RATE
SAR Conversion Clock
Conversion Time in SAR Clocks
Track/Hold Acquisition Time
Throughput Rate
45
47
-51
dB
dB
th
Up to the 5 harmonic
52
dB
6
MHz
clocks
ns
8
300
500
ksps
ANALOG INPUTS
Input Voltage Range
0
VREF
V
Input Capacitance
10
pF
POWER SPECIFICATIONS
Power Supply Current (AV+ sup-
plied to ADC1)
Operating Mode, 500 ksps
420
900
µA
Power Supply Rejection
±0.3
mV/V
82
Rev. 1.4
C8051F020/1/2/3
8.
DACS, 12-BIT VOLTAGE MODE
Each C8051F020/1/2/3 device includes two on-chip 12-bit voltage-mode Digital-to-Analog Converters (DACs).
Each DAC has an output swing of 0V to (VREF-1LSB) for a corresponding input code range of 0x000 to 0xFFF. The
DACs may be enabled/disabled via their corresponding control registers, DAC0CN and DAC1CN. While disabled,
the DAC output is maintained in a high-impedance state, and the DAC supply current falls to 1 µA or less. The volt-
age reference for each DAC is supplied at the VREFD pin (C8051F020/2 devices) or the VREF pin (C8051F021/3
devices). Note that the VREF pin on C8051F021/3 devices may be driven by the internal voltage reference or an
external source. If the internal voltage reference is used it must be enabled in order for the DAC outputs to be valid.
See Section “9. VOLTAGE REFERENCE (C8051F020/2)” on page 91 or Section “10. VOLTAGE REFER-
ENCE (C8051F021/3)” on page 93 for more information on configuring the voltage reference for the DACs.
8.1. DAC Output Scheduling
Each DAC features a flexible output update mechanism which allows for seamless full-scale changes and supports
jitter-free updates for waveform generation. The following examples are written in terms of DAC0, but DAC1 opera-
tion is identical. Note that reads from DAC0L return pre-latch data, meaning the value read is the same as the last
value written to this register, not the value at the DAC0L latch. Reads from DAC0H always return the value at the
DAC0H latch.
Figure 8.1. DAC Functional Block Diagram
DAC0EN
DAC0MD1
DAC0MD0
REF
DAC0DF2
DAC0DF1
DAC0DF0
AV+
8
8
8
8
12
DAC0
DAC0
AGND
DAC1EN
DAC1MD1
DAC1MD0
DAC1DF2
DAC1DF1
DAC1DF0
REF
AV+
8
8
8
8
12
DAC1
DAC1
AGND
Rev. 1.4
83
C8051F020/1/2/3
8.1.1. Update Output On-Demand
In its default mode (DAC0CN.[4:3] = ‘00’) the DAC0 output is updated “on-demand” on a write to the high-byte of
the DAC0 data register (DAC0H). It’s important to note that writes to DAC0L are held, and have no effect on the
DAC0 output until a write to DAC0H takes place. If writing a full 12-bit word to the DAC data registers, the 12-bit
data word is written to the low byte (DAC0L) and high byte (DAC0H) data registers. Data is latched into DAC0 after
a write to the corresponding DAC0H register, so the write sequence should be DAC0L followed by DAC0H if the
full 12-bit resolution is required. The DAC can be used in 8-bit mode by initializing DAC0L to the desired value (typ-
ically 0x00), and writing data to only DAC0H (also see Section 8.2 for information on formatting the 12-bit DAC
data word within the 16-bit SFR space).
8.1.2. Update Output Based on Timer Overflow
Similar to the ADC operation, in which an ADC conversion can be initiated by a timer overflow independently of the
processor, the DAC outputs can use a Timer overflow to schedule an output update event. This feature is useful in
systems where the DAC is used to generate a waveform of a defined sampling rate by eliminating the effects of vari-
able interrupt latency and instruction execution on the timing of the DAC output. When the DAC0MD bits
(DAC0CN.[4:3]) are set to ‘01’, ‘10’, or ‘11’, writes to both DAC data registers (DAC0L and DAC0H) are held until
an associated Timer overflow event (Timer 3, Timer 4, or Timer 2, respectively) occurs, at which time the
DAC0H:DAC0L contents are copied to the DAC input latches allowing the DAC output to change to the new value.
8.2. DAC Output Scaling/Justification
In some instances, input data should be shifted prior to a DAC0 write operation to properly justify data within the
DAC input registers. This action would typically require one or more load and shift operations, adding software over-
head and slowing DAC throughput. To alleviate this problem, the data-formatting feature provides a means for the
user to program the orientation of the DAC0 data word within data registers DAC0H and DAC0L. The three
DAC0DF bits (DAC0CN.[2:0]) allow the user to specify one of five data word orientations as shown in the DAC0CN
register definition.
DAC1 is functionally the same as DAC0 described above. The electrical specifications for both DAC0 and DAC1 are
given in Table 8.1.
84
Rev. 1.4
C8051F020/1/2/3
Figure 8.2. DAC0H: DAC0 High Byte Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xD3
Bits7-0: DAC0 Data Word Most Significant Byte.
Figure 8.3. DAC0L: DAC0 Low Byte Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xD2
Bits7-0: DAC0 Data Word Least Significant Byte.
Rev. 1.4
85
C8051F020/1/2/3
Figure 8.4. DAC0CN: DAC0 Control Register
R/W
DAC0EN
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
R/W
R/W
R/W
R/W
Reset Value
DAC0MD1 DAC0MD0 DAC0DF2 DAC0DF1 DAC0DF0 00000000
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xD4
Bit7:
DAC0EN: DAC0 Enable Bit.
0: DAC0 Disabled. DAC0 Output pin is disabled; DAC0 is in low-power shutdown mode.
1: DAC0 Enabled. DAC0 Output pin is active; DAC0 is operational.
Bits6-5: UNUSED. Read = 00b; Write = don’t care.
Bits4-3: DAC0MD1-0: DAC0 Mode Bits.
00: DAC output updates occur on a write to DAC0H.
01: DAC output updates occur on Timer 3 overflow.
10: DAC output updates occur on Timer 4 overflow.
11: DAC output updates occur on Timer 2 overflow.
Bits2-0: DAC0DF2-0: DAC0 Data Format Bits:
000:
001:
010:
The most significant nibble of the DAC0 Data Word is in DAC0H[3:0], while the least
significant byte is in DAC0L.
DAC0H
DAC0L
MSB
LSB
The most significant 5-bits of the DAC0 Data Word is in DAC0H[4:0], while the least
significant 7-bits are in DAC0L[7:1].
DAC0H
MSB
DAC0L
LSB
The most significant 6-bits of the DAC0 Data Word is in DAC0H[5:0], while the least
significant 6-bits are in DAC0L[7:2].
DAC0H
DAC0L
MSB
LSB
011:
The most significant 7-bits of the DAC0 Data Word is in DAC0H[6:0], while the least
significant 5-bits are in DAC0L[7:3].
DAC0H
DAC0L
MSB
LSB
1xx:
The most significant 8-bits of the DAC0 Data Word is in DAC0H[7:0], while the least
significant 4-bits are in DAC0L[7:4].
DAC0H
DAC0L
MSB
LSB
86
Rev. 1.4
C8051F020/1/2/3
Figure 8.5. DAC1H: DAC1 High Byte Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xD6
Bits7-0: DAC1 Data Word Most Significant Byte.
Figure 8.6. DAC1L: DAC1 Low Byte Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xD5
Bits7-0: DAC1 Data Word Least Significant Byte.
Rev. 1.4
87
C8051F020/1/2/3
Figure 8.7. DAC1CN: DAC1 Control Register
R/W
DAC1EN
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
R/W
R/W
R/W
R/W
Reset Value
DAC1MD1 DAC1MD0 DAC1DF2 DAC1DF1 DAC1DF0 00000000
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xD7
Bit7:
DAC1EN: DAC1 Enable Bit.
0: DAC1 Disabled. DAC1 Output pin is disabled; DAC1 is in low-power shutdown mode.
1: DAC1 Enabled. DAC1 Output pin is active; DAC1 is operational.
Bits6-5: UNUSED. Read = 00b; Write = don’t care.
Bits4-3: DAC1MD1-0: DAC1 Mode Bits:
00: DAC output updates occur on a write to DAC1H.
01: DAC output updates occur on Timer 3 overflow.
10: DAC output updates occur on Timer 4 overflow.
11: DAC output updates occur on Timer 2 overflow.
Bits2-0: DAC1DF2: DAC1 Data Format Bits:
000:
001:
010:
The most significant nibble of the DAC1 Data Word is in DAC1H[3:0], while the least
significant byte is in DAC1L.
DAC1H
DAC1L
MSB
LSB
The most significant 5-bits of the DAC1 Data Word is in DAC1H[4:0], while the least
significant 7-bits are in DAC1L[7:1].
DAC1H
MSB
DAC1L
LSB
The most significant 6-bits of the DAC1 Data Word is in DAC1H[5:0], while the least
significant 6-bits are in DAC1L[7:2].
DAC1H
DAC1L
MSB
LSB
011:
The most significant 7-bits of the DAC1 Data Word is in DAC1H[6:0], while the least
significant 5-bits are in DAC1L[7:3].
DAC1H
DAC1L
MSB
LSB
1xx:
The most significant 8-bits of the DAC1 Data Word is in DAC1H[7:0], while the least
significant 4-bits are in DAC1L[7:4].
DAC1H
DAC1L
MSB
LSB
88
Rev. 1.4
C8051F020/1/2/3
Table 8.1. DAC Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, VREF = 2.40 V (REFBE = 0), No Output Load unless otherwise specified
PARAMETER
STATIC PERFORMANCE
Resolution
Integral Nonlinearity
Differential Nonlinearity
Output Noise
CONDITIONS
MIN
TYP MAX
UNITS
12
±2
±1
250
128
41
bits
LSB
LSB
No Output Filter
100 kHz Output Filter
10 kHz Output Filter
µVrms
Offset Error
Offset Tempco
Gain Error
Gain-Error Tempco
VDD Power Supply Rejection
Ratio
Data Word = 0x014
±3
6
±20
10
±30
±60
mV
ppm/°C
mV
ppm/°C
dB
-60
Output Impedance in Shutdown
Mode
DACnEN = 0
100
kΩ
Output Sink Current
300
15
µA
mA
Output Short-Circuit Current
DYNAMIC PERFORMANCE
Voltage Output Slew Rate
Output Settling Time to 1/2 LSB Load = 40pF, Output swing from code
0xFFF to 0x014
Data Word = 0xFFF
Load = 40pF
0.44
10
V/µs
µs
Output Voltage Swing
0
VREF-
1LSB
V
Startup Time
ANALOG OUTPUTS
Load Regulation
10
60
µs
I = 0.01mA to 0.3mA at code 0xFFF
ppm
µA
L
POWER CONSUMPTION (each DAC)
Power Supply Current (AV+ sup- Data Word = 0x7FF
plied to DAC)
110
400
Rev. 1.4
89
C8051F020/1/2/3
Notes
90
Rev. 1.4
C8051F020/1/2/3
9.
VOLTAGE REFERENCE (C8051F020/2)
The voltage reference circuit offers full flexibility in operating the ADC and DAC modules. Three voltage reference
input pins allow each ADC and the two DACs to reference an external voltage reference or the on-chip voltage refer-
ence output. ADC0 may also reference the DAC0 output internally, and ADC1 may reference the analog power sup-
ply voltage, via the VREF multiplexers shown in Figure 9.1.
The internal voltage reference circuit consists of a 1.2 V, 15 ppm/°C (typical) bandgap voltage reference generator
and a gain-of-two output buffer amplifier. The internal reference may be routed via the VREF pin to external system
components or to the voltage reference input pins shown in Figure 9.1. Bypass capacitors of 0.1 µF and 4.7 µF are
recommended from the VREF pin to AGND, as shown in Figure 9.1. See Table 9.1 for voltage reference specifica-
tions.
The Reference Control Register, REF0CN (defined in Figure 9.2) enables/disables the internal reference generator
and selects the reference inputs for ADC0 and ADC1. The BIASE bit in REF0CN enables the on-board reference
generator while the REFBE bit enables the gain-of-two buffer amplifier which drives the VREF pin. When disabled,
the supply current drawn by the bandgap and buffer amplifier falls to less than 1 µA (typical) and the output of the
buffer amplifier enters a high impedance state. If the internal bandgap is used as the reference voltage generator,
BIASE and REFBE must both be set to logic 1. If the internal reference is not used, REFBE may be set to logic 0.
Note that the BIASE bit must be set to logic 1 if either DAC or ADC is used, regardless of whether the voltage refer-
ence is derived from the on-chip reference or supplied by an off-chip source. If neither the ADC nor the DAC are
being used, both of these bits can be set to logic 0 to conserve power. Bits AD0VRS and AD1VRS select the ADC0
and ADC1 voltage reference sources, respectively. The electrical specifications for the Voltage Reference circuit are
given in Table 9.1.
Figure 9.1. Voltage Reference Functional Block Diagram
REF0CN
ADC1
AV+
Ref
1
VREF1
0
VDD
R1
External
Voltage
Reference
Circuit
ADC0
DGND
VREF0
VREFD
VREF
Ref
0
1
DAC0
Ref
DAC1
BIASE
Bias to
ADCs,
DACs
EN
x2
1.2V
Band-Gap
4.7µ
F
0.1µF
REFBE
Recommended Bypass
Capacitors
Rev. 1.4
91
C8051F020/1/2/3
The temperature sensor connects to the highest order input of the ADC0 input multiplexer (see Section “5.1. Analog
Multiplexer and PGA” on page 43 for C8051F020/1 devices, or Section “6.1. Analog Multiplexer and PGA” on
page 59 for C8051F022/3 devices). The TEMPE bit within REF0CN enables and disables the temperature sensor.
While disabled, the temperature sensor defaults to a high impedance state and any A/D measurements performed on
the sensor while disabled result in undefined data.
Figure 9.2. REF0CN: Reference Control Register
R/W
-
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
R/W
R/W
R/W
BIASE
Bit1
R/W
Reset Value
AD0VRS AD1VRS TEMPE
REFBE 00000000
Bit0
Bit4
Bit3
Bit2
SFR Address:
0xD1
Bits7-5: UNUSED. Read = 000b; Write = don’t care.
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
AD0VRS: ADC0 Voltage Reference Select
0: ADC0 voltage reference from VREF0 pin.
1: ADC0 voltage reference from DAC0 output.
AD1VRS: ADC1 Voltage Reference Select
0: ADC1 voltage reference from VREF1 pin.
1: ADC1 voltage reference from AV+.
TEMPE: Temperature Sensor Enable Bit.
0: Internal Temperature Sensor Off.
1: Internal Temperature Sensor On.
BIASE: ADC/DAC Bias Generator Enable Bit. (Must be ‘1’ if using ADC or DAC).
0: Internal Bias Generator Off.
1: Internal Bias Generator On.
REFBE: Internal Reference Buffer Enable Bit.
0: Internal Reference Buffer Off.
1: Internal Reference Buffer On. Internal voltage reference is driven on the VREF pin.
Table 9.1. Voltage Reference Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, -40°C to +85°C unless otherwise specified
PARAMETER
CONDITIONS
MIN
TYP MAX
UNITS
INTERNAL REFERENCE (REFBE = 1)
Output Voltage
25°C ambient
2.36
2.43
2.48
30
V
mA
ppm/°C
ppm/µA
ms
VREF Short-Circuit Current
VREF Temperature Coefficient
Load Regulation
VREF Turn-on Time 1
VREF Turn-on Time 2
VREF Turn-on Time 3
15
0.5
2
20
10
Load = 0 to 200 µA to AGND
4.7µF tantalum, 0.1µF ceramic bypass
0.1µF ceramic bypass
µs
µs
no bypass cap
EXTERNAL REFERENCE (REFBE = 0)
Input Voltage Range
1.00
(AV+) -
0.3
V
Input Current
0
1
µA
92
Rev. 1.4
C8051F020/1/2/3
10. VOLTAGE REFERENCE (C8051F021/3)
The internal voltage reference circuit consists of a 1.2 V, 15 ppm/°C (typical) bandgap voltage reference generator
and a gain-of-two output buffer amplifier. The internal reference may be routed via the VREF pin to external system
components or to the VREFA input pin shown in Figure 10.1. Bypass capacitors of 0.1 µF and 4.7 µF are recom-
mended from the VREF pin to AGND, as shown in Figure 10.1. See Table 10.1 for voltage reference specifications.
The VREFA pin provides a voltage reference input for ADC0 and ADC1. ADC0 may also reference the DAC0 out-
put internally, and ADC1 may reference the analog power supply voltage, via the VREF multiplexers shown in
Figure 10.1.
The Reference Control Register, REF0CN (defined in Figure 10.2) enables/disables the internal reference generator
and selects the reference inputs for ADC0 and ADC1. The BIASE bit in REF0CN enables the on-board reference
generator while the REFBE bit enables the gain-of-two buffer amplifier which drives the VREF pin. When disabled,
the supply current drawn by the bandgap and buffer amplifier falls to less than 1 µA (typical) and the output of the
buffer amplifier enters a high impedance state. If the internal bandgap is used as the reference voltage generator,
BIASE and REFBE must both be set to 1 (this includes any time a DAC is used). If the internal reference is not used,
REFBE may be set to logic 0. Note that the BIASE bit must be set to logic 1 if either ADC is used, regardless of
whether the voltage reference is derived from the on-chip reference or supplied by an off-chip source. If neither the
ADC nor the DAC are being used, both of these bits can be set to logic 0 to conserve power. Bits AD0VRS and
AD1VRS select the ADC0 and ADC1 voltage reference sources, respectively. The electrical specifications for the
Voltage Reference are given in Table 10.1.
Figure 10.1. Voltage Reference Functional Block Diagram
REF0CN
ADC1
AV+
VDD
R1
Ref
1
0
External
Voltage
Reference
Circuit
VREFA
DGND
ADC0
Ref
0
1
DAC0
Ref
DAC1
BIASE
Bias to
ADCs,
DACs
EN
VREF
x2
1.2V
Band-Gap
4.7µF
0.1µF
REFBE
Recommended Bypass
Capacitors
Rev. 1.4
93
C8051F020/1/2/3
The temperature sensor connects to the highest order input of the ADC0 input multiplexer (see Section “5.1. Analog
Multiplexer and PGA” on page 43 for C8051F020/1 devices, or Section “6.1. Analog Multiplexer and PGA” on
page 59 for C8051F022/3 devices). The TEMPE bit within REF0CN enables and disables the temperature sensor.
While disabled, the temperature sensor defaults to a high impedance state and any A/D measurements performed on
the sensor while disabled result in undefined data.
Figure 10.2. REF0CN: Reference Control Register
R/W
-
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
R/W
R/W
R/W
BIASE
Bit1
R/W
Reset Value
AD0VRS AD1VRS TEMPE
REFBE 00000000
Bit0
Bit4
Bit3
Bit2
SFR Address:
0xD1
Bits7-5: UNUSED. Read = 000b; Write = don’t care.
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
AD0VRS: ADC0 Voltage Reference Select
0: ADC0 voltage reference from VREFA pin.
1: ADC0 voltage reference from DAC0 output.
AD1VRS: ADC1 Voltage Reference Select
0: ADC1 voltage reference from VREFA pin.
1: ADC1 voltage reference from AV+.
TEMPE: Temperature Sensor Enable Bit.
0: Internal Temperature Sensor Off.
1: Internal Temperature Sensor On.
BIASE: ADC/DAC Bias Generator Enable Bit. (Must be ‘1’ if using ADC or DAC).
0: Internal Bias Generator Off.
1: Internal Bias Generator On.
REFBE: Internal Reference Buffer Enable Bit.
0: Internal Reference Buffer Off.
1: Internal Reference Buffer On. Internal voltage reference is driven on the VREF pin.
Table 10.1. Voltage Reference Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, -40°C to +85°C unless otherwise specified
PARAMETER
CONDITIONS
MIN
TYP MAX
UNITS
INTERNAL REFERENCE (REFBE = 1)
Output Voltage
25°C ambient
2.36
2.43
2.48
30
V
mA
ppm/°C
ppm/µA
ms
VREF Short-Circuit Current
VREF Temperature Coefficient
Load Regulation
VREF Turn-on Time 1
VREF Turn-on Time 2
VREF Turn-on Time 3
15
0.5
2
20
10
Load = 0 to 200 µA to AGND
4.7µF tantalum, 0.1µF ceramic bypass
0.1µF ceramic bypass
µs
µs
no bypass cap
EXTERNAL REFERENCE (REFBE = 0)
Input Voltage Range
1.00
(AV+) -
0.3
V
Input Current
0
1
µA
94
Rev. 1.4
C8051F020/1/2/3
11. COMPARATORS
Each MCU includes two on-board voltage comparators as shown in Figure 11.1. The inputs of each Comparator are
available at the package pins. The output of each comparator is optionally available at the package pins via the I/O
crossbar. When assigned to package pins, each comparator output can be programmed to operate in open drain or
push-pull modes. See Section “17. PORT INPUT/OUTPUT” on page 161 for Crossbar and port initialization
details.
The hysteresis of each comparator is software-programmable via its respective Comparator control register (CPT0CN
and CPT1CN for Comparator0 and Comparator1, respectively). The user can program both the amount of hysteresis
voltage (referred to the input voltage) and the positive and negative-going symmetry of this hysteresis around the
threshold voltage. The output of the comparator can be polled in software, or can be used as an interrupt source. Each
comparator can be individually enabled or disabled (shutdown). When disabled, the comparator output (if assigned to
a Port I/O pin via the Crossbar) defaults to the logic low state, its interrupt capability is suspended and its supply cur-
rent falls to less than 1 µA. Comparator inputs can be externally driven from -0.25 V to (AV+) + 0.25 V without dam-
age or upset.
The Comparator0 hysteresis is programmed using bits 3-0 in the Comparator0 Control Register CPT0CN (shown in
Figure 11.1). The amount of negative hysteresis voltage is determined by the settings of the CP0HYN bits; In a simi-
lar way, the amount of positive hysteresis is determined by the setting the CP0HYP bits. See Table 11.1 on page 99
for hysteresis level specifications.
Comparator interrupts can be generated on rising-edge and/or falling-edge output transitions. (For interrupt enable
and priority control, see Section “12.3. Interrupt Handler” on page 116). The CP0FIF flag is set upon a
Comparator0 falling-edge interrupt, and the CP0RIF flag is set upon the Comparator0 rising-edge interrupt. Once set,
these bits remain set until cleared by software. The Output State of Comparator0 can be obtained at any time by read-
ing the CP0OUT bit. Comparator0 is enabled by setting the CP0EN bit to logic 1, and is disabled by clearing this bit
Figure 11.1. Comparator Functional Block Diagram
CP0EN
CP0OUT
CP0RIF
CP0FIF
AV+
CP0HYP1
CP0HYP0
CP0HYN1
CP0HYN0
Reset
Decision
Tree
CP0+
CP0-
+
-
SET
SET
CLR
D
Q
Q
D
Q
Q
Crossbar
CLR
Interrupt
Handler
(SYNCHRONIZER)
AGND
CP1EN
CP1OUT
CP1RIF
AV+
CP1FIF
CP1HYP1
CP1HYP0
CP1HYN1
CP1HYN0
CP1+
CP1-
+
-
SET
CLR
SET
CLR
D
Q
Q
D
Q
Q
Crossbar
Interrupt
Handler
(SYNCHRONIZER)
AGND
Rev. 1.4
95
C8051F020/1/2/3
Figure 11.2. Comparator Hysteresis Plot
CP0+
CP0-
VIN+
VIN-
+
CP0
OUT
_
CIRCUIT CONFIGURATION
Positive Hysteresis Voltage
(Programmed with CP0HYP Bits)
VIN-
Negative Hysteresis Voltage
INPUTS
(Programmed by CP0HYN Bits)
VIN+
VOH
OUTPUT
VOL
Negative Hysteresis
Disabled
Maximum
Negative Hysteresis
Positive Hysteresis
Disabled
Maximum
Positive Hysteresis
to logic 0. Comparator0 can also be programmed as a reset source; for details, see Section “13.6. Comparator0
Reset” on page 129.
The operation of Comparator1 is identical to that of Comparator0, though Comparator1 may not be configured as a
reset source. Comparator1 is controlled by the CPT1CN Register (Figure 11.4). The complete electrical specifications
for the Comparators are given in Table 11.1.
96
Rev. 1.4
C8051F020/1/2/3
Figure 11.3. CPT0CN: Comparator0 Control Register
R/W
CP0EN
Bit7
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
CP0OUT CP0RIF
CP0FIF CP0HYP1 CP0HYP0 CP0HYN1 CP0HYN0 00000000
Bit4
Bit6
Bit5
Bit3
Bit2
Bit1
Bit0
SFR Address:
0x9E
Bit7:
CP0EN: Comparator0 Enable Bit.
0: Comparator0 Disabled.
1: Comparator0 Enabled.
Bit6:
Bit5:
Bit4:
CP0OUT: Comparator0 Output State Flag.
0: Voltage on CP0+ < CP0-.
1: Voltage on CP0+ > CP0-.
CP0RIF: Comparator0 Rising-Edge Interrupt Flag.
0: No Comparator0 Rising Edge Interrupt has occurred since this flag was last cleared.
1: Comparator0 Rising Edge Interrupt has occurred.
CP0FIF: Comparator0 Falling-Edge Interrupt Flag.
0: No Comparator0 Falling-Edge Interrupt has occurred since this flag was last cleared.
1: Comparator0 Falling-Edge Interrupt has occurred.
Bits3-2: CP0HYP1-0: Comparator0 Positive Hysteresis Control Bits.
00: Positive Hysteresis Disabled.
01: Positive Hysteresis = 2 mV.
10: Positive Hysteresis = 4 mV.
11: Positive Hysteresis = 10 mV.
Bits1-0: CP0HYN1-0: Comparator0 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hysteresis = 2 mV.
10: Negative Hysteresis = 4 mV.
11: Negative Hysteresis = 10 mV.
Rev. 1.4
97
C8051F020/1/2/3
Figure 11.4. CPT1CN: Comparator1 Control Register
R/W
CP1EN
Bit7
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
CP1OUT CP1RIF
CP1FIF CP1HYP1 CP1HYP0 CP1HYN1 CP1HYN0 00000000
Bit4
Bit6
Bit5
Bit3
Bit2
Bit1
Bit0
SFR Address:
0x9F
Bit7:
CP1EN: Comparator1 Enable Bit.
0: Comparator1 Disabled.
1: Comparator1 Enabled.
Bit6:
Bit5:
Bit4:
CP1OUT: Comparator1 Output State Flag.
0: Voltage on CP1+ < CP1-.
1: Voltage on CP1+ > CP1-.
CP1RIF: Comparator1 Rising-Edge Interrupt Flag.
0: No Comparator1 Rising Edge Interrupt has occurred since this flag was last cleared.
1: Comparator1 Rising Edge Interrupt has occurred.
CP1FIF: Comparator1 Falling-Edge Interrupt Flag.
0: No Comparator1 Falling-Edge Interrupt has occurred since this flag was last cleared.
1: Comparator1 Falling-Edge Interrupt has occurred.
Bits3-2: CP1HYP1-0: Comparator1 Positive Hysteresis Control Bits.
00: Positive Hysteresis Disabled.
01: Positive Hysteresis = 2 mV.
10: Positive Hysteresis = 4 mV.
11: Positive Hysteresis = 10 mV.
Bits1-0: CP1HYN1-0: Comparator1 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hysteresis = 2 mV.
10: Negative Hysteresis = 4 mV.
11: Negative Hysteresis = 10 mV.
98
Rev. 1.4
C8051F020/1/2/3
Table 11.1. Comparator Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, -40°C to +85°C unless otherwise specified
PARAMETER CONDITIONS
Response Time 1 CP+ - CP- = 100 mV
MIN
TYP MAX
4
UNITS
µs
Response Time 2
CP+ - CP- = 10 mV
12
µs
Common-Mode Rejection Ratio
Positive Hysteresis 1
Positive Hysteresis 2
Positive Hysteresis 3
Positive Hysteresis 4
Negative Hysteresis 1
Negative Hysteresis 2
Negative Hysteresis 3
Negative Hysteresis 4
1.5
0
4.5
9
17
0
4.5
9
4
1
7
13
25
1
7
13
25
(AV+)
+ 0.25
mV/V
mV
mV
mV
mV
mV
mV
mV
mV
V
CPnHYP1-0 = 00
CPnHYP1-0 = 01
CPnHYP1-0 = 10
CPnHYP1-0 = 11
CPnHYN1-0 = 00
CPnHYN1-0 = 01
CPnHYN1-0 = 10
CPnHYN1-0 = 11
2
4
10
2
4
10
17
Inverting or Non-Inverting Input
Voltage Range
-0.25
Input Capacitance
Input Bias Current
Input Offset Voltage
POWER SUPPLY
Power-up Time
7
pF
nA
mV
-5
-10
0.001
+5
+10
CPnEN from 0 to 1
20
0.1
1.5
µs
mV/V
µA
Power Supply Rejection
Supply Current
1
10
Operating Mode (each comparator) at DC
Rev. 1.4
99
C8051F020/1/2/3
Notes
100
Rev. 1.4
C8051F020/1/2/3
12. CIP-51 MICROCONTROLLER
The MCU system controller core is the CIP-51 microcontroller. The CIP-51 is fully compatible with the MCS-51™
instruction set; standard 803x/805x assemblers and compilers can be used to develop software. The MCU family has
a superset of all the peripherals included with a standard 8051. Included are five 16-bit counter/timers (see descrip-
tion in Section 22), two full-duplex UARTs (see description in Section 20 and Section 21), 256 bytes of internal
RAM, 128 byte Special Function Register (SFR) address space (see Section 12.2.6), and 8/4 byte-wide I/O Ports (see
description in Section 17). The CIP-51 also includes on-chip debug hardware (see description in Section 24), and
interfaces directly with the MCUs' analog and digital subsystems providing a complete data acquisition or control-
system solution in a single integrated circuit.
The CIP-51 Microcontroller core implements the standard 8051 organization and peripherals as well as additional
custom peripherals and functions to extend its capability (see Figure 12.1 for a block diagram). The CIP-51 includes
the following features:
-
-
-
-
-
Fully Compatible with MCS-51 Instruction Set
25 MIPS Peak Throughput with 25 MHz Clock
0 to 25 MHz Clock Frequency
-
-
-
-
-
Extended Interrupt Handler
Reset Input
Power Management Modes
On-chip Debug Logic
256 Bytes of Internal RAM
8/4 Byte-Wide I/O Ports
Program and Data Memory Security
Figure 12.1. CIP-51 Block Diagram
DATA BUS
ACCUMULATOR
B REGISTER
STACK POINTER
TMP1
TMP2
SRAM
SRAM
PSW
ADDRESS
REGISTER
(256 X 8)
ALU
DATA BUS
SFR_ADDRESS
D8
BUFFER
SFR_CONTROL
SFR_WRITE_DATA
SFR_READ_DATA
SFR
BUS
D8
D8
DATA POINTER
INTERFACE
PC INCREMENTER
D8
MEM_ADDRESS
MEM_CONTROL
PROGRAM COUNTER (PC)
PRGM. ADDRESS REG.
PIPELINE
MEMORY
A16
D8
MEM_WRITE_DATA
MEM_READ_DATA
INTERFACE
CONTROL
LOGIC
RESET
CLOCK
SYSTEM_IRQs
INTERRUPT
INTERFACE
EMULATION_IRQ
D8
STOP
IDLE
POWER CONTROL
REGISTER
D8
Rev. 1.4
101
C8051F020/1/2/3
Performance
The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the standard 8051
architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system clock cycles to exe-
cute, and usually have a maximum system clock of 12 MHz. By contrast, the CIP-51 core executes 70% of its instruc-
tions in one or two system clock cycles, with no instructions taking more than eight system clock cycles.
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. The CIP-51 has a total of
109 instructions. The table below shows the total number of instructions that require each execution time.
Clocks to Execute
1
2
2/3
5
3
3/4
7
4
3
4/5
1
5
2
8
1
Number of Instructions
26
50
14
Programming and Debugging Support
A JTAG-based serial interface is provided for in-system programming of the FLASH program memory and commu-
nication with on-chip debug support logic. The re-programmable FLASH can also be read and changed a single byte
at a time by the application software using the MOVC and MOVX instructions. This feature allows program memory
to be used for non-volatile data storage as well as updating program code under software control.
The on-chip debug support logic facilitates full speed in-circuit debugging, allowing the setting of hardware break-
points and watch points, starting, stopping and single stepping through program execution (including interrupt service
routines), examination of the program's call stack, and reading/writing the contents of registers and memory. This
method of on-chip debug is completely non-intrusive and non-invasive, requiring no RAM, Stack, timers, or other
on-chip resources.
The CIP-51 is supported by development tools from Silicon Labs and third party vendors. Silicon Labs provides an
integrated development environment (IDE) including editor, macro assembler, debugger and programmer. The IDE's
debugger and programmer interface to the CIP-51 via its JTAG interface to provide fast and efficient in-system
device programming and debugging. Third party macro assemblers and C compilers are also available.
12.1. Instruction Set
The instruction set of the CIP-51 System Controller is fully compatible with the standard MCS-51™ instruction set;
standard 8051 development tools can be used to develop software for the CIP-51. All CIP-51 instructions are the
binary and functional equivalent of their MCS-51™ counterparts, including opcodes, addressing modes and effect on
PSW flags. However, instruction timing is different than that of the standard 8051.
12.1.1. Instruction and CPU Timing
In many 8051 implementations, a distinction is made between machine cycles and clock cycles, with machine cycles
varying from 2 to 12 clock cycles in length. However, the CIP-51 implementation is based solely on clock cycle tim-
ing. All instruction timings are specified in terms of clock cycles.
Due to the pipelined architecture of the CIP-51, most instructions execute in the same number of clock cycles as there
are program bytes in the instruction. Conditional branch instructions take one less clock cycle to complete when the
branch is not taken as opposed to when the branch is taken. Table 12.1 is the CIP-51 Instruction Set Summary, which
includes the mnemonic, number of bytes, and number of clock cycles for each instruction.
12.1.2. MOVX Instruction and Program Memory
In the CIP-51, the MOVX instruction serves three purposes: accessing on-chip XRAM, accessing off-chip XRAM,
and accessing on-chip program FLASH memory. The FLASH access feature provides a mechanism for user software
to update program code and use the program memory space for non-volatile data storage (see Section “15. FLASH
102
Rev. 1.4
C8051F020/1/2/3
MEMORY” on page 139). The External Memory Interface provides a fast access to off-chip XRAM (or memory-
mapped peripherals) via the MOVX instruction. Refer to Section “16. EXTERNAL DATA MEMORY INTER-
FACE AND ON-CHIP XRAM” on page 145 for details.
Table 12.1. CIP-51 Instruction Set Summary
Clock
Mnemonic
Description
Bytes
Cycles
ARITHMETIC OPERATIONS
Add register to A
Add direct byte to A
Add indirect RAM to A
Add immediate to A
ADD A, Rn
ADD A, direct
ADD A, @Ri
ADD A, #data
ADDC A, Rn
ADDC A, direct
ADDC A, @Ri
ADDC A, #data
SUBB A, Rn
SUBB A, direct
SUBB A, @Ri
SUBB A, #data
INC A
1
2
1
2
1
2
1
2
1
2
1
2
1
1
2
1
1
1
2
1
1
1
1
1
1
2
2
2
1
2
2
2
1
2
2
2
1
1
2
2
1
1
2
2
1
4
8
1
Add register to A with carry
Add direct byte to A with carry
Add indirect RAM to A with carry
Add immediate to A with carry
Subtract register from A with borrow
Subtract direct byte from A with borrow
Subtract indirect RAM from A with borrow
Subtract immediate from A with borrow
Increment A
Increment register
Increment direct byte
Increment indirect RAM
Decrement A
Decrement register
Decrement direct byte
Decrement indirect RAM
Increment Data Pointer
Multiply A and B
Divide A by B
Decimal adjust A
INC Rn
INC direct
INC @Ri
DEC A
DEC Rn
DEC direct
DEC @Ri
INC DPTR
MUL AB
DIV AB
DA A
LOGICAL OPERATIONS
AND Register to A
ANL A, Rn
1
2
1
2
2
3
1
2
1
2
2
3
1
2
1
1
2
2
2
2
3
1
2
2
2
2
3
1
2
2
ANL A, direct
ANL A, @Ri
ANL A, #data
ANL direct, A
ANL direct, #data
ORL A, Rn
AND direct byte to A
AND indirect RAM to A
AND immediate to A
AND A to direct byte
AND immediate to direct byte
OR Register to A
OR direct byte to A
OR indirect RAM to A
OR immediate to A
OR A to direct byte
OR immediate to direct byte
Exclusive-OR Register to A
Exclusive-OR direct byte to A
Exclusive-OR indirect RAM to A
ORL A, direct
ORL A, @Ri
ORL A, #data
ORL direct, A
ORL direct, #data
XRL A, Rn
XRL A, direct
XRL A, @Ri
Rev. 1.4
103
C8051F020/1/2/3
Table 12.1. CIP-51 Instruction Set Summary
Clock
Mnemonic
Description
Bytes
Cycles
XRL A, #data
XRL direct, A
XRL direct, #data
CLR A
Exclusive-OR immediate to A
Exclusive-OR A to direct byte
Exclusive-OR immediate to direct byte
Clear A
2
2
3
1
1
1
1
1
1
1
2
2
3
1
1
1
1
1
1
1
CPL A
Complement A
RL A
Rotate A left
Rotate A left through Carry
Rotate A right
Rotate A right through Carry
Swap nibbles of A
DATA TRANSFER
Move Register to A
Move direct byte to A
Move indirect RAM to A
Move immediate to A
Move A to Register
Move direct byte to Register
Move immediate to Register
Move A to direct byte
RLC A
RR A
RRC A
SWAP A
MOV A, Rn
MOV A, direct
MOV A, @Ri
MOV A, #data
MOV Rn, A
MOV Rn, direct
MOV Rn, #data
MOV direct, A
MOV direct, Rn
MOV direct, direct
MOV direct, @Ri
MOV direct, #data
MOV @Ri, A
1
2
1
2
1
2
2
2
2
3
2
3
1
2
2
3
1
1
1
1
1
1
2
2
1
2
1
1
1
2
2
2
1
2
2
2
2
3
2
3
2
2
2
3
3
3
3
3
3
3
2
2
1
2
2
2
Move Register to direct byte
Move direct byte to direct byte
Move indirect RAM to direct byte
Move immediate to direct byte
Move A to indirect RAM
Move direct byte to indirect RAM
Move immediate to indirect RAM
Load DPTR with 16-bit constant
Move code byte relative DPTR to A
Move code byte relative PC to A
Move external data (8-bit address) to A
Move A to external data (8-bit address)
Move external data (16-bit address) to A
Move A to external data (16-bit address)
Push direct byte onto stack
Pop direct byte from stack
Exchange Register with A
Exchange direct byte with A
Exchange indirect RAM with A
Exchange low nibble of indirect RAM with A
BOOLEAN MANIPULATION
Clear Carry
MOV @Ri, direct
MOV @Ri, #data
MOV DPTR, #data16
MOVC A, @A+DPTR
MOVC A, @A+PC
MOVX A, @Ri
MOVX @Ri, A
MOVX A, @DPTR
MOVX @DPTR, A
PUSH direct
POP direct
XCH A, Rn
XCH A, direct
XCH A, @Ri
XCHD A, @Ri
CLR C
1
2
1
2
1
1
2
1
2
1
CLR bit
SETB C
SETB bit
CPL C
Clear direct bit
Set Carry
Set direct bit
Complement Carry
104
Rev. 1.4
C8051F020/1/2/3
Table 12.1. CIP-51 Instruction Set Summary
Clock
Mnemonic
Description
Bytes
Cycles
CPL bit
Complement direct bit
AND direct bit to Carry
AND complement of direct bit to Carry
OR direct bit to carry
2
2
2
2
2
2
2
2
2
3
3
3
2
2
ANL C, bit
ANL C, /bit
ORL C, bit
ORL C, /bit
MOV C, bit
MOV bit, C
JC rel
2
2
OR complement of direct bit to Carry
Move direct bit to Carry
2
2
Move Carry to direct bit
2
Jump if Carry is set
2/3
2/3
3/4
3/4
3/4
JNC rel
Jump if Carry is not set
JB bit, rel
JNB bit, rel
JBC bit, rel
Jump if direct bit is set
Jump if direct bit is not set
Jump if direct bit is set and clear bit
PROGRAM BRANCHING
Absolute subroutine call
ACALL addr11
LCALL addr16
RET
2
3
1
1
2
3
2
1
2
2
3
3
3
3
2
3
1
3
4
Long subroutine call
Return from subroutine
5
RETI
Return from interrupt
5
AJMP addr11
LJMP addr16
SJMP rel
Absolute jump
3
Long jump
4
Short jump (relative address)
Jump indirect relative to DPTR
Jump if A equals zero
3
JMP @A+DPTR
JZ rel
JNZ rel
CJNE A, direct, rel
CJNE A, #data, rel
CJNE Rn, #data, rel
CJNE @Ri, #data, rel
DJNZ Rn, rel
DJNZ direct, rel
NOP
3
2/3
2/3
3/4
3/4
3/4
4/5
2/3
3/4
1
Jump if A does not equal zero
Compare direct byte to A and jump if not equal
Compare immediate to A and jump if not equal
Compare immediate to Register and jump if not equal
Compare immediate to indirect and jump if not equal
Decrement Register and jump if not zero
Decrement direct byte and jump if not zero
No operation
Rev. 1.4
105
C8051F020/1/2/3
Notes on Registers, Operands and Addressing Modes:
Rn - Register R0-R7 of the currently selected register bank.
@Ri - Data RAM location addressed indirectly through R0 or R1.
rel - 8-bit, signed (two’s complement) offset relative to the first byte of the following instruction. Used by SJMP
and all conditional jumps.
direct - 8-bit internal data location’s address. This could be a direct-access Data RAM location (0x00-0x7F) or an
SFR (0x80-0xFF).
#data - 8-bit constant
#data16 - 16-bit constant
bit - Direct-accessed bit in Data RAM or SFR
addr11 - 11-bit destination address used by ACALL and AJMP. The destination must be within the same 2K-byte
page of program memory as the first byte of the following instruction.
addr16 - 16-bit destination address used by LCALL and LJMP. The destination may be anywhere within the 64K-
byte program memory space.
There is one unused opcode (0xA5) that performs the same function as NOP.
All mnemonics copyrighted © Intel Corporation 1980.
106
Rev. 1.4
C8051F020/1/2/3
12.2. Memory Organization
The memory organization of the CIP-51 System Controller is similar to that of a standard 8051. There are two sepa-
rate memory spaces: program memory and data memory. Program and data memory share the same address space but
are accessed via different instruction types. There are 256 bytes of internal data memory and 64k bytes of internal
program memory address space implemented within the CIP-51. The CIP-51 memory organization is shown in
Figure 12.2.
Figure 12.2. Memory Map
DATA MEMORY (RAM)
PROGRAM/DATA MEMORY
(FLASH)
INTERNAL DATA ADDRESS SPACE
0xFF
0x1007F
Scrachpad Memory
(DATA only)
Upper 128 RAM
(Indirect Addressing
Only)
Special Function
Register's
0x10000
0xFFFF
0xFE00
0xFDFF
(Direct Addressing Only)
0x80
0x7F
RESERVED
(Direct and Indirect
Addressing)
Lower 128 RAM
(Direct and Indirect
Addressing)
0x30
0x2F
FLASH
Bit Addressable
0x20
(In-System
Programmable in 512
Byte Sectors)
0x1F
General Purpose
Registers
0x00
EXTERNAL DATA ADDRESS SPACE
0x0000
0xFFFF
Off-chip XRAM space
0x1000
0x0FFF
XRAM - 4096 Bytes
(accessable using MOVX
instruction)
0x0000
12.2.1. Program Memory
The CIP-51 has a 64k byte program memory space. The MCU implements 65536 bytes of this program memory
space as in-system re-programmed FLASH memory, organized in a contiguous block from addresses 0x0000 to
0xFFFF. Note: 512 bytes (0xEE00 to 0xFFFF) of this memory are reserved for factory use and are not available for
user program storage.
Program memory is normally assumed to be read-only. However, the CIP-51 can write to program memory by setting
the Program Store Write Enable bit (PSCTL.0) and using the MOVX instruction. This feature provides a mechanism
for the CIP-51 to update program code and use the program memory space for non-volatile data storage. Refer to Sec-
tion “15. FLASH MEMORY” on page 139 for further details.
Rev. 1.4
107
C8051F020/1/2/3
12.2.2. Data Memory
The CIP-51 implements 256 bytes of internal RAM mapped into the data memory space from 0x00 through 0xFF.
The lower 128 bytes of data memory are used for general purpose registers and scratch pad memory. Either direct or
indirect addressing may be used to access the lower 128 bytes of data memory. Locations 0x00 through 0x1F are
addressable as four banks of general purpose registers, each bank consisting of eight byte-wide registers. The next
16 bytes, locations 0x20 through 0x2F, may either be addressed as bytes or as 128 bit locations accessible with the
direct addressing mode.
The upper 128 bytes of data memory are accessible only by indirect addressing. This region occupies the same
address space as the Special Function Registers (SFR) but is physically separate from the SFR space. The addressing
mode used by an instruction when accessing locations above 0x7F determines whether the CPU accesses the upper
128 bytes of data memory space or the SFRs. Instructions that use direct addressing will access the SFR space.
Instructions using indirect addressing above 0x7F access the upper 128 bytes of data memory. Figure 12.2 illustrates
the data memory organization of the CIP-51.
12.2.3. General Purpose Registers
The lower 32 bytes of data memory, locations 0x00 through 0x1F, may be addressed as four banks of general-purpose
registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only one of these banks may be
enabled at a time. Two bits in the program status word, RS0 (PSW.3) and RS1 (PSW.4), select the active register bank
(see description of the PSW in Figure 12.6). This allows fast context switching when entering subroutines and inter-
rupt service routines. Indirect addressing modes use registers R0 and R1 as index registers.
12.2.4. Bit Addressable Locations
In addition to direct access to data memory organized as bytes, the sixteen data memory locations at 0x20 through
0x2F are also accessible as 128 individually addressable bits. Each bit has a bit address from 0x00 to 0x7F. Bit 0 of
the byte at 0x20 has bit address 0x00 while bit 7 of the byte at 0x20 has bit address 0x07. Bit 7 of the byte at 0x2F has
bit address 0x7F. A bit access is distinguished from a full byte access by the type of instruction used (bit source or
destination operands as opposed to a byte source or destination).
The MCS-51™ assembly language allows an alternate notation for bit addressing of the form XX.B where XX is the
byte address and B is the bit position within the byte. For example, the instruction:
MOV
C, 22.3h
moves the Boolean value at 0x13 (bit 3 of the byte at location 0x22) into the Carry flag.
12.2.5. Stack
A programmer's stack can be located anywhere in the 256 byte data memory. The stack area is designated using the
Stack Pointer (SP, address 0x81) SFR. The SP will point to the last location used. The next value pushed on the stack
is placed at SP+1 and then SP is incremented. A reset initializes the stack pointer to location 0x07; therefore, the first
value pushed on the stack is placed at location 0x08, which is also the first register (R0) of register bank 1. Thus, if
more than one register bank is to be used, the SP should be initialized to a location in the data memory not being used
for data storage. The stack depth can extend up to 256 bytes.
The MCUs also have built-in hardware for a stack record. The stack record is a 32-bit shift register, where each
PUSH or increment SP pushes one record bit onto the register, and each CALL pushes two record bits onto the regis-
ter. (A POP or decrement SP pops one record bit, and a RET pops two record bits, also.) The stack record circuitry
can also detect an overflow or underflow on the 32-bit shift register, and can notify the debug software even with the
MCU running at speed.
108
Rev. 1.4
C8051F020/1/2/3
12.2.6. Special Function Registers
The direct-access data memory locations from 0x80 to 0xFF constitute the special function registers (SFRs). The
SFRs provide control and data exchange with the CIP-51's resources and peripherals. The CIP-51 duplicates the SFRs
found in a typical 8051 implementation as well as implementing additional SFRs used to configure and access the
sub-systems unique to the MCU. This allows the addition of new functionality while retaining compatibility with the
MCS-51™ instruction set. Table 12.2 lists the SFRs implemented in the CIP-51 System Controller.
The SFR registers are accessed anytime the direct addressing mode is used to access memory locations from 0x80 to
0xFF. SFRs with addresses ending in 0x0 or 0x8 (e.g. P0, TCON, P1, SCON, IE, etc.) are bit-addressable as well as
byte-addressable. All other SFRs are byte-addressable only. Unoccupied addresses in the SFR space are reserved for
future use. Accessing these areas will have an indeterminate effect and should be avoided. Refer to the corresponding
pages of the datasheet, as indicated in Table 12.3, for a detailed description of each register.
Table 12.2. Special Function Register (SFR) Memory Map
F8
F0
E8
E0
D8
D0
C8
C0
B8
B0
A8
A0
98
SPI0CN
B
ADC0CN
ACC
PCA0CN
PSW
T2CON
PCA0H
SCON1
PCA0L
XBR0
PCA0CPH0 PCA0CPH1 PCA0CPH2 PCA0CPH3 PCA0CPH4 WDTCN
SBUF1 SADDR1 TL4 TH4 EIP1 EIP2
PCA0CPL0 PCA0CPL1 PCA0CPL2 PCA0CPL3 PCA0CPL4 RSTSRC
XBR1
XBR2
RCAP4L
RCAP4H
EIE1
EIE2
PCA0MD PCA0CPM0 PCA0CPM1 PCA0CPM2 PCA0CPM3 PCA0CPM4
REF0CN
T4CON
DAC0L
RCAP2L
DAC0H
RCAP2H
DAC0CN
TL2
DAC1L
TH2
DAC1H
DAC1CN
SMB0CR
SMB0CN SMB0STA SMB0DAT SMB0ADR ADC0GTL ADC0GTH ADC0LTL ADC0LTH
IP
P3
IE
SADEN0
OSCXCN
SADDR0
EMI0TC
SBUF0
TMR3CN TMR3RLL TMR3RLH
TMOD
SP
AMX0CF AMX0SL
OSCICN
ADC0CF
P1MDIN
P74OUT†
P3IF
ADC0L
FLSCL
SADEN1
ADC0H
FLACL
EMI0CN
ADC1CN
ADC1CF
AMX1SL
P2
EMI0CF P0MDOUT P1MDOUT P2MDOUT P3MDOUT
SCON0
P1
TCON
P0
0(8)
(bit addressable)
SPI0CFG
SPI0DAT
ADC1
TMR3L
TH0
SPI0CKR
TMR3H
TH1
CPT0CN
P7†
CKCON
P6†
CPT1CN
90
88
80
TL0
DPL
2(A)
TL1
DPH
3(B)
PSCTL
PCON
7(F)
P4†
4(C)
P5†
5(D)
1(9)
6(E)
Table 12.3. Special Function Registers
SFRs are listed in alphabetical order. All undefined SFR locations are reserved.
Register
ACC
Address
0xE0
Description
Page No.
page 115
Accumulator
ADC0CF
ADC0CN
ADC0GTH
ADC0GTL
ADC0H
ADC0L
0xBC
0xE8
0xC5
0xC4
0xBF
0xBE
ADC0 Configuration
ADC0 Control
ADC0 Greater-Than High
ADC0 Greater-Than Low
ADC0 Data Word High
ADC0 Data Word Low
page 49*, page 65**
page 50*, page 66**
page 53*, page 69**
page 53*, page 69**
page 51*, page 67**
page 51*, page 67**
Rev. 1.4
109
C8051F020/1/2/3
Table 12.3. Special Function Registers
SFRs are listed in alphabetical order. All undefined SFR locations are reserved.
Register
ADC0LTH
ADC0LTL
ADC1CF
ADC1CN
ADC1
AMX0CF
AMX0SL
AMX1SL
B
Address
0xC7
0xC6
0xAB
0xAA
0x9C
0xBA
0xBB
0xAC
0xF0
0x8E
0x9E
0x9F
0xD4
0xD3
0xD2
0xD7
0xD6
0xD5
0x83
Description
Page No.
page 53*, page 69**
page 53*, page 69**
page 79
ADC0 Less-Than High
ADC0 Less-Than Low
ADC1 Analog Multiplexer Configuration
ADC1 Control
page 80
ADC1 Data Word
page 81
ADC0 Multiplexer Configuration
ADC0 Multiplexer Channel Select
ADC1 Analog Multiplexer Channel Select
B Register
page 47*, page 63**
page 48*, page 64**
page 79
page 115
CKCON
CPT0CN
CPT1CN
DAC0CN
DAC0H
DAC0L
DAC1CN
DAC1H
DAC1L
DPH
Clock Control
page 226
page 97
Comparator 0 Control
Comparator 1 Control
DAC0 Control
page 98
page 86
DAC0 High
page 85
DAC0 Low
page 85
DAC1 Control
page 88
DAC1 High Byte
page 87
DAC1 Low Byte
page 87
Data Pointer High
page 113
DPL
0x82
Data Pointer Low
page 113
EIE1
0xE6
0xE7
0xF6
0xF7
0xAF
0xA3
0xA1
0xB7
0xB6
0xA8
0xB8
0xB2
0xB1
0x80
Extended Interrupt Enable 1
Extended Interrupt Enable 2
External Interrupt Priority 1
External Interrupt Priority 2
External Memory Interface Control
EMIF Configuration
EMIF Timing Control
FLASH Access Limit
FLASH Scale
page 121
page 122
page 123
page 124
page 147
page 147
page 152
page 142
page 143
page 119
EIE2
EIP1
EIP2
EMI0CN
EMI0CF
EMI0TC
FLACL
FLSCL
IE
Interrupt Enable
Interrupt Priority
Internal Oscillator Control
External Oscillator Control
Port 0 Latch
IP
page 120
page 136
page 137
page 173
page 173
page 174
page 174
page 175
page 175
page 175
page 176
page 177
page 176
page 180†
page 180†
OSCICN
OSCXCN
P0
P0MDOUT
P1
P1MDIN
P1MDOUT
P2
P2MDOUT
P3
P3IF
0xA4
0x90
Port 0 Output Mode Configuration
Port 1 Latch
0xBD
0xA5
0xA0
0xA6
0xB0
0xAD
0xA7
0x84
Port 1 Input Mode
Port 1 Output Mode Configuration
Port 2 Latch
Port 2 Output Mode Configuration
Port 3 Latch
Port 3 Interrupt Flags
Port 3 Output Mode Configuration
Port 4 Latch
P3MDOUT
†P4
†P5
0x85
Port 5 Latch
110
Rev. 1.4
C8051F020/1/2/3
Table 12.3. Special Function Registers
SFRs are listed in alphabetical order. All undefined SFR locations are reserved.
Register
†P6
†P7
Address
0x86
0x96
Description
Page No.
page 181†
page 181†
page 179†
page 259
page 263
page 263
page 263
page 263
page 263
page 263
page 263
page 263
page 263
page 263
page 261
page 261
page 261
page 261
page 261
page 262
page 262
page 260
page 126
page 144
page 114
page 239
page 239
page 248
page 248
page 92†, page 94††
page 132
page 214
page 224
page 214
page 224
page 214
page 224
page 213
page 223
page 193
page 191
page 192
page 193
page 194
page 113
Port 6 Latch
Port 7 Latch
†P74OUT
PCA0CN
PCA0CPH0
PCA0CPH1
PCA0CPH2
PCA0CPH3
PCA0CPH4
PCA0CPL0
PCA0CPL1
PCA0CPL2
PCA0CPL3
PCA0CPL4
PCA0CPM0
PCA0CPM1
PCA0CPM2
PCA0CPM3
PCA0CPM4
PCA0H
0xB5
0xD8
0xFA
0xFB
0xFC
0xFD
0xFE
0xEA
0xEB
0xEC
0xED
0xEE
0xDA
0xDB
0xDC
0xDD
0xDE
0xF9
0xE9
0xD9
0x87
0x8F
0xD0
0xCB
0xCA
0xE5
0xE4
0xD1
0xEF
0xA9
0xF3
0xB9
0xAE
0x99
Port 4 through 7 Output Mode
PCA Control
PCA Capture 0 High
PCA Capture 1 High
PCA Capture 2 High
PCA Capture 3 High
PCA Capture 4 High
PCA Capture 0 Low
PCA Capture 1 Low
PCA Capture 2 Low
PCA Capture 3 Low
PCA Capture 4 Low
PCA Module 0 Mode Register
PCA Module 1 Mode Register
PCA Module 2 Mode Register
PCA Module 3 Mode Register
PCA Module 4 Mode Register
PCA Counter High
PCA0L
PCA Counter Low
PCA0MD
PCON
PSCTL
PSW
PCA Mode
Power Control
Program Store R/W Control
Program Status Word
Timer/Counter 2 Capture High
Timer/Counter 2 Capture Low
Timer/Counter 4 Capture High
Timer/Counter 4 Capture Low
Programmable Voltage Reference Control
Reset Source Register
UART0 Slave Address
UART1 Slave Address
UART0 Slave Address Enable
UART1 Slave Address Enable
UART0 Data Buffer
UART1 Data Buffer
UART0 Control
RCAP2H
RCAP2L
RCAP4H
RCAP4L
REF0CN
RSTSRC
SADDR0
SADDR1
SADEN0
SADEN1
SBUF0
SBUF1
0xF2
0x98
SCON0
SCON1
0xF1
0xC3
0xC0
0xCF
0xC2
0xC1
0x81
UART1 Control
SMB0ADR
SMB0CN
SMB0CR
SMB0DAT
SMB0STA
SP
SMBus Slave Address
SMBus Control
SMBus Clock Rate
SMBus Data
SMBus Status
Stack Pointer
Rev. 1.4
111
C8051F020/1/2/3
Table 12.3. Special Function Registers
SFRs are listed in alphabetical order. All undefined SFR locations are reserved.
Register
SPI0CFG
SPI0CKR
SPI0CN
SPI0DAT
T2CON
T4CON
TCON
TH0
Address
0x9A
0x9D
0xF8
0x9B
0xC8
0xC9
0x88
0x8C
0x8D
0xCD
0xF5
0x8A
0x8B
0xCC
0xF4
0x89
0x91
0x95
0x94
0x93
0x92
0xFF
0xE1
0xE2
0xE3
Description
Page No.
page 201
page 203
page 202
page 203
page 238
page 247
page 231
page 233
page 233
page 239
page 248
page 233
page 233
page 239
page 248
page 232
page 241
page 242
page 242
page 242
page 241
page 131
page 170
page 171
page 172
SPI Configuration
SPI Clock Rate Control
SPI Control
SPI Data
Timer/Counter 2 Control
Timer/Counter 4 Control
Timer/Counter Control
Timer/Counter 0 High
Timer/Counter 1 High
Timer/Counter 2 High
Timer/Counter 4 High
Timer/Counter 0 Low
Timer/Counter 1 Low
Timer/Counter 2 Low
Timer/Counter 4 Low
Timer/Counter Mode
Timer 3 Control
TH1
TH2
TH4
TL0
TL1
TL2
TL4
TMOD
TMR3CN
TMR3H
TMR3L
TMR3RLH
TMR3RLL
WDTCN
XBR0
Timer 3 High
Timer 3 Low
Timer 3 Reload High
Timer 3 Reload Low
Watchdog Timer Control
Port I/O Crossbar Control 0
Port I/O Crossbar Control 1
Port I/O Crossbar Control 2
XBR1
XBR2
0x97, 0xA2, 0xB3, 0xB4,
0xCE, 0xDF
Reserved
* Refers to a register in the C8051F020/1 only.
** Refers to a register in the C8051F022/3 only.
† Refers to a register in the C8051F020/2 only.
†† Refers to a register in the C8051F021/3 only.
112
Rev. 1.4
C8051F020/1/2/3
12.2.7. Register Descriptions
Following are descriptions of SFRs related to the operation of the CIP-51 System Controller. Reserved bits should not
be set to logic l. Future product versions may use these bits to implement new features in which case the reset value
of the bit will be logic 0, selecting the feature's default state. Detailed descriptions of the remaining SFRs are included
in the sections of the datasheet associated with their corresponding system function.
Figure 12.3. SP: Stack Pointer
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000111
SFR Address:
0x81
Bits7-0: SP: Stack Pointer.
The Stack Pointer holds the location of the top of the stack. The stack pointer is incremented before
every PUSH operation. The SP register defaults to 0x07 after reset.
Figure 12.4. DPL: Data Pointer Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x82
Bits7-0: DPL: Data Pointer Low.
The DPL register is the low byte of the 16-bit DPTR. DPTR is used to access indirectly addressed
XRAM and FLASH memory.
Figure 12.5. DPH: Data Pointer High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x83
Bits7-0: DPH: Data Pointer High.
The DPH register is the high byte of the 16-bit DPTR. DPTR is used to access indirectly addressed
XRAM and FLASH memory.
Rev. 1.4
113
C8051F020/1/2/3
Figure 12.6. PSW: Program Status Word
R/W
CY
Bit7
R/W
AC
Bit6
R/W
F0
Bit5
R/W
RS1
Bit4
R/W
RS0
Bit3
R/W
OV
Bit2
R/W
F1
Bit1
R
Reset Value
PARITY 00000000
Bit0
SFR Address:
(bit addressable)
0xD0
Bit7:
CY: Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry (addition) or a borrow (subtrac-
tion). It is cleared to 0 by all other arithmetic operations.
Bit6:
Bit5:
AC: Auxiliary Carry Flag
This bit is set when the last arithmetic operation resulted in a carry into (addition) or a borrow from
(subtraction) the high order nibble. It is cleared to 0 by all other arithmetic operations.
F0: User Flag 0.
This is a bit-addressable, general purpose flag for use under software control.
Bits4-3: RS1-RS0: Register Bank Select.
These bits select which register bank is used during register accesses.
RS1
RS0
Register Bank
Address
0
0
1
1
0
1
0
1
0
1
2
3
0x00 - 0x07
0x08 - 0x0F
0x10 - 0x17
0x18 - 0x1F
Bit2:
OV: Overflow Flag.
This bit is set to 1 if the last arithmetic operation resulted in a carry (addition), borrow (subtraction),
or overflow (multiply or divide). It is cleared to 0 by all other arithmetic operations.
F1: User Flag 1.
Bit1:
Bit0:
This is a bit-addressable, general purpose flag for use under software control.
PARITY: Parity Flag.
This bit is set to 1 if the sum of the eight bits in the accumulator is odd and cleared if the sum is even.
114
Rev. 1.4
C8051F020/1/2/3
Figure 12.7. ACC: Accumulator
R/W
ACC.7
Bit7
R/W
ACC.6
Bit6
R/W
ACC.5
Bit5
R/W
ACC.4
Bit4
R/W
ACC.3
Bit3
R/W
ACC.2
Bit2
R/W
ACC.1
Bit1
R/W
ACC.0
Reset Value
00000000
SFR Address:
0xE0
Bit0
(bit addressable)
Bits7-0: ACC: Accumulator.
This register is the accumulator for arithmetic operations.
Figure 12.8. B: B Register
R/W
B.7
Bit7
R/W
B.6
Bit6
R/W
B.5
Bit5
R/W
B.4
Bit4
R/W
B.3
Bit3
R/W
B.2
Bit2
R/W
B.1
Bit1
R/W
B.0
Reset Value
00000000
SFR Address:
0xF0
Bit0
(bit addressable)
Bits7-0: B: B Register.
This register serves as a second accumulator for certain arithmetic operations.
Rev. 1.4
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12.3. Interrupt Handler
The CIP-51 includes an extended interrupt system supporting a total of 22 interrupt sources with two priority levels.
The allocation of interrupt sources between on-chip peripherals and external inputs pins varies according to the spe-
cific version of the device. Each interrupt source has one or more associated interrupt-pending flag(s) located in an
SFR. When a peripheral or external source meets a valid interrupt condition, the associated interrupt-pending flag is
set to logic 1.
If interrupts are enabled for the source, an interrupt request is generated when the interrupt-pending flag is set. As
soon as execution of the current instruction is complete, the CPU generates an LCALL to a predetermined address to
begin execution of an interrupt service routine (ISR). Each ISR must end with an RETI instruction, which returns pro-
gram execution to the next instruction that would have been executed if the interrupt request had not occurred. If
interrupts are not enabled, the interrupt-pending flag is ignored by the hardware and program execution continues as
normal. (The interrupt-pending flag is set to logic 1 regardless of the interrupt's enable/disable state.)
Each interrupt source can be individually enabled or disabled through the use of an associated interrupt enable bit in
an SFR (IE-EIE2). However, interrupts must first be globally enabled by setting the EA bit (IE.7) to logic 1 before the
individual interrupt enables are recognized. Setting the EA bit to logic 0 disables all interrupt sources regardless of
the individual interrupt-enable settings.
Some interrupt-pending flags are automatically cleared by the hardware when the CPU vectors to the ISR. However,
most are not cleared by the hardware and must be cleared by software before returning from the ISR. If an interrupt-
pending flag remains set after the CPU completes the return-from-interrupt (RETI) instruction, a new interrupt
request will be generated immediately and the CPU will re-enter the ISR after the completion of the next instruction.
12.3.1. MCU Interrupt Sources and Vectors
The MCUs support 22 interrupt sources. Software can simulate an interrupt event by setting any interrupt-pending
flag to logic 1. If interrupts are enabled for the flag, an interrupt request will be generated and the CPU will vector to
the ISR address associated with the interrupt-pending flag. MCU interrupt sources, associated vector addresses, prior-
ity order and control bits are summarized in Table 12.4. Refer to the datasheet section associated with a particular on-
chip peripheral for information regarding valid interrupt conditions for the peripheral and the behavior of its inter-
rupt-pending flag(s).
12.3.2. External Interrupts
Two of the external interrupt sources (/INT0 and /INT1) are configurable as active-low level-sensitive or active-low
edge-sensitive inputs depending on the setting of bits IT0 (TCON.0) and IT1 (TCON.2). IE0 (TCON.1) and IE1
(TCON.3) serve as the interrupt-pending flag for the /INT0 and /INT1 external interrupts, respectively. If an /INT0 or
/INT1 external interrupt is configured as edge-sensitive, the corresponding interrupt-pending flag is automatically
cleared by the hardware when the CPU vectors to the ISR. When configured as level sensitive, the interrupt-pending
flag follows the state of the external interrupt's input pin. The external interrupt source must hold the input active until
the interrupt request is recognized. It must then deactivate the interrupt request before execution of the ISR completes
or another interrupt request will be generated.
The remaining 2 external interrupts (External Interrupts 6-7) are edge-sensitive inputs configurable as active-low or
active-high. The interrupt-pending flags and configuration bits for these interrupts are in the Port 3 Interrupt Flag
Register shown in Figure “17.19 P3IF: Port3 Interrupt Flag Register” on page 177.
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Table 12.4. Interrupt Summary
Interrupt Priority
Pending Flag
Enable
Flag
Priority
Control
Interrupt Source
Vector
Order
Always
Enabled
EX0 (IE.0) PX0 (IP.0)
ET0 (IE.1) PT0 (IP.1)
EX1 (IE.2) PX1 (IP.2)
ET1 (IE.3) PT1 (IP.3)
Always
Highest
Reset
0x0000
Top
None
N/A N/A
External Interrupt 0 (/INT0)
Timer 0 Overflow
External Interrupt 1 (/INT1)
Timer 1 Overflow
0x0003
0x000B
0x0013
0x001B
0
1
2
3
IE0 (TCON.1)
TF0 (TCON.5)
IE1 (TCON.3)
TF1 (TCON.7)
RI0 (SCON0.0)
TI0 (SCON0.1)
TF2 (T2CON.7)
Y
Y
Y
Y
Y
Y
Y
Y
UART0
0x0023
0x002B
0x0033
4
5
6
Y
Y
Y
ES0 (IE.4) PS0 (IP.4)
Timer 2 Overflow (or EXF2)
Serial Peripheral Interface
ET2 (IE.5) PT2 (IP.5)
ESPI0
PSPI0
SPIF (SPI0CN.7)
(EIE1.0)
ESMB0
(EIE1.1)
(EIP1.0)
PSMB0
(EIP1.1)
SMBus Interface
0x003B
0x0043
7
8
SI (SMB0CN.3)
Y
Y
AD0WINT
(ADC0CN.2)
CF (PCA0CN.7)
CCFn
EWADC0 PWADC0
(EIE1.2)
ADC0 Window Comparator
(EIP1.2)
EPCA0
(EIE1.3)
PPCA0
(EIP1.3)
Programmable Counter Array 0x004B
9
Y
(PCA0CN.n)
CP0FIF
ECP0F
(EIE1.4)
ECP0R
(EIE1.5)
ECP1F
(EIE1.6)
ECP1R
(EIE1.7)
ET3
(EIE2.0)
EADC0
(EIE2.1)
ET4
(EIE2.2)
EADC1
(EIE2.3)
EX6
(EIE2.4)
EX7
(EIE2.5)
PCP0F
(EIP1.4)
PCP0R
(EIP1.5)
PCP1F
(EIP1.6)
PCP1F
(EIP1.7)
PT3
(EIP2.0)
PADC0
(EIP2.1)
PT4
(EIP2.2)
PADC1
(EIP2.3)
PX6
(EIP2.4)
PX7
(EIP2.5)
Comparator 0 Falling Edge
Comparator 0 Rising Edge
Comparator 1 Falling Edge
Comparator 1 Rising Edge
Timer 3 Overflow
0x0053
0x005B
0x0063
0x006B
0x0073
0x007B
0x0083
0x008B
0x0093
0x009B
0x00A3
0x00AB
10
11
12
13
14
15
16
17
18
19
20
21
(CPT0CN.4)
CP0RIF
(CPT0CN.5)
CP1FIF
(CPT1CN.4)
CP1RIF
(CPT1CN.5)
TF3 (TMR3CN.7)
AD0INT
(ADC0CN.5)
ADC0 End of Conversion
Timer 4 Overflow
Y
TF4 (T4CON.7)
AD1INT
(ADC1CN.5)
ADC1 End of Conversion
External Interrupt 6
IE6 (P3IF.5)
External Interrupt 7
IE7 (P3IF.6)
RI1 (SCON1.0)
TI1 (SCON1.1)
XTLVLD
UART1
ES1
PS1
EXVLD
(EIE2.7)
PXVLD
(EIP2.7)
External Crystal OSC Ready
(OSCXCN.7)
Rev. 1.4
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12.3.3. Interrupt Priorities
Each interrupt source can be individually programmed to one of two priority levels: low or high. A low priority inter-
rupt service routine can be preempted by a high priority interrupt. A high priority interrupt cannot be preempted. Each
interrupt has an associated interrupt priority bit in an SFR (IP-EIP2) used to configure its priority level. Low priority
is the default. If two interrupts are recognized simultaneously, the interrupt with the higher priority is serviced first. If
both interrupts have the same priority level, a fixed priority order is used to arbitrate, given in Table 12.4.
12.3.4. Interrupt Latency
Interrupt response time depends on the state of the CPU when the interrupt occurs. Pending interrupts are sampled
and priority decoded each system clock cycle. Therefore, the fastest possible response time is 5 system clock cycles:
1 clock cycle to detect the interrupt and 4 clock cycles to complete the LCALL to the ISR. If an interrupt is pending
when a RETI is executed, a single instruction is executed before an LCALL is made to service the pending interrupt.
Therefore, the maximum response time for an interrupt (when no other interrupt is currently being serviced or the
new interrupt is of greater priority) occurs when the CPU is performing an RETI instruction followed by a DIV as the
next instruction. In this case, the response time is 18 system clock cycles: 1 clock cycle to detect the interrupt, 5 clock
cycles to execute the RETI, 8 clock cycles to complete the DIV instruction and 4 clock cycles to execute the LCALL
to the ISR. If the CPU is executing an ISR for an interrupt with equal or higher priority, the new interrupt will not be
serviced until the current ISR completes, including the RETI and following instruction.
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12.3.5. Interrupt Register Descriptions
The SFRs used to enable the interrupt sources and set their priority level are described below. Refer to the datasheet
section associated with a particular on-chip peripheral for information regarding valid interrupt conditions for the
peripheral and the behavior of its interrupt-pending flag(s).
Figure 12.9. IE: Interrupt Enable
R/W
EA
Bit7
R/W
IEGF0
Bit6
R/W
ET2
Bit5
R/W
ES0
Bit4
R/W
ET1
Bit3
R/W
EX1
Bit2
R/W
ET0
Bit1
R/W
EX0
Reset Value
00000000
SFR Address:
0xA8
Bit0
(bit addressable)
Bit7:
EA: Enable All Interrupts.
This bit globally enables/disables all interrupts. When set to ‘0’, individual interrupt mask settings are
overridden.
0: Disable all interrupt sources.
1: Enable each interrupt according to its individual mask setting.
IEGF0: General Purpose Flag 0.
Bit6:
Bit5:
This is a general purpose flag for use under software control.
ET2: Enabler Timer 2 Interrupt.
This bit sets the masking of the Timer 2 interrupt.
0: Disable Timer 2 interrupt.
1: Enable interrupt requests generated by the TF2 flag (T2CON.7).
ES0: Enable UART0 Interrupt.
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
This bit sets the masking of the UART0 interrupt.
0: Disable UART0 interrupt.
1: Enable UART0 interrupt.
ET1: Enable Timer 1 Interrupt.
This bit sets the masking of the Timer 1 interrupt.
0: Disable all Timer 1 interrupt.
1: Enable interrupt requests generated by the TF1 flag (TCON.7).
EX1: Enable External Interrupt 1.
This bit sets the masking of external interrupt 1.
0: Disable external interrupt 1.
1: Enable interrupt requests generated by the /INT1 pin.
ET0: Enable Timer 0 Interrupt.
This bit sets the masking of the Timer 0 interrupt.
0: Disable all Timer 0 interrupt.
1: Enable interrupt requests generated by the TF0 flag (TCON.5).
EX0: Enable External Interrupt 0.
This bit sets the masking of external interrupt 0.
0: Disable external interrupt 0.
1: Enable interrupt requests generated by the /INT0 pin.
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Figure 12.10. IP: Interrupt Priority
R/W
-
Bit7
R/W
-
Bit6
R/W
PT2
Bit5
R/W
PS0
Bit4
R/W
PT1
Bit3
R/W
PX1
Bit2
R/W
PT0
Bit1
R/W
PX0
Reset Value
00000000
SFR Address:
0xB8
Bit0
(bit addressable)
Bits7-6: UNUSED. Read = 11b, Write = don't care.
Bit5:
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
PT2: Timer 2 Interrupt Priority Control.
This bit sets the priority of the Timer 2 interrupt.
0: Timer 2 interrupt priority determined by default priority order.
1: Timer 2 interrupts set to high priority level.
PS0: UART0 Interrupt Priority Control.
This bit sets the priority of the UART0 interrupt.
0: UART0 interrupt priority determined by default priority order.
1: UART0 interrupts set to high priority level.
PT1: Timer 1 Interrupt Priority Control.
This bit sets the priority of the Timer 1 interrupt.
0: Timer 1 interrupt priority determined by default priority order.
1: Timer 1 interrupts set to high priority level.
PX1: External Interrupt 1 Priority Control.
This bit sets the priority of the External Interrupt 1 interrupt.
0: External Interrupt 1 priority determined by default priority order.
1: External Interrupt 1 set to high priority level.
PT0: Timer 0 Interrupt Priority Control.
This bit sets the priority of the Timer 0 interrupt.
0: Timer 0 interrupt priority determined by default priority order.
1: Timer 0 interrupt set to high priority level.
PX0: External Interrupt 0 Priority Control.
This bit sets the priority of the External Interrupt 0 interrupt.
0: External Interrupt 0 priority determined by default priority order.
1: External Interrupt 0 set to high priority level.
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Figure 12.11. EIE1: Extended Interrupt Enable 1
R/W
ECP1R
Bit7
R/W
ECP1F
Bit6
R/W
ECP0R
Bit5
R/W
ECP0F
Bit4
R/W
R/W
R/W
R/W
ESPI0
Bit0
Reset Value
00000000
SFR Address:
0xE6
EPCA0 EWADC0 ESMB0
Bit3
Bit2
Bit1
Bit7:
ECP1R: Enable Comparator1 (CP1) Rising Edge Interrupt.
This bit sets the masking of the CP1 interrupt.
0: Disable CP1 Rising Edge interrupt.
1: Enable interrupt requests generated by the CP1RIF flag (CPT1CN.5).
ECP1F: Enable Comparator (CP1) Falling Edge Interrupt.
This bit sets the masking of the CP1 interrupt.
Bit6:
Bit5:
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
0: Disable CP1 Falling Edge interrupt.
1: Enable interrupt requests generated by the CP1FIF flag (CPT1CN.4).
ECP0R: Enable Comparator0 (CP0) Rising Edge Interrupt.
This bit sets the masking of the CP0 interrupt.
0: Disable CP0 Rising Edge interrupt.
1: Enable interrupt requests generated by the CP0RIF flag (CPT0CN.5).
ECP0F: Enable Comparator0 (CP0) Falling Edge Interrupt.
This bit sets the masking of the CP0 interrupt.
0: Disable CP0 Falling Edge interrupt.
1: Enable interrupt requests generated by the CP0FIF flag (CPT0CN.4).
EPCA0: Enable Programmable Counter Array (PCA0) Interrupt.
This bit sets the masking of the PCA0 interrupts.
0: Disable all PCA0 interrupts.
1: Enable interrupt requests generated by PCA0.
EWADC0: Enable Window Comparison ADC0 Interrupt.
This bit sets the masking of ADC0 Window Comparison interrupt.
0: Disable ADC0 Window Comparison Interrupt.
1: Enable Interrupt requests generated by ADC0 Window Comparisons.
ESMB0: Enable System Management Bus (SMBus0) Interrupt.
This bit sets the masking of the SMBus interrupt.
0: Disable all SMBus interrupts.
1: Enable interrupt requests generated by the SI flag (SMB0CN.3).
ESPI0: Enable Serial Peripheral Interface (SPI0) Interrupt.
This bit sets the masking of SPI0 interrupt.
0: Disable all SPI0 interrupts.
1: Enable Interrupt requests generated by the SPIF flag (SPI0CN.7).
Rev. 1.4
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Figure 12.12. EIE2: Extended Interrupt Enable 2
R/W
EXVLD
Bit7
R/W
ES1
Bit6
R/W
EX7
Bit5
R/W
EX6
Bit4
R/W
EADC1
Bit3
R/W
ET4
Bit2
R/W
EADC0
Bit1
R/W
ET3
Bit0
Reset Value
00000000
SFR Address:
0xE7
Bit7:
EXVLD: Enable External Clock Source Valid (XTLVLD) Interrupt.
This bit sets the masking of the XTLVLD interrupt.
0: Disable XTLVLD interrupt.
1: Enable interrupt requests generated by the XTLVLD flag (OSCXCN.7)
ES1: Enable UART1 Interrupt.
Bit6:
Bit5:
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
This bit sets the masking of the UART1 interrupt.
0: Disable UART1 interrupt.
1: Enable UART1 interrupt.
EX7: Enable External Interrupt 7.
This bit sets the masking of External Interrupt 7.
0: Disable External Interrupt 7.
1: Enable interrupt requests generated by the External Interrupt 7 input pin.
EX6: Enable External Interrupt 6.
This bit sets the masking of External Interrupt 6.
0: Disable External Interrupt 6.
1: Enable interrupt requests generated by the External Interrupt 6 input pin.
EADC1: Enable ADC1 End Of Conversion Interrupt.
This bit sets the masking of the ADC1 End of Conversion interrupt.
0: Disable ADC1 End of Conversion interrupt.
1: Enable interrupt requests generated by the ADC1 End of Conversion Interrupt.
ET4: Enable Timer 4 Interrupt
This bit sets the masking of the Timer 4 interrupt.
0: Disable Timer 4 interrupt.
1: Enable interrupt requests generated by the TF4 flag (T4CON.7).
EADC0: Enable ADC0 End of Conversion Interrupt.
This bit sets the masking of the ADC0 End of Conversion Interrupt.
0: Disable ADC0 Conversion Interrupt.
1: Enable interrupt requests generated by the ADC0 Conversion Interrupt.
ET3: Enable Timer 3 Interrupt.
This bit sets the masking of the Timer 3 interrupt.
0: Disable all Timer 3 interrupts.
1: Enable interrupt requests generated by the TF3 flag (TMR3CN.7).
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Figure 12.13. EIP1: Extended Interrupt Priority 1
R/W
PCP1R
Bit7
R/W
PCP1F
Bit6
R/W
PCP0R
Bit5
R/W
PCP0F
Bit4
R/W
PPCA0
Bit3
R/W
R/W
R/W
PSPI0
Bit0
Reset Value
00000000
SFR Address:
0xF6
PWADC0 PSMB0
Bit2
Bit1
Bit7:
PCP1R: Comparator1 (CP1) Rising Interrupt Priority Control.
This bit sets the priority of the CP1 interrupt.
0: CP1 rising interrupt set to low priority level.
1: CP1 rising interrupt set to high priority level.
PCP1F: Comparator1 (CP1) Falling Interrupt Priority Control.
This bit sets the priority of the CP1 interrupt.
0: CP1 falling interrupt set to low priority level.
1: CP1 falling interrupt set to high priority level.
PCP0R: Comparator0 (CP0) Rising Interrupt Priority Control.
This bit sets the priority of the CP0 interrupt.
Bit6:
Bit5:
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
0: CP0 rising interrupt set to low priority level.
1: CP0 rising interrupt set to high priority level.
PCP0F: Comparator0 (CP0) Falling Interrupt Priority Control.
This bit sets the priority of the CP0 interrupt.
0: CP0 falling interrupt set to low priority level.
1: CP0 falling interrupt set to high priority level.
PPCA0: Programmable Counter Array (PCA0) Interrupt Priority Control.
This bit sets the priority of the PCA0 interrupt.
0: PCA0 interrupt set to low priority level.
1: PCA0 interrupt set to high priority level.
PWADC0: ADC0 Window Comparator Interrupt Priority Control.
This bit sets the priority of the ADC0 Window interrupt.
0: ADC0 Window interrupt set to low priority level.
1: ADC0 Window interrupt set to high priority level.
PSMB0: System Management Bus (SMBus0) Interrupt Priority Control.
This bit sets the priority of the SMBus0 interrupt.
0: SMBus interrupt set to low priority level.
1: SMBus interrupt set to high priority level.
PSPI0: Serial Peripheral Interface (SPI0) Interrupt Priority Control.
This bit sets the priority of the SPI0 interrupt.
0: SPI0 interrupt set to low priority level.
1: SPI0 interrupt set to high priority level.
Rev. 1.4
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C8051F020/1/2/3
Figure 12.14. EIP2: Extended Interrupt Priority 2
R/W
PXVLD
Bit7
R/W
EP1
Bit6
R/W
PX7
Bit5
R/W
PX6
Bit4
R/W
PADC1
Bit3
R/W
PT4
Bit2
R/W
PADC0
Bit1
R/W
PT3
Bit0
Reset Value
00000000
SFR Address:
0xF7
Bit7:
PXVLD: External Clock Source Valid (XTLVLD) Interrupt Priority Control.
This bit sets the priority of the XTLVLD interrupt.
0: XTLVLD interrupt set to low priority level.
1: XTLVLD interrupt set to high priority level.
EP1: UART1 Interrupt Priority Control.
Bit6:
Bit5:
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
This bit sets the priority of the UART1 interrupt.
0: UART1 interrupt set to low priority.
1: UART1 interrupt set to high priority.
PX7: External Interrupt 7 Priority Control.
This bit sets the priority of the External Interrupt 7.
0: External Interrupt 7 set to low priority level.
1: External Interrupt 7 set to high priority level.
PX6: External Interrupt 6 Priority Control.
This bit sets the priority of the External Interrupt 6.
0: External Interrupt 6 set to low priority level.
1: External Interrupt 6 set to high priority level.
PADC1: ADC1 End Of Conversion Interrupt Priority Control.
This bit sets the priority of the ADC1 End of Conversion interrupt.
0: ADC1 End of Conversion interrupt set to low priority.
1: ADC1 End of Conversion interrupt set to low priority.
PT4: Timer 4 Interrupt Priority Control.
This bit sets the priority of the Timer 4 interrupt.
0: Timer 4 interrupt set to low priority.
1: Timer 4 interrupt set to low priority.
PADC0: ADC End of Conversion Interrupt Priority Control.
This bit sets the priority of the ADC0 End of Conversion Interrupt.
0: ADC0 End of Conversion interrupt set to low priority level.
1: ADC0 End of Conversion interrupt set to high priority level.
PT3: Timer 3 Interrupt Priority Control.
This bit sets the priority of the Timer 3 interrupts.
0: Timer 3 interrupt priority determined by default priority order.
1: Timer 3 interrupt set to high priority level.
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12.4. Power Management Modes
The CIP-51 core has two software programmable power management modes: Idle and Stop. Idle mode halts the CPU
while leaving the external peripherals and internal clocks active. In Stop mode, the CPU is halted, all interrupts and
timers (except the Missing Clock Detector) are inactive, and the system clock is stopped. Since clocks are running in
Idle mode, power consumption is dependent upon the system clock frequency and the number of peripherals left in
active mode before entering Idle. Stop mode consumes the least power. Figure 12.15 describes the Power Control
Register (PCON) used to control the CIP-51's power management modes.
Although the CIP-51 has Idle and Stop modes built in (as with any standard 8051 architecture), power management
of the entire MCU is better accomplished by enabling/disabling individual peripherals as needed. Each analog periph-
eral can be disabled when not in use and put into low power mode. Digital peripherals, such as timers or serial buses,
draw little power whenever they are not in use. Turning off the Flash memory saves power, similar to entering Idle
mode. Turning off the oscillator saves even more power, but requires a reset to restart the MCU.
12.4.1. Idle Mode
Setting the Idle Mode Select bit (PCON.0) causes the CIP-51 to halt the CPU and enter Idle mode as soon as the
instruction that sets the bit completes. All internal registers and memory maintain their original data. All analog and
digital peripherals can remain active during Idle mode.
Idle mode is terminated when an enabled interrupt or /RST is asserted. The assertion of an enabled interrupt will
cause the Idle Mode Selection bit (PCON.0) to be cleared and the CPU to resume operation. The pending interrupt
will be serviced and the next instruction to be executed after the return from interrupt (RETI) will be the instruction
immediately following the one that set the Idle Mode Select bit. If Idle mode is terminated by an internal or external
reset, the CIP-51 performs a normal reset sequence and begins program execution at address 0x0000.
If enabled, the WDT will eventually cause an internal watchdog reset and thereby terminate the Idle mode. This fea-
ture protects the system from an unintended permanent shutdown in the event of an inadvertent write to the PCON
register. If this behavior is not desired, the WDT may be disabled by software prior to entering the Idle mode if the
WDT was initially configured to allow this operation. This provides the opportunity for additional power savings,
allowing the system to remain in the Idle mode indefinitely, waiting for an external stimulus to wake up the system.
Refer to Section “13.8. Watchdog Timer Reset” on page 129 for more information on the use and configuration of
the WDT.
12.4.2. Stop Mode
Setting the Stop Mode Select bit (PCON.1) causes the CIP-51 to enter Stop mode as soon as the instruction that sets
the bit completes. In Stop mode, the CPU and internal oscillator are stopped, effectively shutting down all digital
peripherals. Each analog peripheral must be shut down individually prior to entering Stop Mode. Stop mode can only
be terminated by an internal or external reset. On reset, the CIP-51 performs the normal reset sequence and begins
program execution at address 0x0000.
If enabled, the Missing Clock Detector will cause an internal reset and thereby terminate the Stop mode. The Missing
Clock Detector should be disabled if the CPU is to be put to sleep for longer than the MCD timeout of 100 µs.
Rev. 1.4
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Figure 12.15. PCON: Power Control
R/W
SMOD0
Bit7
R/W
R/W
R/W
R/W
R/W
R/W
STOP
Bit1
R/W
IDLE
Bit0
Reset Value
00000000
SFR Address:
0x87
SSTAT0 Reserved SMOD1
Bit6
SSTAT1 Reserved
Bit3
Bit5
Bit4
Bit2
Bit7:
SMOD0: UART0 Baud Rate Doubler Enable.
This bit enables/disables the divide-by-two function of the UART0 baud rate logic for configurations
described in the UART0 section.
0: UART0 baud rate divide-by-two enabled.
1: UART0 baud rate divide-by-two disabled.
Bit6:
SSTAT0: UART0 Enhanced Status Mode Select.
This bit controls the access mode of the SM20-SM00 bits in register SCON0.
0: Reads/writes of SM20-SM00 access the SM20-SM00 UART0 mode setting.
1: Reads/writes of SM20-SM00 access the Framing Error (FE0), RX Overrun (RXOV0), and TX
Collision (TXCOL0) status bits.
Bit5:
Bit4:
Reserved. Read is undefined. Must write 0.
SMOD1: UART1 Baud Rate Doubler Enable.
This bit enables/disables the divide-by-two function of the UART1 baud rate logic for configurations
described in the UART1 section.
0: UART1 baud rate divide-by-two enabled.
1: UART1 baud rate divide-by-two disabled.
Bit3:
SSTAT1: UART1 Enhanced Status Mode Select.
This bit controls the access mode of the SM21-SM01 bits in SCON1.
0: Reads/writes of SM21-SM01 access the SM21-SM01 UART1 mode setting.
1: Reads/writes of SM21-SM01 access the Framing Error (FE1), RX Overrun (RXOV1), and TX
Collision (TXCOL1) status bits.
Bit2:
Bit1:
Reserved. Read is undefined. Must write 0.
STOP: STOP Mode Select.
Writing a ‘1’ to this bit will place the CIP-51 into STOP mode. This bit will always read ‘0’.
1: CIP-51 forced into power-down mode. (Turns off internal oscillator).
IDLE: IDLE Mode Select.
Bit0:
Writing a ‘1’ to this bit will place the CIP-51 into IDLE mode. This bit will always read ‘0’.
1: CIP-51 forced into idle mode. (Shuts off clock to CPU, but clock to Timers, Interrupts, and all
peripherals remain active.)
126
Rev. 1.4
C8051F020/1/2/3
13. RESET SOURCES
Reset circuitry allows the controller to be easily placed in a predefined default condition. On entry to this reset state,
the following occur:
•
•
•
•
CIP-51 halts program execution
Special Function Registers (SFRs) are initialized to their defined reset values
External port pins are forced to a known state
Interrupts and timers are disabled.
All SFRs are reset to the predefined values noted in the SFR detailed descriptions. The contents of internal data mem-
ory are unaffected during a reset; any previously stored data is preserved. However, since the stack pointer SFR is
reset, the stack is effectively lost even though the data on the stack are not altered.
The I/O port latches are reset to 0xFF (all logic 1’s), activating internal weak pull-ups which take the external I/O pins
to a high state. Note that weak pull-ups are disabled during the reset, and enabled when the device exits the reset state.
This allows power to be conserved while the part is held in reset. For VDD Monitor resets, the /RST pin is driven low
until the end of the VDD reset timeout.
On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the internal oscillator
running at 2 MHz. Refer to Section “14. OSCILLATORS” on page 135 for information on selecting and configuring
the system clock source. The Watchdog Timer is enabled using its longest timeout interval (see Section
“13.8. Watchdog Timer Reset” on page 129). Once the system clock source is stable, program execution begins at
location 0x0000.
There are seven sources for putting the MCU into the reset state: power-on/power-fail, external /RST pin, external
CNVSTR signal, software command, Comparator0, Missing Clock Detector, and Watchdog Timer. Each reset source
is described in the following sections.
Figure 13.1. Reset Sources
VDD
CNVSTR
(Port
I/O)
Crossbar
Supply
Monitor
(CNVSTR
reset
Supply
Reset
+
enable)
/RST
-
(wired-OR)
Timeout
Comparator0
CP0+
CP0-
+
-
(CP0
reset
enable)
Reset
Funnel
Missing
Clock
Detector
(one-
shot)
WDT
EN
EN
PRE
Internal
Clock
Generator
System
Clock
Software Reset
System Reset
CIP-51
XTAL1
XTAL2
OSC
Microcontroller
Core
Clock Select
Extended Interrupt
Handler
Rev. 1.4
127
C8051F020/1/2/3
13.1. Power-on Reset
The C8051F020/1/2/3 family incorporates a power supply monitor that holds the MCU in the reset state until VDD
rises above the V
level during power-up. See Figure 13.2 for timing diagram, and refer to Table 13.1 for the Elec-
RST
trical Characteristics of the power supply monitor circuit. The /RST pin is asserted low until the end of the 100 ms
VDD Monitor timeout in order to allow the VDD supply to stabilize.
On exit from a power-on reset, the PORSF flag (RSTSRC.1) is set by hardware to logic 1. All of the other reset flags
in the RSTSRC Register are indeterminate. PORSF is cleared by all other resets. Since all resets cause program exe-
cution to begin at the same location (0x0000), software can read the PORSF flag to determine if a power-up was the
cause of reset. The contents of internal data memory should be assumed to be undefined after a power-on reset.
The VDD monitor function is enabled by tying the MONEN pin directly to VDD. This is the recommended
configuration for the MONEN pin.
.
Figure 13.2. Reset Timing
2.70
2.55
VRST
2.0
1.0
t
/RST
Logic HIGH
100ms
100ms
Logic LOW
Power-On Reset
VDD Monitor Reset
13.2. Power-fail Reset
When a power-down transition or power irregularity causes VDD to drop below V , the power supply monitor will
RST
drive the /RST pin low and return the CIP-51 to the reset state. When VDD returns to a level above VRST, the CIP-51
will leave the reset state in the same manner as that for the power-on reset (see Figure 13.2). Note that even though
internal data memory contents are not altered by the power-fail reset, it is impossible to determine if VDD dropped
below the level required for data retention. If the PORSF flag is set to logic 1, the data may no longer be valid.
128
Rev. 1.4
C8051F020/1/2/3
13.3. External Reset
The external /RST pin provides a means for external circuitry to force the MCU into a reset state. Asserting the /RST
pin low will cause the MCU to enter the reset state. It may be desirable to provide an external pull-up and/or decou-
pling of the /RST pin to avoid erroneous noise-induced resets. The MCU will remain in reset until at least 12 clock
cycles after the active-low /RST signal is removed. The PINRSF flag (RSTSRC.0) is set on exit from an external
reset.
13.4. Software Forced Reset
Writing a ‘1’ to the SWRSEF bit forces a Software Reset as described in Section 13.1.
13.5. Missing Clock Detector Reset
The Missing Clock Detector is essentially a one-shot circuit that is triggered by the MCU system clock. If the system
clock goes away for more than 100 µs, the one-shot will time out and generate a reset. After a Missing Clock Detector
reset, the MCDRSF flag (RSTSRC.2) will be set, signifying the MSD as the reset source; otherwise, this bit reads ‘0’.
The state of the /RST pin is unaffected by this reset. Setting the MSCLKE bit in the OSCICN register (see Section
“14. OSCILLATORS” on page 135) enables the Missing Clock Detector.
13.6. Comparator0 Reset
Comparator0 can be configured as a reset input by writing a ‘1’ to the C0RSEF flag (RSTSRC.5). Comparator0
should be enabled using CPT0CN.7 (see Section “11. COMPARATORS” on page 95) prior to writing to C0RSEF to
prevent any turn-on chatter on the output from generating an unwanted reset. The Comparator0 reset is active-low: if
the non-inverting input voltage (CP0+ pin) is less than the inverting input voltage (CP0- pin), the MCU is put into the
reset state. After a Comparator0 Reset, the C0RSEF flag (RSTSRC.5) will read ‘1’ signifying Comparator0 as the
reset source; otherwise, this bit reads ‘0’. The state of the /RST pin is unaffected by this reset.
13.7. External CNVSTR Pin Reset
The external CNVSTR signal can be configured as a reset input by writing a ‘1’ to the CNVRSEF flag (RSTSRC.6).
The CNVSTR signal can appear on any of the P0, P1, P2 or P3 I/O pins as described in Section “17.1. Ports 0
through 3 and the Priority Crossbar Decoder” on page 163. Note that the Crossbar must be configured for the
CNVSTR signal to be routed to the appropriate Port I/O. The Crossbar should be configured and enabled before the
CNVRSEF is set. When configured as a reset, CNVSTR is active-low and level sensitive. After a CNVSTR reset, the
CNVRSEF flag (RSTSRC.6) will read ‘1’ signifying CNVSTR as the reset source; otherwise, this bit reads ‘0’. The
state of the /RST pin is unaffected by this reset.
13.8. Watchdog Timer Reset
The MCU includes a programmable Watchdog Timer (WDT) running off the system clock. A WDT overflow will
force the MCU into the reset state. To prevent the reset, the WDT must be restarted by application software before
overflow. If the system experiences a software/hardware malfunction preventing the software from restarting the
WDT, the WDT will overflow and cause a reset. This should prevent the system from running out of control.
Following a reset the WDT is automatically enabled and running with the default maximum time interval. If desired
the WDT can be disabled by system software or locked on to prevent accidental disabling. Once locked, the WDT
cannot be disabled until the next system reset. The state of the /RST pin is unaffected by this reset.
The WDT consists of a 21-bit timer running from the programmed system clock. The timer measures the period
between specific writes to its control register. If this period exceeds the programmed limit, a WDT reset is generated.
The WDT can be enabled and disabled as needed in software, or can be permanently enabled if desired. Watchdog
features are controlled via the Watchdog Timer Control Register (WDTCN) shown in Figure 13.3.
Rev. 1.4
129
C8051F020/1/2/3
13.8.1. Enable/Reset WDT
The watchdog timer is both enabled and reset by writing 0xA5 to the WDTCN register. The user's application soft-
ware should include periodic writes of 0xA5 to WDTCN as needed to prevent a watchdog timer overflow. The WDT
is enabled and reset as a result of any system reset.
13.8.2. Disable WDT
Writing 0xDE followed by 0xAD to the WDTCN register disables the WDT. The following code segment illustrates
disabling the WDT:
CLR
MOV
MOV
SETB
EA
; disable all interrupts
WDTCN,#0DEh ; disable software watchdog timer
WDTCN,#0ADh
EA
; re-enable interrupts
The writes of 0xDE and 0xAD must occur within 4 clock cycles of each other, or the disable operation is ignored.
Interrupts should be disabled during this procedure to avoid delay between the two writes.
13.8.3. Disable WDT Lockout
Writing 0xFF to WDTCN locks out the disable feature. Once locked out, the disable operation is ignored until the
next system reset. Writing 0xFF does not enable or reset the watchdog timer. Applications always intending to use the
watchdog should write 0xFF to WDTCN in the initialization code.
13.8.4. Setting WDT Interval
WDTCN.[2:0] control the watchdog timeout interval. The interval is given by the following equation:
43 + WDTCN[2 – 0] × Tsysclk ; where T
is the system clock period.
sysclk
For a 2 MHz system clock, this provides an interval range of 0.032 ms to 524 ms. WDTCN.7 must be logic 0 when
setting this interval. Reading WDTCN returns the programmed interval. WDTCN.[2:0] reads 111b after a system
reset.
130
Rev. 1.4
C8051F020/1/2/3
Figure 13.3. WDTCN: Watchdog Timer Control Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
xxxxx111
SFR Address:
0xFF
Bits7-0: WDT Control
Writing 0xA5 both enables and reloads the WDT.
Writing 0xDE followed within 4 system clocks by 0xAD disables the WDT.
Writing 0xFF locks out the disable feature.
Watchdog Status Bit (when Read)
Bit4:
Reading the WDTCN.[4] bit indicates the Watchdog Timer Status.
0: WDT is inactive
1: WDT is active
Bits2-0: Watchdog Timeout Interval Bits
The WDTCN.[2:0] bits set the Watchdog Timeout Interval. When writing these bits, WDTCN.7 must
be set to 0.
Rev. 1.4
131
C8051F020/1/2/3
Figure 13.4. RSTSRC: Reset Source Register
R
-
Bit7
R/W
R/W
R/W
R
R
R/W
R
Reset Value
Variable
SFR Address:
0xEF
CNVRSEF C0RSEF SWRSEF WDTRSF MCDRSF PORSF
PINRSF
Bit0
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
(Note: Do not use read-modify-write operations on this register.)
Bit7:
Bit6:
Reserved.
CNVRSEF: Convert Start Reset Source Enable and Flag
Write: 0: CNVSTR is not a reset source.
1: CNVSTR is a reset source (active low).
Read: 0: Source of prior reset was not CNVSTR.
1: Source of prior reset was CNVSTR.
Bit5:
Bit4:
C0RSEF: Comparator0 Reset Enable and Flag
Write: 0: Comparator0 is not a reset source.
1: Comparator0 is a reset source (active low).
Read: 0: Source of prior reset was not Comparator0.
1: Source of prior reset was Comparator0.
SWRSF: Software Reset Force and Flag
Write: 0: No Effect.
1: Forces an internal reset. /RST pin is not affected.
Read: 0: Prior reset source was not a write to the SWRSF bit.
1: Prior reset source was a write to the SWRSF bit.
WDTRSF: Watchdog Timer Reset Flag
Bit3:
Bit2:
Bit1:
0: Source of prior reset was not WDT timeout.
1: Source of prior reset was WDT timeout.
MCDRSF: Missing Clock Detector Flag
0: Source of prior reset was not Missing Clock Detector timeout.
1: Source of prior reset was Missing Clock Detector timeout.
PORSF: Power-On Reset Force and Flag
Write: 0: No effect.
1: Forces a Power-On Reset. /RST is driven low.
Read: 0: Source of prior reset was not POR.
1: Source of prior reset was POR.
Bit0:
PINRSF: HW Pin Reset Flag
0: Source of prior reset was not /RST pin.
1: Source of prior reset was /RST pin.
132
Rev. 1.4
C8051F020/1/2/3
Table 13.1. Reset Electrical Characteristics
-40°C to +85°C unless otherwise specified.
PARAMETER
CONDITIONS
= -3 mA
MIN
VDD -
0.7
TYP MAX UNITS
I
/RST Output High Voltage
/RST Output Low Voltage
/RST Input High Voltage
V
OH
I
= 8.5 mA, VDD = 2.7 V to 3.6 V
0.6
V
V
OL
0.7 x
VDD
0.3 x
VDD
/RST Input Low Voltage
/RST Input Leakage Current
VDD for /RST Output Valid
AV+ for /RST Output Valid
/RST = 0.0 V
50
µA
V
V
1.0
1.0
2.40
VDD POR Threshold (V
)
2.55
2.70
V
RST
Minimum /RST Low Time to
10
ns
ms
µs
Generate a System Reset
/RST rising edge after VDD crosses
threshold
Reset Time Delay
80
100
220
120
500
V
RST
Time from last system clock to reset
Missing Clock Detector Timeout
100
initiation
Rev. 1.4
133
C8051F020/1/2/3
Notes
134
Rev. 1.4
C8051F020/1/2/3
14. OSCILLATORS
Each MCU includes an internal oscillator and an external oscillator drive circuit, either of which can generate the sys-
tem clock. The MCUs operate from the internal oscillator after any reset. This internal oscillator can be enabled/dis-
abled and its frequency can be set using the Internal Oscillator Control Register (OSCICN) as shown in Figure 14.1.
The internal oscillator's electrical specifications are given in Table 14.1.
Both oscillators are disabled when the /RST pin is held low. The MCUs can run from the internal oscillator perma-
nently, or can switch to the external oscillator if desired using CLKSL bit in the OSCICN Register. The external oscil-
lator requires an external resonator, crystal, capacitor, or RC network connected to the XTAL1/XTAL2 pins (see
Table 14.1). The oscillator circuit must be configured for one of these sources in the OSCXCN register. An external
CMOS clock can also provide the system clock; in this configuration, the XTAL1 pin is used as the CMOS clock
input. The XTAL1 and XTAL2 pins are NOT 5V tolerant.
Figure 14.1. Oscillator Diagram
OSCICN
VDD
EN
Internal Clock
Generator
opt. 2
AV+
SYSCLK
AV+
opt. 1
opt. 4
XTAL1
opt. 3
XTAL1
XTAL1
XTAL1
XTAL2
Input
Circuit
OSC
XTAL2
AGND
OSCXCN
Rev. 1.4
135
C8051F020/1/2/3
Figure 14.2. OSCICN: Internal Oscillator Control Register
R/W
MSCLKE
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
IFRDY
Bit4
R/W
CLKSL
Bit3
R/W
IOSCEN
Bit2
R/W
IFCN1
Bit1
R/W
IFCN0
Bit0
Reset Value
00010100
SFR Address:
0xB2
Bit7:
MSCLKE: Missing Clock Enable Bit
0: Missing Clock Detector Disabled
1: Missing Clock Detector Enabled; reset triggered if clock is missing for more than 100 µs
Bits6-5: UNUSED. Read = 00b, Write = don't care
Bit4:
Bit3:
Bit2:
IFRDY: Internal Oscillator Frequency Ready Flag
0: Internal Oscillator Frequency not running at speed specified by the IFCN bits.
1: Internal Oscillator Frequency running at speed specified by the IFCN bits.
CLKSL: System Clock Source Select Bit
0: Uses Internal Oscillator as System Clock.
1: Uses External Oscillator as System Clock.
IOSCEN: Internal Oscillator Enable Bit
0: Internal Oscillator Disabled
1: Internal Oscillator Enabled
Bits1-0: IFCN1-0: Internal Oscillator Frequency Control Bits
00: Internal Oscillator typical frequency is 2 MHz.
01: Internal Oscillator typical frequency is 4 MHz.
10: Internal Oscillator typical frequency is 8 MHz.
11: Internal Oscillator typical frequency is 16 MHz.
Table 14.1. Internal Oscillator Electrical Characteristics
VDD = 2.7V to 3.6V; T = -40°C to +85°C
a
PARAMETER
CONDITIONS
MIN
TYP MAX UNITS
OSCICN.[1:0] = 00
OSCICN.[1:0] = 01
OSCICN.[1:0] = 10
OSCICN.[1:0] = 11
1.5
2
4
2.4
4.8
3.1
6.2
12.3
Internal Oscillator Frequency
MHz
µA
8
16
9.6
19.2
Internal Oscillator Current
Consumption (from VDD)
OSCICN.2 = 1
200
136
Rev. 1.4
C8051F020/1/2/3
Figure 14.3. OSCXCN: External Oscillator Control Register
R/W
R/W
R/W
R/W
R/W
-
Bit3
R/W
XFCN2
Bit2
R/W
XFCN1
Bit1
R/W
Reset Value
XTLVLD XOSCMD2 XOSCMD1 XOSCMD0
XFCN0 00000000
Bit0
Bit7
Bit6
Bit5
Bit4
SFR Address:
0xB1
Bit7:
XTLVLD: Crystal Oscillator Valid Flag
(Valid only when XOSCMD = 11x.)
0: Crystal Oscillator is unused or not yet stable
1: Crystal Oscillator is running and stable
Bits6-4: XOSCMD2-0: External Oscillator Mode Bits
00x: Off. XTAL1 pin is grounded internally.
010: System Clock from External CMOS Clock on XTAL1 pin.
011: System Clock from External CMOS Clock on XTAL1 pin divided by 2.
10x: RC/C Oscillator Mode with divide by 2 stage.
110: Crystal Oscillator Mode
111: Crystal Oscillator Mode with divide by 2 stage.
RESERVED. Read = undefined, Write = don't care
Bit3:
Bits2-0: XFCN2-0: External Oscillator Frequency Control Bits
000-111:
XFCN
000
001
010
011
Crystal (XOSCMD = 11x)
f < 12 kHz
RC (XOSCMD = 10x)
f < 25 kHz
C (XOSCMD = 10x)
K Factor = 0.44
K Factor = 1.4
K Factor = 4.4
K Factor = 13
12 kHz < f ≤ 30 kHz
30 kHz < f ≤ 95 kHz
95 kHz < f ≤ 270 kHz
270 kHz < f ≤ 720 kHz
720 kHz < f ≤ 2.2 MHz
2.2 MHz < f ≤ 6.7 MHz
f > 6.7 MHz
25 kHz < f ≤ 50 kHz
50 kHz < f ≤ 100 kHz
100 kHz < f ≤ 200 kHz
200 kHz < f ≤ 400 kHz
400 kHz < f ≤ 800 kHz
800 kHz < f ≤ 1.6 MHz
1.6 MHz < f ≤ 3.2 MHz
100
101
110
K Factor = 38
K Factor = 100
K Factor = 420
K Factor = 1400
111
CRYSTAL MODE (Circuit from Figure 14.1, Option 1; XOSCMD = 11x)
Choose XFCN value to match the crystal or ceramic resonator frequency.
RC MODE (Circuit from Figure 14.1, Option 2; XOSCMD = 10x)
Choose oscillation frequency range where:
3
f = 1.23(10 ) / (R * C), where
f = frequency of oscillation in MHz
C = capacitor value in pF
R = Pull-up resistor value in kΩ
C MODE (Circuit from Figure 14.1, Option 3; XOSCMD = 10x)
Choose K Factor (KF) for the oscillation frequency desired:
f = KF / (C * AV+), where
f = frequency of oscillation in MHz
C = capacitor value on XTAL1, XTAL2 pins in pF
AV+ = Analog Power Supply on MCU in volts
Rev. 1.4
137
C8051F020/1/2/3
14.1. External Crystal Example
If a crystal or ceramic resonator is used as an external oscillator source for the MCU, the circuit should be as shown
in Figure 14.1, Option 1. The External Oscillator Frequency Control value (XFCN) should be chosen from the Crys-
tal column of the table in Figure 14.3 (OSCXCN register). For example, an 11.0592 MHz crystal requires an XFCN
setting of 111b.
The Crystal Oscillator Valid Flag (XTLVLD in register OSCXCN) is set to logic 1 by hardware when the external
crystal oscillator is running and stable. The XTLVLD detection circuit requires a startup time of at least 1 ms between
enabling the oscillator and checking the XTLVLD bit. Switching to the external oscillator before the crystal oscillator
has stabilized can result in unpredictable behavior. The recommended procedure is:
Step 1. Enable the external oscillator.
Step 2. Wait at least 1 ms.
Step 3. Poll for XTLVLD => ‘1’.
Step 4. Switch the system clock to the external oscillator.
Important Note: Crystal oscillator circuits are quite sensitive to PCB layout. The crystal should be placed as close as
possible to the XTAL pins on the device, as should the loading capacitors on the crystal pins. The traces should be as
short as possible and shielded with ground plane from any other traces which could introduce noise or interference.
14.2. External RC Example
If an RC network is used as an external oscillator source for the MCU, the circuit should be as shown in Figure 14.1,
Option 2. The capacitor must be no greater than 100 pF; however for small capacitors (less than ~20 pF), the total
capacitance may be dominated by PWB parasitic capacitance. To determine the required External Oscillator Fre-
quency Control value (XFCN) in the OSCXCN Register, first select the RC network value to produce the desired fre-
quency of oscillation. If the frequency desired is 100 kHz, let R = 246 kΩ and C = 50 pF:
3
3
f = 1.23( 10 ) / RC = 1.23 ( 10 ) / [ 246 * 50 ] = 0.1 MHz = 100 kHz
XFCN ≥ log ( f / 25 kHz )
2
XFCN ≥ log ( 100 kHz / 25 kHz ) = log ( 4 )
2
2
XFCN ≥ 2, or code 010b
14.3. External Capacitor Example
If a capacitor is used as an external oscillator for the MCU, the circuit should be as shown in Figure 14.1, Option 3.
The capacitor must be no greater than 100 pF; however for small capacitors (less than ~20 pF), the total capacitance
may be dominated by PWB parasitic capacitance. To determine the required External Oscillator Frequency Control
value (XFCN) in the OSCXCN Register, select the capacitor to be used and find the frequency of oscillation from the
equations below. Assume VDD = 3.0 V and C = 50 pF:
f = KF / ( C * VDD ) = KF / ( 50 * 3 )
f = KF / 150
If a frequency of roughly 90 kHz is desired, select the K Factor from the table in Figure 14.3 as KF = 13:
f = 13 / 150 = 0.087 MHz, or 87 kHz
Therefore, the XFCN value to use in this example is 011b.
138
Rev. 1.4
C8051F020/1/2/3
15. FLASH MEMORY
The C8051F020/1/2/3 family includes 64k + 128 bytes of on-chip, reprogrammable FLASH memory for program
code and non-volatile data storage. The FLASH memory can be programmed in-system, a single byte at a time,
through the JTAG interface or by software. Once cleared to logic 0, a FLASH bit must be erased to set it back to
logic 1. The bytes would typically be erased (set to 0xFF) before being reprogrammed. FLASH write and erase oper-
ations are automatically timed by hardware for proper execution; data polling to determine the end of the write/erase
operation is not required. Refer to Table 15.1 for the electrical characteristics of the FLASH memory.
15.1. Programming The FLASH Memory
The simplest means of programming the FLASH memory is through the JTAG interface using programming tools
provided by Silicon Labs or a third party vendor. This is the only means for programming a non-initialized device.
For details on the JTAG commands to program FLASH memory, see Section “24.2. Flash Programming Com-
mands” on page 268.
The FLASH memory can be programmed by software using a MOVX write instruction, with the address and data
byte to be programmed provided as normal operands. Before writing to FLASH memory using a MOVX write,
FLASH write operations must be enabled by setting the PSWE Program Store Write Enable bit (PSCTL.0) to logic 1.
This directs the MOVX writes to FLASH memory instead of XRAM. The PSWE bit remains set until cleared by soft-
ware. To avoid errant FLASH writes, it is recommended that interrupts be disabled while the PSWE bit is logic 1.
FLASH memory is read using the MOVC read instruction. MOVX reads are always directed to XRAM, regardless of
the state of PSWE.
To ensure the integrity of FLASH contents, it is strongly recommended that the on-chip VDD monitor be
enabled by tying the MONEN pin to VDD in any system which includes code that writes to or erases FLASH
memory from software.
A write to FLASH memory can clear bits but cannot set them; only an erase operation can set bits in FLASH. A byte
location to be programmed must be erased before a new value can be written. The 64k byte FLASH memory is
organized in 512-byte pages. The erase operation applies to an entire page (setting all bytes in the page to 0xFF). The
following steps illustrate the algorithm for programming FLASH by user software.
Step 1. Disable interrupts.
Step 2. Set FLWE (FLSCL.0) to enable FLASH writes/erases via user software.
Step 3. Set PSEE (PSCTL.1) to enable FLASH erases.
Step 4. Set PSWE (PSCTL.0) to redirect MOVX commands to write to FLASH.
Step 5. Use the MOVX command to write a data byte to any location within the 512-byte page to be erased.
Step 6. Clear PSEE to disable FLASH erases
Step 7. Use the MOVX command to write a data byte to the desired byte location within the erased 512-byte
page. Repeat this step until all desired bytes are written (within the target page).
Step 8. Clear the PSWE bit to redirect MOVX commands to the XRAM data space.
Step 9. Re-enable interrupts.
Rev. 1.4
139
C8051F020/1/2/3
Write/Erase timing is automatically controlled by hardware. Note that code execution in the 8051 is stalled while the
FLASH is being programmed or erased. Interrupts that are posted during a FLASH write or erase operation are held
pending until the FLASH operation has completed, at which time they are serviced by the CPU in priority order.
Table 15.1. FLASH Electrical Characteristics
VDD = 2.7V to 3.6V; T = -40°C to +85°C
a
PARAMETER
CONDITIONS
MIN
20k
10
TYP
100k
12
MAX
UNITS
Erase/Write
ms
Endurance
Erase Cycle Time
Write Cycle Time
14
60
40
50
µs
15.2. Non-volatile Data Storage
The FLASH memory can be used for non-volatile data storage as well as program code. This allows data such as cal-
ibration coefficients to be calculated and stored at run time. Data is written using the MOVX write instruction (as
described in the previous section) and read using the MOVC read instruction.
An additional 128-byte sector of FLASH memory is included for non-volatile data storage. Its smaller sector size
makes it particularly well suited as general purpose, non-volatile scratchpad memory. Even though FLASH memory
can be written a single byte at a time, an entire sector must be erased first. In order to change a single byte of a multi-
byte data set, the data must be moved to temporary storage. The 128-byte sector-size facilitates updating data without
wasting program memory or RAM space. The 128-byte sector is double-mapped over the 64k byte FLASH memory;
its address ranges from 0x00 to 0x7F (see Figure 15.1). To access this 128-byte sector, the SFLE bit in PSCTL must
be set to logic 1. Code execution from this 128-byte scratchpad sector is not permitted.
15.3. Security Options
The CIP-51 provides security options to protect the FLASH memory from inadvertent modification by software as
well as prevent the viewing of proprietary program code and constants. The Program Store Write Enable (PSCTL.0)
and the Program Store Erase Enable (PSCTL.1) bits protect the FLASH memory from accidental modification by
software. These bits must be explicitly set to logic 1 before software can modify the FLASH memory. Additional
security features prevent proprietary program code and data constants from being read or altered across the JTAG
interface or by software running on the system controller.
A set of security lock bytes stored at 0xFDFE and 0xFDFF protect the FLASH program memory from being read or
altered across the JTAG interface. Each bit in a security lock-byte protects one 8k-byte block of memory. Clearing a
bit to logic 0 in a Read Lock Byte prevents the corresponding block of FLASH memory from being read across the
JTAG interface. Clearing a bit in the Write/Erase Lock Byte protects the block from JTAG erasures and/or writes. The
128-byte scratchpad sector is locked only when all other sectors are locked.
The Read Lock Byte is at location 0xFDFF. The Write/Erase Lock Byte is located at 0xFDFE. Figure 15.1 shows the
location and bit definitions of the security bytes. The 512-byte sector containing the lock bytes can be written to, but
not erased by software. An attempted read of a read-locked byte returns undefined data. Debugging code in a read-
locked sector is not possible through the JTAG port.
140
Rev. 1.4
C8051F020/1/2/3
Figure 15.1. FLASH Program Memory Map and Security Bytes
Read and Write/Erase Security Bits.
(Bit 7 is MSB.)
SFLE = 0
SFLE = 1
0x007F
0x0000
0xFFFF
Bit Memory Block
Scratchpad Memory
(Data only)
Reserved
7
6
5
4
3
2
1
0
0xE000 - 0xFDFD
0xC000 - 0xDFFF
0xA000 - 0xBFFF
0x8000 - 0x9FFF
0x6000 - 0x7FFF
0x4000 - 0x5FFF
0x2000 - 0x3FFF
0x0000 - 0x1FFF
0xFE00
0xFDFF
Read Lock Byte
0xFDFE
0xFDFD
Write/Erase Lock Byte
Program/Data
Memory Space
Software Read Limit
0x0000
FLASH Read Lock Byte
Bits7-0: Each bit locks a corresponding block of memory. (Bit7 is MSB).
0: Read operations are locked (disabled) for corresponding block across the JTAG interface.
1: Read operations are unlocked (enabled) for corresponding block across the JTAG interface.
FLASH Write/Erase Lock Byte
Bits7-0: Each bit locks a corresponding block of memory.
0: Write/Erase operations are locked (disabled) for corresponding block across the JTAG interface.
1: Write/Erase operations are unlocked (enabled) for corresponding block across the JTAG interface.
NOTE: When the highest block is locked, the security bytes may be written but not erased.
FLASH access Limit Register (FLACL)
The content of this register is used as the high byte of the 16-bit software read limit address. This 16-
bit read limit address value is calculated as 0xNN00 where NN is replaced by content of this register
on reset. Software running at or above this address is prohibited from using the MOVX and MOVC
instructions to read, write, or erase FLASH locations below this address. Any attempts to read loca-
tions below this limit will return the value 0x00.
The lock bits can always be read and cleared to logic 0 regardless of the security setting applied to the block contain-
ing the security bytes. This allows additional blocks to be protected after the block containing the security bytes has
been locked. Important Note: The only means of removing a lock once set is to erase the entire program mem-
ory space by performing a JTAG erase operation (i.e. cannot be done in user firmware). Addressing either
security byte while performing a JTAG erase operation will automatically initiate erasure of the entire pro-
gram memory space (except for the reserved area). This erasure can only be performed via JTAG. If a non-
security byte in the 0xFBFF-0xFDFF page is addressed during the JTAG erasure, only that page (including the
security bytes) will be erased.
The FLASH Access Limit security feature (see Figure 15.1) protects proprietary program code and data from being
read by software running on the C8051F020/1/2/3. This feature provides support for OEMs that wish to program the
Rev. 1.4
141
C8051F020/1/2/3
MCU with proprietary value-added firmware before distribution. The value-added firmware can be protected while
allowing additional code to be programmed in remaining program memory space later.
The Software Read Limit (SRL) is a 16-bit address that establishes two logical partitions in the program memory
space. The first is an upper partition consisting of all the program memory locations at or above the SRL address, and
the second is a lower partition consisting of all the program memory locations starting at 0x0000 up to (but exclud-
ing) the SRL address. Software in the upper partition can execute code in the lower partition, but is prohibited from
reading locations in the lower partition using the MOVC instruction. (Executing a MOVC instruction from the upper
partition with a source address in the lower partition will always return a data value of 0x00.) Software running in the
lower partition can access locations in both the upper and lower partition without restriction.
The Value-added firmware should be placed in the lower partition. On reset, control is passed to the value-added
firmware via the reset vector. Once the value-added firmware completes its initial execution, it branches to a predeter-
mined location in the upper partition. If entry points are published, software running in the upper partition may exe-
cute program code in the lower partition, but it cannot read the contents of the lower partition. Parameters may be
passed to the program code running in the lower partition either through the typical method of placing them on the
stack or in registers before the call or by placing them in prescribed memory locations in the upper partition.
The SRL address is specified using the contents of the FLASH Access Register. The 16-bit SRL address is calculated
as 0xNN00, where NN is the contents of the SRL Security Register. Thus, the SRL can be located on 256-byte bound-
aries anywhere in program memory space. However, the 512-byte erase sector size essentially requires that a 512
boundary be used. The contents of a non-initialized SRL security byte is 0x00, thereby setting the SRL address to
0x0000 and allowing read access to all locations in program memory space by default.
Figure 15.2. FLACL: FLASH Access Limit
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xB7
Bits 7-0: FLACL: FLASH Access Limit.
This register holds the high byte of the 16-bit program memory read/write/erase limit address. The
entire 16-bit access limit address value is calculated as 0xNN00 where NN is replaced by contents of
FLACL. A write to this register sets the FLASH Access Limit. This register can only be written once
after any reset. Any subsequent writes are ignored until the next reset.
142
Rev. 1.4
C8051F020/1/2/3
Figure 15.3. FLSCL: FLASH Memory Control
R/W
FOSE
Bit7
R/W
FRAE
Bit6
R/W
R/W
R/W
R/W
R/W
R/W
FLWE
Bit0
Reset Value
10000000
SFR Address:
0xB6
Reserved Reserved Reserved Reserved Reserved
Bit5
Bit4
Bit3
Bit2
Bit1
Bit7:
FOSE: FLASH One-Shot Timer Enable
This is the timer that turns off the sense amps after a FLASH read.
0: FLASH One-Shot Timer disabled.
1: FLASH One-Shot Timer enabled.
Bit6:
FRAE: FLASH Read Always Enable
0: FLASH reads per One-Shot Timer.
1: FLASH always in read mode.
Bits5-1: RESERVED. Read = 00000b. Must Write 00000b.
Bit0:
FLWE: FLASH Read/Write Enable
This bit must be set to allow FLASH writes from user software.
0: FLASH writes disabled.
1: FLASH writes enabled.
Rev. 1.4
143
C8051F020/1/2/3
Figure 15.4. PSCTL: Program Store Read/Write Control
R/W
-
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
-
Bit4
R/W
-
Bit3
R/W
SFLE
Bit2
R/W
PSEE
Bit1
R/W
PSWE
Bit0
Reset Value
00000000
SFR Address:
0x8F
Bits7-3: UNUSED. Read = 00000b, Write = don't care.
Bit2:
Bit1:
SFLE: Scratchpad FLASH Memory Access Enable.
When this bit is set, FLASH reads and writes from user software are directed to the 128-byte Scratch-
pad FLASH sector. When SFLE is set to logic 1, FLASH accesses out of the address range 0x00-
0x7F should not be attempted. Reads/Writes out of this range will yield unpredictable results.
0: FLASH access from user software directed to the 64k byte Program/Data FLASH sector.
1: FLASH access from user software directed to the 128 byte Scratchpad sector.
PSEE: Program Store Erase Enable.
Setting this bit allows an entire page of the FLASH program memory to be erased provided the
PSWE bit is also set. After setting this bit, a write to FLASH memory using the MOVX instruction
will erase the entire page that contains the location addressed by the MOVX instruction. The value of
the data byte written does not matter.
0: FLASH program memory erasure disabled.
1: FLASH program memory erasure enabled.
Bit0:
PSWE: Program Store Write Enable.
Setting this bit allows writing a byte of data to the FLASH program memory using the MOVX
instruction. The location must be erased before writing data.
0: Write to FLASH program memory disabled.
1: Write to FLASH program memory enabled.
144
Rev. 1.4
C8051F020/1/2/3
16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP XRAM
The C8051F020/1/2/3 MCUs include 4k bytes of on-chip RAM mapped into the external data memory space
(XRAM), as well as an External Data Memory Interface which can be used to access off-chip memories and memory-
mapped devices connected to the GPIO ports. The external memory space may be accessed using the external move
instruction (MOVX) and the data pointer (DPTR), or using the MOVX indirect addressing mode using R0 or R1. If
the MOVX instruction is used with an 8-bit address operand (such as @R1), then the high byte of the 16-bit address
is provided by the External Memory Interface Control Register (EMI0CN, shown in Figure 16.1). Note: the MOVX
instruction can also be used for writing to the FLASH memory. See Section “15. FLASH MEMORY” on page 139
for details. The MOVX instruction accesses XRAM by default. The EMIF can be configured to appear on the lower
I/O ports (P0-P3) or the upper I/O ports (P4-P7).
16.1. Accessing XRAM
The XRAM memory space is accessed using the MOVX instruction. The MOVX instruction has two forms, both of
which use an indirect addressing method. The first method uses the Data Pointer, DPTR, a 16-bit register which con-
tains the effective address of the XRAM location to be read or written. The second method uses R0 or R1 in combina-
tion with the EMI0CN register to generate the effective XRAM address. Examples of both of these methods are given
below.
16.1.1. 16-Bit MOVX Example
The 16-bit form of the MOVX instruction accesses the memory location pointed to by the contents of the DPTR reg-
ister. The following series of instructions reads the value of the byte at address 0x1234 into the accumulator A:
MOV
MOVX
DPTR, #1234h
A, @DPTR
; load DPTR with 16-bit address to read (0x1234)
; load contents of 0x1234 into accumulator A
The above example uses the 16-bit immediate MOV instruction to set the contents of DPTR. Alternately, the DPTR
can be accessed through the SFR registers DPH, which contains the upper 8-bits of DPTR, and DPL, which contains
the lower 8-bits of DPTR.
16.1.2. 8-Bit MOVX Example
The 8-bit form of the MOVX instruction uses the contents of the EMI0CN SFR to determine the upper 8-bits of the
effective address to be accessed and the contents of R0 or R1 to determine the lower 8-bits of the effective address to
be accessed. The following series of instructions read the contents of the byte at address 0x1234 into the accumulator
A.
MOV
MOV
MOVX
EMI0CN, #12h
R0, #34h
a, @R0
; load high byte of address into EMI0CN
; load low byte of address into R0 (or R1)
; load contents of 0x1234 into accumulator A
Rev. 1.4
145
C8051F020/1/2/3
16.2. Configuring the External Memory Interface
Configuring the External Memory Interface consists of four steps:
1. Select EMIF on Low Ports (P3, P2, P1, and P0) or High Ports (P7, P6, P5, and P4).
2. Select Multiplexed mode or Non-multiplexed mode.
3. Select the memory mode (on-chip only, split mode without bank select, split mode with bank select, or
off-chip only).
4. Set up timing to interface with off-chip memory or peripherals.
5. Select the desired output mode for the associated Ports (registers PnMDOUT, P74OUT).
Each of these four steps is explained in detail in the following sections. The Port selection, Multiplexed mode selec-
tion, and Mode bits are located in the EMI0CF register shown in Figure 16.2.
16.3. Port Selection and Configuration
The External Memory Interface can appear on Ports 3, 2, 1, and 0 (C8051F020/1/2/3 devices) or on Ports 7, 6, 5, and
4 (C8051F020/2 devices only), depending on the state of the PRTSEL bit (EMI0CF.5). If the lower Ports are selected,
the EMIFLE bit (XBR2.1) must be set to a ‘1’ so that the Crossbar will skip over P0.7 (/WR), P0.6 (/RD), and if mul-
tiplexed mode is selected P0.5 (ALE). For more information about the configuring the Crossbar, see Section
“17. PORT INPUT/OUTPUT” on page 161.
The External Memory Interface claims the associated Port pins for memory operations ONLY during the execution of
an off-chip MOVX instruction. Once the MOVX instruction has completed, control of the Port pins reverts to the Port
latches or to the Crossbar (on Ports 3, 2, 1, and 0). See Section “17. PORT INPUT/OUTPUT” on page 161 for
more information about the Crossbar and Port operation and configuration. The Port latches should be explicitly
configured to ‘park’ the External Memory Interface pins in a dormant state, most commonly by setting them
to a logic 1.
During the execution of the MOVX instruction, the External Memory Interface will explicitly disable the drivers on
all Port pins that are acting as Inputs (Data[7:0] during a READ operation, for example). The Output mode of the Port
pins (whether the pin is configured as Open-Drain or Push-Pull) is unaffected by the External Memory Interface oper-
ation, and remains controlled by the PnMDOUT registers. See Section “17. PORT INPUT/OUTPUT” on page 161
for more information about Port output mode configuration.
146
Rev. 1.4
C8051F020/1/2/3
Figure 16.1. EMI0CN: External Memory Interface Control
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
PGSEL7 PGSEL6 PGSEL5 PGSEL4 PGSEL3 PGSEL2 PGSEL1 PGSEL0 00000000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xAF
Bits7-0: PGSEL[7:0]: XRAM Page Select Bits.
The XRAM Page Select Bits provide the high byte of the 16-bit external data memory address when
using an 8-bit MOVX command, effectively selecting a 256-byte page of RAM.
0x00: 0x0000 to 0x00FF
0x01: 0x0100 to 0x01FF
...
0xFE: 0xFE00 to 0xFEFF
0xFF: 0xFF00 to 0xFFFF
Figure 16.2. EMI0CF: External Memory Configuration
R/W
-
Bit7
R/W
-
Bit6
R/W
PRTSEL
Bit5
R/W
EMD2
Bit4
R/W
EMD1
Bit3
R/W
EMD0
Bit2
R/W
EALE1
Bit1
R/W
Reset Value
EALE0 00000011
Bit0
SFR Address:
0xA3
Bits7-6: Unused. Read = 00b. Write = don’t care.
Bit5:
PRTSEL: EMIF Port Select.
0: EMIF active on P0-P3.
1: EMIF active on P4-P7.
Bit4:
EMD2: EMIF Multiplex Mode Select.
0: EMIF operates in multiplexed address/data mode.
1: EMIF operates in non-multiplexed mode (separate address and data pins).
Bits3-2: EMD1-0: EMIF Operating Mode Select.
These bits control the operating mode of the External Memory Interface.
00: Internal Only: MOVX accesses on-chip XRAM only. All effective addresses alias to on-chip
memory space.
01: Split Mode without Bank Select: Accesses below the 4k boundary are directed on-chip. Accesses
above the 4k boundary are directed off-chip. 8-bit off-chip MOVX operations use the current contents
of the Address High port latches to resolve upper address byte. Note that in order to access off-chip
space, EMI0CN must be set to a page that is not contained in the on-chip address space.
10: Split Mode with Bank Select: Accesses below the 4k boundary are directed on-chip. Accesses
above the 4k boundary are directed off-chip. 8-bit off-chip MOVX operations use the contents of
EMI0CN to determine the high-byte of the address.
11: External Only: MOVX accesses off-chip XRAM only. On-chip XRAM is not visible to the CPU.
Bits1-0: EALE1-0: ALE Pulse-Width Select Bits (only has effect when EMD2 = 0).
00: ALE high and ALE low pulse width = 1 SYSCLK cycle.
01: ALE high and ALE low pulse width = 2 SYSCLK cycles.
10: ALE high and ALE low pulse width = 3 SYSCLK cycles.
11: ALE high and ALE low pulse width = 4 SYSCLK cycles.
Rev. 1.4
147
C8051F020/1/2/3
16.4. Multiplexed and Non-multiplexed Selection
The External Memory Interface is capable of acting in a Multiplexed mode or a Non-multiplexed mode, depending
on the state of the EMD2 (EMI0CF.4) bit.
16.4.1. Multiplexed Configuration
In Multiplexed mode, the Data Bus and the lower 8-bits of the Address Bus share the same Port pins: AD[7:0]. In this
mode, an external latch (74HC373 or equivalent logic gate) is used to hold the lower 8-bits of the RAM address. The
external latch is controlled by the ALE (Address Latch Enable) signal, which is driven by the External Memory Inter-
face logic. An example of a Multiplexed Configuration is shown in Figure 16.3.
In Multiplexed mode, the external MOVX operation can be broken into two phases delineated by the state of the ALE
signal. During the first phase, ALE is high and the lower 8-bits of the Address Bus are presented to AD[7:0]. During
this phase, the address latch is configured such that the ‘Q’ outputs reflect the states of the ‘D’ inputs. When ALE
falls, signaling the beginning of the second phase, the address latch outputs remain fixed and are no longer dependent
on the latch inputs. Later in the second phase, the Data Bus controls the state of the AD[7:0] port at the time /RD or
/WR is asserted.
See Section “16.6.2. Multiplexed Mode” on page 156 for more information.
Figure 16.3. Multiplexed Configuration Example
A[15:8]
ADDRESS BUS
74HC373
A[15:8]
A[7:0]
ALE
G
E
M
I
AD[7:0]
ADDRESS/DATA BUS
VDD
D
Q
64K X 8
SRAM
8
I/O[7:0]
F
CE
WE
OE
/WR
/RD
148
Rev. 1.4
C8051F020/1/2/3
16.4.2. Non-multiplexed Configuration
In Non-multiplexed mode, the Data Bus and the Address Bus pins are not shared. An example of a Non-multiplexed
Configuration is shown in Figure 16.4. See Section “16.6.1. Non-multiplexed Mode” on page 153 for more infor-
mation about Non-multiplexed operation.
Figure 16.4. Non-multiplexed Configuration Example
A[15:0]
ADDRESS BUS
DATA BUS
A[15:0]
E
M
I
VDD
8
64K X 8
SRAM
I/O[7:0]
D[7:0]
CE
WE
OE
F
/WR
/RD
Rev. 1.4
149
C8051F020/1/2/3
16.5. Memory Mode Selection
The external data memory space can be configured in one of four modes, shown in Figure 16.5, based on the EMIF
Mode bits in the EMI0CF register (Figure 16.2). These modes are summarized below. More information about the
different modes can be found in Section “ .” on page 152.
16.5.1. Internal XRAM Only
When EMI0CF.[3:2] are set to ‘00’, all MOVX instructions will target the internal XRAM space on the device. Mem-
ory accesses to addresses beyond the populated space will wrap on 4k boundaries. As an example, the addresses
0x1000 and 0x2000 both evaluate to address 0x0000 in on-chip XRAM space.
•
•
8-bit MOVX operations use the contents of EMI0CN to determine the high-byte of the effective address and R0
or R1 to determine the low-byte of the effective address.
16-bit MOVX operations use the contents of the 16-bit DPTR to determine the effective address.
16.5.2. Split Mode without Bank Select
When EMI0CF.[3:2] are set to ‘01’, the XRAM memory map is split into two areas, on-chip space and off-chip space.
•
•
•
Effective addresses below the 4k boundary will access on-chip XRAM space.
Effective addresses beyond the 4k boundary will access off-chip space.
8-bit MOVX operations use the contents of EMI0CN to determine whether the memory access is on-chip or off-
chip. The lower 8-bits of the Address Bus A[7:0] are driven as defined by R0 or R1. However, in the “No Bank
Select” mode, an 8-bit MOVX operation will not drive the upper 8-bits A[15:8] of the Address Bus during an
off-chip access. This allows the user to manipulate the upper address bits at will by setting the Port state directly.
This behavior is in contrast with “Split Mode with Bank Select” described below.
16-bit MOVX operations use the contents of DPTR to determine whether the memory access is on-chip or off-
chip, and unlike 8-bit MOVX operations, the full 16-bits of the Address Bus A[15:0] are driven during the off-
chip transaction.
•
Figure 16.5. EMIF Operating Modes
EMI0CF[3:2] = 00
EMI0CF[3:2] = 01
EMI0CF[3:2] = 10
EMI0CF[3:2] = 11
0xFFFF
0xFFFF
0xFFFF
0xFFFF
On-Chip XRAM
On-Chip XRAM
On-Chip XRAM
On-Chip XRAM
On-Chip XRAM
On-Chip XRAM
Off-Chip
Memory
Off-Chip
Memory
(No Bank Select)
(Bank Select)
Off-Chip
Memory
On-Chip XRAM
On-Chip XRAM
0x0000
0x0000
0x0000
0x0000
150
Rev. 1.4
C8051F020/1/2/3
16.5.3. Split Mode with Bank Select
When EMI0CF.[3:2] are set to ‘10’, the XRAM memory map is split into two areas, on-chip space and off-chip space.
•
•
•
Effective addresses below the 4k boundary will access on-chip XRAM space.
Effective addresses beyond the 4k boundary will access off-chip space.
8-bit MOVX operations use the contents of EMI0CN to determine whether the memory access is on-chip or off-
chip. The upper 8-bits of the Address Bus A[15:8] are determined by EMI0CN, and the lower 8-bits of the
Address Bus A[7:0] are determined by R0 or R1. All 16-bits of the Address Bus A[15:0] are driven in “Bank
Select” mode.
16-bit MOVX operations use the contents of DPTR to determine whether the memory access is on-chip or off-
chip, and the full 16-bits of the Address Bus A[15:0] are driven during the off-chip transaction.
•
16.5.4. External Only
When EMI0CF[3:2] are set to ‘11’, all MOVX operations are directed to off-chip space. On-chip XRAM is not visi-
ble to the CPU. This mode is useful for accessing off-chip memory located between 0x0000 and the 4k boundary.
•
8-bit MOVX operations ignore the contents of EMI0CN. The upper Address bits A[15:8] are not driven (identi-
cal behavior to an off-chip access in “Split Mode without Bank Select” described above). This allows the user to
manipulate the upper address bits at will by setting the Port state directly. The lower 8-bits of the effective
address A[7:0] are determined by the contents of R0 or R1.
16-bit MOVX operations use the contents of DPTR to determine the effective address A[15:0]. The full 16-bits
of the Address Bus A[15:0] are driven during the off-chip transaction.
•
16.6. Timing
The timing parameters of the External Memory Interface can be configured to enable connection to devices having
different setup and hold time requirements. The Address Setup time, Address Hold time, /RD and /WR strobe widths,
and in multiplexed mode, the width of the ALE pulse are all programmable in units of SYSCLK periods through
EMI0TC, shown in Figure 16.6, and EMI0CF[1:0].
The timing for an off-chip MOVX instruction can be calculated by adding 4 SYSCLK cycles to the timing parameters
defined by the EMI0TC register. Assuming non-multiplexed operation, the minimum execution time for an off-chip
XRAM operation is 5 SYSCLK cycles (1 SYSCLK for /RD or /WR pulse + 4 SYSCLKs). For multiplexed opera-
tions, the Address Latch Enable signal will require a minimum of 2 additional SYSCLK cycles. Therefore, the mini-
mum execution time of an off-chip XRAM operation in multiplexed mode is 7 SYSCLK cycles (2 SYSCLKs for
/ALE, 1 for /RD or /WR + 4 SYSCLKs). The programmable setup and hold times default to the maximum delay set-
tings after a reset.
Table 16.1 lists the AC parameters for the External Memory Interface, and Figure 16.7 through Figure 16.11 show the
timing diagrams for the different External Memory Interface modes and MOVX operations
Rev. 1.4
151
C8051F020/1/2/3
.
Figure 16.6. EMI0TC: External Memory Timing Control
R/W
EAS1
Bit7
R/W
EAS0
Bit6
R/W
EWR3
Bit5
R/W
EWR2
Bit4
R/W
EWR1
Bit3
R/W
EWR0
Bit2
R/W
EAH1
Bit1
R/W
EAH0
Bit0
Reset Value
11111111
SFR Address:
0xA1
Bits7-6: EAS1-0: EMIF Address Setup Time Bits.
00: Address setup time = 0 SYSCLK cycles.
01: Address setup time = 1 SYSCLK cycle.
10: Address setup time = 2 SYSCLK cycles.
11: Address setup time = 3 SYSCLK cycles.
Bits5-2: EWR3-0: EMIF /WR and /RD Pulse-Width Control Bits.
0000: /WR and /RD pulse width = 1 SYSCLK cycle.
0001: /WR and /RD pulse width = 2 SYSCLK cycles.
0010: /WR and /RD pulse width = 3 SYSCLK cycles.
0011: /WR and /RD pulse width = 4 SYSCLK cycles.
0100: /WR and /RD pulse width = 5 SYSCLK cycles.
0101: /WR and /RD pulse width = 6 SYSCLK cycles.
0110: /WR and /RD pulse width = 7 SYSCLK cycles.
0111: /WR and /RD pulse width = 8 SYSCLK cycles.
1000: /WR and /RD pulse width = 9 SYSCLK cycles.
1001: /WR and /RD pulse width = 10 SYSCLK cycles.
1010: /WR and /RD pulse width = 11 SYSCLK cycles.
1011: /WR and /RD pulse width = 12 SYSCLK cycles.
1100: /WR and /RD pulse width = 13 SYSCLK cycles.
1101: /WR and /RD pulse width = 14 SYSCLK cycles.
1110: /WR and /RD pulse width = 15 SYSCLK cycles.
1111: /WR and /RD pulse width = 16 SYSCLK cycles.
Bits1-0: EAH1-0: EMIF Address Hold Time Bits.
00: Address hold time = 0 SYSCLK cycles.
01: Address hold time = 1 SYSCLK cycle.
10: Address hold time = 2 SYSCLK cycles.
11: Address hold time = 3 SYSCLK cycles.
152
Rev. 1.4
C8051F020/1/2/3
16.6.1. Non-multiplexed Mode
16.6.1.1.16-bit MOVX: EMI0CF[4:2] = ‘101’, ‘110’, or ‘111’.
Figure 16.7. Non-multiplexed 16-bit MOVX Timing
Nonmuxed 16-bit WRITE
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
P1/P5
P2/P6
P3/P7
EMIF ADDRESS (8 MSBs) from DPH
P1/P5
P2/P6
P3/P7
EMIF ADDRESS (8 LSBs) from DPL
EMIF WRITE DATA
T
T
WDS
WDH
T
T
T
ACS
ACW
ACH
/WR
/RD
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
Nonmuxed 16-bit READ
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
P1/P5
P2/P6
P3/P7
EMIF ADDRESS (8 MSBs) from DPH
EMIF ADDRESS (8 LSBs) from DPL
EMIF READ DATA
P1/P5
P2/P6
P3/P7
T
T
RDS
ACW
RDH
T
T
T
ACS
ACH
/RD
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
/WR
Rev. 1.4
153
C8051F020/1/2/3
16.6.1.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘101’ or ‘111’.
Figure 16.8. Non-multiplexed 8-bit MOVX without Bank Select Timing
Nonmuxed 8-bit WRITE without Bank Select
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
P1/P5
P2/P6
P3/P7
EMIF ADDRESS (8 LSBs) from R0 or R1
EMIF WRITE DATA
P2/P6
P3/P7
T
T
WDS
WDH
T
T
T
ACS
ACW
ACH
/WR
/RD
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
Nonmuxed 8-bit READ without Bank Select
P1/P5
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
P2/P6
P3/P7
EMIF ADDRESS (8 LSBs) from R0 or R1
EMIF READ DATA
P2/P6
P3/P7
T
T
RDS
ACW
RDH
T
T
T
ACS
ACH
/RD
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
/WR
154
Rev. 1.4
C8051F020/1/2/3
16.6.1.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘110’.
Figure 16.9. Non-multiplexed 8-bit MOVX with Bank Select Timing
Nonmuxed 8-bit WRITE with Bank Select
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
P1/P5
P2/P6
P3/P7
EMIF ADDRESS (8 MSBs) from EMI0CN
EMIF ADDRESS (8 LSBs) from R0 or R1
EMIF WRITE DATA
P1/P5
P2/P6
P3/P7
T
T
WDS
WDH
T
T
T
ACS
ACW
ACH
/WR
/RD
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
Nonmuxed 8-bit READ with Bank Select
EMIF ADDRESS (8 MSBs) from EMI0CN
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
P1/P5
P2/P6
P3/P7
P1/P5
P2/P6
P3/P7
EMIF ADDRESS (8 LSBs) from R0 or R1
EMIF READ DATA
T
T
RDS
ACW
RDH
T
T
T
ACS
ACH
/RD
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
/WR
Rev. 1.4
155
C8051F020/1/2/3
16.6.2. Multiplexed Mode
16.6.2.1.16-bit MOVX: EMI0CF[4:2] = ‘001’, ‘010’, or ‘011’.
Figure 16.10. Multiplexed 16-bit MOVX Timing
Muxed 16-bit WRITE
ADDR[15:8]
AD[7:0]
P2/P6
P3/P7
EMIF ADDRESS (8 MSBs) from DPH
P2/P6
P3/P7
EMIF ADDRESS (8 LSBs) from
DPL
EMIF WRITE DATA
T
T
ALEL
ALEH
ALE
P0.5/P4.5
P0.5/P4.5
T
T
WDH
WDS
T
T
T
ACS
ACW
ACH
/WR
/RD
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
Muxed 16-bit READ
EMIF ADDRESS (8 MSBs) from DPH
ADDR[15:8]
AD[7:0]
P2/P6
P3/P7
P2/P6
P3/P7
EMIF ADDRESS (8 LSBs) from
DPL
EMIF READ DATA
T
T
ALEL
ALEH
T
T
RDH
RDS
ALE
P0.5/P4.5
P0.5/P4.5
T
T
T
ACH
ACS
ACW
/RD
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
/WR
156
Rev. 1.4
C8051F020/1/2/3
16.6.2.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘001’ or ‘011’.
Figure 16.11. Multiplexed 8-bit MOVX without Bank Select Timing
Muxed 8-bit WRITE Without Bank Select
ADDR[15:8]
AD[7:0]
P2/P6
EMIF ADDRESS (8 LSBs) from
P3/P7
EMIF WRITE DATA
P3/P7
R0 or R1
T
T
ALEL
ALEH
ALE
P0.5/P4.5
P0.5/P4.5
T
T
WDH
WDS
T
T
T
ACS
ACW
ACH
/WR
/RD
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
Muxed 8-bit READ Without Bank Select
P2/P6
ADDR[15:8]
AD[7:0]
EMIF ADDRESS (8 LSBs) from
R0 or R1
P3/P7
EMIF READ DATA
P3/P7
T
T
ALEL
ALEH
T
T
RDH
RDS
ALE
P0.5/P4.5
P0.5/P4.5
T
T
T
ACH
ACS
ACW
/RD
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
/WR
Rev. 1.4
157
C8051F020/1/2/3
16.6.2.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘010’.
Figure 16.12. Multiplexed 8-bit MOVX with Bank Select Timing
Muxed 8-bit WRITE with Bank Select
ADDR[15:8]
AD[7:0]
P2/P6
P3/P7
EMIF ADDRESS (8 MSBs) from EMI0CN
P2/P6
P3/P7
EMIF ADDRESS (8 LSBs) from
R0 or R1
EMIF WRITE DATA
T
T
ALEL
ALEH
ALE
P0.5/P4.5
P0.5/P4.5
T
T
WDH
WDS
T
T
T
ACS
ACW
ACH
/WR
/RD
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
Muxed 8-bit READ with Bank Select
EMIF ADDRESS (8 MSBs) from EMI0CN
ADDR[15:8]
AD[7:0]
P2/P6
P3/P7
P2/P6
P3/P7
EMIF ADDRESS (8 LSBs) from
R0 or R1
EMIF READ DATA
T
T
ALEL
ALEH
T
T
RDH
RDS
ALE
P0.5/P4.5
P0.5/P4.5
T
T
T
ACH
ACS
ACW
/RD
P0.6/P4.6
P0.7/P4.7
P0.6/P4.6
P0.7/P4.7
/WR
158
Rev. 1.4
C8051F020/1/2/3
Table 16.1. AC Parameters for External Memory Interface
PARAMETER
DESCRIPTION
System Clock Period
MIN
40
MAX
UNITS
T
ns
SYSCLK
T
Address / Control Setup Time
Address / Control Pulse Width
Address / Control Hold Time
Address Latch Enable High Time
Address Latch Enable Low Time
Write Data Setup Time
0
3*T
ns
ns
ns
ns
ns
ns
ns
ns
ns
ACS
SYSCLK
T
1*T
16*T
ACW
SYSCLK
SYSCLK
SYSCLK
SYSCLK
SYSCLK
T
0
3*T
4*T
4*T
ACH
T
1*T
1*T
1*T
ALEH
SYSCLK
SYSCLK
T
ALEL
T
19*T
WDS
WDH
RDS
SYSCLK
SYSCLK
3*T
SYSCLK
T
T
T
Write Data Hold Time
0
Read Data Setup Time
20
0
Read Data Hold Time
RDH
Rev. 1.4
159
C8051F020/1/2/3
Notes
160
Rev. 1.4
C8051F020/1/2/3
17. PORT INPUT/OUTPUT
The C8051F020/1/2/3 are fully integrated mixed-signal System on a Chip MCUs with 64 digital I/O pins
(C8051F020/2) or 32 digital I/O pins (C8051F021/3), organized as 8-bit Ports. The lower ports: P0, P1, P2, and P3,
are both bit- and byte-addressable through their corresponding Port Data registers. The upper ports: P4, P5, P6, and
P7 are byte-addressable. All Port pins are 5 V-tolerant, and all support configurable Open-Drain or Push-Pull output
modes and weak pull-ups. A block diagram of the Port I/O cell is shown in Figure 17.1. Complete Electrical Specifi-
cations for the Port I/O pins are given in Table 16.1.
Figure 17.1. Port I/O Cell Block Diagram
/WEAK-PULLUP
VDD
VDD
PUSH-PULL
/PORT-OUTENABLE
(WEAK)
PORT
PAD
PORT-OUTPUT
DGND
Analog Select
(Port 1 Only)
ANALOG INPUT
PORT-INPUT
Table 17.1. Port I/O DC Electrical Characteristics
VDD = 2.7 V to 3.6 V, -40°C to +85°C unless otherwise specified.
PARAMETER CONDITIONS
MIN
TYP
MAX UNITS
Output High Voltage (V ) I = -10 µA, Port I/O Push-Pull
VDD - 0.1
VDD - 0.7
OH
OH
OH
OH
V
I
I
= -3 mA, Port I/O Push-Pull
= -10 mA, Port I/O Push-Pull
VDD - 0.8
1.0
Output Low Voltage (V ) I = 10 µA
0.1
0.6
OL
OL
OL
OL
V
I
I
= 8.5 mA
= 25 mA
Input High Voltage (VIH)
Input Low Voltage (VIL)
0.7 x VDD
V
V
0.3 x
VDD
Input Leakage Current
Input Capacitance
DGND < Port Pin < VDD, Pin Tri-state
Weak Pull-up Off
Weak Pull-up On
µA
± 1
10
5
pF
Rev. 1.4
161
C8051F020/1/2/3
The C8051F020/1/2/3 devices have a wide array of digital resources which are available through the four lower I/O
Ports: P0, P1, P2, and P3. Each of the pins on P0, P1, P2, and P3, can be defined as a General-Purpose I/O (GPIO) pin
or can be controlled by a digital peripheral or function (like UART0 or /INT1 for example), as shown in Figure 17.2.
The system designer controls which digital functions are assigned pins, limited only by the number of pins available.
This resource assignment flexibility is achieved through the use of a Priority Crossbar Decoder. Note that the state of
a Port I/O pin can always be read from its associated Data register regardless of whether that pin has been assigned to
a digital peripheral or behaves as GPIO. The Port pins on Port 1 can be used as Analog Inputs to ADC1.
An External Memory Interface which is active during the execution of a MOVX instruction whose target address
resides in off-chip memory can be active on either the lower Ports or the upper Ports. See Section “16. EXTERNAL
DATA MEMORY INTERFACE AND ON-CHIP XRAM” on page 145 for more information about the External
Memory Interface.
The upper Ports (available on C8051F020/2) can be byte-accessed as GPIO pins.
Figure 17.2. Lower Port I/O Functional Block Diagram
XBR0, XBR1,
XBR2, P1MDIN
Registers
P0MDOUT, P1MDOUT,
P2MDOUT, P3MDOUT
Registers
2
4
Highest
Priority
UART0
SPI
External
Pins
2
2
6
SMBus
UART1
PCA
Priority
Decoder
P0.0
Highest
Priority
P0
I/O
8
8
8
8
Cells
P0.7
2
Comptr.
Outputs
Digital
P1.0
P1.7
P1
I/O
Crossbar
Cells
T0, T1,
T2, T2EX,
T4,T4EX
/INT0,
8
P2.0
P2.7
/INT1
P2
I/O
Cells
Lowest
Priority
/SYSCLK
CNVSTR
P3.0
P3.7
P3
I/O
8
Lowest
Priority
Cells
P0
(P0.0-P0.7)
8
P1
P2
P3
(P1.0-P1.7)
8
To External
Memory
Interface
(EMIF)
To
Port
ADC1
Input
Latches
(P2.0-P2.7)
8
(P3.0-P3.7)
162
Rev. 1.4
C8051F020/1/2/3
17.1. Ports 0 through 3 and the Priority Crossbar Decoder
The Priority Crossbar Decoder, or “Crossbar”, allocates and assigns Port pins on Port 0 through Port 3 to the digital
peripherals (UARTs, SMBus, PCA, Timers, etc.) on the device using a priority order. The Port pins are allocated in
order starting with P0.0 and continue through P3.7 if necessary. The digital peripherals are assigned Port pins in a pri-
ority order which is listed in Figure 17.3, with UART0 having the highest priority and CNVSTR having the lowest
priority.
17.1.1. Crossbar Pin Assignment and Allocation
The Crossbar assigns Port pins to a peripheral if the corresponding enable bits of the peripheral are set to a logic 1 in
the Crossbar configuration registers XBR0, XBR1, and XBR2, shown in Figure 17.7, Figure 17.8, and Figure 17.9.
For example, if the UART0EN bit (XBR0.2) is set to a logic 1, the TX0 and RX0 pins will be mapped to P0.0 and
P0.1 respectively. Because UART0 has the highest priority, its pins will always be mapped to P0.0 and P0.1 when
UART0EN is set to a logic 1. If a digital peripheral’s enable bits are not set to a logic 1, then its ports are not accessi-
ble at the Port pins of the device. Also note that the Crossbar assigns pins to all associated functions when a serial
communication peripheral is selected (i.e. SMBus, SPI, UART). It would be impossible, for example, to assign TX0
Figure 17.3. Priority Crossbar Decode Table
(EMIFLE = 0; P1MDIN = 0xFF)
P0
P1
P2
P3
Crossbar Register Bits
UART0EN: XBR0.2
PIN I/O
TX0
0
●
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
RX0
●
●
SCK
MISO
MOSI
NSS
SDA
SCL
●
●
●
●
●
●
●
●
●
●
●
●
●
SPI0EN: XBR0.1
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
SMB0EN: XBR0.0
UART1EN: XBR2.2
●
●
●
●
TX1
●
RX1
● ● ●
● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ● ● ●
● ● ● ● ● ● ●
CEX0
CEX1
CEX2
CEX3
CEX4
ECI
PCA0ME: XBR0.[5:3]
ECI0E: XBR0.6
CP0E: XBR0.7
CP1E: XBR1.0
T0E: XBR1.1
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
CP0
CP1
T0
/INT0
T1
INT0E: XBR1.2
T1E: XBR1.3
/INT1
T2
INT1E: XBR1.4
T2E: XBR1.5
T2EX
T4
T2EXE: XBR1.6
T4E: XBR2.3
T4EX
/SYSCLK
CNVSTR
T4EXE: XBR2.4
SYSCKE: XBR1.7
CNVSTE: XBR2.0
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L Muxed Data/Non-muxed Data
Rev. 1.4
163
C8051F020/1/2/3
to a Port pin without assigning RX0 as well. Each combination of enabled peripherals results in a unique device
pinout.
All Port pins on Ports 0 through 3 that are not allocated by the Crossbar can be accessed as General-Purpose I/O
(GPIO) pins by reading and writing the associated Port Data registers (See Figure 17.10, Figure 17.12, Figure 17.15,
and Figure 17.17), a set of SFRs which are both byte- and bit-addressable. The output states of Port pins that are allo-
cated by the Crossbar are controlled by the digital peripheral that is mapped to those pins. Writes to the Port Data reg-
isters (or associated Port bits) will have no effect on the states of these pins.
A Read of a Port Data register (or Port bit) will always return the logic state present at the pin itself, regardless of
whether the Crossbar has allocated the pin for peripheral use or not. An exception to this occurs during the execution
of a read-modify-write instruction (ANL, ORL, XRL, CPL, INC, DEC, DJNZ, JBC, CLR, SET, and the bitwise MOV
operation). During the read cycle of the read-modify-write instruction, it is the contents of the Port Data register, not
the state of the Port pins themselves, which is read.
Because the Crossbar registers affect the pinout of the peripherals of the device, they are typically configured in the
initialization code of the system before the peripherals themselves are configured. Once configured, the Crossbar reg-
isters are typically left alone.
Once the Crossbar registers have been properly configured, the Crossbar is enabled by setting XBARE (XBR2.6) to a
logic 1. Until XBARE is set to a logic 1, the output drivers on Ports 0 through 3 are explicitly disabled in order
to prevent possible contention on the Port pins while the Crossbar registers and other registers which can
affect the device pinout are being written.
The output drivers on Crossbar-assigned input signals (like RX0, for example) are explicitly disabled; thus the values
of the Port Data registers and the PnMDOUT registers have no effect on the states of these pins.
17.1.2. Configuring the Output Modes of the Port Pins
The output drivers on Ports 0 through 3 remain disabled until the Crossbar is enabled by setting XBARE (XBR2.6) to
a logic 1.
The output mode of each port pin can be configured as either Open-Drain or Push-Pull; the default state is Open-
Drain. In the Push-Pull configuration, writing a logic 0 to the associated bit in the Port Data register will cause the
Port pin to be driven to GND, and writing a logic 1 will cause the Port pin to be driven to VDD. In the Open-Drain
configuration, writing a logic 0 to the associated bit in the Port Data register will cause the Port pin to be driven to
GND, and a logic 1 will cause the Port pin to assume a high-impedance state. The Open-Drain configuration is useful
to prevent contention between devices in systems where the Port pin participates in a shared interconnection in which
multiple outputs are connected to the same physical wire (like the SDA signal on an SMBus connection).
The output modes of the Port pins on Ports 0 through 3 are determined by the bits in the associated PnMDOUT regis-
ters (See Figure 17.11, Figure 17.14, Figure 17.16, and Figure 17.18). For example, a logic 1 in P3MDOUT.7 will
configure the output mode of P3.7 to Push-Pull; a logic 0 in P3MDOUT.7 will configure the output mode of P3.7 to
Open-Drain. All Port pins default to Open-Drain output.
The PnMDOUT registers control the output modes of the port pins regardless of whether the Crossbar has allocated
the Port pin for a digital peripheral or not. The exceptions to this rule are: the Port pins connected to SDA, SCL, RX0
(if UART0 is in Mode 0), and RX1 (if UART1 is in Mode 0) are always configured as Open-Drain outputs, regardless
of the settings of the associated bits in the PnMDOUT registers.
164
Rev. 1.4
C8051F020/1/2/3
17.1.3. Configuring Port Pins as Digital Inputs
A Port pin is configured as a digital input by setting its output mode to “Open-Drain” and writing a logic 1 to the
associated bit in the Port Data register. For example, P3.7 is configured as a digital input by setting P3MDOUT.7 to a
logic 0 and P3.7 to a logic 1.
If the Port pin has been assigned to a digital peripheral by the Crossbar and that pin functions as an input (for example
RX0, the UART0 receive pin), then the output drivers on that pin are automatically disabled.
17.1.4. External Interrupts (IE6 and IE7)
In addition to the external interrupts /INT0 and /INT1, whose Port pins are allocated and assigned by the Crossbar,
P3.6 and P3.7 can be configured to generate edge sensitive interrupts; these interrupts are configurable as falling- or
rising-edge sensitive using the IE6CF (P3IF.2) and IE7CF (P3IF.3) bits. When an active edge is detected on P3.6 or
P3.7, a corresponding External Interrupt flag (IE6 or IE7) will be set to a logic 1 in the P3IF register (See
Figure 17.19). If the associated interrupt is enabled, an interrupt will be generated and the CPU will vector to the
associated interrupt vector location. See Section “12.3. Interrupt Handler” on page 116 for more information about
interrupts.
17.1.5. Weak Pull-ups
By default, each Port pin has an internal weak pull-up device enabled which provides a resistive connection (about
100 kΩ) between the pin and VDD. The weak pull-up devices can be globally disabled by writing a logic 1 to the
Weak Pull-up Disable bit, (WEAKPUD, XBR2.7). The weak pull-up is automatically deactivated on any pin that is
driving a logic 0; that is, an output pin will not contend with its own pull-up device. The weak pull-up device can also
be explicitly disabled on a Port 1 pin by configuring the pin as an Analog Input, as described below.
17.1.6. Configuring Port 1 Pins as Analog Inputs (AIN1.[7:0])
The pins on Port 1 can serve as analog inputs to the ADC1 analog MUX. A Port pin is configured as an Analog Input
by writing a logic 0 to the associated bit in the P1MDIN register (see Figure 17.13). All Port pins default to a Digital
Input mode. Configuring a Port pin as an analog input:
1. Disables the digital input path from the pin. This prevents additional power supply current
from being drawn when the voltage at the pin is near VDD / 2. A read of the Port Data bit will
return a logic 0 regardless of the voltage at the Port pin.
2. Disables the weak pull-up device on the pin.
3. Causes the Crossbar to “skip over” the pin when allocating Port pins for digital peripherals.
Note that the output drivers on a pin configured as an Analog Input are not explicitly disabled. Therefore, the
associated P1MDOUT bits of pins configured as Analog Inputs should explicitly be set to logic 0 (Open-Drain output
mode), and the associated Port Data bits should be set to logic 1 (high-impedance). Also note that it is not required to
configure a Port pin as an Analog Input in order to use it as an input to the ADC1 MUX; however, it is strongly rec-
ommended. See Section “7. ADC1 (8-Bit ADC)” on page 75 for more information about ADC1.
Rev. 1.4
165
C8051F020/1/2/3
17.1.7. External Memory Interface Pin Assignments
If the External Memory Interface (EMIF) is enabled on the Low ports (Ports 0 through 3), EMIFLE (XBR2.1) should
be set to a logic 1 so that the Crossbar will not assign peripherals to P0.7 (/WR), P0.6 (/RD), and if the External Mem-
ory Interface is in Multiplexed mode, P0.5 (ALE). Figure 17.4 shows an example Crossbar Decode Table with
EMIFLE=1 and the EMIF in Multiplexed mode. Figure 17.5 shows an example Crossbar Decode Table with
EMIFLE=1 and the EMIF in Non-multiplexed mode.
If the External Memory Interface is enabled on the Low ports and an off-chip MOVX operation occurs, the External
Memory Interface will control the output states of the affected Port pins during the execution phase of the MOVX
instruction, regardless of the settings of the Crossbar registers or the Port Data registers. The output configuration of
the Port pins is not affected by the EMIF operation, except that Read operations will explicitly disable the output
drivers on the Data Bus. See Section “16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP
XRAM” on page 145 for more information about the External Memory Interface.
Figure 17.4. Priority Crossbar Decode Table
EMIFLE = 1; EMIF in Multiplexed Mode; P1MDIN = 0xFF)
P0
P1
P2
P3
Crossbar Register Bits
UART0EN: XBR0.2
PIN I/O
TX0
0
●
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
RX0
●
●
SCK
MISO
MOSI
NSS
SDA
SCL
●
●
●
●
●
●
●
●
●
●
●
●
●
SPI0EN: XBR0.1
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
SMB0EN: XBR0.0
UART1EN: XBR2.2
●
●
●
●
TX1
●
RX1
● ● ●
● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ● ● ●
● ● ● ● ● ● ●
CEX0
CEX1
CEX2
CEX3
CEX4
ECI
PCA0ME: XBR0.[5:3]
ECI0E: XBR0.6
CP0E: XBR0.7
CP1E: XBR1.0
T0E: XBR1.1
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
CP0
CP1
T0
/INT0
T1
INT0E: XBR1.2
T1E: XBR1.3
/INT1
T2
INT1E: XBR1.4
T2E: XBR1.5
T2EX
T4
T2EXE: XBR1.6
T4E: XBR2.3
T4EX
/SYSCLK
CNVSTR
T4EXE: XBR2.4
SYSCKE: XBR1.7
CNVSTE: XBR2.0
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L Muxed Data/Non-muxed Data
166
Rev. 1.4
C8051F020/1/2/3
Figure 17.5. Priority Crossbar Decode Table
(EMIFLE = 1; EMIF in Non-multiplexed Mode; P1MDIN = 0xFF)
P0
P1
P2
P3
Crossbar Register Bits
UART0EN: XBR0.2
PIN I/O
TX0
0
●
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
RX0
●
●
SCK
MISO
MOSI
NSS
SDA
SCL
●
●
●
●
●
●
●
●
●
●
●
●
●
SPI0EN: XBR0.1
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
SMB0EN: XBR0.0
UART1EN: XBR2.2
●
●
●
●
TX1
●
RX1
● ● ●
● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ● ● ●
● ● ● ● ● ● ●
CEX0
CEX1
CEX2
CEX3
CEX4
ECI
PCA0ME: XBR0.[5:3]
ECI0E: XBR0.6
CP0E: XBR0.7
CP1E: XBR1.0
T0E: XBR1.1
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
CP0
CP1
T0
/INT0
T1
INT0E: XBR1.2
T1E: XBR1.3
/INT1
T2
INT1E: XBR1.4
T2E: XBR1.5
T2EX
T4
T2EXE: XBR1.6
T4E: XBR2.3
T4EX
/SYSCLK
CNVSTR
T4EXE: XBR2.4
SYSCKE: XBR1.7
CNVSTE: XBR2.0
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L Muxed Data/Non-muxed Data
Rev. 1.4
167
C8051F020/1/2/3
17.1.8. Crossbar Pin Assignment Example
In this example (Figure 17.6), we configure the Crossbar to allocate Port pins for UART0, the SMBus, UART1,
/INT0, and /INT1 (8 pins total). Additionally, we configure the External Memory Interface to operate in Multiplexed
mode and to appear on the Low ports. Further, we configure P1.2, P1.3, and P1.4 for Analog Input mode so that the
voltages at these pins can be measured by ADC1. The configuration steps are as follows:
1. XBR0, XBR1, and XBR2 are set such that UART0EN = 1, SMB0EN = 1, INT0E = 1, INT1E
= 1, and EMIFLE = 1. Thus: XBR0 = 0x05, XBR1 = 0x14, and XBR2 = 0x02.
2. We configure the External Memory Interface to use Multiplexed mode and to appear on the
Low ports. PRTSEL = 0, EMD2 = 0.
3. We configure the desired Port 1 pins to Analog Input mode by setting P1MDIN to 0xE3 (P1.4,
P1.3, and P1.2 are Analog Inputs, so their associated P1MDIN bits are set to logic 0).
4. We enable the Crossbar by setting XBARE = 1: XBR2 = 0x46.
-
-
-
UART0 has the highest priority, so P0.0 is assigned to TX0, and P0.1 is assigned to RX0.
The SMBus is next in priority order, so P0.2 is assigned to SDA, and P0.3 is assigned to SCL.
UART1 is next in priority order, so P0.4 is assigned to TX1. Because the External Memory Inter-
face is selected on the lower Ports, EMIFLE = 1, which causes the Crossbar to skip P0.6 (/RD) and
P0.7 (/WR). Because the External Memory Interface is configured in Multiplexed mode, the Cross-
bar will also skip P0.5 (ALE). RX1 is assigned to the next non-skipped pin, which in this case is
P1.0.
-
-
/INT0 is next in priority order, so it is assigned to P1.1.
P1MDIN is set to 0xE3, which configures P1.2, P1.3, and P1.4 as Analog Inputs, causing the
Crossbar to skip these pins.
/INT1 is next in priority order, so it is assigned to the next non-skipped pin, which is P1.5.
The External Memory Interface will drive Ports 2 and 3 (denoted by red dots in Figure 17.6) during
the execution of an off-chip MOVX instruction.
-
-
5. We set the UART0 TX pin (TX0, P0.0), UART1 TX pin (TX1, P0.4), ALE, /RD, /WR
(P0.[7:3]) outputs to Push-Pull by setting P0MDOUT = 0xF1.
6. We configure the output modes of the EMIF Ports (P2, P3) to Push-Pull by setting P2MDOUT
= 0xFF and P3MDOUT = 0xFF.
7. We explicitly disable the output drivers on the 3 Analog Input pins by setting P1MDOUT =
0x00 (configure outputs to Open-Drain) and P1 = 0xFF (a logic 1 selects the high-impedance
state).
168
Rev. 1.4
C8051F020/1/2/3
Figure 17.6. Crossbar Example:
(EMIFLE = 1; EMIF in Multiplexed Mode; P1MDIN = 0xE3;
XBR0 = 0x05; XBR1 = 0x14; XBR2 = 0x46)
P0
P1
P2
P3
Crossbar Register Bits
UART0EN: XBR0.2
PIN I/O
TX0
0
●
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
RX0
●
●
SCK
MISO
MOSI
NSS
SDA
SCL
●
●
●
●
●
●
●
●
●
●
●
●
●
SPI0EN: XBR0.1
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
SMB0EN: XBR0.0
UART1EN: XBR2.2
●
●
●
●
TX1
●
RX1
● ● ●
● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ● ● ●
● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
CEX0
CEX1
CEX2
CEX3
CEX4
ECI
PCA0ME: XBR0.[5:3]
ECI0E: XBR0.6
CP0E: XBR0.7
CP1E: XBR1.0
T0E: XBR1.1
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ●
● ●
● ●
● ●
● ●
● ●
● ●
● ●
● ●
● ●
● ●
● ●
● ●
CP0
CP1
T0
/INT0
T1
INT0E: XBR1.2
T1E: XBR1.3
/INT1
T2
INT1E: XBR1.4
T2E: XBR1.5
T2EX
T4
T2EXE: XBR1.6
T4E: XBR2.3
T4EX
/SYSCLK
CNVSTR
T4EXE: XBR2.4
SYSCKE: XBR1.7
CNVSTE: XBR2.0
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L Muxed Data/Non-muxed Data
Rev. 1.4
169
C8051F020/1/2/3
Figure 17.7. XBR0: Port I/O Crossbar Register 0
R/W
CP0E
Bit7
R/W
ECI0E
Bit6
R/W
Bit5
R/W
PCA0ME
Bit4
R/W
Bit3
R/W
R/W
R/W
Reset Value
UART0EN SPI0EN SMB0EN 00000000
Bit2
Bit1
Bit0
SFR Address:
0xE1
Bit7:
CP0E: Comparator 0 Output Enable Bit.
0: CP0 unavailable at Port pin.
1: CP0 routed to Port pin.
Bit6:
ECI0E: PCA0 External Counter Input Enable Bit.
0: PCA0 External Counter Input unavailable at Port pin.
1: PCA0 External Counter Input (ECI0) routed to Port pin.
Bits5-3: PCA0ME: PCA0 Module I/O Enable Bits.
000: All PCA0 I/O unavailable at Port pins.
001: CEX0 routed to Port pin.
010: CEX0, CEX1 routed to 2 Port pins.
011: CEX0, CEX1, and CEX2 routed to 3 Port pins.
100: CEX0, CEX1, CEX2, and CEX3 routed to 4 Port pins.
101: CEX0, CEX1, CEX2, CEX3, and CEX4 routed to 5 Port pins.
110: RESERVED
111: RESERVED
Bit2:
Bit1:
Bit0:
UART0EN: UART0 I/O Enable Bit.
0: UART0 I/O unavailable at Port pins.
1: UART0 TX routed to P0.0, and RX routed to P0.1.
SPI0EN: SPI0 Bus I/O Enable Bit.
0: SPI0 I/O unavailable at Port pins.
1: SPI0 SCK, MISO, MOSI, and NSS routed to 4 Port pins.
SMB0EN: SMBus0 Bus I/O Enable Bit.
0: SMBus0 I/O unavailable at Port pins.
1: SMBus0 SDA and SCL routed to 2 Port pins.
170
Rev. 1.4
C8051F020/1/2/3
Figure 17.8. XBR1: Port I/O Crossbar Register 1
R/W
SYSCKE
Bit7
R/W
T2EXE
Bit6
R/W
T2E
Bit5
R/W
INT1E
Bit4
R/W
T1E
Bit3
R/W
INT0E
Bit2
R/W
T0E
Bit1
R/W
CP1E
Bit0
Reset Value
00000000
SFR Address:
0xE2
Bit7:
SYSCKE: /SYSCLK Output Enable Bit.
0: /SYSCLK unavailable at Port pin.
1: /SYSCLK routed to Port pin.
T2EXE: T2EX Input Enable Bit.
0: T2EX unavailable at Port pin.
1: T2EX routed to Port pin.
T2E: T2 Input Enable Bit.
Bit6:
Bit5:
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
0: T2 unavailable at Port pin.
1: T2 routed to Port pin.
INT1E: /INT1 Input Enable Bit.
0: /INT1 unavailable at Port pin.
1: /INT1 routed to Port pin.
T1E: T1 Input Enable Bit.
0: T1 unavailable at Port pin.
1: T1 routed to Port pin.
INT0E: /INT0 Input Enable Bit.
0: /INT0 unavailable at Port pin.
1: /INT1 routed to Port pin.
T0E: T0 Input Enable Bit.
0: T0 unavailable at Port pin.
1: T0 routed to Port pin.
CP1E: CP1 Output Enable Bit.
0: CP1 unavailable at Port pin.
1: CP1 routed to Port pin.
Rev. 1.4
171
C8051F020/1/2/3
Figure 17.9. XBR2: Port I/O Crossbar Register 2
R/W
R/W
R/W
-
Bit5
R/W
T4EXE
Bit4
R/W
T4E
Bit3
R/W
R/W
R/W
Reset Value
WEAKPUD XBARE
UART1E EMIFLE CNVSTE 00000000
Bit7
Bit6
Bit2
Bit1
Bit0
SFR Address:
0xE3
Bit7:
Bit6:
WEAKPUD: Weak Pull-Up Disable Bit.
0: Weak pull-ups globally enabled.
1: Weak pull-ups globally disabled.
XBARE: Crossbar Enable Bit.
0: Crossbar disabled. All pins on Ports 0, 1, 2, and 3, are forced to Input mode.
1: Crossbar enabled.
Bit5:
Bit4:
UNUSED. Read = 0, Write = don't care.
T4EXE: T4EX Input Enable Bit.
0: T4EX unavailable at Port pin.
1: T4EX routed to Port pin.
Bit3:
Bit2:
Bit1:
T4E: T4 Input Enable Bit.
0: T4 unavailable at Port pin.
1: T4 routed to Port pin.
UART1E: UART1 I/O Enable Bit.
0: UART1 I/O unavailable at Port pins.
1: UART1 TX and RX routed to 2 Port pins.
EMIFLE: External Memory Interface Low-Port Enable Bit.
0: P0.7, P0.6, and P0.5 functions are determined by the Crossbar or the Port latches.
1: If EMI0CF.4 = ‘0’ (External Memory Interface is in Multiplexed mode)
P0.7 (/WR), P0.6 (/RD), and P0.5 (ALE) are ‘skipped’ by the Crossbar and their output
states are determined by the Port latches and the External Memory Interface.
1: If EMI0CF.4 = ‘1’ (External Memory Interface is in Non-multiplexed mode)
P0.7 (/WR) and P0.6 (/RD) are ‘skipped’ by the Crossbar and their output states are
determined by the Port latches and the External Memory Interface.
CNVSTE: External Convert Start Input Enable Bit.
Bit0:
0: CNVSTR unavailable at Port pin.
1: CNVSTR routed to Port pin.
172
Rev. 1.4
C8051F020/1/2/3
Figure 17.10. P0: Port0 Data Register
R/W
P0.7
Bit7
R/W
P0.6
Bit6
R/W
P0.5
Bit5
R/W
P0.4
Bit4
R/W
P0.3
Bit3
R/W
P0.2
Bit2
R/W
P0.1
Bit1
R/W
P0.0
Reset Value
11111111
SFR Address:
0x80
Bit0
(bit addressable)
Bits7-0: P0.[7:0]: Port0 Output Latch Bits.
(Write - Output appears on I/O pins per XBR0, XBR1, XBR2, and XBR3 Registers)
0: Logic Low Output.
1: Logic High Output (open if corresponding P0MDOUT.n bit = 0).
(Read - Regardless of XBR0, XBR1, XBR2, and XBR3 Register settings).
0: P0.n pin is logic low.
1: P0.n pin is logic high.
Note: P0.7 (/WR), P0.6 (/RD), and P0.5 (ALE) can be driven by the External Data Memory Interface.
See Section “16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP XRAM” on
page 145 for more information. See also Figure 17.9 for information about configuring the Crossbar
for External Memory accesses.
Figure 17.11. P0MDOUT: Port0 Output Mode Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xA4
Bits7-0: P0MDOUT.[7:0]: Port0 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
Note:
SDA, SCL, and RX0 (when UART0 is in Mode 0) and RX1 (when UART1 is in Mode 0) are always
configured as Open-Drain when they appear on Port pins.
Rev. 1.4
173
C8051F020/1/2/3
Figure 17.12. P1: Port1 Data Register
R/W
P1.7
Bit7
R/W
P1.6
Bit6
R/W
P1.5
Bit5
R/W
P1.4
Bit4
R/W
P1.3
Bit3
R/W
P1.2
Bit2
R/W
P1.1
Bit1
R/W
P1.0
Reset Value
11111111
SFR Address:
0x90
Bit0
(bit addressable)
Bits7-0: P1.[7:0]: Port1 Output Latch Bits.
(Write - Output appears on I/O pins per XBR0, XBR1, XBR2, and XBR3 Registers)
0: Logic Low Output.
1: Logic High Output (open if corresponding P1MDOUT.n bit = 0).
(Read - Regardless of XBR0, XBR1, XBR2, and XBR3 Register settings).
0: P1.n pin is logic low.
1: P1.n pin is logic high.
Notes:
1.
P1.[7:0] can be configured as inputs to ADC1 as AIN1.[7:0], in which case they are ‘skipped’ by the
Crossbar assignment process and their digital input paths are disabled, depending on P1MDIN (See
Figure 17.13). Note that in analog mode, the output mode of the pin is determined by the Port 1 latch
and P1MDOUT (Figure 17.14). See Section “7. ADC1 (8-Bit ADC)” on page 75 for more informa-
tion about ADC1.
P1.[7:0] can be driven by the External Data Memory Interface (as Address[15:8] in Non-multiplexed
mode). See Section “16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP XRAM”
on page 145 for more information about the External Memory Interface.
2.
Figure 17.13. P1MDIN: Port1 Input Mode Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
11111111
SFR Address:
0xBD
Bits7-0: P1MDIN.[7:0]: Port 1 Input Mode Bits.
0: Port Pin is configured in Analog Input mode. The digital input path is disabled (a read from the
Port bit will always return ‘0’). The weak pull-up on the pin is disabled.
1: Port Pin is configured in Digital Input mode. A read from the Port bit will return the logic level at
the Pin. The state of the weak pull-up is determined by the WEAKPUD bit (XBR2.7, see
Figure 17.9).
174
Rev. 1.4
C8051F020/1/2/3
Figure 17.14. P1MDOUT: Port1 Output Mode Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xA5
Bits7-0: P1MDOUT.[7:0]: Port1 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
Note:
SDA, SCL, and RX0 (when UART0 is in Mode 0) and RX1 (when UART1 is in Mode 0) are always
configured as Open-Drain when they appear on Port pins.
Figure 17.15. P2: Port2 Data Register
R/W
P2.7
Bit7
R/W
P2.6
Bit6
R/W
P2.5
Bit5
R/W
P2.4
Bit4
R/W
P2.3
Bit3
R/W
P2.2
Bit2
R/W
P2.1
Bit1
R/W
P2.0
Reset Value
11111111
SFR Address:
0xA0
Bit0
(bit addressable)
Bits7-0: P2.[7:0]: Port2 Output Latch Bits.
(Write - Output appears on I/O pins per XBR0, XBR1, XBR2, and XBR3 Registers)
0: Logic Low Output.
1: Logic High Output (open if corresponding P2MDOUT.n bit = 0).
(Read - Regardless of XBR0, XBR1, XBR2, and XBR3 Register settings).
0: P2.n pin is logic low.
1: P2.n pin is logic high.
Note:
P2.[7:0] can be driven by the External Data Memory Interface (as Address[15:8] in Multiplexed
mode, or as Address[7:0] in Non-multiplexed mode). See Section “16. EXTERNAL DATA MEM-
ORY INTERFACE AND ON-CHIP XRAM” on page 145 for more information about the External
Memory Interface.
Figure 17.16. P2MDOUT: Port2 Output Mode Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xA6
Bits7-0: P2MDOUT.[7:0]: Port2 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
Note:
SDA, SCL, and RX0 (when UART0 is in Mode 0) and RX1 (when UART1 is in Mode 0) are always
configured as Open-Drain when they appear on Port pins.
Rev. 1.4
175
C8051F020/1/2/3
Figure 17.17. P3: Port3 Data Register
R/W
P3.7
Bit7
R/W
P3.6
Bit6
R/W
P3.5
Bit5
R/W
P3.4
Bit4
R/W
P3.3
Bit3
R/W
P3.2
Bit2
R/W
P3.1
Bit1
R/W
P3.0
Reset Value
11111111
SFR Address:
0xB0
Bit0
(bit addressable)
Bits7-0: P3.[7:0]: Port3 Output Latch Bits.
(Write - Output appears on I/O pins per XBR0, XBR1, XBR2, and XBR3 Registers)
0: Logic Low Output.
1: Logic High Output (open if corresponding P3MDOUT.n bit = 0).
(Read - Regardless of XBR0, XBR1, XBR2, and XBR3 Register settings).
0: P3.n pin is logic low.
1: P3.n pin is logic high.
Note:
P3.[7:0] can be driven by the External Data Memory Interface (as AD[7:0] in Multiplexed mode, or
as D[7:0] in Non-multiplexed mode). See Section “16. EXTERNAL DATA MEMORY INTER-
FACE AND ON-CHIP XRAM” on page 145 for more information about the External Memory
Interface.
Figure 17.18. P3MDOUT: Port3 Output Mode Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xA7
Bits7-0: P3MDOUT.[7:0]: Port3 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
Note:
SDA, SCL, and RX0 (when UART0 is in Mode 0) and RX1 (when UART1 is in Mode 0) are always
configured as Open-Drain when they appear on Port pins.
176
Rev. 1.4
C8051F020/1/2/3
Figure 17.19. P3IF: Port3 Interrupt Flag Register
R/W
IE7
Bit7
R/W
IE6
Bit6
R
-
Bit5
R
-
Bit4
R/W
IE7CF
Bit3
R/W
IE6CF
Bit2
R/W
-
Bit1
R/W
-
Bit0
Reset Value
00000000
SFR Address:
0xAD
Bit7:
Bit6:
IE7: External Interrupt 7 Pending Flag
0: No falling edge has been detected on P3.7 since this bit was last cleared.
1: This flag is set by hardware when a falling edge on P3.7 is detected.
IE6: External Interrupt 6 Pending Flag
0: No falling edge has been detected on P3.6 since this bit was last cleared.
1: This flag is set by hardware when a falling edge on P3.6 is detected.
Bits5-4: UNUSED. Read = 00b, Write = don’t care.
Bit3:
IE7CF: External Interrupt 7 Edge Configuration
0: External Interrupt 7 triggered by a falling edge on the IE7 input.
1: External Interrupt 7 triggered by a rising edge on the IE7 input.
IE6CF: External Interrupt 6 Edge Configuration
Bit2:
0: External Interrupt 6 triggered by a falling edge on the IE6 input.
1: External Interrupt 6 triggered by a rising edge on the IE6 input.
Bits1-0: UNUSED. Read = 00b, Write = don’t care.
17.2. Ports 4 through 7 (C8051F020/2 only)
All Port pins on Ports 4 through 7 can be accessed as General-Purpose I/O (GPIO) pins by reading and writing the
associated Port Data registers (See Figure 17.21, Figure 17.22, Figure 17.23, and Figure 17.24), a set of SFRs which
are byte-addressable.
A Read of a Port Data register (or Port bit) will always return the logic state present at the pin itself, regardless of
whether the Crossbar has allocated the pin for peripheral use or not. An exception to this occurs during the execution
of a read-modify-write instruction (ANL, ORL, XRL, CPL, INC, DEC, DJNZ, JBC, CLR, SET, and the bitwise MOV
operation). During the read cycle of the read-modify-write instruction, it is the contents of the Port Data register, not
the state of the Port pins themselves, which is read.
17.2.1. Configuring Ports which are not Pinned Out
Although P4, P5, P6, and P7 are not brought out to pins on the C8051F021/3 devices, the Port Data registers are still
present and can be used by software. Because the digital input paths also remain active, it is recommended that these
pins not be left in a ‘floating’ state in order to avoid unnecessary power dissipation arising from the inputs floating to
non-valid logic levels. This condition can be prevented by any of the following:
1. Leave the weak pull-up devices enabled by setting WEAKPUD (XBR2.7) to a logic 0.
2. Configure the output modes of P4, P5, P6, and P7 to “Push-Pull” by writing P74OUT = 0xFF.
3. Force the output states of P4, P5, P6, and P7 to logic 0 by writing zeros to the Port Data regis-
ters: P4 = 0x00, P5 = 0x00, P6= 0x00, and P7 = 0x00.
17.2.2. Configuring the Output Modes of the Port Pins
The output mode of each port pin can be configured to be either Open-Drain or Push-Pull. In the Push-Pull configura-
tion, a logic 0 in the associated bit in the Port Data register will cause the Port pin to be driven to GND, and a logic 1
will cause the Port pin to be driven to VDD. In the Open-Drain configuration, a logic 0 in the associated bit in the
Rev. 1.4
177
C8051F020/1/2/3
Port Data register will cause the Port pin to be driven to GND, and a logic 1 will cause the Port pin to assume a high-
impedance state. The Open-Drain configuration is useful to prevent contention between devices in systems where the
Port pin participates in a shared interconnection in which multiple outputs are connected to the same physical wire.
The output modes of the Port pins on Ports 4 through 7 are determined by the bits in the P74OUT register (see
Figure 17.20). Each bit in P74OUT controls the output mode of a 4-bit bank of Port pins on Ports 4, 5, 6, and 7. A
logic 1 in P74OUT.7 will configure the output modes of 4 most-significant bits of Port 7, P7.[7:4], to Push-Pull; a
logic 0 in P74OUT.7 will configure the output modes of P7.[7:4] to Open-Drain.
17.2.3. Configuring Port Pins as Digital Inputs
A Port pin is configured as a digital input by setting its output mode to “Open-Drain” and writing a logic 1 to the
associated bit in the Port Data register. For example, P7.7 is configured as a digital input by setting P74OUT.7 to a
logic 0 and P7.7 to a logic 1.
17.2.4. Weak Pull-ups
By default, each Port pin has an internal weak pull-up device enabled which provides a resistive connection (about
100 kΩ) between the pin and VDD. The weak pull-up devices can be globally disabled by writing a logic 1 to the
Weak Pull-up Disable bit, (WEAKPUD, XBR2.7). The weak pull-up is automatically deactivated on any pin that is
driving a logic 0; that is, an output pin will not contend with its own pull-up device.
17.2.5. External Memory Interface
If the External Memory Interface (EMIF) is enabled on the High ports (Ports 4 through 7), EMIFLE (XBR2.1) should
be set to a logic 0.
If the External Memory Interface is enabled on the High ports and an off-chip MOVX operation occurs, the External
Memory Interface will control the output states of the affected Port pins during the execution phase of the MOVX
instruction, regardless of the settings of the Port Data registers. The output configuration of the Port pins is not
affected by the EMIF operation, except that Read operations will explicitly disable the output drivers on the Data Bus
during the MOVX execution. See Section “16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP
XRAM” on page 145 for more information about the External Memory Interface.
178
Rev. 1.4
C8051F020/1/2/3
Figure 17.20. P74OUT: Ports 7 - 4 Output Mode Register
R/W
P7H
Bit7
R/W
P7L
Bit6
R/W
P6H
Bit5
R/W
P6L
Bit4
R/W
P5H
Bit3
R/W
P5L
Bit2
R/W
P4H
Bit1
R/W
P4L
Bit0
Reset Value
00000000
SFR Address:
0xB5
Bit7:
P7H: Port7 Output Mode High Nibble Bit.
0: P7.[7:4] configured as Open-Drain.
1: P7.[7:4] configured as Push-Pull.
P7L: Port7 Output Mode Low Nibble Bit.
0: P7.[3:0] configured as Open-Drain.
1: P7.[3:0] configured as Push-Pull.
P6H: Port6 Output Mode High Nibble Bit.
0: P6.[7:4] configured as Open-Drain.
1: P6.[7:4] configured as Push-Pull.
P6L: Port6 Output Mode Low Nibble Bit.
0: P6.[3:0] configured as Open-Drain.
1: P6.[3:0] configured as Push-Pull.
P5H: Port5 Output Mode High Nibble Bit.
0: P5.[7:4] configured as Open-Drain.
1: P5.[7:4] configured as Push-Pull.
P5L: Port5 Output Mode Low Nibble Bit.
0: P5.[3:0] configured as Open-Drain.
1: P5.[3:0] configured as Push-Pull.
P4H: Port4 Output Mode High Nibble Bit.
0: P4.[7:4] configured as Open-Drain.
1: P4.[7:4] configured as Push-Pull.
P4L: Port4 Output Mode Low Nibble Bit.
0: P4.[3:0] configured as Open-Drain.
1: P4.[3:0] configured as Push-Pull.
Bit6:
Bit5:
Bit4:
Bit3:
Bit2:
Bit1:
Bit0:
Rev. 1.4
179
C8051F020/1/2/3
Figure 17.21. P4: Port4 Data Register
R/W
P4.7
Bit7
R/W
P4.6
Bit6
R/W
P4.5
Bit5
R/W
P4.4
Bit4
R/W
P4.3
Bit3
R/W
P4.2
Bit2
R/W
P4.1
Bit1
R/W
P4.0
Bit0
Reset Value
11111111
SFR Address:
0x84
Bits7-0: P4.[7:0]: Port4 Output Latch Bits.
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Output (Open-Drain if corresponding P74OUT bit = 0). See Figure 17.20.
Read - Returns states of I/O pins.
0: P4.n pin is logic low.
1: P4.n pin is logic high.
Note: P4.7 (/WR), P4.6 (/RD), and P4.5 (ALE) can be driven by the External Data Memory Interface.
See Section “16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP XRAM” on
page 145 for more information.
Figure 17.22. P5: Port5 Data Register
R/W
P5.7
Bit7
R/W
P5.6
Bit6
R/W
P5.5
Bit5
R/W
P5.4
Bit4
R/W
P5.3
Bit3
R/W
P5.2
Bit2
R/W
P5.1
Bit1
R/W
P5.0
Bit0
Reset Value
11111111
SFR Address:
0x85
Bits7-0: P5.[7:0]: Port5 Output Latch Bits.
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Output (Open-Drain if corresponding P74OUT bit = 0). See Figure 17.20.
Read - Returns states of I/O pins.
0: P5.n pin is logic low.
1: P5.n pin is logic high.
Note:
P5.[7:0] can be driven by the External Data Memory Interface (as Address[15:8] in Non-multiplexed
mode). See Section “16. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP XRAM”
on page 145 for more information about the External Memory Interface.
180
Rev. 1.4
C8051F020/1/2/3
Figure 17.23. P6: Port6 Data Register
R/W
P6.7
Bit7
R/W
P6.6
Bit6
R/W
P6.5
Bit5
R/W
P6.4
Bit4
R/W
P6.3
Bit3
R/W
P6.2
Bit2
R/W
P6.1
Bit1
R/W
P6.0
Bit0
Reset Value
11111111
SFR Address:
0x86
Bits7-0: P6.[7:0]: Port6 Output Latch Bits.
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Output (Open-Drain if corresponding P74OUT bit = 0). See Figure 17.20.
Read - Returns states of I/O pins.
0: P6.n pin is logic low.
1: P6.n pin is logic high.
Note:
P6.[7:0] can be driven by the External Data Memory Interface (as Address[15:8] in Multiplexed
mode, or as Address[7:0] in Non-multiplexed mode). See Section “16. EXTERNAL DATA MEM-
ORY INTERFACE AND ON-CHIP XRAM” on page 145 for more information about the External
Memory Interface.
Figure 17.24. P7: Port7 Data Register
R/W
P7.7
Bit7
R/W
P7.6
Bit6
R/W
P7.5
Bit5
R/W
P7.4
Bit4
R/W
P7.3
Bit3
R/W
P7.2
Bit2
R/W
P7.1
Bit1
R/W
P7.0
Bit0
Reset Value
11111111
SFR Address:
0x96
Bits7-0: P7.[7:0]: Port7 Output Latch Bits.
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Output (Open-Drain if corresponding P74OUT bit = 0). See Figure 17.20.
Read - Returns states of I/O pins.
0: P7.n pin is logic low.
1: P7.n pin is logic high.
Note:
P7.[7:0] can be driven by the External Data Memory Interface (as AD[7:0] in Multiplexed mode, or
as D[7:0] in Non-multiplexed mode). See Section “16. EXTERNAL DATA MEMORY INTER-
FACE AND ON-CHIP XRAM” on page 145 for more information about the External Memory
Interface.
Rev. 1.4
181
C8051F020/1/2/3
Notes
182
Rev. 1.4
C8051F020/1/2/3
18. SYSTEM MANAGEMENT BUS / I2C BUS (SMBUS0)
The SMBus0 I/O interface is a two-wire, bi-directional serial bus. SMBus0 is compliant with the System Manage-
2
ment Bus Specification, version 1.1, and compatible with the I C serial bus. Reads and writes to the interface by the
system controller are byte oriented with the SMBus0 interface autonomously controlling the serial transfer of the
data. Data can be transferred at up to 1/8th of the system clock if desired (this can be faster than allowed by the
SMBus specification, depending on the system clock used). A method of extending the clock-low duration is avail-
able to accommodate devices with different speed capabilities on the same bus.
SMBus0 may operate as a master and/or slave, and may function on a bus with multiple masters. SMBus0 provides
control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration logic, and START/STOP
control and generation. SMBus0 is controlled by SFRs as described in Section 18.4 on page 189.
Figure 18.1. SMBus0 Block Diagram
SFR Bus
SMB0CN
SMB0STA
SMB0CR
B
U
S
Y
E
N
S
M
B
S
T
A
S
T
S
I
A
A
F
T
E
T
O
E
S
T
A
7
S
T
A
6
S
T
A
5
S
T
A
4
S
T
A
3
S
T
A
2
S
T
A
1
S
T
A
0
C
R
7
C
R
6
C
R
5
C
R
4
C
R
3
C
R
2
C
R
1
C
R
0
O
Clock Divide
Logic
SYSCLK
SCL
FILTER
SMBUS CONTROL LOGIC
Arbitration
SMBUS
IRQ
Interrupt
Request
SCL Synchronization
Status Generation
SCL Generation (Master Mode)
IRQ Generation
SCL
Control
N
SDA
Data Path
Control
Control
C
R
O
S
S
B
A
R
Port I/O
B
A
B
A
0000000b
7 MSBs
8
7
SMB0DAT
7 6 5 4 3 2 1 0
SDA
FILTER
8
8
1
0
S
L
V
6
S
L
V
5
S
L
V
4
S
L
V
3
S
L
V
2
S
L
V
1
S
L
V
0
N
G
C
Read
SMB0DAT
Write to
SMB0ADR
SMB0DAT
SFR Bus
Rev. 1.4
183
C8051F020/1/2/3
Figure 18.2 shows a typical SMBus configuration. The SMBus0 interface will work at any voltage between 3.0 V and
5.0 V and different devices on the bus may operate at different voltage levels. The bi-directional SCL (serial clock)
and SDA (serial data) lines must be connected to a positive power supply voltage through a pull-up resistor or similar
circuit. Every device connected to the bus must have an open-drain or open-collector output for both the SCL and
SDA lines, so that both are pulled high when the bus is free. The maximum number of devices on the bus is limited
only by the requirement that the rise and fall times on the bus will not exceed 300 ns and 1000 ns, respectively.
Figure 18.2. Typical SMBus Configuration
VDD = 5V
VDD = 3V
VDD = 5V
VDD = 3V
Master
Device
Slave
Slave
Device 1
Device 2
SDA
SCL
18.1. Supporting Documents
It is assumed the reader is familiar with or has access to the following supporting documents:
2
1. The I C-bus and how to use it (including specifications), Philips Semiconductor.
2
2. The I C-Bus Specification -- Version 2.0, Philips Semiconductor.
3. System Management Bus Specification -- Version 1.1, SBS Implementers Forum.
184
Rev. 1.4
C8051F020/1/2/3
18.2. SMBus Protocol
Two types of data transfers are possible: data transfers from a master transmitter to an addressed slave receiver
(WRITE), and data transfers from an addressed slave transmitter to a master receiver (READ). The master device ini-
tiates both types of data transfers and provides the serial clock pulses on SCL. Note: multiple master devices on the
same bus are supported. If two or more masters attempt to initiate a data transfer simultaneously, an arbitration
scheme is employed with a single master always winning the arbitration. Note that it is not necessary to specify one
device as the master in a system; any device who transmits a START and a slave address becomes the master for that
transfer.
A typical SMBus transaction consists of a START condition followed by an address byte (Bits7-1: 7-bit slave
address; Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Each byte that is received (by a
master or slave) must be acknowledged (ACK) with a low SDA during a high SCL (see Figure 18.3). If the receiving
device does not ACK, the transmitting device will read a “not acknowledge” (NACK), which is a high SDA during a
high SCL.
The direction bit (R/W) occupies the least-significant bit position of the address. The direction bit is set to logic 1 to
indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation.
All transactions are initiated by a master, with one or more addressed slave devices as the target. The master gener-
ates the START condition and then transmits the slave address and direction bit. If the transaction is a WRITE opera-
tion from the master to the slave, the master transmits the data a byte at a time waiting for an ACK from the slave at
the end of each byte. For READ operations, the slave transmits the data waiting for an ACK from the master at the
end of each byte. At the end of the data transfer, the master generates a STOP condition to terminate the transaction
and free the bus. Figure 18.3 illustrates a typical SMBus transaction.
Figure 18.3. SMBus Transaction
SCL
SDA
SLA6
SLA5-0
R/W
D7
D6-0
START
Slave Address + R/W
ACK
Data Byte
NACK
STOP
18.2.1. Arbitration
A master may start a transfer only if the bus is free. The bus is free after a STOP condition or after the SCL and SDA
lines remain high for a specified time (see Section 18.2.4). In the event that two or more devices attempt to begin a
transfer at the same time, an arbitration scheme is employed to force one master to give up the bus. The master
devices continue transmitting until one attempts a HIGH while the other transmits a LOW. Since the bus is open-
drain, the bus will be pulled LOW. The master attempting the HIGH will detect a LOW SDA and give up the bus. The
winning master continues its transmission without interruption; the losing master becomes a slave and receives the
rest of the transfer. This arbitration scheme is non-destructive: one device always wins, and no data is lost.
18.2.2. Clock Low Extension
2
SMBus provides a clock synchronization mechanism, similar to I C, which allows devices with different speed capa-
bilities to coexist on the bus. A clock-low extension is used during a transfer in order to allow slower slave devices to
communicate with faster masters. The slave may temporarily hold the SCL line LOW to extend the clock low period,
effectively decreasing the serial clock frequency.
Rev. 1.4
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C8051F020/1/2/3
18.2.3. SCL Low Timeout
If the SCL line is held low by a slave device on the bus, no further communication is possible. Furthermore, the mas-
ter cannot force the SCL line high to correct the error condition. To solve this problem, the SMBus protocol specifies
that devices participating in a transfer must detect any clock cycle held low longer than 25 ms as a “timeout” condi-
tion. Devices that have detected the timeout condition must reset the communication no later than 10 ms after detect-
ing the timeout condition.
18.2.4. SCL High (SMBus Free) Timeout
The SMBus specification stipulates that if the SCL and SDA lines remain high for more that 50 µs, the bus is desig-
nated as free. If an SMBus device is waiting to generate a Master START, the START will be generated following a
bus free timeout.
186
Rev. 1.4
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18.3. SMBus Transfer Modes
The SMBus0 interface may be configured to operate as a master and/or a slave. At any particular time, the interface
will be operating in one of the following modes: Master Transmitter, Master Receiver, Slave Transmitter, or Slave
Receiver. See Table 18.1 for transfer mode status decoding using the SMB0STA status register. The following mode
descriptions illustrate an interrupt-driven SMBus0 application; SMBus0 may alternatively be operated in polled
mode.
18.3.1. Master Transmitter Mode
Serial data is transmitted on SDA while the serial clock is output on SCL. SMBus0 generates a START condition and
then transmits the first byte containing the address of the target slave device and the data direction bit. In this case the
data direction bit (R/W) will be logic 0 to indicate a "WRITE" operation. The SMBus0 interface transmits one or
more bytes of serial data, waiting for an acknowledge (ACK) from the slave after each byte. To indicate the end of the
serial transfer, SMBus0 generates a STOP condition.
Figure 18.4. Typical Master Transmitter Sequence
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupt
Interrupt
Interrupt
Interrupt
S = START
P = STOP
A = ACK
Received by SMBus
Interface
W = WRITE
Transmitted by
SLA = Slave Address
SMBus Interface
18.3.2. Master Receiver Mode
Serial data is received on SDA while the serial clock is output on SCL. The SMBus0 interface generates a START
followed by the first data byte containing the address of the target slave and the data direction bit. In this case the data
direction bit (R/W) will be logic 1 to indicate a "READ" operation. The SMBus0 interface receives serial data from
the slave and generates the clock on SCL. After each byte is received, SMBus0 generates an ACK or NACK depend-
ing on the state of the AA bit in register SMB0CN. SMBus0 generates a STOP condition to indicate the end of the
serial transfer.
Figure 18.5. Typical Master Receiver Sequence
S
SLA
R
A
Data Byte
A
Data Byte
N
P
Interrupt
Interrupt
Interrupt
Interrupt
S = START
P = STOP
A = ACK
Received by SMBus
Interface
N = NACK
R = READ
Transmitted by
SMBus Interface
SLA = Slave Address
Rev. 1.4
187
C8051F020/1/2/3
18.3.3. Slave Transmitter Mode
Serial data is transmitted on SDA while the serial clock is received on SCL. The SMBus0 interface receives a START
followed by data byte containing the slave address and direction bit. If the received slave address matches the address
held in register SMB0ADR, the SMBus0 interface generates an ACK. SMBus0 will also ACK if the general call
address (0x00) is received and the General Call Address Enable bit (SMB0ADR.0) is set to logic 1. In this case the
data direction bit (R/W) will be logic 1 to indicate a "READ" operation. The SMBus0 interface receives the clock on
SCL and transmits one or more bytes of serial data, waiting for an ACK from the master after each byte. SMBus0
exits slave mode after receiving a STOP condition from the master.
Figure 18.6. Typical Slave Transmitter Sequence
Interrupt
S
SLA
R
A
Data Byte
A
Data Byte
N
P
Interrupt
Interrupt
Interrupt
S = START
P = STOP
N = NACK
W = WRITE
Received by SMBus
Interface
Transmitted by
SLA = Slave Address
SMBus Interface
18.3.4. Slave Receiver Mode
Serial data is received on SDA while the serial clock is received on SCL. The SMBus0 interface receives a START
followed by data byte containing the slave address and direction bit. If the received slave address matches the address
held in register SMB0ADR, the interface generates an ACK. SMBus0 will also ACK if the general call address
(0x00) is received and the General Call Address Enable bit (SMB0ADR.0) is set to logic 1. In this case the data direc-
tion bit (R/W) will be logic 0 to indicate a "WRITE" operation. The SMBus0 interface receives one or more bytes of
serial data; after each byte is received, the interface transmits an ACK or NACK depending on the state of the AA bit
in SMB0CN. SMBus0 exits Slave Receiver Mode after receiving a STOP condition from the master.
Figure 18.7. Typical Slave Receiver Sequence
Interrupt
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupt
Interrupt
Interrupt
S = START
P = STOP
A = ACK
Received by SMBus
Interface
R = READ
Transmitted by
SLA = Slave Address
SMBus Interface
188
Rev. 1.4
C8051F020/1/2/3
18.4. SMBus Special Function Registers
The SMBus0 serial interface is accessed and controlled through five SFRs: SMB0CN Control Register, SMB0CR
Clock Rate Register, SMB0ADR Address Register, SMB0DAT Data Register and SMB0STA Status Register. The
five special function registers related to the operation of the SMBus0 interface are described in the following sec-
tions.
18.4.1. Control Register
The SMBus0 Control register SMB0CN is used to configure and control the SMBus0 interface. All of the bits in the
register can be read or written by software. Two of the control bits are also affected by the SMBus0 hardware. The
Serial Interrupt flag (SI, SMB0CN.3) is set to logic 1 by the hardware when a valid serial interrupt condition occurs.
It can only be cleared by software. The Stop flag (STO, SMB0CN.4) is cleared to logic 0 by hardware when a STOP
condition is detected on the bus.
Setting the ENSMS flag to logic 1 enables the SMBus0 interface. Clearing the ENSMB flag to logic 0 disables the
SMBus0 interface and removes it from the bus. Momentarily clearing the ENSMB flag and then resetting it to logic 1
will reset SMBus0 communication. However, ENSMB should not be used to temporarily remove a device from the
bus since the bus state information will be lost. Instead, the Assert Acknowledge (AA) flag should be used to tempo-
rarily remove the device from the bus (see description of AA flag below).
Setting the Start flag (STA, SMB0CN.5) to logic 1 will put SMBus0 in a master mode. If the bus is free, SMBus0 will
generate a START condition. If the bus is not free, SMBus0 waits for a STOP condition to free the bus and then gen-
erates a START condition after a 5 µs delay per the SMB0CR value (In accordance with the SMBus protocol, the
SMBus0 interface also considers the bus free if the bus is idle for 50 µs and no STOP condition was recognized). If
STA is set to logic 1 while SMBus0 is in master mode and one or more bytes have been transferred, a repeated
START condition will be generated. To ensure proper operation, the STO bit should be explicitly cleared to ‘0’ before
setting the STA bit to ‘1’.
When the Stop flag (STO, SMB0CN.4) is set to logic 1 while the SMBus0 interface is in master mode, the interface
generates a STOP condition. In a slave mode, the STO flag may be used to recover from an error condition. In this
case, a STOP condition is not generated on the bus, but the SMBus hardware behaves as if a STOP condition has been
received and enters the "not addressed" slave receiver mode. Note that this simulated STOP will not cause the bus to
appear free to SMBus0. The bus will remain occupied until a STOP appears on the bus or a Bus Free Timeout occurs.
Hardware automatically clears the STO flag to logic 0 when a STOP condition is detected on the bus.
The Serial Interrupt flag (SI, SMB0CN.3) is set to logic 1 by hardware when the SMBus0 interface enters one of 27
possible states. If interrupts are enabled for the SMBus0 interface, an interrupt request is generated when the SI flag
is set. The SI flag must be cleared by software.
Important Note: If SI is set to logic 1 while the SCL line is low, the clock-low period of the serial clock will be
stretched and the serial transfer is suspended until SI is cleared to logic 0. A high level on SCL is not affected by the
setting of the SI flag.
The Assert Acknowledge flag (AA, SMB0CN.2) is used to set the level of the SDA line during the acknowledge
clock cycle on the SCL line. Setting the AA flag to logic 1 will cause an ACK (low level on SDA) to be sent during
the acknowledge cycle if the device has been addressed. Setting the AA flag to logic 0 will cause a NACK (high level
on SDA) to be sent during acknowledge cycle. After the transmission of a byte in slave mode, the slave can be tempo-
rarily removed from the bus by clearing the AA flag. The slave's own address and general call address will be
ignored. To resume operation on the bus, the AA flag must be reset to logic 1 to allow the slave's address to be recog-
nized.
Rev. 1.4
189
C8051F020/1/2/3
Setting the SMBus0 Free Timer Enable bit (FTE, SMB0CN.1) to logic 1 enables the timer in SMB0CR. When SCL
goes high, the timer in SMB0CR counts up. A timer overflow indicates a free bus timeout: if SMBus0 is waiting to
generate a START, it will do so after this timeout. The bus free period should be less than 50 µs (see Figure 18.9,
SMBus0 Clock Rate Register).
When the TOE bit in SMB0CN is set to logic 1, Timer 3 is used to detect SCL low timeouts. If Timer 3 is enabled
(see Section “22.2. Timer 3” on page 240), Timer 3 is forced to reload when SCL is high, and forced to count when
SCL is low. With Timer 3 enabled and configured to overflow after 25 ms (and TOE set), a Timer 3 overflow indi-
cates a SCL low timeout; the Timer 3 interrupt service routine can then be used to reset SMBus0 communication in
the event of an SCL low timeout.
190
Rev. 1.4
C8051F020/1/2/3
Figure 18.8. SMB0CN: SMBus0 Control Register
R
R/W
ENSMB
Bit6
R/W
STA
Bit5
R/W
STO
Bit4
R/W
SI
Bit3
R/W
AA
Bit2
R/W
FTE
Bit1
R/W
TOE
Reset Value
00000000
SFR Address:
0xC0
BUSY
Bit7
Bit0
(bit addressable)
Bit7:
BUSY: Busy Status Flag.
0: SMBus0 is free
1: SMBus0 is busy
Bit6:
Bit5:
ENSMB: SMBus Enable.
This bit enables/disables the SMBus serial interface.
0: SMBus0 disabled.
1: SMBus0 enabled.
STA: SMBus Start Flag.
0: No START condition is transmitted.
1: When operating as a master, a START condition is transmitted if the bus is free. (If the bus is not
free, the START is transmitted after a STOP is received.) If STA is set after one or more bytes have
been transmitted or received and before a STOP is received, a repeated START condition is transmit-
ted. To ensure proper operation, the STO bit should be explicitly cleared to ‘0’ before setting the STA
bit to ‘1’.
Bit4:
STO: SMBus Stop Flag.
0: No STOP condition is transmitted.
1: Setting STO to logic 1 causes a STOP condition to be transmitted. When a STOP condition is
received, hardware clears STO to logic 0. If both STA and STO are set, a STOP condition is transmit-
ted followed by a START condition. In slave mode, setting the STO flag causes SMBus to behave as
if a STOP condition was received.
Bit3:
Bit2:
SI: SMBus Serial Interrupt Flag.
This bit is set by hardware when one of 27 possible SMBus0 states is entered. (Status code 0xF8 does
not cause SI to be set.) When the SI interrupt is enabled, setting this bit causes the CPU to vector to
the SMBus interrupt service routine. This bit is not automatically cleared by hardware and must be
cleared by software.
AA: SMBus Assert Acknowledge Flag.
This bit defines the type of acknowledge returned during the acknowledge cycle on the SCL line.
0: A "not acknowledge" (high level on SDA) is returned during the acknowledge cycle.
1: An "acknowledge" (low level on SDA) is returned during the acknowledge cycle.
FTE: SMBus Free Timer Enable Bit
Bit1:
Bit0:
0: No timeout when SCL is high
1: Timeout when SCL high time exceeds limit specified by the SMB0CR value.
TOE: SMBus Timeout Enable Bit
0: No timeout when SCL is low.
Rev. 1.4
191
C8051F020/1/2/3
18.4.2. Clock Rate Register
Figure 18.9. SMB0CR: SMBus0 Clock Rate Register
R/W
Bit7
R/W
Bit6
R/W
R/W
R/W
R/W
R/W
R/W
Bit0
Reset Value
00000000
SFR Address:
0xCF
Bit5
Bit4
Bit3
Bit2
Bit1
Bits7-0: SMB0CR.[7:0]: SMBus0 Clock Rate Preset
The SMB0CR Clock Rate register controls the frequency of the serial clock SCL in master mode. The
8-bit word stored in the SMB0CR Register preloads a dedicated 8-bit timer. The timer counts up, and
when it rolls over to 0x00, the SCL logic state toggles.
The SMB0CR setting should be bounded by the following equation , where SMB0CR is the unsigned
8-bit value in register SMB0CR, and SYSCLK is the system clock frequency in Hz:
SMB0CR < ((288 – 0.85 ⋅ SYSCLK) ⁄ 1.125)
The resulting SCL signal high and low times are given by the following equations:
TLOW = (256 – SMB0CR) ⁄ SYSCLK
T
HIGH ≅ (258 – SMB0CR) ⁄ SYSCLK + 625ns
Using the same value of SMB0CR from above, the Bus Free Timeout period is given in the following
equation:
(256 – SMB0CR) + 1
----------------------------------------------------
BFT ≅ 10 ×
T
SYSCLK
192
Rev. 1.4
C8051F020/1/2/3
18.4.3. Data Register
The SMBus0 Data register SMB0DAT holds a byte of serial data to be transmitted or one that has just been received.
Software can read or write to this register while the SI flag is set to logic 1; software should not attempt to access the
SMB0DAT register when the SMBus is enabled and the SI flag is cleared to logic 0 since the hardware may be in the
process of shifting a byte of data in or out of the register.
Data in SMB0DAT is always shifted out MSB first. After a byte has been received, the first bit of received data is
located at the MSB of SMB0DAT. While data is being shifted out, data on the bus is simultaneously being shifted in.
Therefore, SMB0DAT always contains the last data byte present on the bus. In the event of lost arbitration, the transi-
tion from master transmitter to slave receiver is made with the correct data in SMB0DAT.
Figure 18.10. SMB0DAT: SMBus0 Data Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xC2
Bits7-0: SMB0DAT: SMBus0 Data.
The SMB0DAT register contains a byte of data to be transmitted on the SMBus0 serial interface or a
byte that has just been received on the SMBus0 serial interface. The CPU can read from or write to
this register whenever the SI serial interrupt flag (SMB0CN.3) is set to logic 1. When the SI flag is
not set, the system may be in the process of shifting data in/out and the CPU should not attempt to
access this register.
18.4.4. Address Register
The SMB0ADR Address register holds the slave address for the SMBus0 interface. In slave mode, the seven most-
significant bits hold the 7-bit slave address. The least significant bit (Bit0) is used to enable the recognition of the
general call address (0x00). If Bit0 is set to logic 1, the general call address will be recognized. Otherwise, the general
call address is ignored. The contents of this register are ignored when SMBus0 is operating in master mode.
Figure 18.11. SMB0ADR: SMBus0 Address Register
R/W
SLV6
Bit7
R/W
SLV5
Bit6
R/W
SLV4
Bit5
R/W
SLV3
Bit4
R/W
SLV2
Bit3
R/W
SLV1
Bit2
R/W
SLV0
Bit1
R/W
GC
Bit0
Reset Value
00000000
SFR Address:
0xC3
Bits7-1: SLV6-SLV0: SMBus0 Slave Address.
These bits are loaded with the 7-bit slave address to which SMBus0 will respond when operating as a
slave transmitter or slave receiver. SLV6 is the most significant bit of the address and corresponds to
the first bit of the address byte received.
Bit0:
GC: General Call Address Enable.
This bit is used to enable general call address (0x00) recognition.
0: General call address is ignored.
1: General call address is recognized.
Rev. 1.4
193
C8051F020/1/2/3
18.4.5. Status Register
The SMB0STA Status register holds an 8-bit status code indicating the current state of the SMBus0 interface. There
are 28 possible SMBus0 states, each with a corresponding unique status code. The five most significant bits of the
status code vary while the three least-significant bits of a valid status code are fixed at zero when SI = ‘1’. Therefore,
all possible status codes are multiples of eight. This facilitates the use of status codes in software as an index used to
branch to appropriate service routines (allowing 8 bytes of code to service the state or jump to a more extensive ser-
vice routine).
For the purposes of user software, the contents of the SMB0STA register is only defined when the SI flag is logic 1.
Software should never write to the SMB0STA register; doing so will yield indeterminate results. The 28 SMBus0
states, along with their corresponding status codes, are given in Table 1.1.
Figure 18.12. SMB0STA: SMBus0 Status Register
R/W
STA7
Bit7
R/W
STA6
Bit6
R/W
STA5
Bit5
R/W
STA4
Bit4
R/W
STA3
Bit3
R/W
STA2
Bit2
R/W
STA1
Bit1
R/W
STA0
Bit0
Reset Value
00000000
SFR Address:
0xC1
Bits7-3: STA7-STA3: SMBus0 Status Code.
These bits contain the SMBus0 Status Code. There are 28 possible status codes; each status code cor-
responds to a single SMBus state. A valid status code is present in SMB0STA when the SI flag
(SMB0CN.3) is set to logic 1. The content of SMB0STA is not defined when the SI flag is logic 0.
Writing to the SMB0STA register at any time will yield indeterminate results.
Bits2-0: STA2-STA0: The three least significant bits of SMB0STA are always read as logic 0 when the SI flag
is logic 1.
194
Rev. 1.4
C8051F020/1/2/3
Table 18.1. SMB0STA Status Codes and States
Status
Code
Mode
SMBus State
Typical Action
0x08
0x10
0x18
0x20
START condition transmitted.
Load SMB0DAT with Slave Address +
R/W. Clear STA.
Repeated START condition transmitted.
Load SMB0DAT with Slave Address +
R/W. Clear STA.
Slave Address + W transmitted. ACK
received.
Load SMB0DAT with data to be transmit-
ted.
Slave Address + W transmitted. NACK
received.
Acknowledge poll to retry. Set STO +
STA.
1) Load SMB0DAT with next byte, OR
2) Set STO, OR
0x28
0x30
Data byte transmitted. ACK received.
3) Clear STO then set STA for repeated
START.
Data byte transmitted. NACK received.
Arbitration Lost.
1) Retry transfer OR
2) Set STO.
0x38
0x40
Save current data.
Slave Address + R transmitted. ACK received. If only receiving one byte, clear AA (send
NACK after received byte). Wait for
received data.
0x48
0x50
0x58
Slave Address + R transmitted. NACK
received.
Acknowledge poll to retry. Set STO +
STA.
Data byte received. ACK transmitted.
Read SMB0DAT. Wait for next byte. If
next byte is last byte, clear AA.
Data byte received. NACK transmitted.
Set STO.
Rev. 1.4
195
C8051F020/1/2/3
Table 18.1. SMB0STA Status Codes and States
Status
Code
Mode
SMBus State
Typical Action
0x60
Own slave address + W received. ACK trans-
mitted.
Wait for data.
0x68
Arbitration lost in sending SLA + R/W as mas-
Save current data for retry when bus is
ter. Own address + W received. ACK transmit- free. Wait for data.
ted.
0x70
0x78
General call address received. ACK transmit-
ted.
Wait for data.
Arbitration lost in sending SLA + R/W as mas-
ter. General call address received. ACK trans-
mitted.
Save current data for retry when bus is
free.
0x80
Data byte received. ACK transmitted.
Read SMB0DAT. Wait for next byte or
STOP.
0x88
0x90
Data byte received. NACK transmitted.
Set STO to reset SMBus.
Data byte received after general call address.
ACK transmitted.
Read SMB0DAT. Wait for next byte or
STOP.
0x98
Data byte received after general call address.
NACK transmitted.
Set STO to reset SMBus.
0xA0
0xA8
0xB0
STOP or repeated START received.
No action necessary.
Own address + R received. ACK transmitted.
Load SMB0DAT with data to transmit.
Arbitration lost in transmitting SLA + R/W as
master. Own address + R received. ACK
transmitted.
Save current data for retry when bus is
free. Load SMB0DAT with data to trans-
mit.
0xB8
0xC0
0xC8
Data byte transmitted. ACK received.
Data byte transmitted. NACK received.
Load SMB0DAT with data to transmit.
Wait for STOP.
Last data byte transmitted (AA=0). ACK
received.
Set STO to reset SMBus.
0xD0
SCL Clock High Timer per SMB0CR timed out Set STO to reset SMBus.
0x00
0xF8
Bus Error (illegal START or STOP)
Idle
Set STO to reset SMBus.
State does not set SI.
196
Rev. 1.4
C8051F020/1/2/3
19. SERIAL PERIPHERAL INTERFACE BUS (SPI0)
The Serial Peripheral Interface (SPI0) provides access to a four-wire, full-duplex, serial bus. SPI0 may operate as a
master or a slave, and supports the connection of multiple slaves and masters on the same bus. A slave-select input
(NSS) is included in the SPI0 interface to select SPI0 as a slave; additional general purpose port I/O can be used as
slave-select outputs when SPI0 is operating as a master. Collision detection is provided when two or more masters
attempt a data transfer at the same time. When the SPI is configured as a master, the maximum data transfer rate (bits/
sec) is one-half the system clock frequency.
When the SPI is configured as a slave, the maximum data transfer rate (bits/sec) for full-duplex operation is 1/10 the
system clock frequency, provided that the master issues SCK, NSS, and the serial input data synchronously with the
system clock. If the master issues SCK, NSS, and the serial input data asynchronously, the maximum data transfer
rate (bits/sec) must be less that 1/10 the system clock frequency. In the special case where the master only wants to
transmit data to the slave and does not need to receive data from the slave (i.e. half-duplex operation), the SPI slave
can receive data at a maximum data transfer rate (bits/sec) of 1/4 the system clock frequency. This is provided that the
master issues SCK, NSS, and the serial input data synchronously with the system clock.
Figure 19.1. SPI Block Diagram
SFR Bus
SPI0CKR
SPI0CFG
SPI0CN
S
C
R
7
S
C
R
6
S
C
R
5
S
C
R
4
S
C
R
3
S
C
R
2
S
C
R
1
S
C
R
0
C
K
P
H
A
C
K
P
O
L
B
C
2
B
C
1
B
C
0
F
R
S
2
F
R
S
1
F
R
S
0
S
P
I
W
C
O
L
M
O
D
F
R
X
O
V
R
N
T
X
B
S
Y
S
L
M
S
T
S
P
I
V
S
E
L
F
E
N
E
N
Clock Divide
Logic
Bit Count
Logic
SYSCLK
SPI CONTROL LOGIC
SPI IRQ
Data Path
Control
SPI Clock
Pin Control
Interface
(Master Mode)
SCK
C
R
O
S
S
B
A
R
MOSI
MISO
NSS
Tx Data
Pin
SPI0DAT
Control
Logic
Port I/O
Shift Register
7 6 5 4 3 2 1 0
Rx Data
Receive Data Register
Read
Write to
SPI0DAT
SPI0DAT
SFR Bus
Rev. 1.4
197
C8051F020/1/2/3
19.1. Signal Descriptions
The four signals used by SPI0 (MOSI, MISO, SCK, NSS) are described below.
19.1.1. Master Out, Slave In (MOSI)
The master-out, slave-in (MOSI) signal is an output from a master device and an input to slave devices. It is used to
serially transfer data from the master to the slave. This signal is an output when SPI0 is operating as a master, and an
input when SPI0 is operating as a slave. Data is transferred most-significant bit first.
19.1.2. Master In, Slave Out (MISO)
The master-in, slave-out (MISO) signal is an output from a slave device and an input to the master device. It is used
to serially transfer data from the slave to the master. This signal is an input when SPI0 is operating as a master, and an
output when SPI0 is operating as a slave. Data is transferred most-significant bit first. A SPI slave places the MISO
pin in a high-impedance state when the slave is not selected.
19.1.3. Serial Clock (SCK)
The serial clock (SCK) signal is an output from the master device and an input to slave devices. It is used to synchro-
nize the transfer of data between the master and slave on the MOSI and MISO lines. SPI0 generates this signal when
operating as a master.
19.1.4. Slave Select (NSS)
The slave select (NSS) signal is an input used to select SPI0 as a slave, or to disable SPI0 as a master. Note that the
NSS signal is always an input to SPI0; with SPI0 operating as a master, slave select signals must be output via general
purpose port I/O pins. See Figure 19.2 for a typical configuration; see Section “17.1. Ports 0 through 3 and the Pri-
ority Crossbar Decoder” on page 163 for general purpose port configuration.
The NSS signal must be low to initiate a transfer with SPI0 as a slave; SPI0 will exit slave mode when NSS is
released high. Note that received data is not latched into the receive buffer until NSS is high. For multiple-byte trans-
fers, NSS must be released high for at least 4 system clocks following each byte that is received by the SPI0 slave.
Figure 19.2. Typical SPI Interconnection
NSS
NSS
NSS
Slave
Slave
Slave
Device
Device
Device
VDD
GPIO
Master
Device
MISO
MOSI
SCK
MISO
MOSI
SCK
198
Rev. 1.4
C8051F020/1/2/3
19.2. SPI0 Operation
Only a SPI master device can initiate a data transfer. SPI0 is placed in master mode by setting the Master Enable flag
(MSTEN, SPI0CN.1). Writing a byte of data to the SPI0 data register (SPI0DAT) when in Master Mode starts a data
transfer. The SPI0 master immediately shifts out the data serially on the MOSI line while providing the serial clock
on SCK. The SPIF (SPI0CN.7) flag is set to logic 1 at the end of the transfer. If interrupts are enabled, an interrupt
request is generated when the SPIF flag is set. The SPI0 master can be configured to shift in/out from one to eight bits
in a transfer operation in order to accommodate slave devices with different word lengths. The SPIFRS bits in the
SP0I Configuration Register (SPI0CFG.[2:0]) are used to select the number of bits to shift in/out in a transfer opera-
tion.
While the SPI0 master transfers data to a slave on the MOSI line, the addressed SPI slave device simultaneously
transfers the contents of its shift register to the SPI master on the MISO line in a full-duplex operation. The data byte
received from the slave replaces the data in the master's data register. Therefore, the SPIF flag serves as both a trans-
mit-complete and receive-data-ready flag. The data transfer in both directions is synchronized with the serial clock
generated by the master. Figure 19.3 illustrates the full-duplex operation of an SPI master and an addressed slave.
Figure 19.3. Full Duplex Operation
MASTER DEVICE
SLAVE DEVICE
MOSI
MISO
NSS
SCK
Px.y
MOSI
MISO
NSS
SPI SHIFT REGISTER
7 6 5 4 3 2 1 0
SPI SHIFT REGISTER
7 6 5 4 3 2 1 0
VDD
Receive Buffer
Receive Buffer
SCK
Baud Rate
Generator
When SPI0 is enabled and not configured as a master, it will operate as an SPI slave. Another SPI device acting as a
master will initiate a transfer by driving the NSS input signal low. The master then shifts data out of the shift register
on the MOSI pin using the its serial clock. The SPIF flag is set to logic 1 when the NSS signal goes high, indicating
the end of a data transfer. Note that following a rising edge on NSS, the receive buffer will always contain the last
8 bits of data in the slave shift register. The slave can load its shift register for the next data transfer by writing to the
SPI0 data register. The slave must make the write to the data register at least one SPI serial clock cycle before the
master starts the next transmission. Otherwise, the byte of data already in the slave's shift register will be transferred.
Note that the NSS signal must be driven low at least 2 system clocks before the first active edge of SCK for each byte
transfer.
The SPI0 data register is double buffered on reads, but not on writes. If a write to SPI0DAT is attempted during a data
transfer, the WCOL flag (SPI0CN.6) will be set to logic 1 and the write will be ignored. The current data transfer will
continue uninterrupted. A read of the SPI0 data register by the system controller actually reads the receive buffer. The
receive overrun flag (RXOVRN in register SPI0CN) is set anytime a SPI0 slave detects a rising edge on NSS while
the receive buffer still holds unread data from a previous transfer. The new data is not transferred to the receive
buffer, allowing the previously received data byte to be read. The data byte causing the overrun is lost.
Rev. 1.4
199
C8051F020/1/2/3
Multiple masters may reside on the same bus. A Mode Fault flag (MODF, SPI0CN.5) is set to logic 1 when SPI0 is
configured as a master (MSTEN = 1) and its slave select signal NSS is pulled low. When the Mode Fault flag is set,
the MSTEN and SPIEN bits of the SPI control register are cleared by hardware, thereby placing the SPI0 module in
an "off-line" state. In a multiple-master environment, the system controller should check the state of the SLVSEL flag
(SPI0CN.2) to ensure the bus is free before setting the MSTEN bit and initiating a data transfer.
19.3. Serial Clock Timing
As shown in Figure 19.4, four combinations of serial clock phase and polarity can be selected using the clock control
bits in the SPI0 Configuration Register (SPI0CFG). The CKPHA bit (SPI0CFG.7) selects one of two clock phases
(edge used to latch the data). The CKPOL bit (SPI0CFG.6) selects between an active-high or active-low clock. Both
master and slave devices must be configured to use the same clock phase and polarity. Note: SPI0 should be disabled
(by clearing the SPIEN bit, SPI0CN.0) while changing the clock phase and polarity.
The SPI0 Clock Rate Register (SPI0CKR) as shown in Figure 19.7 controls the master mode serial clock frequency.
This register is ignored when operating in slave mode.
Figure 19.4. Data/Clock Timing Diagram
SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=0)
SCK
(CKPOL=1, CKPHA=1)
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
MISO/MOSI
NSS
200
Rev. 1.4
C8051F020/1/2/3
19.4. SPI Special Function Registers
SPI0 is accessed and controlled through four special function registers in the system controller: SPI0CN Control Reg-
ister, SPI0DAT Data Register, SPI0CFG Configuration Register, and SPI0CKR Clock Rate Register. The four special
function registers related to the operation of the SPI0 Bus are described in the following section.
Figure 19.5. SPI0CFG: SPI0 Configuration Register
R/W
CKPHA
Bit7
R/W
CKPOL
Bit6
R
BC2
Bit5
R
BC1
Bit4
R
BC0
Bit3
R/W
R/W
R/W
Reset Value
SPIFRS2 SPIFRS1 SPIFRS0 00000111
Bit2
Bit1
Bit0
SFR Address:
0x9A
Bit7:
CKPHA: SPI0 Clock Phase.
This bit controls the SPI0 clock phase.
0: Data sampled on first edge of SCK period.
1: Data sampled on second edge of SCK period.
CKPOL: SPI0 Clock Polarity.
Bit6:
This bit controls the SPI0 clock polarity.
0: SCK line low in idle state.
1: SCK line high in idle state.
Bits5-3: BC2-BC0: SPI0 Bit Count.
Indicates which of the up to 8 bits of the SPI0 word have been transmitted.
BC2-BC0
BIT Transmitted
Bit 0 (LSB)
Bit 1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7 (MSB)
Bits2-0: SPIFRS2-SPIFRS0: SPI0 Frame Size.
These three bits determine the number of bits to shift in/out of the SPI0 shift register during a data
transfer in master mode. They are ignored in slave mode.
SPIFRS
Bits Shifted
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
1
2
3
4
5
6
7
8
Rev. 1.4
201
C8051F020/1/2/3
Figure 19.6. SPI0CN: SPI0 Control Register
R/W
SPIF
Bit7
R/W
WCOL
Bit6
R/W
R/W
R
R
R/W
MSTEN
Bit1
R/W
SPIEN
Reset Value
00000000
SFR Address:
0xF8
MODF RXOVRN TXBSY
Bit5
SLVSEL
Bit2
Bit4
Bit3
Bit0
(bit addressable)
Bit7:
SPIF: SPI0 Interrupt Flag.
This bit is set to logic 1 by hardware at the end of a data transfer. If interrupts are enabled, setting this
bit causes the CPU to vector to the SPI0 interrupt service routine. This bit is not automatically cleared
by hardware. It must be cleared by software.
Bit6:
Bit5:
Bit4:
WCOL: Write Collision Flag.
This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) to indicate a write to the SPI0
data register was attempted while a data transfer was in progress. If interrupts are enabled, setting this
bit causes the CPU to vector to the SPI0 interrupt service routine. This bit is not automatically cleared
by hardware. It must be cleared by software.
MODF: Mode Fault Flag.
This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) when a master mode collision is
detected (NSS is low and MSTEN = 1). If interrupts are enabled, setting this bit causes the CPU to
vector to the SPI0 interrupt service routine. This bit is not automatically cleared by hardware. It must
be cleared by software.
RXOVRN: Receive Overrun Flag.
This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) when the receive buffer still
holds unread data from a previous transfer and the last bit of the current transfer is shifted into the
SPI0 shift register. If interrupts are enabled, setting this bit causes the CPU to vector to the SPI0 inter-
rupt service routine. This bit is not automatically cleared by hardware. It must be cleared by software.
TXBSY: Transmit Busy Flag.
Bit3:
Bit2:
Bit1:
Bit0:
This bit is set to logic 1 by hardware while a master mode transfer is in progress. It is cleared by hard-
ware at the end of the transfer.
SLVSEL: Slave Selected Flag.
This bit is set to logic 1 whenever the NSS pin is low indicating it is enabled as a slave. It is cleared to
logic 0 when NSS is high (slave disabled).
MSTEN: Master Mode Enable.
0: Disable master mode. Operate in slave mode.
1: Enable master mode. Operate as a master.
SPIEN: SPI0 Enable.
This bit enables/disables the SPI.
0: SPI disabled.
202
Rev. 1.4
C8051F020/1/2/3
Figure 19.7. SPI0CKR: SPI0 Clock Rate Register
R/W
SCR7
Bit7
R/W
SCR6
Bit6
R/W
SCR5
Bit5
R/W
SCR4
Bit4
R/W
SCR3
Bit3
R/W
SCR2
Bit2
R/W
SCR1
Bit1
R/W
SCR0
Bit0
Reset Value
00000000
SFR Address:
0x9D
Bits7-0: SCR7-SCR0: SPI0 Clock Rate
These bits determine the frequency of the SCK output when the SPI0 module is configured for master
mode operation. The SCK clock frequency is a divided down version of the system clock, and is
given in the following equation, where SYSCLK is the system clock frequency and SPI0CR is the 8-
bit value held in the SPI0CR register.
SYSCLK
fSCK = ------------------------------------------------
2 × (SPI0CKR + 1)
for 0 <= SPI0CKR <= 255
Example: If SYSCLK = 2 MHz and SPI0CKR = 0x04,
2000000
fSCK = -------------------------
2 × (4 + 1)
fSCK = 200kHz
Figure 19.8. SPI0DAT: SPI0 Data Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x9B
Bits7-0: SPI0DAT: SPI0 Transmit and Receive Data.
The SPI0DAT register is used to transmit and receive SPI0 data. Writing data to SPI0DAT places the
data immediately into the shift register and initiates a transfer when in Master Mode. A read of
SPI0DAT returns the contents of the receive buffer.
Rev. 1.4
203
C8051F020/1/2/3
Notes
204
Rev. 1.4
C8051F020/1/2/3
20. UART0
UART0 is an enhanced serial port with frame error detection and address recognition hardware. UART0 may operate
in full-duplex asynchronous or half-duplex synchronous modes, and mutiproccessor communication is fully sup-
ported. Receive data is buffered in a holding register, allowing UART0 to start reception of a second incoming data
byte before software has finished reading the previous data byte. A Receive Overrun bit indicates when new received
data is latched into the receive buffer before the previous received byte is read.
UART0 is accessed via its associated SFRs, Serial Control (SCON0) and Serial Data Buffer (SBUF0). The single
SBUF0 location provides access to both transmit and receive registers. Reads access the Receive register and writes
access the Transmit register automatically.
UART0 may be operated in polled or interrupt mode. UART0 has two sources of interrupts: a Transmit Interrupt flag,
TI0 (SCON0.1) set when transmission of a data byte is complete, and a Receive Interrupt flag, RI0 (SCON0.0) set
when reception of a data byte is complete. UART0 interrupt flags are not cleared by hardware when the CPU vectors
to the interrupt service routine; they must be cleared manually by software. This allows software to determine the
cause of the UART0 interrupt (transmit complete or receive complete).
Figure 20.1. UART0 Block Diagram
SFR Bus
Write to
SBUF
TB8
SET
SBUF
D
Q
TX
(Transmit Shift)
CLR
Crossbar
Zero Detector
Shift
Stop Bit
Gen.
Data
Tx Control
Start
Tx Clock
Send
Tx IRQ
TI
SCON
UART
Baud Rate
Generation
Logic
Serial Port
S
M
0
S
S
M
2
R
E
N
T
B
8
R
B
8
T
I
R
I
(UART0/1)
Interrupt
M
1
RI
EN
Rx IRQ
Rx Clock
Start
Load
SBUF
Rx Control
Address
Match
Port I/O
Shift
0x1FF
Frame Error
Detection
Input Shift Register
(9 bits)
Load SBUF
RB8
SADDR
SADEN
SBUF
Match Detect
(Receive Latch)
Read
SBUF
SFR Bus
RX
Crossbar
Rev. 1.4
205
C8051F020/1/2/3
20.1. UART0 Operational Modes
UART0 provides four operating modes (one synchronous and three asynchronous) selected by setting configuration
bits in the SCON0 register. These four modes offer different baud rates and communication protocols. The four
modes are summarized in Table 20.1.
Table 20.1. UART0 Modes
Mode
Synchronization
Synchronous
Asynchronous
Asynchronous
Asynchronous
Baud Clock
SYSCLK / 12
Data Bits Start/Stop Bits
0
1
2
3
8
8
9
9
None
Timer 1 or 2 Overflow
SYSCLK / 32 or SYSCLK / 64
Timer 1 or 2 Overflow
1 Start, 1 Stop
1 Start, 1 Stop
1 Start, 1 Stop
20.1.1. Mode 0: Synchronous Mode
Mode 0 provides synchronous, half-duplex communication. Serial data is transmitted and received on the RX0 pin.
The TX0 pin provides the shift clock for both transmit and receive. The MCU must be the master since it generates
the shift clock for transmission in both directions (see the interconnect diagram in Figure 20.2).
Data transmission begins when an instruction writes a data byte to the SBUF0 register. Eight data bits are transferred
LSB first (see the timing diagram in Figure 20.3), and the TI0 Transmit Interrupt Flag (SCON0.1) is set at the end of
the eighth bit time. Data reception begins when the REN0 Receive Enable bit (SCON0.4) is set to logic 1 and the RI0
Receive Interrupt Flag (SCON0.0) is cleared. One cycle after the eighth bit is shifted in, the RI0 flag is set and recep-
tion stops until software clears the RI0 bit. An interrupt will occur if enabled when either TI0 or RI0 are set.
The Mode 0 baud rate is SYSCLK / 12. RX0 is forced to open-drain in Mode 0, and an external pull-up will typically
be required.
Figure 20.2. UART0 Mode 0 Interconnect
C8051FxxxTX
CLK
Shift
Reg.
RX
DATA
8 Extra Outputs
Figure 20.3. UART0 Mode 0 Timing Diagram
MODE 0 TRANSMIT
D0
D1
D2
D3
D4
D5
D6
D7
RX (data out)
TX (clk out)
MODE 0 RECEIVE
D0
D1
D2
D3
D4
D5
D6
D7
RX (data in)
TX (clk out)
206
Rev. 1.4
C8051F020/1/2/3
20.1.2. Mode 1: 8-Bit UART, Variable Baud Rate
Mode 1 provides standard asynchronous, full duplex communication using a total of 10 bits per data byte: one start
bit, eight data bits (LSB first), and one stop bit. Data are transmitted from the TX0 pin and received at the RX0 pin.
On receive, the eight data bits are stored in SBUF0 and the stop bit goes into RB80 (SCON0.2).
Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI0 Transmit Interrupt
Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin
any time after the REN0 Receive Enable bit (SCON0.4) is set to logic 1. After the stop bit is received, the data byte
will be loaded into the SBUF0 receive register if the following conditions are met: RI0 must be logic 0, and if SM20
is logic 1, the stop bit must be logic 1.
If these conditions are met, the eight bits of data are stored in SBUF0, the stop bit is stored in RB80 and the RI0 flag
is set. If these conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not be set. An inter-
rupt will occur if enabled when either TI0 or RI0 is set.
Figure 20.4. UART0 Mode 1 Timing Diagram
MARK
START
BIT
STOP
BIT
D0
D1
D2
D3
D4
D5
D6
D7
SPACE
BIT TIMES
BIT SAMPLING
The baud rate generated in Mode 1 is a function of timer overflow, shown in Equation 20.1 and Equation 20.2.
UART0 can use Timer 1 operating in 8-Bit Auto-Reload Mode, or Timer 2 operating in Baud Rate Generator Mode to
generate the baud rate (note that the TX and RX clocks are selected separately). On each timer overflow event (a roll-
over from all ones - (0xFF for Timer 1, 0xFFFF for Timer 2) - to zero) a clock is sent to the baud rate logic.
Timer 2 is selected as TX and/or RX baud clock source by setting the TCLK0 (T2CON.4) and/or RCLK0 (T2CON.5)
bits, respectively (see Section “22. TIMERS” on page 225 for complete timer configuration details). When either
TCLK0 or RCLK0 is set to logic 1, Timer 2 is forced into Baud Rate Generator Mode, with SYSCLK / 2 as its clock
source. If TCLK0 and/or RCLK0 is logic 0, Timer 1 acts as the baud clock source for the TX and/or RX circuits,
respectively.
The Mode 1 baud rate equations are shown below, where T1M is the Timer 1 Clock Select bit (register CKCON),
TH1 is the 8-bit reload register for Timer 1, SMOD0 is the UART0 baud rate doubler (register PCON) and
[RCAP2H , RCAP2L] is the 16-bit reload register for Timer 2.
Equation 20.1. Mode 1 Baud Rate using Timer 1
2SMOD0
SYSCLK × 12(T1M – 1))
------------------
-------------------------------------------------------
BaudRate =
×
32
(256 – TH1)
Equation 20.2. Mode 1 Baud Rate using Timer 2
SYSCLK
BaudRate = --------------------------------------------------------------------------------------------
32 × (65536 – [RCAP2H, RCAP2L])
Rev. 1.4
207
C8051F020/1/2/3
20.1.3. Mode 2: 9-Bit UART, Fixed Baud Rate
Mode 2 provides asynchronous, full-duplex communication using a total of eleven bits per data byte: a start bit, 8 data
bits (LSB first), a programmable ninth data bit, and a stop bit. Mode 2 supports multiprocessor communications and
hardware address recognition (see Section “20.2. Multiprocessor Communications” on page 210). On transmit,
the ninth data bit is determined by the value in TB80 (SCON0.3). It can be assigned the value of the parity flag P in
the PSW or used in multiprocessor communications. On receive, the ninth data bit goes into RB80 (SCON0.2) and
the stop bit is ignored.
Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI0 Transmit Interrupt
Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin
any time after the REN0 Receive Enable bit (SCON0.4) is set to logic 1. After the stop bit is received, the data byte
will be loaded into the SBUF0 receive register if RI0 is logic 0 and one of the following requirements are met:
1. SM20 is logic 0
2. SM20 is logic 1, the received 9th bit is logic 1, and the received address matches the UART0 address as
described in Section 20.2.
If the above conditions are satisfied, the eight bits of data are stored in SBUF0, the ninth bit is stored in RB80 and the
RI0 flag is set. If these conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not be set.
An interrupt will occur if enabled when either TI0 or RI0 is set.
The baud rate in Mode 2 is either SYSCLK / 32 or SYSCLK / 64, depending on the value of the SMOD0 bit in regis-
ter PCON.
Equation 20.3. Mode 2 Baud Rate
SYSCLK
BaudRate = 2SMOD0
×
---------------------
64
Figure 20.5. UART Modes 2 and 3 Timing Diagram
MARK
START
BIT
STOP
BIT
D0
D1
D2
D3
D4
D5
D6
D7
D8
SPACE
BIT TIMES
BIT SAMPLING
208
Rev. 1.4
C8051F020/1/2/3
Figure 20.6. UART Modes 1, 2, and 3 Interconnect Diagram
TX
RX
RS-232
LEVEL
XLTR
RS-232
C8051Fxxx
OR
TX
RX
MCU
TXC8051Fxxx
RX
20.1.4. Mode 3: 9-Bit UART, Variable Baud Rate
Mode 3 uses the Mode 2 transmission protocol with the Mode 1 baud rate generation. Mode 3 operation transmits
11 bits: a start bit, 8 data bits (LSB first), a programmable ninth data bit, and a stop bit. The baud rate is derived from
Timer 1 or Timer 2 overflows, as defined by Equation 20.1 and Equation 20.2. Multiprocessor communications and
hardware address recognition are supported, as described in Section 20.2.
Rev. 1.4
209
C8051F020/1/2/3
20.2. Multiprocessor Communications
Modes 2 and 3 support multiprocessor communication between a master processor and one or more slave processors
by special use of the ninth data bit and the built-in UART0 address recognition hardware. A master processor begins
a transfer with an address byte to select one or more target slave devices. An address byte differs from a data byte in
that its ninth bit is logic 1; in a data byte, the ninth bit is always set to logic 0.
The UART0 address is configured via two SFRs: SADDR0 (Serial Address) and SADEN0 (Serial Address Enable).
SADEN0 sets the bit mask for the address held in SADDR0: bits set to logic 1 in SADEN0 correspond to bits in
SADDR0 that are checked against the received address byte; bits set to logic 0 in SADEN0 correspond to “don’t
care” bits in SADDR0.
Example 1
Example 2
Example 3
SADDR0
SADEN0
= 00110101
= 00001111
SADDR0
SADEN0
= 00110101
= 11110011
SADDR0
SADEN0
= 00110101
= 11000000
UART0 Address = xxxx0101
UART0 Address = 0011xx01
UART0 Address = 00xxxxxx
Setting the SM20 bit (SCON0.5) configures UART0 such that when a stop bit is received, UART0 will generate an
interrupt only if the ninth bit is logic 1 (RB80 = 1) and the received data byte matches the UART0 slave address. Fol-
lowing the received address interrupt, the slave should clear its SM20 bit to enable interrupts on the reception of the
following data byte(s). Once the entire message is received, the addressed slave should reset its SM20 bit to ignore all
transmissions until it receives the next address byte. While SM20 is logic 1, UART0 ignores all bytes that do not
match the UART0 address and include a ninth bit that is logic 1.
Multiple addresses can be assigned to a single slave and/or a single address can be assigned to multiple slaves,
thereby enabling "broadcast" transmissions to more than one slave simultaneously. The broadcast address is the logi-
cal OR of registers SADDR0 and SADEN0, and ‘0’s of the result are treated as “don’t cares”. Typically a broadcast
address of 0xFF (hexadecimal) is acknowledged by all slaves, assuming “don’t care” bits as ‘1’s. The master proces-
sor can be configured to receive all transmissions or a protocol can be implemented such that the master/slave role is
temporarily reversed to enable half-duplex transmission between the original master and slave(s).
Figure 20.7. UART Multi-Processor Mode Interconnect Diagram
Master
Device
Slave
Slave
Slave
Device
Device
Device
+5V
RX
TX
RX
TX
RX
TX
RX
TX
210
Rev. 1.4
C8051F020/1/2/3
20.3. Frame and Transmission Error Detection
Frame error detection is available in the following modes when the SSTAT0 bit in register PCON is set to logic 1.
Note: The SSTAT0 bit must be logic 1 to access any of the status bits (FE0, RXOVR0, and TXCOL0). To access the
UART0 Mode Select bits (SM00, SM10, and SM20), the SSTAT0 bit must be logic 0.
All Modes:
The Transmit Collision bit (TXCOL0 bit in register SCON0) reads ‘1’ if user software writes data to the SBUF0 reg-
ister while a transmit is in progress. Note that the TXCOL0 bit also functions as the SM20 bit when the SSTAT0 bit in
register PCON is logic 0.
Modes 1, 2, and 3:
The Receive Overrun bit (RXOVR0 in register SCON0) reads ‘1’ if a new data byte is latched into the receive buffer
before software has read the previous byte. Note that the RXOVR0 bit also functions as the SM10 bit when the
SSTAT0 bit in register PCON is logic 0.
The Frame Error bit (FE0 in register SCON0) reads ‘1’ if an invalid (low) STOP bit is detected. Note that the FE0 bit
also functions as the SM00 bit when the SSTAT0 bit in register PCON is logic 0.
Rev. 1.4
211
C8051F020/1/2/3
Table 20.2. Oscillator Frequencies for Standard Baud Rates
Oscillator frequency (MHz) Divide Factor Timer 1 Load Value* Resulting Baud Rate (Hz)**
25.0
25.0
24.576
24.576
24.0
24.0
23.592
23.592
22.1184
22.1184
18.432
18.432
16.5888
16.5888
14.7456
14.7456
12.9024
12.9024
11.0592
11.0592
9.216
9.216
7.3728
7.3728
5.5296
5.5296
3.6864
3.6864
1.8432
1.8432
434
868
320
848
208
833
205
819
192
768
160
640
144
576
128
512
112
448
96
348
80
320
64
256
48
192
32
0xE5
0xCA
0xEC
0xCB
0XF3
0xCC
0xF3
0xCD
0xF4
0xD0
0xF6
0xD8
0xF7
0xDC
0xF8
0xE0
0xF9
0xE4
0xFA
0xE8
0xFB
0xEC
0xFC
0xF0
0xFD
0xF4
0xFE
0xF8
0xFF
0xFC
57600 (57870)
28800
76800
28800 (28921)
115200 (115384)
28800 (28846)
115200 (113423)
28800 (28911)
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
128
16
64
28800
* Assumes SMOD0=1 and T1M=1.
** Numbers in parenthesis show the actual baud rate.
212
Rev. 1.4
C8051F020/1/2/3
Figure 20.8. SCON0: UART0 Control Register
R/W
R/W
R/W
R/W
REN0
Bit4
R/W
TB80
Bit3
R/W
RB80
Bit2
R/W
TI0
Bit1
R/W
RI0
Bit0
Reset Value
00000000
SFR Address:
0x98
SM00/FE0 SM10/RXOV0 SM20/TXCOL0
Bit7
Bit6
Bit5
Bits7-6: The function of these bits is determined by the SSTAT0 bit in register PCON.
If SSTAT0 is logic 1, these bits are UART0 status indicators as described in Section 20.3.
If SSTAT0 is logic 0, these bits select the Serial Port Operation Mode as shown below.
SM00-SM10: Serial Port Operation Mode:
SM00
SM10 Mode
0
0
1
1
0
Mode 0: Synchronous Mode
1
0
1
Mode 1: 8-Bit UART, Variable Baud Rate
Mode 2: 9-Bit UART, Fixed Baud Rate
Mode 3: 9-Bit UART, Variable Baud Rate
Bit5:
SM20: Multiprocessor Communication Enable.
If SSTAT0 is logic 1, this bit is a UART0 status indicator as described in Section 20.3.
If SSTAT0 is logic 0, the function of this bit is dependent on the Serial Port Operation Mode.
Mode 0: No effect.
Mode 1: Checks for valid stop bit.
0: Logic level of stop bit is ignored.
1: RI0 will only be activated if stop bit is logic level 1.
Modes 2 and 3: Multiprocessor Communications Enable.
0: Logic level of ninth bit is ignored.
1: RI0 is set and an interrupt is generated only when the ninth bit is logic 1 and the received
address matches the UART0 address or the broadcast address.
REN0: Receive Enable.
Bit4:
This bit enables/disables the UART0 receiver.
0: UART0 reception disabled.
1: UART0 reception enabled.
Bit3:
Bit2:
Bit1:
TB80: Ninth Transmission Bit.
The logic level of this bit will be assigned to the ninth transmission bit in Modes 2 and 3. It is not used
in Modes 0 and 1. Set or cleared by software as required.
RB80: Ninth Receive Bit.
The bit is assigned the logic level of the ninth bit received in Modes 2 and 3. In Mode 1, if SM20 is
logic 0, RB80 is assigned the logic level of the received stop bit. RB8 is not used in Mode 0.
TI0: Transmit Interrupt Flag.
Set by hardware when a byte of data has been transmitted by UART0 (after the 8th bit in Mode 0, or
at the beginning of the stop bit in other modes). When the UART0 interrupt is enabled, setting this bit
causes the CPU to vector to the UART0 interrupt service routine. This bit must be cleared manually
by software
Bit0:
RI0: Receive Interrupt Flag.
Set by hardware when a byte of data has been received by UART0 (as selected by the SM20 bit).
When the UART0 interrupt is enabled, setting this bit causes the CPU to vector to the UART0 inter-
rupt service routine. This bit must be cleared manually by software.
Rev. 1.4
213
C8051F020/1/2/3
Figure 20.9. SBUF0: UART0 Data Buffer Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x99
Bits7-0: SBUF0.[7:0]: UART0 Buffer Bits 7-0 (MSB-LSB)
This SFR accesses two registers; a transmit shift register and a receive latch register. When data is
written to SBUF0, it goes to the transmit shift register and is held for serial transmission. Writing a
byte to SBUF0 is what initiates the transmission. A read of SBUF0 returns the contents of the receive
latch.
Figure 20.10. SADDR0: UART0 Slave Address Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xA9
Bits7-0: SADDR0.[7:0]: UART0 Slave Address
The contents of this register are used to define the UART0 slave address. Register SADEN0 is a bit
mask to determine which bits of SADDR0 are checked against a received address: corresponding bits
set to logic 1 in SADEN0 are checked; corresponding bits set to logic 0 are “don’t cares”.
Figure 20.11. SADEN0: UART0 Slave Address Enable Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xB9
Bits7-0: SADEN0.[7:0]: UART0 Slave Address Enable
Bits in this register enable corresponding bits in register SADDR0 to determine the UART0 slave
address.
0: Corresponding bit in SADDR0 is a “don’t care”.
1: Corresponding bit in SADDR0 is checked against a received address.
214
Rev. 1.4
C8051F020/1/2/3
21. UART1
UART1 is an enhanced serial port with frame error detection and address recognition hardware. UART1 may operate
in full-duplex asynchronous or half-duplex synchronous modes, and mutiproccessor communication is fully sup-
ported. Receive data is buffered in a holding register, allowing UART1 to start reception of a second incoming data
byte before software has finished reading the previous data byte. A Receive Overrun bit indicates when new received
data is latched into the receive buffer before the previous received byte is read.
UART1 is accessed via its associated SFRs, Serial Control (SCON1) and Serial Data Buffer (SBUF1). The single
SBUF1 location provides access to both transmit and receive registers. Reads access the Receive register and writes
access the Transmit register automatically.
UART1 may be operated in polled or interrupt mode. UART1 has two sources of interrupts: a Transmit Interrupt flag,
TI1 (SCON1.1) set when transmission of a data byte is complete, and a Receive Interrupt flag, RI1 (SCON1.0) set
when reception of a data byte is complete. UART1 interrupt flags are not cleared by hardware when the CPU vectors
to the interrupt service routine; they must be cleared manually by software. This allows software to determine the
cause of the UART1 interrupt (transmit complete or receive complete).
Figure 21.1. UART1 Block Diagram
SFR Bus
Write to
SBUF
TB8
SET
SBUF
D
Q
TX
(Transmit Shift)
CLR
Crossbar
Zero Detector
Shift
Stop Bit
Gen.
Data
Tx Control
Start
Tx Clock
Send
Tx IRQ
TI
SCON
UART
Baud Rate
Generation
Logic
Serial Port
S
M
0
S
S
M
2
R
E
N
T
B
8
R
B
8
T
I
R
I
(UART0/1)
Interrupt
M
1
RI
EN
Rx IRQ
Rx Clock
Start
Load
SBUF
Rx Control
Address
Match
Port I/O
Shift
0x1FF
Frame Error
Detection
Input Shift Register
(9 bits)
Load SBUF
RB8
SADDR
SADEN
SBUF
Match Detect
(Receive Latch)
Read
SBUF
SFR Bus
RX
Crossbar
Rev. 1.4
215
C8051F020/1/2/3
21.1. UART1 Operational Modes
UART1 provides four operating modes (one synchronous and three asynchronous) selected by setting configuration
bits in the SCON1 register. These four modes offer different baud rates and communication protocols. The four
modes are summarized in Table 21.1.
Table 21.1. UART1 Modes
Mode
Synchronization
Synchronous
Asynchronous
Asynchronous
Asynchronous
Baud Clock
SYSCLK / 12
Data Bits Start/Stop Bits
0
1
2
3
8
8
9
9
None
Timer 1 or 4 Overflow
SYSCLK / 32 or SYSCLK / 64
Timer 1 or 4 Overflow
1 Start, 1 Stop
1 Start, 1 Stop
1 Start, 1 Stop
21.1.1. Mode 0: Synchronous Mode
Mode 0 provides synchronous, half-duplex communication. Serial data is transmitted and received on the RX1 pin.
The TX1 pin provides the shift clock for both transmit and receive. The MCU must be the master since it generates
the shift clock for transmission in both directions (see the interconnect diagram in Figure 21.2).
Data transmission begins when an instruction writes a data byte to the SBUF1 register. Eight data bits are transferred
LSB first (see the timing diagram in Figure 21.3), and the TI1 Transmit Interrupt Flag (SCON1.1) is set at the end of
the eighth bit time. Data reception begins when the REN1 Receive Enable bit (SCON1.4) is set to logic 1 and the RI1
Receive Interrupt Flag (SCON1.0) is cleared. One cycle after the eighth bit is shifted in, the RI1 flag is set and recep-
tion stops until software clears the RI1 bit. An interrupt will occur if enabled when either TI1 or RI1 are set.
The Mode 0 baud rate is SYSCLK / 12. RX1 is forced to open-drain in Mode 0, and an external pull-up will typically
be required.
Figure 21.2. UART1 Mode 0 Interconnect
C8051FxxxTX
CLK
Shift
Reg.
RX
DATA
8 Extra Outputs
Figure 21.3. UART1 Mode 0 Timing Diagram
MODE 0 TRANSMIT
D0
D1
D2
D3
D4
D5
D6
D7
RX (data out)
TX (clk out)
MODE 0 RECEIVE
D0
D1
D2
D3
D4
D5
D6
D7
RX (data in)
TX (clk out)
216
Rev. 1.4
C8051F020/1/2/3
21.1.2. Mode 1: 8-Bit UART, Variable Baud Rate
Mode 1 provides standard asynchronous, full duplex communication using a total of 10 bits per data byte: one start
bit, eight data bits (LSB first), and one stop bit. Data are transmitted from the TX1 pin and received at the RX1 pin.
On receive, the eight data bits are stored in SBUF1 and the stop bit goes into RB81 (SCON1.2).
Data transmission begins when an instruction writes a data byte to the SBUF1 register. The TI1 Transmit Interrupt
Flag (SCON1.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin
any time after the REN1 Receive Enable bit (SCON1.4) is set to logic 1. After the stop bit is received, the data byte
will be loaded into the SBUF1 receive register if the following conditions are met: RI1 must be logic 0, and if SM21
is logic 1, the stop bit must be logic 1.
If these conditions are met, the eight bits of data are stored in SBUF1, the stop bit is stored in RB81 and the RI1 flag
is set. If these conditions are not met, SBUF1 and RB81 will not be loaded and the RI1 flag will not be set. An inter-
rupt will occur if enabled when either TI1 or RI1 is set.
Figure 21.4. UART1 Mode 1 Timing Diagram
MARK
START
BIT
STOP
BIT
D0
D1
D2
D3
D4
D5
D6
D7
SPACE
BIT TIMES
BIT SAMPLING
The baud rate generated in Mode 1 is a function of timer overflow, shown in Equation 21.1 and Equation 21.2.
UART1 can use Timer 1 operating in 8-Bit Auto-Reload Mode, or Timer 4 operating in Baud Rate Generator Mode to
generate the baud rate (note that the TX and RX clocks are selected separately). On each timer overflow event (a roll-
over from all ones - (0xFF for Timer 1, 0xFFFF for Timer 4) - to zero) a clock is sent to the baud rate logic.
Timer 4 is selected as TX and/or RX baud clock source by setting the TCLK1 (T4CON.4) and/or RCLK1 (T4CON.5)
bits, respectively (see Section “22. TIMERS” on page 225 for complete timer configuration details). When either
TCLK1 or RCLK1 is set to logic 1, Timer 4 is forced into Baud Rate Generator Mode, with SYSCLK / 2 as its clock
source. If TCLK1 and/or RCLK1 is logic 0, Timer 1 acts as the baud clock source for the TX and/or RX circuits,
respectively.
The Mode 1 baud rate equations are shown below, where T1M is the Timer 1 Clock Select bit (register CKCON),
TH1 is the 8-bit reload register for Timer 1, SMOD1 is the UART1 baud rate doubler (register PCON), and
[RCAP4H , RCAP4L] is the 16-bit reload register for Timer 4.
Equation 21.1. Mode 1 Baud Rate using Timer 1
2SMOD1
SYSCLK × 12(T1M – 1))
------------------
-------------------------------------------------------
BaudRate =
×
32
(256 – TH1)
Equation 21.2. Mode 1 Baud Rate using Timer 4
SYSCLK
BaudRate = -------------------------------------------------------------------------------------------------
[32 × (65536 – [RCAP4H, RCAP4L])]
Rev. 1.4
217
C8051F020/1/2/3
21.1.3. Mode 2: 9-Bit UART, Fixed Baud Rate
Mode 2 provides asynchronous, full-duplex communication using a total of eleven bits per data byte: a start bit, 8 data
bits (LSB first), a programmable ninth data bit, and a stop bit. Mode 2 supports multiprocessor communications and
hardware address recognition (see Section “21.2. Multiprocessor Communications” on page 220). On transmit,
the ninth data bit is determined by the value in TB81 (SCON1.3). It can be assigned the value of the parity flag P in
the PSW or used in multiprocessor communications. On receive, the ninth data bit goes into RB81 (SCON1.2) and
the stop bit is ignored.
Data transmission begins when an instruction writes a data byte to the SBUF1 register. The TI1 Transmit Interrupt
Flag (SCON1.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin
any time after the REN1 Receive Enable bit (SCON1.4) is set to logic 1. After the stop bit is received, the data byte
will be loaded into the SBUF1 receive register if RI1 is logic 0 and one of the following requirements are met:
1. SM21 is logic 0
2. SM21 is logic 1, the received 9th bit is logic 1, and the received address matches the UART1 address as
described in Section 21.2.
If the above conditions are satisfied, the eight bits of data are stored in SBUF1, the ninth bit is stored in RB81 and the
RI1 flag is set. If these conditions are not met, SBUF1 and RB81 will not be loaded and the RI1 flag will not be set.
An interrupt will occur if enabled when either TI1 or RI1 is set.
The baud rate in Mode 2 is either SYSCLK / 32 or SYSCLK / 64, depending on the value of the SMOD1 bit in regis-
ter PCON.
Equation 21.3. Mode 2 Baud Rate
SYSCLK
BaudRate = 2SMOD1
×
---------------------
64
Figure 21.5. UART Modes 2 and 3 Timing Diagram
MARK
START
BIT
STOP
BIT
D0
D1
D2
D3
D4
D5
D6
D7
D8
SPACE
BIT TIMES
BIT SAMPLING
218
Rev. 1.4
C8051F020/1/2/3
Figure 21.6. UART Modes 1, 2, and 3 Interconnect Diagram
TX
RX
RS-232
LEVEL
XLTR
RS-232
C8051Fxxx
OR
TX
RX
MCU
TXC8051Fxxx
RX
21.1.4. Mode 3: 9-Bit UART, Variable Baud Rate
Mode 3 uses the Mode 2 transmission protocol with the Mode 1 baud rate generation. Mode 3 operation transmits
11 bits: a start bit, 8 data bits (LSB first), a programmable ninth data bit, and a stop bit. The baud rate is derived from
Timer 1 or Timer 4 overflows, as defined by Equation 21.1 and Equation 21.2. Multiprocessor communications and
hardware address recognition are supported, as described in Section 21.2.
Rev. 1.4
219
C8051F020/1/2/3
21.2. Multiprocessor Communications
Modes 2 and 3 support multiprocessor communication between a master processor and one or more slave processors
by special use of the ninth data bit and the built-in UART1 address recognition hardware. A master processor begins
a transfer with an address byte to select one or more target slave devices. An address byte differs from a data byte in
that its ninth bit is logic 1; in a data byte, the ninth bit is always set to logic 0.
The UART1 address is configured via two SFRs: SADDR1 (Serial Address) and SADEN1 (Serial Address Enable).
SADEN1 sets the bit mask for the address held in SADDR1: bits set to logic 1 in SADEN1 correspond to bits in
SADDR1 that are checked against the received address byte; bits set to logic 0 in SADEN1 correspond to “don’t
care” bits in SADDR1.
Example 1
Example 2
Example 3
SADDR1
SADEN1
= 00110101
= 00001111
SADDR1
SADEN1
= 00110101
= 11110011
SADDR1
SADEN1
= 00110101
= 11000000
UART1 Address = xxxx0101
UART1 Address = 0011xx01
UART1 Address = 00xxxxxx
Setting the SM21 bit (SCON1.5) configures UART1 such that when a stop bit is received, UART1 will generate an
interrupt only if the ninth bit is logic 1 (RB81 = 1) and the received data byte matches the UART1 slave address. Fol-
lowing the received address interrupt, the slave should clear its SM21 bit to enable interrupts on the reception of the
following data byte(s). Once the entire message is received, the addressed slave should reset its SM21 bit to ignore all
transmissions until it receives the next address byte. While SM21 is logic 1, UART1 ignores all bytes that do not
match the UART1 address and include a ninth bit that is logic 1.
Multiple addresses can be assigned to a single slave and/or a single address can be assigned to multiple slaves,
thereby enabling "broadcast" transmissions to more than one slave simultaneously. The broadcast address is the logi-
cal OR of registers SADDR1 and SADEN1, and ‘0’s of the result are treated as “don’t cares”. Typically a broadcast
address of 0xFF (hexadecimal) is acknowledged by all slaves, assuming “don’t care” bits as ‘1’s. The master proces-
sor can be configured to receive all transmissions or a protocol can be implemented such that the master/slave role is
temporarily reversed to enable half-duplex transmission between the original master and slave(s).
Figure 21.7. UART Multi-Processor Mode Interconnect Diagram
Master
Device
Slave
Slave
Slave
Device
Device
Device
+5V
RX
TX
RX
TX
RX
TX
RX
TX
220
Rev. 1.4
C8051F020/1/2/3
21.3. Frame and Transmission Error Detection
Frame error detection is available in the following modes when the SSTAT1 bit in register PCON is set to logic 1.
Note: The SSTAT1 bit must be logic 1 to access any of the status bits (FE1, RXOVR1, and TXCOL1). To access the
UART1 Mode Select bits (SM01, SM11, and SM21), the SSTAT1 bit must be logic 0.
All Modes:
The Transmit Collision bit (TXCOL1 bit in register SCON1) reads ‘1’ if user software writes data to the SBUF1 reg-
ister while a transmit is in progress. Note that the TXCOL1 bit also functions as the SM21 bit when the SSTAT1 bit in
register PCON is logic 0.
Modes 1, 2, and 3:
The Receive Overrun bit (RXOVR1 in register SCON1) reads ‘1’ if a new data byte is latched into the receive buffer
before software has read the previous byte. Note that the RXOVR1 bit also functions as the SM11 bit when the
SSTAT1 bit in register PCON is logic 0.
The Frame Error bit (FE1 in register SCON1) reads ‘1’ if an invalid (low) STOP bit is detected. Note that the FE1 bit
also functions as the SM01 bit when the SSTAT1 bit in register PCON is logic 0.
Rev. 1.4
221
C8051F020/1/2/3
Table 21.2. Oscillator Frequencies for Standard Baud Rates
Oscillator frequency (MHz) Divide Factor Timer 1 Load Value* Resulting Baud Rate (Hz)**
25.0
25.0
24.576
24.576
24.0
24.0
23.592
23.592
22.1184
22.1184
18.432
18.432
16.5888
16.5888
14.7456
14.7456
12.9024
12.9024
11.0592
11.0592
9.216
9.216
7.3728
7.3728
5.5296
5.5296
3.6864
3.6864
1.8432
1.8432
434
868
320
848
208
833
205
819
192
768
160
640
144
576
128
512
112
448
96
348
80
320
64
256
48
192
32
0xE5
0xCA
0xEC
0xCB
0XF3
0xCC
0xF3
0xCD
0xF4
0xD0
0xF6
0xD8
0xF7
0xDC
0xF8
0xE0
0xF9
0xE4
0xFA
0xE8
0xFB
0xEC
0xFC
0xF0
0xFD
0xF4
0xFE
0xF8
0xFF
0xFC
57600 (57870)
28800
76800
28800 (28921)
115200 (115384)
28800 (28846)
115200 (113423)
28800 (28911)
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
28800
115200
128
16
64
28800
* Assumes SMOD1=1 and T1M=1.
** Numbers in parenthesis show the actual baud rate.
222
Rev. 1.4
C8051F020/1/2/3
Figure 21.8. SCON1: UART1 Control Register
R/W
R/W
R/W
R/W
REN1
Bit4
R/W
TB81
Bit3
R/W
RB81
Bit2
R/W
TI1
Bit1
R/W
RI1
Bit0
Reset Value
00000000
SFR Address:
0xF1
SM01/FE1 SM11/RXOV1 SM21/TXCOL1
Bit7
Bit6
Bit5
Bits7-6: The function of these bits is determined by the SSTAT1 bit in register PCON.
If SSTAT1 is logic 1, these bits are UART1 status indicators as described in Section 21.3.
If SSTAT1 is logic 0, these bits select the Serial Port Operation Mode as shown below.
SM01-SM11: Serial Port Operation Mode:
SM01
SM11 Mode
0
0
1
1
0
Mode 0: Synchronous Mode
1
0
1
Mode 1: 8-Bit UART, Variable Baud Rate
Mode 2: 9-Bit UART, Fixed Baud Rate
Mode 3: 9-Bit UART, Variable Baud Rate
Bit5:
SM21: Multiprocessor Communication Enable.
If SSTAT1 is logic 1, this bit is a UART1 status indicator as described in Section 21.3.
If SSTAT1 is logic 0, the function of this bit is dependent on the Serial Port Operation Mode.
Mode 0: No effect.
Mode 1: Checks for valid stop bit.
0: Logic level of stop bit is ignored.
1: RI1 will only be activated if stop bit is logic level 1.
Modes 2 and 3: Multiprocessor Communications Enable.
0: Logic level of ninth bit is ignored.
1: RI1 is set and an interrupt is generated only when the ninth bit is logic 1 and the received
address matches the UART1 address or the broadcast address.
REN1: Receive Enable.
Bit4:
This bit enables/disables the UART1 receiver.
0: UART1 reception disabled.
1: UART1 reception enabled.
Bit3:
Bit2:
Bit1:
TB81: Ninth Transmission Bit.
The logic level of this bit will be assigned to the ninth transmission bit in Modes 2 and 3. It is not used
in Modes 0 and 1. Set or cleared by software as required.
RB81: Ninth Receive Bit.
The bit is assigned the logic level of the ninth bit received in Modes 2 and 3. In Mode 1, if SM21 is
logic 0, RB81 is assigned the logic level of the received stop bit. RB8 is not used in Mode 0.
TI1: Transmit Interrupt Flag.
Set by hardware when a byte of data has been transmitted by UART1 (after the 8th bit in Mode 0, or
at the beginning of the stop bit in other modes). When the UART1 interrupt is enabled, setting this bit
causes the CPU to vector to the UART1 interrupt service routine. This bit must be cleared manually
by software
Bit0:
RI1: Receive Interrupt Flag.
Set by hardware when a byte of data has been received by UART1 (as selected by the SM21 bit).
When the UART1 interrupt is enabled, setting this bit causes the CPU to vector to the UART1 inter-
rupt service routine. This bit must be cleared manually by software.
Rev. 1.4
223
C8051F020/1/2/3
Figure 21.9. SBUF1: UART1 Data Buffer Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xF2
Bits7-0: SBUF1.[7:0]: UART1 Buffer Bits 7-0 (MSB-LSB)
This SFR accesses two registers; a transmit shift register and a receive latch register. When data is
written to SBUF1, it goes to the transmit shift register and is held for serial transmission. Writing a
byte to SBUF1 is what initiates the transmission. A read of SBUF1 returns the contents of the receive
latch.
Figure 21.10. SADDR1: UART1 Slave Address Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xF3
Bits7-0: SADDR1.[7:0]: UART1 Slave Address
The contents of this register are used to define the UART1 slave address. Register SADEN1 is a bit
mask to determine which bits of SADDR1 are checked against a received address: corresponding bits
set to logic 1 in SADEN1 are checked; corresponding bits set to logic 0 are “don’t cares”.
Figure 21.11. SADEN1: UART1 Slave Address Enable Register
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xAE
Bits7-0: SADEN1.[7:0]: UART1 Slave Address Enable
Bits in this register enable corresponding bits in register SADDR1 to determine the UART1 slave
address.
0: Corresponding bit in SADDR1 is a “don’t care”.
1: Corresponding bit in SADDR1 is checked against a received address.
224
Rev. 1.4
C8051F020/1/2/3
22. TIMERS
The C8051F020/1/2/3 devices contain 5 counter/timers: three are 16-bit counter/timers compatible with those found
in the standard 8051, and two are 16-bit auto-reload timers for use with the ADCs, SMBus, UART1, or for general
purpose use. These can be used to measure time intervals, count external events and generate periodic interrupt
requests. Timer 0 and Timer 1 are nearly identical and have four primary modes of operation. Timer 2 offers addi-
tional capabilities not available in Timers 0 and 1. Timer 3 is similar to Timer 2, but without the capture or Baud Rate
Generator modes. Timer 4 is identical to Timer 2, and can supply baud-rate generation capabilities to UART1.
Timer 0 and Timer 1:
Timer 2:
16-bit counter/timer with
auto-reload
Timer 3:
16-bit timer with auto-
reload
Timer 4
16-bit counter/timer with
auto-reload
13-bit counter/timer
16-bit counter/timer with
capture
Baud rate generator for
UART0
16-bit counter/timer with
capture
Baud rate generator for
UART1
16-bit counter/timer
8-bit counter/timer with
auto-reload
Two 8-bit counter/timers
(Timer 0 only)
When functioning as a timer, the counter/timer registers are incremented on each clock tick. Clock ticks are derived
from the system clock divided by either one or twelve as specified by the Timer Clock Select bits (T4M-T0M) in
CKCON, shown in Figure 22.1. The twelve-clocks-per-tick option provides compatibility with the older generation
of the 8051 family. Applications that require a faster timer can use the one-clock-per-tick option.
When functioning as a counter, a counter/timer register is incremented on each high-to-low transition at the selected
input pin. Events with a frequency of up to one-fourth the system clock's frequency can be counted. The input signal
need not be periodic, but it should be held at a given level for at least two full system clock cycles to ensure the level
is sampled.
Rev. 1.4
225
C8051F020/1/2/3
Figure 22.1. CKCON: Clock Control Register
R/W
-
Bit7
R/W
T4M
Bit6
R/W
T2M
Bit5
R/W
T1M
Bit4
R/W
T0M
Bit3
R/W
R/W
R/W
Reset Value
Reserved Reserved Reserved 00000000
Bit2
Bit1
Bit0
SFR Address:
0x8E
Bit7:
Bit6:
UNUSED. Read = 0b, Write = don’t care.
T4M: Timer 4 Clock Select.
This bit controls the division of the system clock supplied to Timer 4. This bit is ignored when the
timer is in baud rate generator mode or counter mode (i.e. C/T4 = 1).
0: Timer 4 uses the system clock divided by 12.
1: Timer 4 uses the system clock.
T2M: Timer 2 Clock Select.
Bit5:
This bit controls the division of the system clock supplied to Timer 2. This bit is ignored when the
timer is in baud rate generator mode or counter mode (i.e. C/T2 = 1).
0: Timer 2 uses the system clock divided by 12.
1: Timer 2 uses the system clock.
Bit4:
Bit3:
T1M: Timer 1 Clock Select.
This bit controls the division of the system clock supplied to Timer 1.
0: Timer 1 uses the system clock divided by 12.
1: Timer 1 uses the system clock.
T0M: Timer 0 Clock Select.
This bit controls the division of the system clock supplied to Counter/Timer 0.
0: Counter/Timer uses the system clock divided by 12.
1: Counter/Timer uses the system clock.
Bits2-0: Reserved. Read = 000b, Must Write = 000.
226
Rev. 1.4
C8051F020/1/2/3
22.1. Timer 0 and Timer 1
Timer 0 and Timer 1 are accessed and controlled through SFRs. Each counter/timer is implemented as a 16-bit regis-
ter accessed as two separate bytes: a low byte (TL0 or TL1) and a high byte (TH0 or TH1). The Counter/Timer Con-
trol (TCON) register is used to enable Timer 0 and Timer 1 as well as indicate their status. Both counter/timers
operate in one of four primary modes selected by setting the Mode Select bits M1-M0 in the Counter/Timer Mode
(TMOD) register. Each timer can be configured independently. Following is a detailed description of each operating
mode.
22.1.1. Mode 0: 13-bit Counter/Timer
Timer 0 and Timer 1 operate as a 13-bit counter/timer in Mode 0. The following describes the configuration and oper-
ation of Timer 0. However, both timers operate identically and Timer 1 is configured in the same manner as described
for Timer 0.
The TH0 register holds the eight MSBs of the 13-bit counter/timer. TL0 holds the five LSBs in bit positions TL0.4-
TL0.0. The three upper bits of TL0 (TL0.7-TL0.5) are indeterminate and should be masked out or ignored when read-
ing. As the 13-bit timer register increments and overflows from 0x1FFF (all ones) to 0x0000, the timer overflow flag
TF0 (TCON.5) is set and an interrupt will occur if enabled.
The C/T0 bit (TMOD.2) selects the counter/timer's clock source. Clearing C/T selects the system clock as the input
for the timer. When C/T0 is set to logic 1, high-to-low transitions at the selected input pin (T0) increment the timer
register. (Refer to Section “17.1. Ports 0 through 3 and the Priority Crossbar Decoder” on page 163 for informa-
tion on selecting and configuring external I/O pins for digital peripherals.)
Setting the TR0 bit (TCON.4) enables the timer when either GATE0 (TMOD.3) is 0 or the input signal /INT0 is
logic-level one. Setting GATE0 to logic 1 allows the timer to be controlled by the external input signal /INT0, facili-
tating pulse width measurements.
TR0
GATE0
/INT0
Counter/Timer
Disabled
0
1
1
1
X
0
X
X
0
Enabled
1
1
Disabled
Enabled
1
X = Don't Care
Setting TR0 does not reset the timer register. The timer register should be initialized to the desired value before
enabling the timer.
TL1 and TH1 form the 13-bit register for Timer 1 in the same manner as described above for TL0 and TH0. Timer 1
is configured and controlled using the relevant TCON and TMOD bits just as with Timer 0.
Rev. 1.4
227
C8051F020/1/2/3
Figure 22.2. T0 Mode 0 Block Diagram
CKCON
T T T T
4 2 1 0
M MMM
TMOD
G C T T G C T T
A
/ 1 1 A / 0 0
T T M M T T M M
E 1 1 0 E 0 1 0
1
0
12
0
1
SYSCLK
0
1
TF1
TR1
TF0
TR0
IE1
IT1
T0
Interrupt
TCLK
TL0
TH0
Crossbar
(5 bits)
(8 bits)
TR0
/INT0
IE0
IT0
GATE0
22.1.2. Mode 1: 16-bit Counter/Timer
Mode 1 operation is the same as Mode 0, except that the counter/timer registers use all 16 bits. The counter/timers are
enabled and configured in Mode 1 in the same manner as for Mode 0.
228
Rev. 1.4
C8051F020/1/2/3
22.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures Timer 0 and Timer 1 to operate as 8-bit counter/timers with automatic reload of the start value.
The TL0 holds the count and TH0 holds the reload value. When the counter in TL0 overflows from all ones to 0x00,
the timer overflow flag TF0 (TCON.5) is set and the counter value in TL0 is reloaded from TH0. If enabled, an inter-
rupt will occur when the TF0 flag is set. The reload value in TH0 is not changed. TL0 must be initialized to the
desired value before enabling the timer for the first count to be correct. When in Mode 2, Timer 1 operates identically
to Timer 0. Both counter/timers are enabled and configured in Mode 2 in the same manner as Mode 0.
Figure 22.3. T0 Mode 2 (8-bit Auto-Reload) Block Diagram
CKCON
T T T T
4 2 1 0
M M M M
TMOD
G C T T G C T T
A
/ 1 1 A / 0 0
T T M M T T M M
E 1 1 0 E 0 1 0
1
0
12
0
1
SYSCLK
0
1
T0
TF1
TR1
TF0
TR0
IE1
IT1
TCLK
TL0
Interrupt
Crossbar
(8 bits)
TR0
/INT0
IE0
IT0
GATE0
TH0
Reload
(8 bits)
Rev. 1.4
229
C8051F020/1/2/3
22.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)
Timer 0 and Timer 1 behave differently in Mode 3. Timer 0 is configured as two separate 8-bit counter/timers held in
TL0 and TH0. The counter/timer in TL0 is controlled using the Timer 0 control/status bits in TCON and TMOD:
TR0, C/T0, GATE0 and TF0. It can use either the system clock or an external input signal as its timebase. The timer
in the TH0 register is restricted to a timer function sourced by the system clock. TH0 is enabled using the Timer 1 run
control bit TR1. TH0 sets the Timer 1 overflow flag TF1 on overflow and thus controls the Timer 1 interrupt.
Timer 1 is inactive in Mode 3, so with Timer 0 in Mode 3, Timer 1 can be turned off and on by switching it into and
out of its Mode 3. When Timer 0 is in Mode 3, Timer 1 can be operated in Modes 0, 1 or 2, but cannot be clocked by
external signals nor set the TF1 flag and generate an interrupt. However, the Timer 1 overflow can be used to gener-
ate the baud clock for UART0 and/or UART1. Refer to Section “20. UART0” on page 205 and Section
“21. UART1” on page 215 for information on configuring Timer 1 for baud rate generation.
Figure 22.4. T0 Mode 3 (Two 8-bit Timers) Block Diagram
CKCON
T T T T
4 2 1 0
M M M M
TMOD
G C T T G C T T
A
/ 1 1 A / 0 0
T T M M T T M M
E 1 1 0 E 0 1 0
1
0
12
0
1
TH0
TR1
Interrupt
Interrupt
TF1
TR1
TF0
TR0
IE1
SYSCLK
(8 bits)
0
1
IT1
IE0
IT0
T0
TL0
Crossbar
(8 bits)
TR0
/INT0
GATE0
230
Rev. 1.4
C8051F020/1/2/3
Figure 22.5. TCON: Timer Control Register
R/W
TF1
Bit7
R/W
TR1
Bit6
R/W
TF0
Bit5
R/W
TR0
Bit4
R/W
IE1
Bit3
R/W
IT1
Bit2
R/W
IE0
Bit1
R/W
IT0
Reset Value
00000000
SFR Address:
0x88
Bit0
(bit addressable)
Bit7:
TF1: Timer 1 Overflow Flag.
Set by hardware when Timer 1 overflows. This flag can be cleared by software but is automatically
cleared when the CPU vectors to the Timer 1 interrupt service routine.
0: No Timer 1 overflow detected.
1: Timer 1 has overflowed.
Bit6:
Bit5:
TR1: Timer 1 Run Control.
0: Timer 1 disabled.
1: Timer 1 enabled.
TF0: Timer 0 Overflow Flag.
Set by hardware when Timer 0 overflows. This flag can be cleared by software but is automatically
cleared when the CPU vectors to the Timer 0 interrupt service routine.
0: No Timer 0 overflow detected.
1: Timer 0 has overflowed.
Bit4:
Bit3:
TR0: Timer 0 Run Control.
0: Timer 0 disabled.
1: Timer 0 enabled.
IE1: External Interrupt 1.
This flag is set by hardware when an edge/level of type defined by IT1 is detected. It can be cleared
by software but is automatically cleared when the CPU vectors to the External Interrupt 1 service rou-
tine if IT1 = 1. This flag is the inverse of the /INT1 input signal's logic level when IT1 = 0.
IT1: Interrupt 1 Type Select.
Bit2:
This bit selects whether the configured /INT1 signal will detect falling edge or active-low level-sensi-
tive interrupts.
0: /INT1 is level triggered.
1: /INT1 is edge triggered.
Bit1:
Bit0:
IE0: External Interrupt 0.
This flag is set by hardware when an edge/level of type defined by IT0 is detected. It can be cleared
by software but is automatically cleared when the CPU vectors to the External Interrupt 0 service rou-
tine if IT0 = 1. This flag is the inverse of the /INT0 input signal's logic level when IT0 = 0.
IT0: Interrupt 0 Type Select.
This bit selects whether the configured /INT0 signal will detect falling edge or active-low level-sensi-
tive interrupts.
0: /INT0 is level triggered.
1: /INT0 is edge triggered.
Rev. 1.4
231
C8051F020/1/2/3
Figure 22.6. TMOD: Timer Mode Register
R/W
GATE1
Bit7
R/W
C/T1
Bit6
R/W
T1M1
Bit5
R/W
T1M0
Bit4
R/W
GATE0
Bit3
R/W
C/T0
Bit2
R/W
T0M1
Bit1
R/W
T0M0
Bit0
Reset Value
00000000
SFR Address:
0x89
Bit7:
GATE1: Timer 1 Gate Control.
0: Timer 1 enabled when TR1 = 1 irrespective of /INT1 logic level.
1: Timer 1 enabled only when TR1 = 1 AND /INT1 = logic 1.
C/T1: Counter/Timer 1 Select.
Bit6:
0: Timer Function: Timer 1 incremented by clock defined by T1M bit (CKCON.4).
1: Counter Function: Timer 1 incremented by high-to-low transitions on external input pin (T1).
Bits5-4: T1M1-T1M0: Timer 1 Mode Select.
These bits select the Timer 1 operation mode.
T1M1
T1M0 Mode
0
0
1
1
0
1
Mode 0: 13-bit counter/timer
Mode 1: 16-bit counter/timer
0
1
Mode 2: 8-bit counter/timer with auto-reload
Mode 3: Timer 1 inactive
Bit3:
Bit2:
GATE0: Timer 0 Gate Control.
0: Timer 0 enabled when TR0 = 1 irrespective of /INT0 logic level.
1: Timer 0 enabled only when TR0 = 1 AND /INT0 = logic 1.
C/T0: Counter/Timer Select.
0: Timer Function: Timer 0 incremented by clock defined by T0M bit (CKCON.3).
1: Counter Function: Timer 0 incremented by high-to-low transitions on external input pin (T0).
Bits1-0: T0M1-T0M0: Timer 0 Mode Select.
These bits select the Timer 0 operation mode.
T0M1
T0M0 Mode
0
0
1
1
0
1
Mode 0: 13-bit counter/timer
Mode 1: 16-bit counter/timer
0
1
Mode 2: 8-bit counter/timer with auto-reload
Mode 3: Two 8-bit counter/timers
232
Rev. 1.4
C8051F020/1/2/3
Figure 22.7. TL0: Timer 0 Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x8A
Bits 7-0: TL0: Timer 0 Low Byte.
The TL0 register is the low byte of the 16-bit Timer 0.
Figure 22.8. TL1: Timer 1 Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x8B
Bits 7-0: TH0: Timer 0 High Byte.
The TH0 register is the low byte of the 16-bit Timer 1.
Figure 22.9. TH0 Timer 0 High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x8C
Bits 7-0: TH0: Timer 0 High Byte.
The TH0 register is the high byte of the 16-bit Timer 0.
Figure 22.10. TH1: Timer 1 High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x8D
Bits 7-0: TH1: Timer 1 High Byte.
The TH1 register is the high byte of the 16-bit Timer 1.
Rev. 1.4
233
C8051F020/1/2/3
22.1. Timer 2
Timer 2 is a 16-bit counter/timer formed by the two 8-bit SFRs: TL2 (low byte) and TH2 (high byte). As with
Timers 0 and 1, Timer 2 can use either the system clock or transitions on an external input pin (T2) as its clock
source. The Counter/Timer Select bit C/T2 bit (T2CON.1) selects the clock source for Timer 2. Clearing C/T2 selects
the system clock as the input for the timer (divided by either one or twelve as specified by the Timer Clock Select bit
T2M in CKCON). When C/T2 is set to 1, high-to-low transitions at the T2 input pin increment the counter/timer reg-
ister. (Refer to Section “17.1. Ports 0 through 3 and the Priority Crossbar Decoder” on page 163 for information
on selecting and configuring external I/O pins for digital peripherals.) Timer 2 can also be used to start an ADC Data
Conversion.
Timer 2 offers capabilities not found in Timer 0 and Timer 1. It operates in one of three modes: 16-bit Counter/Timer
with Capture, 16-bit Counter/Timer with Auto-Reload or Baud Rate Generator Mode. Timer 2's operating mode is
selected by setting configuration bits in the Timer 2 Control register (T2CON). Below is a summary of the Timer 2
operating modes and the T2CON bits used to configure the counter/timer. Detailed descriptions of each mode follow.
RCLK0
TCLK0
CP/RL2
TR2
Mode
0
0
0
0
1
0
1
1
1
1
1
0
16-bit Counter/Timer with Capture
16-bit Counter/Timer with Auto-Reload
Baud Rate Generator for UART0
Baud Rate Generator for UART0
Baud Rate Generator for UART0
Off
0
1
X
X
X
X
1
0
1
1
X
X
234
Rev. 1.4
C8051F020/1/2/3
22.1.1. Mode 0: 16-bit Counter/Timer with Capture
In this mode, Timer 2 operates as a 16-bit counter/timer with capture facility. A high-to-low transition on the T2EX
input pin causes the following to occur:
1. The 16-bit value in Timer 2 (TH2, TL2) is loaded into the capture registers (RCAP2H, RCAP2L).
2. The Timer 2 External Flag (EXF2) is set to ‘1’.
3. A Timer 2 interrupt is generated if enabled.
Timer 2 can use either SYSCLK, SYSCLK divided by 12, or high-to-low transitions on the T2 input pin as its clock
source when operating in Capture mode. Clearing the C/T2 bit (T2CON.1) selects the system clock as the input for
the timer (divided by one or twelve as specified by the Timer Clock Select bit T2M in CKCON). When C/T2 is set to
logic 1, a high-to-low transition at the T2 input pin increments the counter/timer register. As the 16-bit counter/timer
register increments and overflows from 0xFFFF to 0x0000, the TF2 timer overflow flag (T2CON.7) is set and an
interrupt will occur if the interrupt is enabled.
Counter/Timer with Capture mode is selected by setting the Capture/Reload Select bit CP/RL2 (T2CON.0) and the
Timer 2 Run Control bit TR2 (T2CON.2) to logic 1. The Timer 2 External Enable EXEN2 (T2CON.3) must also be
set to logic 1 to enable a capture. If EXEN2 is cleared, transitions on T2EX will be ignored.
Figure 22.11. T2 Mode 0 Block Diagram
CKCON
T T T T
4 2 1 0
M MM M
12
0
1
SYSCLK
0
1
TCLK
T2
TL2
TH2
CP/RL2
C/T2
TR2
TR2
Crossbar
EXEN2
TCLK0
RCLK0
EXF2
TF2
Interrupt
T2EX
Capture
RCAP2L RCAP2H
EXEN2
Rev. 1.4
235
C8051F020/1/2/3
22.1.2. Mode 1: 16-bit Counter/Timer with Auto-Reload
The Counter/Timer with Auto-Reload mode sets the TF2 timer overflow flag when the counter/timer register over-
flows from 0xFFFF to 0x0000. An interrupt is generated if enabled. On overflow, the 16-bit value held in the two
capture registers (RCAP2H, RCAP2L) is automatically loaded into the counter/timer register and the timer is
restarted.
Counter/Timer with Auto-Reload mode is selected by clearing the CP/RL2 bit. Setting TR2 to logic 1 enables and
starts the timer. Timer 2 can use either the system clock or transitions on an external input pin (T2) as its clock source,
as specified by the C/T2 bit. If EXEN2 is set to logic 1, a high-to-low transition on T2EX will also cause a Timer 2
reload, and a Timer 2 interrupt if enabled. If EXEN2 is logic 0, transitions on T2EX will be ignored.
Figure 22.12. T2 Mode 1 Block Diagram
CKCON
T T T T
4 2 1 0
MM MM
12
0
1
SYSCLK
0
TL2
TH2
TCLK
CP/RL2
C/T2
1
T2
TR2
Crossbar
EXEN2
TCLK0
RCLK0
EXF2
TF2
TR2
T2EX
Interrupt
Reload
RCAP2L RCAP2H
EXEN2
236
Rev. 1.4
C8051F020/1/2/3
22.1.3. Mode 2: Baud Rate Generator
Timer 2 can be used as a baud rate generator for UART0 when UART0 is operated in modes 1 or 3 (refer to Section
“20.1. UART0 Operational Modes” on page 206 for more information on the UART0 operational modes). In Baud
Rate Generator mode, Timer 2 works similarly to the auto-reload mode. On overflow, the 16-bit value held in the two
capture registers (RCAP2H, RCAP2L) is automatically loaded into the counter/timer register. However, the TF2
overflow flag is not set and no interrupt is generated. Instead, the overflow event is used as the input to the UART's
shift clock. Timer 2 overflows can be selected to generate baud rates for transmit and/or receive independently.
The Baud Rate Generator mode is selected by setting RCLK0 (T2CON.5) and/or TCLK0 (T2CON.2) to ‘1’. When
RCLK0 or TCLK0 is set to logic 1, Timer 2 operates in the auto-reload mode regardless of the state of the CP/RL2
bit. Note that in Baud Rate Generator mode, the Timer 2 timebase is the system clock divided by two. When selected
as the UART0 baud clock source, Timer 2 defines the UART0 baud rate as follows:
Baud Rate = SYSCLK / ((65536 - [RCAP2H, RCAP2L] ) * 32)
If a different time base is required, setting the C/T2 bit to logic 1 will allow the timebase to be derived from the exter-
nal input pin T2. In this case, the baud rate for the UART is calculated as:
Baud Rate = F
/ ( (65536 - [RCAP2H, RCAP2L] ) * 16)
CLK
Where F
is the frequency of the signal (TCLK) supplied to Timer 2 and [RCAP2H, RCAP2L] is the 16-bit value
CLK
held in the capture registers.
As explained above, in Baud Rate Generator mode, Timer 2 does not set the TF2 overflow flag and therefore cannot
generate an interrupt. However, if EXEN2 is set to logic 1, a high-to-low transition on the T2EX input pin will set the
EXF2 flag and a Timer 2 interrupt will occur if enabled. Therefore, the T2EX input may be used as an additional
external interrupt source.
Figure 22.13. T2 Mode 2 Block Diagram
C/T2
SYSCLK
T2
2
0
1
RCLK0
0
Timer 2
Overflow
Crossbar
TL2
TH2
TCLK
16
RX0 Clock
TX0 Clock
TR2
1
0
PCON
Reload
S S S S S I
M S M S T D
O T O T O L
D A D A P E
0 T 1 T
RCAP2L RCAP2H
0
1
16
2
0
1
1
Timer 1
Overflow
CP/RL2
C/T2
TCLK0
TR2
EXEN2
TCLK0
RCLK0
EXEN2
EXF2
TF2
Interrupt
Crossbar
T2EX
Rev. 1.4
237
C8051F020/1/2/3
Figure 22.14. T2CON: Timer 2 Control Register
R/W
TF2
Bit7
R/W
EXF2
Bit6
R/W
RCLK0
Bit5
R/W
TCLK0
Bit4
R/W
EXEN2
Bit3
R/W
TR2
Bit2
R/W
C/T2
Bit1
R/W
Reset Value
CP/RL2 00000000
Bit0
SFR Address:
(bit addressable)
0xC8
Bit7:
TF2: Timer 2 Overflow Flag.
Set by hardware when Timer 2 overflows. When the Timer 2 interrupt is enabled, setting this bit
causes the CPU to vector to the Timer 2 interrupt service routine. This bit is not automatically cleared
by hardware and must be cleared by software. TF2 will not be set when RCLK0 and/or TCLK0 are
logic 1.
Bit6:
EXF2: Timer 2 External Flag.
Set by hardware when either a capture or reload is caused by a high-to-low transition on the T2EX
input pin and EXEN2 is logic 1. When the Timer 2 interrupt is enabled, setting this bit causes the
CPU to vector to the Timer 2 Interrupt service routine. This bit is not automatically cleared by hard-
ware and must be cleared by software.
Bit5:
Bit4:
Bit3:
RCLK0: Receive Clock Flag for UART0.
Selects which timer is used for the UART0 receive clock in modes 1 or 3.
0: Timer 1 overflows used for receive clock.
1: Timer 2 overflows used for receive clock.
TCLK0: Transmit Clock Flag for UART0.
Selects which timer is used for the UART0 transmit clock in modes 1 or 3.
0: Timer 1 overflows used for transmit clock.
1: Timer 2 overflows used for transmit clock.
EXEN2: Timer 2 External Enable.
Enables high-to-low transitions on T2EX to trigger captures or reloads when Timer 2 is not operating
in Baud Rate Generator mode.
0: High-to-low transitions on T2EX ignored.
1: High-to-low transitions on T2EX cause a capture or reload.
TR2: Timer 2 Run Control.
Bit2:
This bit enables/disables Timer 2.
0: Timer 2 disabled.
1: Timer 2 enabled.
Bit1:
Bit0:
C/T2: Counter/Timer Select.
0: Timer Function: Timer 2 incremented by clock defined by T2M (CKCON.5).
1: Counter Function: Timer 2 incremented by high-to-low transitions on external input pin (T2).
CP/RL2: Capture/Reload Select.
This bit selects whether Timer 2 functions in capture or auto-reload mode. EXEN2 must be logic 1 for
high-to-low transitions on T2EX to be recognized and used to trigger captures or reloads. If RCLK0
or TCLK0 is set, this bit is ignored and Timer 2 will function in auto-reload mode.
0: Auto-reload on Timer 2 overflow or high-to-low transition at T2EX (EXEN2 = 1).
1: Capture on high-to-low transition at T2EX (EXEN2 = 1).
238
Rev. 1.4
C8051F020/1/2/3
Figure 22.15. RCAP2L: Timer 2 Capture Register Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xCA
Bits 7-0: RCAP2L: Timer 2 Capture Register Low Byte.
The RCAP2L register captures the low byte of Timer 2 when Timer 2 is configured in capture mode.
When Timer 2 is configured in auto-reload mode, it holds the low byte of the reload value.
Figure 22.16. RCAP2H: Timer 2 Capture Register High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xCB
Bits 7-0: RCAP2H: Timer 2 Capture Register High Byte.
The RCAP2H register captures the high byte of Timer 2 when Timer 2 is configured in capture mode.
When Timer 2 is configured in auto-reload mode, it holds the high byte of the reload value.
Figure 22.17. TL2: Timer 2 Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xCC
Bits 7-0: TL2: Timer 2 Low Byte.
The TL2 register contains the low byte of the 16-bit Timer 2.
Figure 22.18. TH2 Timer 2 High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xCD
Bits 7-0: TH2: Timer 2 High Byte.
The TH2 register contains the high byte of the 16-bit Timer 2.
Rev. 1.4
239
C8051F020/1/2/3
22.2. Timer 3
Timer 3 is a 16-bit timer formed by the two 8-bit SFRs, TMR3L (low byte) and TMR3H (high byte). Timer 3 may be
clocked by the external oscillator source (divided by eight) or the system clock (divided by either one or twelve as
specified by the Timer 3 Clock Select bit T3M in the Timer 3 Control Register TMR3CN). Timer 3 is always config-
ured as an auto-reload timer, with the reload value held in the TMR3RLL (low byte) and TMR3RLH (high byte) reg-
isters.
The Timer 3 external clock source feature offers a real-time clock (RTC) mode. When bit T3XCLK (TMR3CN.0) is
set to logic 1, Timer 3 is clocked by the external oscillator input (divided by 8) regardless of the system clock selec-
tion. This split clock domain allows Timer 3 to be clocked by a precision external source while the system clock is
derived from the high-speed internal oscillator. When T3XCLK is logic 0, the Timer 3 clock source is specified by bit
T3M (TMR3CN.1).
Timer 3 can also be used to start an ADC Data Conversion, for SMBus timing (see Section “18. SYSTEM MAN-
AGEMENT BUS / I2C BUS (SMBUS0)” on page 183), or as a general-purpose timer. Timer 3 does not have a
counter mode.
Figure 22.19. Timer 3 Block Diagram
T3XCLK
External
(to ADC)
TF3
8
Oscillator Source
1
0
TMR3L
TMR3H
Interrupt
TCLK
12
0
1
SYSCLK
TR3
TR3
T3M
(from SMBus) TOE
Reload
T3XCLK
TMR3RLL TMR3RLH
T3M
SCL
Crossbar
240
Rev. 1.4
C8051F020/1/2/3
Figure 22.20. TMR3CN: Timer 3 Control Register
R/W
TF3
Bit7
R/W
-
Bit6
R/W
-
Bit5
R/W
-
Bit4
R/W
-
Bit3
R/W
TR3
Bit2
R/W
T3M
Bit1
R/W
Reset Value
T3XCLK 00000000
Bit0
SFR Address:
0x91
Bit7:
TF3: Timer3 Overflow Flag.
Set by hardware when Timer 3 overflows from 0xFFFF to 0x0000. When the Timer 3 interrupt is
enabled, setting this bit causes the CPU to vector to the Timer 3 Interrupt service routine. This bit is
not automatically cleared by hardware and must be cleared by software.
Bits6-3: UNUSED. Read = 0000b, Write = don't care.
Bit2:
Bit1:
Bit0:
TR3: Timer 3 Run Control.
This bit enables/disables Timer 3.
0: Timer 3 disabled.
1: Timer 3 enabled.
T3M: Timer 3 Clock Select.
This bit controls the division of the system clock supplied to Counter/Timer 3.
0: Counter/Timer 3 uses the system clock divided by 12.
1: Counter/Timer 3 uses the system clock.
T3XCLK: Timer 3 External Clock Select
This bit selects the external oscillator input divided by 8 as the Timer 3 clock source. When T3XCLK
is logic 1, bit T3M (TMR3CN.1) is ignored.
0: Timer 3 clock source defined by bit T3M (TMR3CN.1).
1: Timer 3 clock source is the external oscillator input divided by 8.
Figure 22.21. TMR3RLL: Timer 3 Reload Register Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x92
Bits 7-0: TMR3RLL: Timer 3 Reload Register Low Byte.
Timer 3 is configured as an auto-reload timer. This register holds the low byte of the reload value.
Rev. 1.4
241
C8051F020/1/2/3
Figure 22.22. TMR3RLH: Timer 3 Reload Register High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x93
Bits 7-0: TMR3RLH: Timer 3 Reload Register High Byte.
Timer 3 is configured as an auto-reload timer. This register holds the high byte of the reload value.
Figure 22.23. TMR3L: Timer 3 Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x94
Bits 7-0: TMR3L: Timer 3 Low Byte.
The TMR3L register is the low byte of Timer 3.
Figure 22.24. TMR3H: Timer 3 High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0x95
Bits 7-0: TMR3H: Timer 3 High Byte.
The TMR3H register is the high byte of Timer 3.
242
Rev. 1.4
C8051F020/1/2/3
22.3. Timer 4
Timer 4 is a 16-bit counter/timer formed by the two 8-bit SFRs: TL4 (low byte) and TH4 (high byte). As with
Timers 0 and 1, Timer 4 can use either the system clock or transitions on an external input pin (T4) as its clock
source. The Counter/Timer Select bit C/T4 bit (T4CON.1) selects the clock source for Timer 4. Clearing C/T4 selects
the system clock as the input for the timer (divided by either one or twelve as specified by the Timer Clock Select bit
T4M in CKCON). When C/T4 is set to 1, high-to-low transitions at the T4 input pin increment the counter/timer reg-
ister. Refer to Section “17.1. Ports 0 through 3 and the Priority Crossbar Decoder” on page 163 for information
on selecting and configuring external I/O pins for digital peripherals.
Timer 4 offers capabilities not found in Timer 0 and Timer 1. It operates in one of three modes: 16-bit Counter/Timer
with Capture, 16-bit Counter/Timer with Auto-Reload or Baud Rate Generator Mode. Timer 4's operating mode is
selected by setting configuration bits in the Timer 4 Control register (T4CON). Below is a summary of the Timer 4
operating modes and the T4CON bits used to configure the counter/timer. Detailed descriptions of each mode follow.
RCLK1
TCLK1
CP/RL4
TR4
Mode
0
0
0
0
1
0
1
1
1
1
1
0
16-bit Counter/Timer with Capture
16-bit Counter/Timer with Auto-Reload
Baud Rate Generator for UART1
Baud Rate Generator for UART1
Baud Rate Generator for UART1
Off
0
1
X
X
X
X
1
0
1
1
X
X
Rev. 1.4
243
C8051F020/1/2/3
22.3.1. Mode 0: 16-bit Counter/Timer with Capture
In this mode, Timer 4 operates as a 16-bit counter/timer with capture facility. A high-to-low transition on the T4EX
input pin causes the following to occur:
1. The 16-bit value in Timer 4 (TH4, TL4) is loaded into the capture registers (RCAP4H, RCAP4L).
2. The Timer 4 External Flag (EXF2) is set to ‘1’.
3. A Timer 4 interrupt is generated if enabled.
Timer 4 can use either SYSCLK, SYSCLK divided by 12, or high-to-low transitions on the T4 input pin as its clock
source when operating in Capture mode. Clearing the C/T4 bit (T4CON.1) selects the system clock as the input for
the timer (divided by one or twelve as specified by the Timer Clock Select bit T4M in CKCON). When C/T4 is set to
logic 1, a high-to-low transition at the T4 input pin increments the counter/timer register. As the 16-bit counter/timer
register increments and overflows from 0xFFFF to 0x0000, the TF4 timer overflow flag (T4CON.7) is set and an
interrupt will occur if the interrupt is enabled.
Counter/Timer with Capture mode is selected by setting the Capture/Reload Select bit CP/RL4 (T4CON.0) and the
Timer 4 Run Control bit TR4 (T4CON.2) to logic 1. The Timer 4 External Enable EXEN4 (T4CON.3) must also be
set to logic 1 to enable a capture. If EXEN4 is cleared, transitions on T4EX will be ignored.
Figure 22.25. T4 Mode 0 Block Diagram
CKCON
T T T T
4 2 1 0
M MM M
12
0
1
SYSCLK
0
1
TCLK
T4
TL4
TH4
CP/RL4
C/T4
TR4
TR4
Crossbar
EXEN4
TCLK0
RCLK0
EXF4
TF4
Interrupt
T4EX
Capture
RCAP4L RCAP4H
EXEN4
244
Rev. 1.4
C8051F020/1/2/3
22.3.2. Mode 1: 16-bit Counter/Timer with Auto-Reload
The Counter/Timer with Auto-Reload mode sets the TF4 timer overflow flag when the counter/timer register over-
flows from 0xFFFF to 0x0000. An interrupt is generated if enabled. On overflow, the 16-bit value held in the two
capture registers (RCAP4H, RCAP4L) is automatically loaded into the counter/timer register and the timer is
restarted.
Counter/Timer with Auto-Reload mode is selected by clearing the CP/RL4 bit. Setting TR4 to logic 1 enables and
starts the timer. Timer 4 can use either the system clock or transitions on an external input pin (T2) as its clock source,
as specified by the C/T4 bit. If EXEN4 is set to logic 1, a high-to-low transition on T4EX will also cause a Timer 4
reload, and a Timer 4 interrupt if enabled. If EXEN4 is logic 0, transitions on T4EX will be ignored.
Figure 22.26. T4 Mode 1 Block Diagram
CKCON
T T T T
4 2 1 0
MM MM
12
0
1
SYSCLK
0
TL4
TH4
TCLK
CP/RL4
C/T4
1
T4
TR4
Crossbar
EXEN4
TCLK0
RCLK0
EXF4
TF4
TR4
T4EX
Interrupt
Reload
RCAP4L RCAP4H
EXEN4
Rev. 1.4
245
C8051F020/1/2/3
22.3.3. Mode 2: Baud Rate Generator
Timer 4 can be used as a baud rate generator for UART1 when UART1 is operated in modes 1 or 3 (refer to Section
“21.1. UART1 Operational Modes” on page 216 for more information on the UART1 operational modes). In Baud
Rate Generator mode, Timer 4 works similarly to the auto-reload mode. On overflow, the 16-bit value held in the two
capture registers (RCAP4H, RCAP4L) is automatically loaded into the counter/timer register. However, the TF4
overflow flag is not set and no interrupt is generated. Instead, the overflow event is used as the input to the UART's
shift clock. Timer 4 overflows can be selected to generate baud rates for transmit and/or receive independently.
The Baud Rate Generator mode is selected by setting RCLK1 (T4CON.5) and/or TCLK1 (T4CON.4) to ‘1’. When
RCLK1 or TCLK1 is set to logic 1, Timer 4 operates in the auto-reload mode regardless of the state of the CP/RL4
bit. Note that in Baud Rate Generator mode, the Timer 4 timebase is the system clock divided by two. When selected
as the UART1 baud clock source, Timer 4 defines the UART1 baud rate as follows:
Baud Rate = SYSCLK / ((65536 - [RCAP4H, RCAP4L] ) * 32)
If a different time base is required, setting the C/T4 bit to logic 1 will allow the timebase to be derived from the exter-
nal input pin T4. In this case, the baud rate for the UART is calculated as:
Baud Rate = F
/ ( (65536 - [RCAP4H, RCAP4L] ) * 16)
CLK
Where F
is the frequency of the signal (TCLK) supplied to Timer 4 and [RCAP4H, RCAP4L] is the 16-bit value
CLK
held in the capture registers.
As explained above, in Baud Rate Generator mode, Timer 4 does not set the TF4 overflow flag and therefore cannot
generate an interrupt. However, if EXEN4 is set to logic 1, a high-to-low transition on the T4EX input pin will set the
EXF4 flag and a Timer 4 interrupt will occur if enabled. Therefore, the T4EX input may be used as an additional
external interrupt source.
Figure 22.27. T4 Mode 2 Block Diagram
C/T2
SYSCLK
T2
2
0
1
RCLK0
0
Timer 2
Overflow
Crossbar
TL2
TH2
TCLK
16
RX0 Clock
TX0 Clock
TR2
1
0
Reload
PCON
S
M
O
D
0
RCAP2L RCAP2H
S I
T D
O L
P E
16
2
0
1
1
Timer 1
Overflow
CP/RL2
C/T2
TCLK0
TR2
EXEN2
TCLK0
RCLK0
EXEN2
EXF2
TF2
Interrupt
Crossbar
T2EX
246
Rev. 1.4
C8051F020/1/2/3
Figure 22.28. T4CON: Timer 4 Control Register
R/W
TF4
Bit7
R/W
EXF4
Bit6
R/W
RCLK1
Bit5
R/W
TCLK1
Bit4
R/W
EXEN4
Bit3
R/W
TR4
Bit2
R/W
C/T4
Bit1
R/W
Reset Value
CP/RL4 00000000
Bit0
SFR Address:
0xC9
Bit7:
TF4: Timer 4 Overflow Flag.
Set by hardware when Timer 4 overflows. When the Timer 4 interrupt is enabled, setting this bit
causes the CPU to vector to the Timer 4 interrupt service routine. This bit is not automatically cleared
by hardware and must be cleared by software. TF4 will not be set when RCLK1 and/or TCLK1 are
logic 1.
Bit6:
EXF4: Timer 4 External Flag.
Set by hardware when either a capture or reload is caused by a high-to-low transition on the T4EX
input pin and EXEN4 is logic 1. When the Timer 4 interrupt is enabled, setting this bit causes the
CPU to vector to the Timer 4 Interrupt service routine. This bit is not automatically cleared by hard-
ware and must be cleared by software.
Bit5:
Bit4:
Bit3:
RCLK1: Receive Clock Flag for UART1.
Selects which timer is used for the UART1 receive clock in modes 1 or 3.
0: Timer 1 overflows used for receive clock.
1: Timer 4 overflows used for receive clock.
TCLK1: Transmit Clock Flag for UART1.
Selects which timer is used for the UART1 transmit clock in modes 1 or 3.
0: Timer 1 overflows used for transmit clock.
1: Timer 4 overflows used for transmit clock.
EXEN4: Timer 4 External Enable.
Enables high-to-low transitions on T4EX to trigger captures or reloads when Timer 4 is not operating
in Baud Rate Generator mode.
0: High-to-low transitions on T4EX ignored.
1: High-to-low transitions on T4EX cause a capture or reload.
TR4: Timer 4 Run Control.
Bit2:
This bit enables/disables Timer 4.
0: Timer 4 disabled.
1: Timer 4 enabled.
Bit1:
Bit0:
C/T4: Counter/Timer Select.
0: Timer Function: Timer 4 incremented by clock defined by T4M (CKCON.6).
1: Counter Function: Timer 4 incremented by high-to-low transitions on external input pin (T2).
CP/RL4: Capture/Reload Select.
This bit selects whether Timer 4 functions in capture or auto-reload mode. EXEN4 must be logic 1 for
high-to-low transitions on T4EX to be recognized and used to trigger captures or reloads. If RCLK1
or TCLK1 is set, this bit is ignored and Timer 4 will function in auto-reload mode.
0: Auto-reload on Timer 4 overflow or high-to-low transition at T4EX (EXEN4 = 1).
1: Capture on high-to-low transition at T4EX (EXEN4 = 1).
Rev. 1.4
247
C8051F020/1/2/3
Figure 22.29. RCAP4L: Timer 4 Capture Register Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xE4
Bits 7-0: RCAP4L: Timer 4 Capture Register Low Byte.
The RCAP4L register captures the low byte of Timer 4 when Timer 4 is configured in capture mode.
When Timer 4 is configured in auto-reload mode, it holds the low byte of the reload value.
Figure 22.30. RCAP4H: Timer 4 Capture Register High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xE5
Bits 7-0: RCAP4H: Timer 4 Capture Register High Byte.
The RCAP4H register captures the high byte of Timer 4 when Timer 4 is configured in capture mode.
When Timer 4 is configured in auto-reload mode, it holds the high byte of the reload value.
Figure 22.31. TL4: Timer 4 Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xF4
Bits 7-0: TL4: Timer 4 Low Byte.
The TL4 register contains the low byte of the 16-bit Timer 4.
Figure 22.32. TH4 Timer 4 High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xF5
Bits 7-0: TH4: Timer 4 High Byte.
The TH4 register contains the high byte of the 16-bit Timer 4.
248
Rev. 1.4
C8051F020/1/2/3
23. PROGRAMMABLE COUNTER ARRAY
The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU interven-
tion than the standard 8051 counter/timers. PCA0 consists of a dedicated 16-bit counter/timer and five 16-bit capture/
compare modules. Each capture/compare module has its own associated I/O line (CEXn) which is routed through the
Crossbar to Port I/O when enabled (See Section “17.1. Ports 0 through 3 and the Priority Crossbar Decoder” on
page 163). The counter/timer is driven by a programmable timebase that can select between six inputs as its source:
system clock, system clock divided by four, system clock divided by twelve, the external oscillator clock source
divided by 8, Timer 0 overflow, or an external clock signal on the ECI line. Each capture/compare module may be
configured to operate independently in one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Out-
put, Frequency Output, 8-Bit PWM, or 16-Bit PWM (each is described in Section 23.2). The PCA is configured and
controlled through the system controller's Special Function Registers. The basic PCA block diagram is shown in
Figure 23.1.
Figure 23.1. PCA Block Diagram
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
PCA
16-Bit Counter/Timer
CLOCK
MUX
ECI
SYSCLK
External Clock/8
Capture/Compare
Module 0
Capture/Compare
Module 1
Capture/Compare
Module 2
Capture/Compare
Module 3
Capture/Compare
Module 4
Crossbar
Port I/O
Rev. 1.4
249
C8051F020/1/2/3
23.1. PCA Counter/Timer
The 16-bit PCA counter/timer consists of two 8-bit SFRs: PCA0L and PCA0H. PCA0H is the high byte (MSB) of the
16-bit counter/timer and PCA0L is the low byte (LSB). Reading PCA0L automatically latches the value of PCA0H
into a “snapshot” register; the following PCA0H read accesses this “snapshot” register. Reading the PCA0L Register
first guarantees an accurate reading of the entire 16-bit PCA0 counter. Reading PCA0H or PCA0L does not disturb
the counter operation. The CPS2-CPS0 bits in the PCA0MD register select the timebase for the counter/timer as
shown in Table 23.1. Note that in ‘External oscillator source divided by 8’ mode, the external oscillator source
is synchronized with the system clock, and must have a frequency less than or equal to the system clock.
When the counter/timer overflows from 0xFFFF to 0x0000, the Counter Overflow Flag (CF) in PCA0MD is set to
logic 1 and an interrupt request is generated if CF interrupts are enabled. Setting the ECF bit in PCA0MD to logic 1
enables the CF flag to generate an interrupt request. The CF bit is not automatically cleared by hardware when the
CPU vectors to the interrupt service routine, and must be cleared by software (Note: PCA0 interrupts must be glo-
bally enabled before CF interrupts are recognized. PCA0 interrupts are globally enabled by setting the EA bit (IE.7)
and the EPCA0 bit in EIE1 to logic 1). Clearing the CIDL bit in the PCA0MD register allows the PCA to continue
normal operation while the CPU is in Idle mode.
Table 23.1. PCA Timebase Input Options
CPS2
CPS1
CPS0 Timebase
0
0
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
System clock divided by 12
System clock divided by 4
Timer 0 overflow
‡
High-to-low transitions on ECI (max rate = system clock divided by 4)
System clock
External oscillator source divided by 8
†
†
‡
External oscillator source divided by 8 is synchronized with the system clock.
The minimum high or low time for the ECI input signal is at least 2 system clock cycles.
Figure 23.2. PCA Counter/Timer Block Diagram
IDLE
PCA0MD
PCA0CN
C
I
W W C C C E
D D P P P C
T L S S S F
E C 2 1 0
K
C C C C C C C
F R C C C C C
F F F F F
D
L
4 3 2 1 0
To SFR Bus
PCA0L
read
Snapshot
Register
SYSCLK/12
SYSCLK/4
000
001
010
011
100
101
Timer 0 Overflow
ECI
0
Overflow
To PCA Interrupt System
PCA0H
PCA0L
1
SYSCLK
CF
To PCA Modules
External Clock/8
250
Rev. 1.4
C8051F020/1/2/3
Important Note About the PCA0CN Register: If the main PCA counter (PCA0H : PCA0L) overflows during the
execution phase of a read-modify-write instruction (bit-wise SETB or CLR, ANL, ORL, XRL) that targets the
PCA0CN register, the CF (Counter Overflow) bit will not be set. The following steps should be taken when perform-
ing a bit-wise operation on the PCA0CN register:
Step 1. Disable global interrupts (EA = 0).
Step 2. Read PCA0L. This will latch the value of PCA0H.
Step 3. Read PCA0H, saving the value.
Step 4. Execute the bit-wise operation on CCFn (for example, CLR CCF0, or CCF0 = 0;).
Step 5. Read PCA0L.
Step 6. Read PCA0H, saving the value.
Step 7. If the value of PCA0H read in Step 3 is 0xFF and the value for PCA0H read in Step 6 is 0x00, then
manually set the CF bit in software (for example, SETB CF, or CF = 1;).
Step 8. Re-enable interrupts (EA = 1).
Rev. 1.4
251
C8051F020/1/2/3
23.2. Capture/Compare Modules
Each module can be configured to operate independently in one of six operation modes: Edge-triggered Capture,
Software Timer, High Speed Output, Frequency Output, 8-Bit Pulse Width Modulator, or 16-Bit Pulse Width Modu-
lator. Each module has Special Function Registers (SFRs) associated with it in the CIP-51 system controller. These
registers are used to exchange data with a module and configure the module's mode of operation.
Table 23.2 summarizes the bit settings in the PCA0CPMn registers used to select the PCA0 capture/compare mod-
ule’s operating modes. Setting the ECCFn bit in a PCA0CPMn register enables the module's CCFn interrupt. Note:
PCA0 interrupts must be globally enabled before individual CCFn interrupts are recognized. PCA0 interrupts are glo-
bally enabled by setting the EA bit (IE.7) and the EPCA0 bit (EIE1.3) to logic 1. See Figure 23.3 for details on the
PCA interrupt configuration.
Table 23.2. PCA0CPM Register Settings for PCA Capture/Compare Modules
PWM16 ECOM CAPP CAPN MAT TOG PWM ECCF Operation Mode
Capture triggered by positive edge on
X
X
X
X
X
X
1
0
1
0
1
1
0
0
0
0
0
0
0
0
0
X
X
X
CEXn
Capture triggered by negative edge on
CEXn
Capture triggered by transition on
CEXn
X
X
X
0
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
1
1
X
X
X
0
1
1
0
0
0
0
1
1
1
X
X
X
X
X
Software Timer
High Speed Output
Frequency Output
8-Bit Pulse Width Modulator
16-Bit Pulse Width Modulator
1
X = Don’t Care
Figure 23.3. PCA Interrupt Block Diagram
(for n = 0 to 4)
PCA0CPMn
PCA0CN
PCA0MD
P
W
M
1
E C C M T
C A A A O
O P P T G
M P N n n
n n n
P
W
M
n
E
C
C
F
n
C C C C C C C
F R C C C C C
F F F F F
C
I
D
L
C C C E
P P P C
S S S F
2 1 0
4 3 2 1 0
6
n
0
1
PCA Counter/
Timer Overflow
ECCF0
ECCF1
ECCF2
ECCF3
ECCF4
EPCA0
(EIE1.3)
EA
(IE.7)
0
1
PCA Module 0
(CCF0)
Interrupt
Priority
0
1
0
1
Decoder
0
1
PCA Module 1
(CCF1)
0
1
PCA Module 2
(CCF2)
0
1
PCA Module 3
(CCF3)
0
1
PCA Module 4
(CCF4)
252
Rev. 1.4
C8051F020/1/2/3
23.2.1. Edge-triggered Capture Mode
In this mode, a valid transition on the CEXn pin causes PCA0 to capture the value of the PCA0 counter/timer and
load it into the corresponding module's 16-bit capture/compare register (PCA0CPLn and PCA0CPHn). The CAPPn
and CAPNn bits in the PCA0CPMn register are used to select the type of transition that triggers the capture: low-to-
high transition (positive edge), high-to-low transition (negative edge), or either transition (positive or negative edge).
When a capture occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic 1 and an interrupt request is
generated if CCF interrupts are enabled. The CCFn bit is not automatically cleared by hardware when the CPU vec-
tors to the interrupt service routine, and must be cleared by software.
Figure 23.4. PCA Capture Mode Diagram
PCA Interrupt
PCA0CPMn
PCA0CN
P
W
M
1
6
n
E C C M T
C A A A O
O P P T G
M P N n n
n n n
P
W
M
n
E
C
C
F
n
C C C C C C C
F R C C C C C
F F F F F
4 3 2 1 0
PCA0CPLn
PCA0CPHn
PCA0H
0
1
CEXn
Capture
Port I/O
Crossbar
0
1
PCA
PCA0L
Timebase
Note: The CEXn input signal must remain high or low for at least 2 system clock cycles in order to be valid.
Rev. 1.4
253
C8051F020/1/2/3
23.2.2. Software Timer (Compare) Mode
In Software Timer mode, the PCA0 counter/timer is compared to the module's 16-bit capture/compare register
(PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic
1 and an interrupt request is generated if CCF interrupts are enabled. The CCFn bit is not automatically cleared by
hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. Setting the ECOMn
and MATn bits in the PCA0CPMn register enables Software Timer mode.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare
registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to ‘0’; writing to
PCA0CPHn sets ECOMn to ‘1’.
Figure 23.5. PCA Software Timer Mode Diagram
Write to
0
PCA0CPLn
Reset
ENB
Write to
PCA0CPHn
PCA Interrupt
ENB
1
PCA0CPMn
PCA0CN
P
W
M
1
6
n
E C C M T
C A A A O
O P P T G
M P N n n
n n n
P
W
M
n
E
C
C
F
n
C C C C C C C
F R C C C C C
F F F F F
PCA0CPLn
PCA0CPHn
4 3 2 1 0
x
0 0
0 0
x
0
1
Enable
Match
16-bit Comparator
PCA
PCA0L
PCA0H
Timebase
254
Rev. 1.4
C8051F020/1/2/3
23.2.3. High Speed Output Mode
In High Speed Output mode, a module’s associated CEXn pin is toggled each time a match occurs between the PCA
Counter and the module's 16-bit capture/compare register (PCA0CPHn and PCA0CPLn) Setting the TOGn, MATn,
and ECOMn bits in the PCA0CPMn register enables the High-Speed Output mode.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare
registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to ‘0’; writing to
PCA0CPHn sets ECOMn to ‘1’.
Figure 23.6. PCA High Speed Output Mode Diagram
Write to
0
PCA0CPLn
Reset
ENB
PCA0CPMn
Write to
PCA0CPHn
P
W
M
1
6
n
E C C M T
C A A A O
O P P T G
M P N n n
n n n
P
W
M
n
E
C
C
F
n
ENB
1
x
0 0
0
x
PCA Interrupt
PCA0CN
C C C C C C C
F R C C C C C
F F F F F
PCA0CPLn
PCA0CPHn
4 3 2 1 0
0
1
Enable
Match
16-bit Comparator
TOGn
Toggle
0
CEXn
Crossbar
Port I/O
1
PCA
Timebase
PCA0L
PCA0H
Rev. 1.4
255
C8051F020/1/2/3
23.2.4. Frequency Output Mode
Frequency Output Mode produces a programmable-frequency square wave on the module’s associated CEXn pin.
The capture/compare module high byte holds the number of PCA clocks to count before the output is toggled. The
frequency of the square wave is then defined by Equation 23.1.
Equation 23.1. Square Wave Frequency Output
FPCA
FCEXn = ----------------------------------------
2 × PCA0CPHn
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
Where F
is the frequency of the clock selected by the CPS2-0 bits in the PCA mode register, PCA0MD. The
PCA
lower byte of the capture/compare module is compared to the PCA0 counter low byte; on a match, CEXn is toggled
and the offset held in the high byte is added to the matched value in PCA0CPLn. Frequency Output Mode is enabled
by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn register.
Figure 23.7. PCA Frequency Output Mode
Write to
0
PCA0CPLn
Reset
ENB
PCA0CPMn
P
W
M
1
6
n
E C C M T
C A A A O
O P P T G
M P N n n
n n n
P
W
M
n
E
C
C
F
n
Write to
PCA0CPHn
ENB
PCA0CPLn
8-bit Adder
PCA0CPHn
1
Adder
Enable
TOGn
x
0
0
0
x
Toggle
0
CEXn
8-bit
match
Enable
Crossbar
Port I/O
1
Comparator
PCA Timebase
PCA0L
256
Rev. 1.4
C8051F020/1/2/3
23.2.5. 8-Bit Pulse Width Modulator Mode
Each module can be used independently to generate pulse width modulated (PWM) outputs on its associated CEXn
pin. The frequency of the output is dependent on the timebase for the PCA0 counter/timer. The duty cycle of the
PWM output signal is varied using the module's PCA0CPLn capture/compare register. When the value in the low
byte of the PCA0 counter/timer (PCA0L) is equal to the value in PCA0CPLn, the output on the CEXn pin will be
asserted high. When the count value in PCA0L overflows, the CEXn output will be asserted low (see Figure 23.8).
Also, when the counter/timer low byte (PCA0L) overflows from 0xFF to 0x00, PCA0CPLn is reloaded automatically
with the value stored in the counter/timer's high byte (PCA0H) without software intervention. Setting the ECOMn
and PWMn bits in the PCA0CPMn register enables 8-Bit Pulse Width Modulator mode. The duty cycle for 8-Bit
PWM Mode is given by Equation 23.2.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare
registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to ‘0’; writing to
PCA0CPHn sets ECOMn to ‘1’.
Equation 23.2. 8-Bit PWM Duty Cycle
(256 – PCA0CPHn)
DutyCycle = ---------------------------------------------------
256
Using Equation 23.2, the largest duty cycle is 100% (PCA0CPHn = 0), and the smallest duty cycle is 0.39%
(PCA0CPHn = 0xFF). A 0% duty cycle may be generated by clearing the ECOMn bit to ‘0’.
Figure 23.8. PCA 8-Bit PWM Mode Diagram
PCA0CPHn
Write to
PCA0CPLn
Reset
0
ENB
PCA0CPMn
Write to
PCA0CPHn
P
W
M
1
6
n
E C C M T
C A A A O
O P P T G
M P N n n
n n n
P
W
M
n
E
C
C
F
n
ENB
1
PCA0CPLn
0
0
0
x
0
x
SET
CLR
8-bit
match
CEXn
Enable
S
R
Q
Q
Crossbar
Port I/O
Comparator
PCA Timebase
PCA0L
Overflow
Rev. 1.4
257
C8051F020/1/2/3
23.2.6. 16-Bit Pulse Width Modulator Mode
Each PCA0 module may also be operated in 16-Bit PWM mode. In this mode, the 16-bit capture/compare module
defines the number of PCA0 clocks for the low time of the PWM signal. When the PCA0 counter matches the module
contents, the output on CEXn is asserted high; when the counter overflows, CEXn is asserted low. To output a vary-
ing duty cycle, new value writes should be synchronized with PCA0 CCFn match interrupts. 16-Bit PWM Mode is
enabled by setting the ECOMn, PWMn, and PWM16n bits in the PCA0CPMn register. For a varying duty cycle,
CCFn should also be set to logic 1 to enable match interrupts. The duty cycle for 16-Bit PWM Mode is given by
Equation 23.3.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare
registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to ‘0’; writing to
PCA0CPHn sets ECOMn to ‘1’
Equation 23.3. 16-Bit PWM Duty Cycle
(65536 – PCA0CPn)
DutyCycle = ----------------------------------------------------
65536
Using Equation 23.3, the largest duty cycle is 100% (PCA0CPn = 0), and the smallest duty cycle is 0.0015%
(PCA0CPn = 0xFFFF). A 0% duty cycle may be generated by clearing the ECOMn bit to ‘0’.
Figure 23.9. PCA 16-Bit PWM Mode
PCA0CPMn
P
W
M
1
6
n
E C C M T
C A A A O
O P P T G
M P N n n
n n n
P
W
M
n
E
C
C
F
n
PCA0CPHn
PCA0CPLn
1
0 0 0 0
0
SET
CLR
match
CEXn
Enable
16-bit Comparator
S
R
Q
Q
Crossbar
Port I/O
PCA Timebase
PCA0H
PCA0L
Overflow
258
Rev. 1.4
C8051F020/1/2/3
23.3. Register Descriptions for PCA0
Following are detailed descriptions of the special function registers related to the operation of PCA0.
Figure 23.10. PCA0CN: PCA Control Register
R/W
CF
Bit7
R/W
CR
Bit6
R/W
-
Bit5
R/W
CCF4
Bit4
R/W
CCF3
Bit3
R/W
CCF2
Bit2
R/W
CCF1
Bit1
R/W
CCF0
Reset Value
00000000
SFR Address:
0xD8
Bit0
(bit addressable)
Bit7:
CF: PCA Counter/Timer Overflow Flag.
Set by hardware when the PCA0 Counter/Timer overflows from 0xFFFF to 0x0000. When the
Counter/Timer Overflow (CF) interrupt is enabled, setting this bit causes the CPU to vector to the CF
interrupt service routine. This bit is not automatically cleared by hardware and must be cleared by
software. See “Important Note About the PCA0CN Register” on page 251.
CR: PCA0 Counter/Timer Run Control.
Bit6:
This bit enables/disables the PCA0 Counter/Timer.
0: PCA0 Counter/Timer disabled.
1: PCA0 Counter/Timer enabled.
Bit5:
Bit4:
UNUSED. Read = 0b, Write = don't care.
CCF4: PCA0 Module 4 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is enabled, set-
ting this bit causes the CPU to vector to the CCF interrupt service routine. This bit is not automati-
cally cleared by hardware and must be cleared by software.
Bit3:
Bit2:
Bit1:
Bit0:
CCF3: PCA0 Module 3 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is enabled, set-
ting this bit causes the CPU to vector to the CCF interrupt service routine. This bit is not automati-
cally cleared by hardware and must be cleared by software.
CCF2: PCA0 Module 2 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is enabled, set-
ting this bit causes the CPU to vector to the CCF interrupt service routine. This bit is not automati-
cally cleared by hardware and must be cleared by software.
CCF1: PCA0 Module 1 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is enabled, set-
ting this bit causes the CPU to vector to the CCF interrupt service routine. This bit is not automati-
cally cleared by hardware and must be cleared by software.
CCF0: PCA0 Module 0 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is enabled, set-
ting this bit causes the CPU to vector to the CCF interrupt service routine. This bit is not automati-
cally cleared by hardware and must be cleared by software.
Rev. 1.4
259
C8051F020/1/2/3
Figure 23.11. PCA0MD: PCA0 Mode Register
R/W
CIDL
Bit7
R/W
Bit6
R/W
Bit5
R/W
-
Bit4
R/W
CPS2
Bit3
R/W
CPS1
Bit2
R/W
CPS0
Bit1
R/W
ECF
Bit0
Reset Value
01000000
SFR Address:
0xD9
Bit7:
CIDL: PCA0 Counter/Timer Idle Control.
Specifies PCA0 behavior when CPU is in Idle Mode.
0: PCA0 continues to function normally while the system controller is in Idle Mode.
1: PCA0 operation is suspended while the system controller is in Idle Mode.
Bits6-4: UNUSED. Read = 000b, Write = don't care.
Bits3-1: CPS2-CPS0: PCA0 Counter/Timer Pulse Select.
These bits select the timebase source for the PCA0 counter
CPS2
CPS1
CPS0 Timebase
0
0
0
0
0
1
0
1
0
System clock divided by 12
System clock divided by 4
Timer 0 overflow
†
High-to-low transitions on ECI
0
1
1
(max rate = system clock divided by 4)
System clock
1
1
1
1
0
0
1
1
0
1
0
1
‡
External clock divided by 8
Reserved
Reserved
†
‡
The minimum high or low time for the ECI input signal is at least 2 system clock cycles.
External oscillator source divided by 8 is synchronized with the system clock.
Bit0:
ECF: PCA Counter/Timer Overflow Interrupt Enable.
This bit sets the masking of the PCA0 Counter/Timer Overflow (CF) interrupt.
0: Disable the CF interrupt.
1: Enable a PCA0 Counter/Timer Overflow interrupt request when CF (PCA0CN.7) is set.
260
Rev. 1.4
C8051F020/1/2/3
Figure 23.12. PCA0CPMn: PCA0 Capture/Compare Mode Registers
R/W
R/W
R/W
CAPPn
Bit5
R/W
CAPNn
Bit4
R/W
MATn
Bit3
R/W
TOGn
Bit2
R/W
PWMn
Bit1
R/W
ECCFn
Bit0
Reset Value
PWM16n ECOMn
00000000
SFR Address:
0xDA-0xDE
Bit7
Bit6
PCA0CPMn Address:
PCA0CPM0 = 0xDA (n = 0)
PCA0CPM1 = 0xDB (n = 1)
PCA0CPM2 = 0xDC (n = 2)
PCA0CPM3 = 0xDD (n = 3)
PCA0CPM4 = 0xDE (n = 4)
Bit7:
Bit6:
Bit5:
Bit4:
Bit3:
PWM16n: 16-bit Pulse Width Modulation Enable
This bit selects 16-bit mode when Pulse Width Modulation mode is enabled (PWMn = 1).
0: 8-bit PWM selected.
1: 16-bit PWM selected.
ECOMn: Comparator Function Enable.
This bit enables/disables the comparator function for PCA0 module n.
0: Disabled.
1: Enabled.
CAPPn: Capture Positive Function Enable.
This bit enables/disables the positive edge capture for PCA0 module n.
0: Disabled.
1: Enabled.
CAPNn: Capture Negative Function Enable.
This bit enables/disables the negative edge capture for PCA0 module n.
0: Disabled.
1: Enabled.
MATn: Match Function Enable.
This bit enables/disables the match function for PCA0 module n. When enabled, matches of the
PCA0 counter with a module's capture/compare register cause the CCFn bit in PCA0MD register to
be set to logic 1.
0: Disabled.
1: Enabled.
Bit2:
Bit1:
Bit0:
TOGn: Toggle Function Enable.
This bit enables/disables the toggle function for PCA0 module n. When enabled, matches of the
PCA0 counter with a module's capture/compare register cause the logic level on the CEXn pin to tog-
gle. If the PWMn bit is also set to logic 1, the module operates in Frequency Output Mode.
0: Disabled.
1: Enabled.
PWMn: Pulse Width Modulation Mode Enable.
This bit enables/disables the PWM function for PCA0 module n. When enabled, a pulse width modu-
lated signal is output on the CEXn pin. 8-bit PWM is used if PWM16n is logic 0; 16-bit mode is used
if PWM16n logic 1. If the TOGn bit is also set, the module operates in Frequency Output Mode.
0: Disabled.
1: Enabled.
ECCFn: Capture/Compare Flag Interrupt Enable.
This bit sets the masking of the Capture/Compare Flag (CCFn) interrupt.
0: Disable CCFn interrupts.
1: Enable a Capture/Compare Flag interrupt request when CCFn is set.
Rev. 1.4
261
C8051F020/1/2/3
Figure 23.13. PCA0L: PCA0 Counter/Timer Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xE9
Bits 7-0: PCA0L: PCA0 Counter/Timer Low Byte.
The PCA0L register holds the low byte (LSB) of the 16-bit PCA0 Counter/Timer.
Figure 23.14. PCA0H: PCA0 Counter/Timer High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xF9
Bits 7-0: PCA0H: PCA0 Counter/Timer High Byte.
The PCA0H register holds the high byte (MSB) of the 16-bit PCA0 Counter/Timer.
262
Rev. 1.4
C8051F020/1/2/3
Figure 23.15. PCA0CPLn: PCA0 Capture Module Low Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xEA - 0xEE
PCA0CPLn Address:
PCA0CPL0 = 0xEA (n = 0)
PCA0CPL1 = 0xEB (n = 1)
PCA0CPL2 = 0xEC (n = 2)
PCA0CPL3 = 0xED (n = 3)
PCA0CPL4 = 0xEE (n = 4)
Bits7-0: PCA0CPLn: PCA0 Capture Module Low Byte.
The PCA0CPLn register holds the low byte (LSB) of the 16-bit capture module n.
Figure 23.16. PCA0CPHn: PCA0 Capture Module High Byte
R/W
Bit7
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
Bit3
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
00000000
SFR Address:
0xFA - 0xFE
PCA0CPHn Address:
PCA0CPH0 = 0xFA (n = 0)
PCA0CPH1 = 0xFB (n = 1)
PCA0CPH2 = 0xFC (n = 2)
PCA0CPH3 = 0xFD (n = 3)
PCA0CPH4 = 0xFE (n = 4)
Bits7-0: PCA0CPHn: PCA0 Capture Module High Byte.
The PCA0CPHn register holds the high byte (MSB) of the 16-bit capture module n.
Rev. 1.4
263
C8051F020/1/2/3
Notes
264
Rev. 1.4
C8051F020/1/2/3
24. JTAG (IEEE 1149.1)
Each MCU has an on-chip JTAG interface and logic to support boundary scan for production and in-system testing,
Flash read/write operations, and non-intrusive in-circuit debug. The JTAG interface is fully compliant with the IEEE
1149.1 specification. Refer to this specification for detailed descriptions of the Test Interface and Boundary-Scan
Architecture. Access of the JTAG Instruction Register (IR) and Data Registers (DR) are as described in the Test
Access Port and Operation of the IEEE 1149.1 specification.
The JTAG interface is accessed via four dedicated pins on the MCU: TCK, TMS, TDI, and TDO.
Through the 16-bit JTAG Instruction Register (IR), any of the seven instructions shown in Figure 24.1 can be com-
manded. There are three DR’s associated with JTAG Boundary-Scan, and four associated with Flash read/write oper-
ations on the MCU.
Figure 24.1. IR: JTAG Instruction Register
Reset Value
0x0000
Bit15
Bit0
IR Value
0x0000
Instruction
EXTEST
SAMPLE/
PRELOAD
IDCODE
BYPASS
Description
Selects the Boundary Data Register for control and observability of all device pins
Selects the Boundary Data Register for observability and presetting the scan-path
latches
0x0002
0x0004
0xFFFF
Selects device ID Register
Selects Bypass Data Register
Selects FLASHCON Register to control how the interface logic responds to reads
and writes to the FLASHDAT Register
Selects FLASHDAT Register for reads and writes to the Flash memory
Selects FLASHADR Register which holds the address of all Flash read, write, and
erase operations
0x0082
0x0083
0x0084
Flash Control
Flash Data
Flash Address
Rev. 1.4
265
C8051F020/1/2/3
24.1. Boundary Scan
The DR in the Boundary Scan path is an 134-bit shift register. The Boundary DR provides control and observability
of all the device pins as well as the SFR bus and Weak Pullup feature via the EXTEST and SAMPLE commands.
Table 24.1. Boundary Data Register Bit Definitions
EXTEST provides access to both capture and update actions, while Sample only performs a capture.
Bit
0
Action
Target
Capture Reset Enable from MCU (C8051F021/3 devices)
Update Reset Enable to /RST pin (C8051F021/3 devices)
Capture Reset input from /RST pin (C8051F021/3 devices)
Update Reset output to /RST pin (C8051F021/3 devices)
Capture Reset Enable from MCU (C8051F020/2 devices)
Update Reset Enable to /RST pin (C8051F020/2 devices)
Capture Reset input from /RST pin (C8051F020/2 devices)
Update Reset output to /RST pin (C8051F020/2 devices)
Capture External Clock from XTAL1 pin
Update Not used
Capture Weak pullup enable from MCU
Update Weak pullup enable to Port Pins
6, 8, 10, 12, 14, 16, Capture P0.n output enable from MCU (e.g. Bit6=P0.0, Bit8=P0.1, etc.)
18, 20
7, 9, 11, 13, 15, 17, Capture P0.n input from pin (e.g. Bit7=P0.0, Bit9=P0.1, etc.)
19, 21
22, 24, 26, 28, 30, Capture P1.n output enable from MCU
32, 34, 36
23, 25, 27, 29, 31, Capture P1.n input from pin
33, 35, 37
38, 40, 42, 44, 46, Capture P2.n output enable from MCU
48, 50, 52
39, 41, 43, 45, 47, Capture P2.n input from pin
49, 51, 53
54, 56, 58, 60, 62, Capture P3.n output enable from MCU
64, 66, 68
55, 57, 59, 61, 63, Capture P3.n input from pin
65, 67, 69
70, 72, 74, 76, 78, Capture P4.n output enable from MCU
80, 82, 84
71, 73, 75, 77, 79, Capture P4.n input from pin
81, 83, 85
86, 88, 90, 92, 94, Capture P5.n output enable from MCU
96, 98, 100
87, 89, 91, 93, 95, Capture P5.n input from pin
97, 99, 101
102, 104, 106, 108, Capture P6.n output enable from MCU
110, 112, 114, 116
103, 105, 107, 109, Capture P6.n input from pin
111, 113, 115, 117
1
2
3
4
5
Update
Update
Update
Update
Update
Update
Update
Update
Update
Update
Update
Update
Update
Update
P0.n output enable to pin (e.g. Bit6=P0.0oe, Bit8=P0.1oe, etc.)
P0.n output to pin (e.g. Bit7=P0.0, Bit9=P0.1, etc.)
P1.n output enable to pin
P1.n output to pin
P2.n output enable to pin
P2.n output to pin
P3.n output enable to pin
P3.n output to pin
P4.n output enable to pin
P4.n output to pin
P5.n output enable to pin
P5.n output to pin
P6.n output enable to pin
P6.n output to pin
266
Rev. 1.4
C8051F020/1/2/3
Table 24.1. Boundary Data Register Bit Definitions
Bit
118, 120, 122, 124, Capture P7.n output enable from MCU
126, 128, 130, 132
119, 121, 123, 125, Capture P7.n input from pin
127, 129, 131, 133
Action
Target
Update
P7.n output enable to pin
Update
P7.n output to pin
24.1.1. EXTEST Instruction
The EXTEST instruction is accessed via the IR. The Boundary DR provides control and observability of all the
device pins as well as the Weak Pullup feature. All inputs to on-chip logic are set to logic 1.
24.1.2. SAMPLE Instruction
The SAMPLE instruction is accessed via the IR. The Boundary DR provides observability and presetting of the scan-
path latches.
24.1.3. BYPASS Instruction
The BYPASS instruction is accessed via the IR. It provides access to the standard JTAG Bypass data register.
24.1.4. IDCODE Instruction
The IDCODE instruction is accessed via the IR. It provides access to the 32-bit Device ID register.
Figure 24.2. DEVICEID: JTAG Device ID Register
Reset Value
Version
Part Number
Manufacturer ID
1
Bit0
0xn0003243
Bit31
Bit28 Bit27
Bit12 Bit11
Bit1
Version = 0000b
Part Number = 0000 0000 0000 0011b (C8051F020/1/2/3)
Manufacturer ID = 0010 0100 001b (Silicon Labs)
Rev. 1.4
267
C8051F020/1/2/3
24.2. Flash Programming Commands
The Flash memory can be programmed directly over the JTAG interface using the Flash Control, Flash Data, Flash
Address, and Flash Scale registers. These Indirect Data Registers are accessed via the JTAG Instruction Register.
Read and write operations on indirect data registers are performed by first setting the appropriate DR address in the
IR register. Each read or write is then initiated by writing the appropriate Indirect Operation Code (IndOpCode) to the
selected data register. Incoming commands to this register have the following format:
19:18
17:0
IndOpCode
WriteData
IndOpCode: These bit set the operation to perform according to the following table:
IndOpCode
Operation
Poll
0x
10
11
Read
Write
The Poll operation is used to check the Busy bit as described below. Although a Capture-DR is performed, no
Update-DR is allowed for the Poll operation. Since updates are disabled, polling can be accomplished by shifting in/
out a single bit.
The Read operation initiates a read from the register addressed by the DRAddress. Reads can be initiated by shifting
only 2 bits into the indirect register. After the read operation is initiated, polling of the Busy bit must be performed to
determine when the operation is complete.
The write operation initiates a write of WriteData to the register addressed by DRAddress. Registers of any width up
to 18 bits can be written. If the register to be written contains fewer than 18 bits, the data in WriteData should be left-
justified, i.e. its MSB should occupy bit 17 above. This allows shorter registers to be written in fewer JTAG clock
cycles. For example, an 8-bit register could be written by shifting only 10 bits. After a Write is initiated, the Busy bit
should be polled to determine when the next operation can be initiated. The contents of the Instruction Register
should not be altered while either a read or write operation is busy.
Outgoing data from the indirect Data Register has the following format:
19
0
18:1
ReadData
0
Busy
The Busy bit indicates that the current operation is not complete. It goes high when an operation is initiated and
returns low when complete. Read and Write commands are ignored while Busy is high. In fact, if polling for Busy to
be low will be followed by another read or write operation, JTAG writes of the next operation can be made while
checking for Busy to be low. They will be ignored until Busy is read low, at which time the new operation will ini-
tiate. This bit is placed ate bit 0 to allow polling by single-bit shifts. When waiting for a Read to complete and Busy is
0, the following 18 bits can be shifted out to obtain the resulting data. ReadData is always right-justified. This allows
registers shorter than 18 bits to be read using a reduced number of shifts. For example, the results from a byte-read
requires 9 bit shifts (Busy + 8 bits).
268
Rev. 1.4
C8051F020/1/2/3
Figure 24.3. FLASHCON: JTAG Flash Control Register
Reset Value
SFLE
Bit7
WRMD2 WRMD1 WRMD0 RDMD3
RDMD2
RDMD1
RDMD0
00000000
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
This register determines how the Flash interface logic will respond to reads and writes to the FLASHDAT
Register.
Bit7:
SFLE: Scratchpad FLASH Memory Access Enable.
When this bit is set, FLASH reads and writes are directed to the 128-byte Scratchpad FLASH sector.
When SFLE is set to logic 1, FLASH accesses out of the address range 0x00-0x7F should not be
attempted. Reads/Writes out of this range will yield unpredictable results.
0:
1:
FLASH access directed to the 64k byte Program/Data FLASH sector.
FLASH access directed to the 128 byte Scratchpad sector.
Bits6-4: WRMD2-0: Write Mode Select Bits.
The Write Mode Select Bits control how the interface logic responds to writes to the FLASHDAT
Register per the following values:
000:
001:
A FLASHDAT write replaces the data in the FASHDAT register, but is otherwise ignored.
A FLASHDAT write initiates a write of FLASHDAT into the memory address by the
FLASHADR register. FLASHADR is incremented by one when complete.
A FLASHDAT write initiates an erasure (sets all bytes to 0xFF) of the Flash page containing
the address in FLASHADR. The data written must be 0xA5 for the erase to occur.
FLASHADR is not affected. If FLASHADR = 0x7DFE - 0x7DFF, the entire user space will
be erased (i.e. entire Flash memory except for Reserved area 0x7E00 - 0x7FFF).
010:
(All other values for WRMD3-0 are reserved.)
Bits3-0: RDMD3-0: Read Mode Select Bits.
The Read Mode Select Bits control how the interface logic responds to reads to the FLASHDAT Reg-
ister per the following values:
0000: A FLASHDAT read provides the data in the FASHDAT register, but is otherwise ignored.
0001: A FLASHDAT read initiates a read of the byte addressed by the FLASHADR register if no
operation is currently active. This mode is used for block reads.
0010: A FLASHDAT read initiates a read of the byte addressed by FLASHADR only if no
operation is active and any data from a previous read has already been read from
FLASHDAT. This mode allows single bytes to be read (or the last byte of a block) without
initiating an extra read.
(All other values for RDMD3-0 are reserved.)
Rev. 1.4
269
C8051F020/1/2/3
Figure 24.4. FLASHADR: JTAG Flash Address Register
Reset Value
0x0000
Bit15
Bit0
This register holds the address for all JTAG Flash read, write, and erase operations. This register autoincrements
after each read or write, regardless of whether the operation succeeded or failed.
Bits15-0: Flash Operation 16-bit Address.
Figure 24.5. FLASHDAT: JTAG Flash Data Register
Reset Value
0000000000
Bit9
Bit0
This register is used to read or write data to the Flash memory across the JTAG interface.
Bits9-2: DATA7-0: Flash Data Byte.
Bit1:
FAIL: Flash Fail Bit.
0: Previous Flash memory operation was successful.
1: Previous Flash memory operation failed. Usually indicates the associated memory location
was locked.
Bit0:
BUSY: Flash Busy Bit.
0: Flash interface logic is not busy.
1: Flash interface logic is processing a request. Reads or writes while BUSY = 1 will not
initiate another operation
270
Rev. 1.4
C8051F020/1/2/3
24.3. Debug Support
Each MCU has on-chip JTAG and debug logic that provides non-intrusive, full speed, in-circuit debug support using
the production part installed in the end application, via the four pin JTAG I/F. Silicon Labs' debug system supports
inspection and modification of memory and registers, breakpoints, and single stepping. No additional target RAM,
program memory, or communications channels are required. All the digital and analog peripherals are functional and
work correctly (remain synchronized) while debugging. The Watchdog Timer (WDT) is disabled when the MCU is
halted during single stepping or at a breakpoint.
The C8051F020DK is a development kit with all the hardware and software necessary to develop application code
and perform in-circuit debug with each MCU in the C8051F020 family. Each kit includes an Integrated Development
Environment (IDE) which has a debugger and integrated 8051 assembler. The kit also includes an RS-232 to JTAG
interface module referred to as the Serial Adapter, a target application board with a C8051F020 installed, RS-232 and
JTAG cables, and wall-mount power supply.
Rev. 1.4
271
C8051F020/1/2/3
Contact Information
Silicon Laboratories Inc.
4635 Boston Lane
Austin, TX 78735
Tel: 1+(512) 416-8500
Fax: 1+(512) 416-9669
Toll Free: 1+(877) 444-3032
Email: productinfo@silabs.com
Internet: www.silabs.com
The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without
notice. Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences
resulting from the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the function-
ing of undescribed features or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon
Laboratories makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose,
nor does Silicon Laboratories assume any liability arising out of the application or use of any product or circuit, and specifically
disclaims any and all liability, including without limitation consequential or incidental damages. Silicon Laboratories products are
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Silicon Laboratories and Silicon Labs are trademarks of Silicon Laboratories Inc.
Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holder.
272
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