XR16M770IL32-0B-EB_技术文档

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

DECEMBER 2009

REV. 1.0.2

FEATURES

GENERAL DESCRIPTION

• Pin-to-pin compatible with XR16L570 in 24-QFN

1

The XR16M770 (M770) is an enhanced Universal

and 32-QFN packages

Asynchronous Receiver and Transmitter (UART) with

64 bytes of transmit and receive FIFOs,

programmable transmit and receive FIFO trigger

levels, automatic hardware and software flow control,

and data rates of up to 16 Mbps at 3.3V, 12.5 Mbps at

2.5V and 7.5 Mbps at 1.8V with 4X data sampling

rate.

• Intel data bus Interface

• 16 Mbps maximum data rate

• Programmable TX/RX FIFO Trigger Levels

• TX/RX FIFO Level Counters

• Independent TX/RX Baud Rate Generator

• Fractional Baud Rate Generator

• Auto RTS/CTS Hardware Flow Control

• Auto XON/XOFF Software Flow Control

• Auto RS-485 Half-Duplex Direction Control

• Multidrop mode w/ Auto Address Detect

• Sleep Mode with Automatic Wake-up

• PowerSave mode in 24-pin QFN package

• Infrared (IrDA 1.0 and 1.1) mode

• 1.62V to 3.63V supply operation

• Crystal oscillator or external clock input

APPLICATIONS

The Auto RS-485 Half-Duplex Direction control

feature simplifies both the hardware and software for

half-duplex RS-485 applications. In addition, the

Multidrop mode with Auto Address detection

increases the performance by simplifying the

software routines.

The Independent TX/RX Baud Rate Generator

feature allows the transmitter and receiver to operate

at different baud rates. Power consumption of the

M770 can be minimized by enabling the sleep mode

and PowerSave mode.

The M770 has a 16550 compatible register set that

provide users with operating status and control,

receiver error indications, and modem serial interface

controls. An internal loopback capability allows

onboard diagnostics. The M770 is available in 24-pin

QFN, 32-pin QFN and 25-pin BGA packages. All

three packages offer the 16 mode (Intel bus) interface

only.

• Personal Digital Assistants (PDA)

• Cellular Phones/Data Devices

• Battery-Operated Devices

NOTE: 1 Covered by U.S. Patent #5,649,122.

• Global Positioning System (GPS)

• Bluetooth

FIGURE 1. XR16M770 BLOCK DIAGRAM

V C C

(1.62 to 3.63 V )

P w rS ave

A 2:A 0

G N D

D 7:D 0

IO R #

U A R T

T X , R X ,

IO W #

C S #

64 B yte T X FIF O

U A R T

R T S #, C TS #,

D T R #, D S R #,

R I#, C D #

R egs

TX &

R X

IR

E N D E C

IN T

Intel

R E S E T

64 B yte R X F IF O

B R G

D ata B us

Interface

X T A L1

X T A L2

C rystal O sc/B uffer

Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

FIGURE 2. PIN OUT ASSIGNMENT FOR 24-PIN QFN, 32-PIN QFN AND 25-BGA PACKAGES

REV. 1.0.2

24

23

22 21 20 19 18

17

16

18 17 16 15 14 13

VCC

D0

A2

19

12

NC

DSR# 25

CD#

RI#

VCC

D0

26

27

28

29

30

31

15

14

13

NC

IOR#

20

11

IOR #

GND

IOW #

XTAL 2

XTAL 1

NC

D1 21

D2 22

10 GND

24-pin QFN

32-pin QFN

9

8

7

IOW#

12

11

10

9

23

24

D3

D4

CLK

D1

D2

D3

PwrSave

32

1

2

3

4

5

6

7

6

8

2

3

4

5

1

A1 Corner

1 2 3 4

5

A

B

C

D

E

Transparent Top View

CTS#

VCC

D0

RESET

DTR#

D6

INT

RTS#

D7

A1

A0

A2

IOR#

IOW#

XTAL1

GND

DSR#

CS#

RX

D3

D1

TX

D4

D2

D5

ORDERING INFORMATION

OPERATING TEMPERATURE

RANGE

PART NUMBER

PACKAGE

DEVICE STATUS

XR16M770IL24

XR16M770IL32

XR16M770IB25

24-Pin QFN

32-Pin QFN

25-Pin BGA

-40°C to +85°C

Active

2

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

PIN DESCRIPTIONS

Pin Description

24-QFN 32-QFN 25-BGA

NAME

TYPE

DESCRIPTION

PIN#

DATA BUS INTERFACE

A2

A1

A0

12

13

14

17

18

19

A5

A4

B4

I

Address lines [2:0]. These 3 address lines select the internal regis-

ters in UART during a data bus transaction.

D7

D6

D5

D4

D3

D2

D1

D0

3

5

4

C3

C2

E3

E1

D1

E2

D2

C1

I/O

Data bus lines [7:0] (bidirectional).

2

1

3

24

23

22

21

20

1

32

31

30

29

IOR#

11

14

B5

I

This input is read strobe (active low). The falling edge instigates an

internal read cycle and retrieves the data byte from an internal reg-

ister pointed by the address lines [A2:A0], puts the data byte on the

data bus to allow the host processor to read it on the rising edge.

IOW#

9

12

C5

This input is write strobe (active low). The falling edge instigates the

internal write cycle and the rising edge transfers the data byte on

the data bus to an internal register pointed by the address lines.

CS#

INT

6

8

D4

A3

I

This input is chip select (active low) to enable the device.

15

20

O

This output is the active high device interrupt output. The output

state is defined by the user through the software setting of MCR[3].

INT is set to the active mode when MCR[3] is set to a logic 1. INT is

set to the three state mode when MCR[3] is set to a logic 0. See

MCR[3].

MODEM OR SERIAL I/O INTERFACE

TX

5

7

D3

O

UART Transmit Data or infrared encoder data. Standard transmit

and receive interface is enabled when MCR[6] = 0. In this mode,

the TX signal will be a logic 1 during reset or idle (no data). Infrared

IrDA transmit and receive interface is enabled when MCR[6] = 1. In

the Infrared mode, the inactive state (no data) for the Infrared

encoder/decoder interface is a logic 0. If it is not used, leave it

unconnected.

RX

4

16

18

-

6

E4

B3

A1

B2

I

UART Receive Data or infrared receive data. Normal receive data

input must idle at logic 1 condition. The infrared receiver idles at

logic 0. This input should be connected to VCC when not used.

RTS#

CTS#

DTR#

21

24

22

O

I

UART Request-to-Send (active low) or general purpose output.

This output must be asserted prior to using auto RTS flow control,

see EFR[6], MCR[1] and IER[6].

UART Clear-to-Send (active low) or general purpose input. It can

be used for auto CTS flow control, see EFR[7], MSR[4] and IER[7].

This input should be connected to VCC when not used.

O

UART Data-Terminal-Ready (active low) or general purpose output.

3

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

Pin Description

REV. 1.0.2

24-QFN 32-QFN 25-BGA

NAME

TYPE

DESCRIPTION

PIN#

DSR#

-

25

C4

I

UART Data-Set-Ready (active low) or general purpose input. This

input should be connected to VCC when not used.

CD#

RI#

-

26

27

-

I

UART Carrier-Detect (active low) or general purpose input. This

input should be connected to VCC when not used.

UART Ring-Indicator (active low) or general purpose input. This

input should be connected to VCC when not used.

ANCILLARY SIGNALS

XTAL1

XTAL2

8

-

10

11

-

D5

I

O

I

Crystal or external clock input.

Crystal or buffered clock output.

-

PwrSave

7

Power-Save (active high). This feature isolates the M770’s data bus

interface from the host preventing other bus activities that cause

higher power drain during sleep mode. See Sleep Mode with Auto

Wake-up and Power-Save Feature section for details. This pin does

not have a pull-down resistor. This input should be connected to

GND when not used.

RESET

17

23

A2

I

This input is active high. A 40 ns minimum active pulse on this pin

will reset the internal registers and all outputs of the UART. The

UART transmitter output will be held at logic 1, the receiver input

will be ignored and outputs are reset during reset period (see UART

Reset Conditions).

VCC

GND

19

10

28

13

B1

E5

-

Pwr

1.62V to 3.63V power supply.

Power supply common, ground.

Center

Pad

Center

Pad

The center pad on the backside of the QFN package is metallic and

should be connected to GND on the PCB. The thermal pad size on

the PCB should be the approximate size of this center pad and

should be solder mask defined. The solder mask opening should be

at least 0.0025" inwards from the edge of the PCB thermal pad.

NC

-

2, 9, 15,

16

-

No Connects.

Pin type: I=Input, O=Output, I/O= Input/output.

4

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

1.0 PRODUCT DESCRIPTION

The XR16M770 (M770) is a high performance single channel UART. The configuration registers set is 16550

UART compatible for control, status and data transfer. Additionally, the M770 channel has 64 bytes of transmit

and receive FIFOs, Automatic RTS/CTS Hardware Flow Control, Automatic Xon/Xoff and Special Character

Software Flow Control, infrared encoder and decoder (IrDA ver 1.0 and 1.1), programmable fractional baud

rate generator with a prescaler of divide by 1 or 4, and data rate up to 16 Mbps. The XR16M770 can operate

from 1.62 to 3.63 volts. The M770 is fabricated with an advanced CMOS process.

Larger FIFO

The M770 provides a solution that supports 64 bytes of transmit and receive FIFO memory, instead of 16 bytes

in the XR16L580. The M770 is designed to work with high performance data communication systems, that

requires fast data processing time. Increased performance is realized in the M770 by the larger transmit and

receive FIFOs, FIFO trigger level control and automatic flow control mechanism. This allows the external

processor to handle more networking tasks within a given time. For example, the XR16L580 with a 16 byte

FIFO, unloads 16 bytes of receive data in 1.53 ms (This example uses a character length of 11 bits, including

start/stop bits at 115.2Kbps). This means the external CPU will have to service the receive FIFO at 1.53 ms

intervals. However with the 64 byte FIFO in the M770, the data buffer will not require unloading/loading for 6.1

ms. This increases the service interval giving the external CPU additional time for other applications and

reducing the overall UART interrupt servicing time. In addition, the programmable FIFO level trigger interrupt

and automatic hardware/software flow control is uniquely provided for maximum data throughput performance

especially when operating in a multi-channel system. The combination of the above greatly reduces the CPU’s

bandwidth requirement, increases performance, and reduces power consumption.

Data Rate

The M770 is capable of operation up to 16 Mbps at 3.3V with 4X internal sampling clock rate. The device can

operate at 3.3V with a 24 MHz crystal on pins XTAL1 and XTAL2, or external clock source of 64 MHz on XTAL1

pin. With a typical crystal of 14.7456 MHz and through a software option, the user can set the prescaler bit and

sampling rate for data rates of up to 3.68 Mbps.

Enhanced Features

The rich feature set of the M770 is available through the internal registers. Automatic hardware/software flow

control, programmable transmit and receive FIFO trigger levels, selectable baud rates, infrared encoder/

decoder, modem interface controls, and a sleep mode are all standard features. MCR bit-5 provides a facility

for turning off (Xon) software flow control with any incoming (RX) character. The M770 includes new features

such as 9-bit (Multidrop) mode, auto RS-485 half-duplex direction control, different baud rate for TX and RX,

fast IR mode and fractional baud rate generator.

5

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

2.0 FUNCTIONAL DESCRIPTIONS

REV. 1.0.2

2.1

CPU Interface

The CPU interface is 8 data bits wide with 3 address lines and control signals to execute data bus read and

write transactions. The M770 data interface supports the Intel compatible types of CPUs. No clock (oscillator

nor external clock) is required for a data bus transaction. Each bus cycle is asynchronous using CS#, IOR#

and IOW# inputs. A typical data bus interconnection for Intel mode is shown in Figure 3.

FIGURE 3. XR16M770 TYPICAL INTEL DATA BUS INTERCONNECTIONS

VCC

D0

D1

D2

D3

D4

D5

D6

D7

D0

D1

D2

D3

D4

D5

D6

D7

TX

RX

Serial Transceivers of

RS-232

RS-485

RS-422

DTR#

A0

A1

A2

A0

A1

A2

RTS#

CTS#

DSR#

CD#

Or Infrared

IOR#

IOW#

IOR#

IOW#

CS#

UART_CS#

UART_INT

RI#

INT

POWERSAVE

UART_RESET

PwrSave

GND

RESET

Intel Data Bus Interconnections

6

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

2.2

Serial Interface

The M770 is typically used with RS-232, RS-485 and IR transceivers. The following figure shows typical

connections from the UART to the different transceivers. For more information on RS-232 and RS-485/422

transceivers, go to www.exar.com or send an e-mail to uarttechsupport@exar.com.

FIGURE 4. XR16M770 TYPICAL SERIAL INTERFACE CONNECTIONS

V C C

R S -232

T ransceiver

T X

R X

T1 IN

R 1 O U T

D T R #

T 2IN

T 3IN

R T S #

C T S #

D S R #

C D #

U A R T

R 2O U T

R 3O U T

R 4O U T

R I#

R 5O U T

G N D

R S -232 F u ll-M o d em S erial In terface

VCC

RS-485

Transceiver

Full-duplex

TX+

TX-

TX

RX

DI

RO

VCC

NC

RTS#

VCC

RX+

RX-

DTR#

CTS#

DSR#

UART

DE

RE#

CD

#

RI

GND

RS-485 Full-Duplex Serial Interface

7

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

FIGURE 5. XR16M770 TYPICAL SERIAL INTERFACE CONNECTIONS

VCC

RS-485

Y

Z

Transceiver

Half-duplex

TX

RX

DI

RO

DE

RTS#

VCC

A

RE#

NC

DTR#

CTS#

DSR#

UART

B

CD

#

RI#

GND

RS-485 Half-Duplex Serial Interface

VCC

IR

Transceiver

TX

RX

TXD

RXD

NC

DTR#

RTS#

CTS#

DSR#

CD#

UART

VCC

RI#

GND

Infrared Connection

8

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

2.3

Device Reset

The RESET input resets the internal registers and the serial interface outputs to their default state (see

Table 18). An active high pulse of longer than 40 ns duration will be required to activate the reset function in

the device. Following a power-on reset or an external reset, the M770 is software compatible with previous

generation of UARTs, XR16L570 and ST16C550.

2.4

Internal Registers

The M770 has a set of 16550 compatible registers for controlling, monitoring and data loading and unloading.

These registers function as data holding registers (THR/RHR), interrupt status and control registers (ISR/IER),

a FIFO control register (FCR), receive line status and control registers (LSR/LCR), modem status and control

registers (MSR/MCR), programmable data rate (clock) divisor registers (DLL/DLM/DLD), and a user accessible

scratchpad register (SPR).

Beyond the general 16C550 features and capabilities, the M770 offers enhanced feature registers (EFR, Xon1/

Xoff 1, Xon2/Xoff 2, DLD, FCTR, EMSR, FC and TRIG) that provide automatic RTS and CTS hardware flow

control, automatic Xon/Xoff software flow control, 9-bit (Multidrop) mode, auto RS-485 half duplex control,

different baud rate for TX and RX and fractional baud rate generator. All the register functions are discussed in

full detail later in “Section 3.0, UART INTERNAL REGISTERS” on page 23.

2.5

INT Ouput

The interrupt outputs change according to the operating mode and enhanced features setup. Table 1 and 2

summarize the operating behavior for the transmitter and receiver. Also see Figure 19 through 22.

TABLE 1: INT PIN OPERATION FOR TRANSMITTER

FCR BIT-0 = 0 (FIFO DISABLED)

FCR BIT-0 = 1 (FIFO ENABLED)

LOW = FIFO above trigger level

INT Pin

LOW = One byte in THR

HIGH = THR empty

HIGH = FIFO below trigger level or FIFO empty

TABLE 2: INT PIN OPERATION FOR RECEIVER

FCR BIT-0 = 0 (FIFO DISABLED)

FCR BIT-0 = 1 (FIFO ENABLED)

HIGH = One byte in RHR

LOW = RHR empty

LOW = FIFO below trigger level

HIGH = FIFO above trigger level or RX Data Timeout

9

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

2.6

Crystal Oscillator or External Clock Input

The M770 includes an on-chip oscillator to produce a clock for the baud rate generators in the device when a

crystal is connected between XTAL1 and XTAL2 as show below. The CPU data bus does not require this clock

for bus operation. The crystal oscillator provides a system clock to the Baud Rate Generators (BRGs) in the

UART. XTAL1 is the input to the oscillator or external clock buffer input with XTAL2 pin being the output. For

programming details, see “Section 2.7, Programmable Baud Rate Generator with Fractional Divisor” on

page 11.

FIGURE 6. TYPICAL CRYSTAL CONNECTIONS

XTAL1

XTAL2

R1

0-120

(Optional)

R2

500K - 1M

1.8432 MHz

to

Y1

24 MHz

C1

C2

22-47pF

The on-chip oscillator is designed to use an industry standard microprocessor crystal (parallel resonant,

fundamental frequency with 10-22 pF capacitance load, ESR of 20-120 ohms and 100ppm frequency

tolerance) connected externally between the XTAL1 and XTAL2 pins. Typical oscillator connections are shown

in Figure 6. Alternatively, an external clock can be connected to the XTAL1 pin to clock the internal baud rate

generator for standard or custom rates. The BGA package has XTAL1 only, the external clock is required. For

further reading on oscillator circuit, see application note DAN108 on EXAR’s web site.

10

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

2.7

Programmable Baud Rate Generator with Fractional Divisor

The M770 has independent Baud Rate Generators (BRGs) with prescalers for the transmitter and receiver.

The prescalers are controlled by a software bit in the MCR register. The MCR register bit-7 sets the prescaler

to divide the input crystal or external clock by 1 or 4. The output of the prescaler clocks to the BRG. The BRG

16

further divides this clock by a programmable divisor between 1 and (2 - 0.0625) in increments of 0.0625 (1/

16) to obtain a 16X or 8X or 4X sampling clock of the serial data rate. The sampling clock is used by the

transmitter for data bit shifting and receiver for data sampling. For transmitter and receiver, the M770 provides

respective BRG divisors. The BRG divisor (DLL, DLM, and DLD registers) defaults to the value of ’1’ (DLL =

0x01, DLM = 0x00 and DLD = 0x00) upon reset. Therefore, the BRG must be programmed during initialization

to the operating data rate. The DLL and DLM registers provide the integer part of the divisor and the DLD

registers provides the fractional part of the divisor. The four lower bits of the DLD are used to select a value

from 0 (for setting 0000) to 0.9375 or 15/16 (for setting 1111). Programming the Baud Rate Generator

Registers DLL, DLM and DLD provides the capability for selecting the operating data rate. Table 3 shows the

standard data rates available with a 24MHz crystal or external clock at 16X clock rate. If the pre-scaler is used

(MCR bit-7 = 1), the output data rate will be 4 times less than that shown in Table 3. At 8X sampling rate, these

data rates would double. And at 4X sampling rate, they would quadruple. Also, when using 8X sampling mode,

please note that the bit-time will have a jitter (+/- 1/16) whenever the DLD is non-zero and is an odd number.

When using a non-standard data rate crystal or external clock, the divisor value can be calculated with the

following equation(s):

Required Divisor (decimal)=(XTAL1 clock frequency / prescaler) /(serial data rate x 16), with 16X mode, DLD[5:4]=’00’

Required Divisor (decimal)= (XTAL1 clock frequency / prescaler / (serial data rate x 8), with 8X mode, DLD[5:4] = ’01’

Required Divisor (decimal)= (XTAL1 clock frequency / prescaler / (serial data rate x 4), with 4X mode, DLD[5:4] = ’10’

The closest divisor that is obtainable in the M770 can be calculated using the following formula:

ROUND( (Required Divisor - TRUNC(Required Divisor) )*16)/16 + TRUNC(Required Divisor), where

DLM = TRUNC(Required Divisor) >> 8

DLL = TRUNC(Required Divisor) & 0xFF

DLD = ROUND( (Required Divisor-TRUNC(Required Divisor) )*16)

In the formulas above, please note that:

TRUNC (N) = Integer Part of N. For example, TRUNC (5.6) = 5.

ROUND (N) = N rounded towards the closest integer. For example, ROUND (7.3) = 7 and ROUND (9.9) = 10.

A >> B indicates right shifting the value ’A’ by ’B’ number of bits. For example, 0x78A3 >> 8 = 0x0078.

2.7.1

Independent TX/RX BRG

The XR16M770 has two independent sets of TX and RX baud rate generator. See Figure 7. TX and RX can

work in different baud rate by setting DLD, DLL and DLM register. For example, TX can transmit data to the

remote UART at 9600 bps while RX receives data from remote UART at 921.6 Kbps. For the baud rate setting,

please See ”Section 4.13, Baud Rate Generator Registers (DLL, DLM and DLD) - Read/Write” on

page 37.

11

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

FIGURE 7. BAUD RATE GENERATOR

DLD[7]=0

DLL

16X or 8X or 4X

Sampling Rate Clock

to Transmitter

Prescaler

DLM

-

MCR Bit 7=0

Divide by 1

DLD[5:0]

(default)

Crystal

Osc/

Buffer

XTAL1

XTAL2

0

1

16X or 8X or 4X

Sampling Rate Clock

to Receiver

MCR Bit-7=1

DLL

DLM

Prescaler

Divide by 4

DLD[5:0]

DLD[7]=1

DLD[6]

TABLE 3: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING

Required

Output Data

Rate

DIVISOR FOR 16x

Clock

DIVISOR

OBTAINABLE IN

M770

DLM PROGRAM DLL PROGRAM DLD PROGRAM DATA ERROR

VALUE (HEX)

RATE (%)

(Decimal)

400

2400

3750

625

3750

625

E

2

1

0

A6

71

38

9C

96

4E

3C

34

27

1E

1A

14

F

0

8

4

0

2

0

1

0

1

0

C

8

B

8

0

C

4

0

A

8

0

4800

312.5

156.25

150

312 8/16

156 4/16

150

0

9600

0

10000

19200

25000

28800

38400

50000

57600

75000

100000

115200

153600

200000

225000

230400

250000

300000

400000

460800

500000

750000

921600

1000000

0

78.125

60

78 2/16

60

0

52.0833

39.0625

30

52 1/16

39 1/16

30

0.04

0

26.0417

20

26 1/16

20

0.08

0

15

0

13.0208

9.7656

7.5

13

D

0.16

0

9 12/16

7 8/16

6 11/16

6 8/16

6

9

7

6.6667

6.5104

6

0.31

0.16

0

6

5

0

3.75

3 12/16

3 4/16

3

0

3.2552

3

0.16

0

3

2

0

1.6276

1.5

1 10/16

1 8/16

1

0.16

0

1

12

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

2.8

Transmitter

The transmitter section comprises of an 8-bit Transmit Shift Register (TSR) and 64 bytes of FIFO which

includes a byte-wide Transmit Holding Register (THR). TSR shifts out every data bit with the 16X/8X/4X

internal clock. A bit time is 16/8/4 clock periods. The transmitter sends the start-bit followed by the number of

data bits, inserts the proper parity-bit if enabled, and adds the stop-bit(s). The status of the FIFO and TSR are

reported in the Line Status Register (LSR bit-5 and bit-6).

2.8.1

Transmit Holding Register (THR) - Write Only

The transmit holding register is an 8-bit register providing a data interface to the host processor. The host

writes transmit data byte to the THR to be converted into a serial data stream including start-bit, data bits,

parity-bit and stop-bit(s). The least-significant-bit (Bit-0) becomes first data bit to go out. The THR is the input

register to the transmit FIFO of 64 bytes when FIFO operation is enabled by FCR bit-0. Every time a write

operation is made to the THR, the FIFO data pointer is automatically bumped to the next sequential data

location.

2.8.2

Transmitter Operation in non-FIFO Mode

The host loads transmit data to THR one character at a time. The THR empty flag (LSR bit-5) is set when the

data byte is transferred to TSR. THR flag can generate a transmit empty interrupt (ISR bit-1) when it is enabled

by IER bit-1. The TSR flag (LSR bit-6) is set when TSR becomes completely empty.

FIGURE 8. TRANSMITTER OPERATION IN NON-FIFO MODE

Data

Byte

Transmit

Holding

Register

(THR)

THR Interrupt (ISR bit-1)

Enabled by IER bit-1

16X or 8X or 4X

Clock

( DLD[5:4] )

M

S

B

L

S

B

Transmit Shift Register (TSR)

TXNOFIFO1

13

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

2.8.3

Transmitter Operation in FIFO Mode

The host may fill the transmit FIFO with up to 64 bytes of transmit data. The THR empty flag (LSR bit-5) is set

whenever the FIFO is empty. The THR empty flag can generate a transmit empty interrupt (ISR bit-1) when the

FIFO becomes empty. The transmit empty interrupt is enabled by IER bit-1. The TSR flag (LSR bit-6) is set

when TSR/FIFO becomes empty.

FIGURE 9. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE

Transmit

FIFO

Transmit

Data Byte

THR Interrupt (ISR bit-1) falls

below the programmed Trigger

Level and then when becomes

empty. FIFO is Enabled by FCR

bit-0=1

Auto CTS Flow Control (CTS# pin)

Flow Control Characters

(Xoff1/2 and Xon1/2 Reg.)

Auto Software Flow Control

16X or 8X or 4X Clock

(DLD[5:4])

Transmit Data Shift Register

(TSR)

TXFIFO1

2.9

Receiver

The receiver section contains an 8-bit Receive Shift Register (RSR) and 64 bytes of FIFO which includes a

byte-wide Receive Holding Register (RHR). The RSR uses the 16X/8X/4X clock (DLD[5:4]) for timing. It

verifies and validates every bit on the incoming character in the middle of each data bit. On the falling edge of

a start or false start bit, an internal receiver counter starts counting at the 16X/8X/4X clock rate. After 8 clocks

(or 4 if 8X or 2 if 4X) the start bit period should be at the center of the start bit. At this time the start bit is

sampled and if it is still a logic 0 it is validated. Evaluating the start bit in this manner prevents the receiver from

assembling a false character. The rest of the data bits and stop bits are sampled and validated in this same

manner to prevent false framing. If there were any error(s), they are reported in the LSR register bits 2-4. Upon

unloading the receive data byte from RHR, the receive FIFO pointer is bumped and the error tags are

immediately updated to reflect the status of the data byte in RHR register. RHR can generate a receive data

ready interrupt upon receiving a character or delay until it reaches the FIFO trigger level. Furthermore, data

delivery to the host is guaranteed by a receive data ready time-out interrupt when data is not received for 4

word lengths as defined by LCR[1:0] plus 12 bits time. This is equivalent to 3.7-4.6 character times. The RHR

interrupt is enabled by IER bit-0. See Figure 10 and Figure 11 below.

2.9.1

Receive Holding Register (RHR) - Read-Only

The Receive Holding Register is an 8-bit register that holds a receive data byte from the Receive Shift

Register. It provides the receive data interface to the host processor. The RHR register is part of the receive

FIFO of 64 bytes by 11-bits wide, the 3 extra bits are for the 3 error tags to be reported in LSR register. When

the FIFO is enabled by FCR bit-0, the RHR contains the first data character received by the FIFO. After the

RHR is read, the next character byte is loaded into the RHR and the errors associated with the current data

byte are immediately updated in the LSR bits 2-4.

14

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

FIGURE 10. RECEIVER OPERATION IN NON-FIFO MODE

16X or 8X or 4X Clock

( DLD[5:4] )

Receive Data Shift

Data Bit

Register (RSR)

Validation

Receive Data Characters

Error

Tags in

LSR bits

4:2

Receive

Data Byte

and Errors

Receive Data

Holding Register

(RHR)

RHR Interrupt (ISR bit-2)

RXFIFO1

FIGURE 11. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE

16X or 8X or 4X Clock

( DLD[5:4] )

Receive Data Shift

Register (RSR)

Data Bit

Validation

Receive Data Characters

Example

- RX FIFO trigger level selected at 16 bytes

:

(See Note Below)

64 bytes by 11-bit wide

FIFO

Data falls to

8

RTS# re-asserts when data falls below the flow

control trigger level to restart remote transmitter.

Enable by EFR bit-6=1, MCR bit-1.

Receive

Data FIFO

FIFO

Trigger=16

RHR Interrupt (ISR bit-2) programmed for

desired FIFO trigger level.

FIFO is Enabled by FCR bit-0=1

Data fills to

56

RTS# de-asserts when data fills above the flow

control trigger level to suspend remote transmitter.

Enable by EFR bit-6=1, MCR bit-1.

Receive

Data

Receive Data

Byte and Errors

RXFIFO1

15

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

2.10 Auto RTS (Hardware) Flow Control

REV. 1.0.2

Automatic RTS hardware flow control is used to prevent data overrun to the local receiver FIFO. The RTS#

output is used to request remote unit to suspend/resume data transmission. The auto RTS flow control

features is enabled to fit specific application requirement (see Figure 12):

• Enable auto RTS flow control using EFR bit-6.

• The auto RTS function must be started by asserting RTS# output pin (MCR bit-1 to logic 1 after it is enabled).

If using the Auto RTS interrupt:

• Enable RTS interrupt through IER bit-6 (after setting EFR bit-4). The UART issues an interrupt when the

RTS# pin makes a transition from low to high: ISR bit-5 will be set to logic 1.

2.11 Auto RTS Hysteresis

With the Auto RTS function enabled, an interrupt is generated when the receive FIFO reaches the selected RX

trigger level. The RTS# pin will not be forced HIGH (RTS off) until the receive FIFO reaches one trigger level

above the selected trigger level in the trigger table (Table 9). The RTS# pin will return LOW after the RX FIFO

is unloaded to one level below the selected trigger level. Under the above described conditions, the M770 will

continue to accept data until the receive FIFO gets full. The Auto RTS function is initiated when the RTS#

output pin is asserted LOW (RTS On).

TABLE 4: AUTO RTS (HARDWARE) FLOW CONTROL

RTS# DE-ASSERTED (HIGH)

(CHARACTERS IN RX FIFO)

RTS# ASSERTED (LOW)

(CHARACTERS IN RX FIFO)

RX TRIGGER LEVEL

INT PIN ACTIVATION

8

16

56

60

0

8

16

56

60

16

56

60

16

56

2.12 Auto CTS Flow Control

Automatic CTS flow control is used to prevent data overrun to the remote receiver FIFO. The CTS# input is

monitored to suspend/restart the local transmitter. The auto CTS flow control feature is selected to fit specific

application requirement (see Figure 12):

• Enable auto CTS flow control using EFR bit-7.

If needed, the CTS interrupt can be enabled through IER bit-7 (after setting EFR bit-4). The UART issues an

interrupt when the CTS# pin is de-asserted (HIGH): ISR bit-5 will be set to 1, and UART will suspend

16

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

transmission as soon as the stop bit of the character in process is shifted out. Transmission is resumed after

the CTS# input is re-asserted (LOW), indicating more data may be sent.

FIGURE 12. AUTO RTS AND CTS FLOW CONTROL OPERATION

Local UART

UARTA

Remote UART

UARTB

RXA

TXB

Receiver FIFO

Trigger Reached

Transmitter

RTSA#

TXA

CTSB#

RXB

Auto RTS

Auto CTS

Monitor

Trigger Level

Receiver FIFO

Trigger Reached

Transmitter

CTSA#

RTSB#

Auto CTS

Monitor

Auto RTS

Trigger Level

Assert RTS# to Begin

Transmission

1

10

ON

RTSA#

OFF

7

2

ON

3

11

CTSB#

TXB

8

Restart

9

Data Starts

6

Suspend

4

RXA FIFO

Receive

Data

RX FIFO

12

RTS High

Threshold

RTS Low

Threshold

5

RX FIFO

Trigger Level

INTA

(RXA FIFO

Interrupt)

RTSCTS1

The local UART (UARTA) starts data transfer by asserting RTSA# (1). RTSA# is normally connected to CTSB# (2) of

remote UART (UARTB). CTSB# allows its transmitter to send data (3). TXB data arrives and fills UARTA receive FIFO

(4). When RXA data fills up to its receive FIFO trigger level, UARTA activates its RXA data ready interrupt (5) and con-

tinues to receive and put data into its FIFO. If interrupt service latency is long and data is not being unloaded, UARTA

monitors its receive data fill level to match the upper threshold of RTS delay and de-assert RTSA# (6). CTSB# follows

(7) and request UARTB transmitter to suspend data transfer. UARTB stops or finishes sending the data bits in its trans-

mit shift register (8). When receive FIFO data in UARTA is unloaded to match the lower threshold of RTS delay (9),

UARTA re-asserts RTSA# (10), CTSB# recognizes the change (11) and restarts its transmitter and data flow again until

next receive FIFO trigger (12). This same event applies to the reverse direction when UARTA sends data to UARTB

with RTSB# and CTSA# controlling the data flow.

17

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

2.13 Auto Xon/Xoff (Software) Flow Control

REV. 1.0.2

When software flow control is enabled (See Table 17), the M770 compares one or two sequential receive data

characters with the programmed Xon or Xoff-1,2 character value(s). If receive character(s) (RX) match the

programmed values, the M770 will halt transmission (TX) as soon as the current character has completed

transmission. When a match occurs, the Xoff (if enabled via IER bit-5) flag will be set and the interrupt output

pin will be activated. Following a suspension due to a match of the Xoff character, the M770 will monitor the

receive data stream for a match to the Xon-1,2 character. If a match is found, the M770 will resume operation

and clear the flags (ISR bit-4).

Reset initially sets the contents of the Xon/Xoff 8-bit flow control registers to a logic 0. Following reset the user

can write any Xon/Xoff value desired for software flow control. Different conditions can be set to detect Xon/

Xoff characters (See Table 17) and suspend/resume transmissions. When double 8-bit Xon/Xoff characters

are selected, the M770 compares two consecutive receive characters with two software flow control 8-bit

values (Xon1, Xon2, Xoff1, Xoff2) and controls TX transmissions accordingly. Under the above described flow

control mechanisms, flow control characters are not placed (stacked) in the user accessible RX data buffer or

FIFO.

In the event that the receive buffer is overfilling and flow control needs to be executed, the M770 automatically

sends an Xoff message (when enabled) via the serial TX output to the remote modem. The M770 sends the

Xoff-1,2 characters two-character-times (= time taken to send two characters at the programmed baud rate)

after the receive FIFO crosses the programmed trigger level. To clear this condition, the M770 will transmit the

programmed Xon-1,2 characters as soon as receive FIFO is less than one trigger level below the programmed

trigger level. Table 5 below explains this.

TABLE 5: AUTO XON/XOFF (SOFTWARE) FLOW CONTROL

XOFF CHARACTER(S) SENT

(CHARACTERS IN RX FIFO)

XON CHARACTER(S) SENT

(CHARACTERS IN RX FIFO)

RX TRIGGER LEVEL

INT PIN ACTIVATION

8

8*

0

8

16

56

60

16

56

60

16*

56*

60*

16

56

* After the trigger level is reached, an xoff character is sent after a short span of time (= time required to send 2 characters);

for example, after 2.083ms has elapsed for 9600 baud and 10-bit word length setting.

2.14

Special Character Detect

A special character detect feature is provided to detect an 8-bit character when bit-5 is set in the Enhanced

Feature Register (EFR). When this character (Xoff2) is detected, it will be placed in the FIFO along with normal

incoming RX data.

The M770 compares each incoming receive character with Xoff-2 data. If a match exists, the received data will

be transferred to the RX FIFO and ISR bit-4 will be set to indicate detection of special character. Although the

Internal Register Table shows Xon, Xoff Registers with eight bits of character information, the actual number of

bits is dependent on the programmed word length. Line Control Register (LCR) bits 0-1 defines the number of

character bits, i.e., either 5 bits, 6 bits, 7 bits, or 8 bits. The word length selected by LCR bits 0-1 also

determines the number of bits that will be used for the special character comparison. Bit-0 in the Xon, Xoff

Registers corresponds with the LSB bit for the receive character.

2.15 Normal Multidrop Mode

Normal multidrop mode is enabled when MSR[6] = 1 (requires EFR[4] = 1) and EFR[5] = 0 (Special Character

Detect disabled). The receiver is set to Force Parity 0 (LCR[5:3] = ’111’) in order to detect address bytes.

With the receiver initially disabled, it ignores all the data bytes (parity bit = 0) until an address byte is received

(parity bit = 1). This address byte will cause the UART to set the parity error. The UART will generate an LSR

18

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

interrupt and place the address byte in the RX FIFO. The software then examines the byte and enables the

receiver if the address matches its slave address, otherwise, it does not enable the receiver.

If the receiver has been enabled, the receiver will receive the subsequent data. If an address byte is received,

it will generate an LSR interrupt. The software again examines the byte and if the address matches its slave

address, it does not have to do anything. If the address does not match its slave address, then the receiver

should be disabled.

2.15.1 Auto Address Detection

Auto address detection mode is enabled when MSR[6] = 1 (requires EFR[4] = 1) and EFR bit-5 = 1. The

desired slave address will need to be written into the XOFF2 register. The receiver will try to detect an address

byte that matches the porgrammed character in the XOFF2 register. If the received byte is a data byte or an

address byte that does not match the programmed character in the XOFF2 register, the receiver will discard

these data. Upon receiving an address byte that matches the XOFF2 character, the receiver will be

automatically enabled if not already enabled, and the address character is pushed into the RX FIFO along with

the parity bit (in place of the parity error bit). The receiver also generates an LSR interrupt. The receiver will

then receive the subsequent data. If another address byte is received and this address does not match the

programmed XOFF2 character, then the receiver will automatically be disabled and the address byte is

ignored. If the address byte matches XOFF2, the receiver will put this byte in the RX FIFO along with the parity

bit in the parity error bit.

2.16 Infrared Mode

The M770 UART includes the infrared encoder and decoder compatible to the IrDA (Infrared Data Association)

version 1.0 and 1.1. The IrDA 1.0 standard that stipulates the infrared encoder sends out a 3/16 of a bit wide

HIGH-pulse for each “0” bit in the transmit data stream with a data rate up to 115.2 Kbps. For the IrDA 1.1

standard, the infrared encoder sends out a 1/4 of a bit time wide HIGH-pulse for each "0" bit in the transmit

data stream with a data rate up to 1.152 Mbps. This signal encoding reduces the on-time of the infrared LED,

hence reduces the power consumption. See Figure 13 below.

The infrared encoder and decoder are enabled by setting MCR register bit-6 to a ‘1’. With this bit enabled, the

infrared encoder and decoder is compatible to the IrDA 1.0 standard. For the infrared encoder and decoder to

be compatible to the IrDA 1.1 standard, MSR bit-7 will also need to be set to a ’1’ when EFR bit-4 is set to ’1’.

Likewise, the RX input assumes an idle level of logic zero from a reset and power up, see Figure 13.

Typically, the wireless infrared decoder receives the input pulse from the infrared sensing diode on the RX pin.

Each time it senses a light pulse, it returns a logic 1 to the data bit stream.

19

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

FIGURE 13. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING

Character

Data Bits

1

0

TX Data

Transmit

IR Pulse

(TX Pin)

1/2 Bit Time

Bit Time

3/16 or 1/4 Bit Time

IrEncoder-1

Receive

IR Pulse

(RX pin)

Bit Time

1/16 Clock Delay

1

0

RX Data

Data Bits

Character

IRdecoder-1

2.17 Sleep Mode with Auto Wake-Up and Power-Save feature

The M770 supports low voltage system designs, hence, a sleep mode with auto wake-up and power-save

feature is included to reduce its power consumption when the chip is not actively used.

2.17.1 Sleep mode

All of these conditions must be satisfied for the M770 to enter sleep mode:

■ no interrupts pending (ISR bit-0 = 1)

■ sleep mode is enabled (IER bit-4 = 1)

■ modem inputs are not toggling (MSR bits 0-3 = 0)

■ RX input pin is idling HIGH in normal mode or LOW in infrared mode

■ divisor is non-zero

■ TX and RX FIFOs are empty

The M770 stops its crystal oscillator to conserve power in the sleep mode. User can check the XTAL2 pin for

no clock output as an indication that the device has entered the sleep mode.

The M770 resumes normal operation by any of the following:

■ a receive data start bit transition (HIGH to LOW)

■ a data byte is loaded to the transmitter, THR or FIFO

■ a change of logic state on any of the modem or general purpose serial inputs: CTS#, DSR#, CD#, RI#

If the M770 is awakened by any one of the above conditions, it will return to the sleep mode automatically after

all interrupting conditions have been serviced and cleared. If the M770 is awakened by the modem inputs, a

read to the MSR is required to reset the modem inputs. In any case, the sleep mode will not be entered while

20

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

an interrupt is pending from any channel. The M770 will stay in the sleep mode of operation until it is disabled

by setting IER bit-4 to a logic 0.

A word of caution: owing to the starting up delay of the crystal oscillator after waking up from sleep mode, the

first few receive characters may be lost. Also, make sure the RX pin is idling HIGH or “marking” condition

during sleep mode. This may not occur when the external interface transceivers (RS-232, RS-485 or another

type) are also put to sleep mode and cannot maintain the “marking” condition. To avoid this, the system design

engineer can use a 47k ohm pull-up resistor on each of the RX input.

2.17.2 Power-Save Feature

If the address lines, data bus lines, IOW#, IOR#, CS# and modem input lines remain steady when the M770 is

in sleep mode, the maximum current will be in the microamp range as specified in the DC Electrical

Characteristics on page 43. If the input lines are floating or are toggling while the M770 is in sleep mode, the

current can be up to 100 times more. If not using the Power-Save feature, an external buffer would be required

to keep the address and data bus lines from toggling or floating to achieve the low current. But if the Power-

Save feature is enabled (PwrSave pin connected to VCC), this will eliminate the need for an external buffer by

internally isolating the address, data and control signals (see Figure 1 on page 1) from other bus activities that

could cause wasteful power drain. The M770 enters Power-Save mode when this pin is connected to VCC and

the M770 is in sleep mode (see Sleep Mode section above).

Since Power-Save mode isolates the address, data and control signals, the device will wake-up only by:

■ a receive data start bit transition (HIGH to LOW) at the RX input or

■ a change of logic state on the modem or general purpose serial input CTS#, DSR#, CD#, RI#

The M770 will return to the Power-Save mode automatically after a read to the MSR (to reset the modem input

CTS#) and all interrupting conditions have been serviced and cleared. The M770 will stay in the Power-Save

mode of operation until it is disabled by setting IER bit-4 to a logic 0 and/or the Power-Save pin is connected to

GND.

2.17.3 Wake-up Interrupt

The M770 has the wake up interrupt. By setting the FCR bit-3, wake up interrupt is enabled or disabled. The

default status of wake up interrupt is disabled. Please See ”Section 4.5, FIFO Control Register (FCR) -

Write-Only” on page 29.

21

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

2.18

Internal Loopback

The M770 UART provides an internal loopback capability for system diagnostic purposes. The internal

loopback mode is enabled by setting MCR register bit-4 to logic 1. All regular UART functions operate normally.

Figure 14 shows how the modem port signals are re-configured. Transmit data from the transmit shift register

output is internally routed to the receive shift register input allowing the system to receive the same data that it

was sending. The TX pin is held HIGH or mark condition while RTS# and DTR# are de-asserted, and CTS#,

DSR# CD# and RI# inputs are ignored. Caution: the RX input must be held HIGH during loopback test else

upon exiting the loopback test the UART may detect and report a false “break” signal.

FIGURE 14. INTERNAL LOOPBACK

VCC

TX

Transm it Shift Register

(THR/FIFO )

M CR bit-4=1

Receive Shift Register

(RHR/FIFO)

RX

VCC

RTS#

CTS#

VCC

DTR#

DSR#

O P1#

RI#

O P2#

CD#

22

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

3.0 UART INTERNAL REGISTERS

The complete register set for the M770 is shown in Table 6 and Table 7.

TABLE 6: UART INTERNAL REGISTERS

A2 A1 A0

REGISTER

READ/WRITE

COMMENTS

ADDRESSES

16C550 COMPATIBLE REGISTERS

0

0 0

0 1

0 0

0 1

1 0

DREV - Device Revision

Read-only

Read/Write

LCR[7] = 1, LCR ≠ 0xBF,

DLL = 0x00, DLM = 0x00

DVID - Device Identification Register

DLL - Divisor LSB Register

LCR[7] = 1, LCR ≠ 0xBF

See DLD[7:6]

DLM - Divisor MSB Register

DLD - Divisor Fractional Register

LCR[7] = 1, LCR ≠ 0xBF,

EFR[4] = 1

0

0 0

RHR - Receive Holding Register

THR - Transmit Holding Register

Read-only

Write-only

LCR[7] = 0

0

0 1

1 0

IER - Interrupt Enable Register

Read/Write

ISR - Interrupt Status Register

FCR - FIFO Control Register

Read-only

Write-only

LCR[7] = 0 if EFR[4] = 1

or

LCR ≠ 0xBF if EFR[4] = 0

0

1

1 1

0 0

0 1

1 0

LCR - Line Control Register

MCR - Modem Control Register

LSR - Line Status Register

Read/Write

Read-only

Write-only

LCR ≠ 0xBF

MSR - Modem Status Register

LCR ≠ 0xBF

EFR[4] = 1

1

1 1

SPR - Scratch Pad Register

Read/Write

Write-only

Read-only

LCR ≠ 0xBF, FCTR[6] = 0

EMSR - Enhanced Mode Select Register

FC - RX/TX FIFO Level Counter Register

LCR ≠ 0xBF, FCTR[6] = 1

ENHANCED REGISTERS

0

1

0 0

0 1

1 0

0 0

0 1

1 0

1 1

FC - RX/TX FIFO Level Counter Register

TRIG - RX/TX FIFO Trigger Level Register

FCTR - Feature Control Register

EFR - Enhanced Function Reg

Xon-1 - Xon Character 1

Read-only

Write-only

Read/Write

LCR = 0xBF

Xon-2 - Xon Character 2

Xoff-1 - Xoff Character 1

Xoff-2 - Xoff Character 2

23

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

TABLE 7: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1

ADDRESS

REG

READ/

WRITE

BIT-7

BIT-6

BIT-5

BIT-4

BIT-3

BIT-2

BIT-1

BIT-0

COMMENT

A2-A0

NAME

16C550 Compatible Registers

0 0 0

0 0 1

RHR

THR

RD

Bit-7

0/

Bit-6

0/

Bit-5

0/

Bit-4

0/

Bit-3

Bit-2

Bit-1

Bit-0

WR

IER RD/WR

Modem RXLine

Stat. Int.

Enable

TX

Empty

Int

RX

Data

Int.

LCR[7] = 0

Stat.

Int.

CTS#

Int.

Enable Enable

RTS#

Int.

Xoff Int.

Enable

Sleep

Mode

Enable

Enable Enable Enable

0 1 0

ISR

RD

FIFOs FIFOs

0/

INT

INT INT INT

Enabled Enabled

Source Source Source Source

LCR[7] = 0

if EFR[4]=1

RTS

CTS

Interrupt

Xoff

Bit-3

Bit-2

Bit-1

Bit-0

Interrupt

or

LCR≠0xBF

if EFR[4]=0

0 1 0

0 1 1

FCR

WR RXFIFO RXFIFO TXFIFO TXFIFO Wake up

Trigger Trigger Trigger

TX

RX

FIFOs

Trigger Int Enable FIFO

FIFO Enable

Reset Reset

LCR RD/WR Divisor Set TX

Set

Even

Parity

Stop

Word

Enable

Break

Parity

Enable

Bits Length Length

Parity

Bit-1 Bit-0

1 0 0

1 0 1

MCR RD/WR

0/

Internal INT Out- OP1# RTS# DTR#

Lopback

Enable

put

Enable

Output Output

Control Control

BRG

Pres-

caler

IR Mode XonAny

ENable

(OP2#)

LSR

RD

RXFIFO THR &

THR

RX Break RX Fram-

RX

Global

Error

TSR

Empty

ing Error Parity Over-

Data

Ready

Error

run

Error

LCR≠0xBF

1 1 0

MSR

RD

CD#

Input

RI#

Input

DSR#

Input

CTS#

Input

Delta

CD#

Delta

RI#

Delta

DSR# CTS#

Delta

WR

Fast IR Enable Disable Disable

0

9-bit

RX

TX

mode

1 1 1

SPR RD/WR

Bit-7

Xoff

Bit-6

LSR

Bit-5

RTS

Bit-4

RTS

Bit-3

Bit-2

Bit-1

Bit-0 LCR≠0xBF

FCTR[6]=0

EMSR

WR

Invert

Send

TX

FIFO

count

FIFO

count

interrupt interrupt delay bit- delay bit- RTS in

mode

select

mode

select

3

2

RS485

mode

imme- control control

LCR≠0xBF

FCTR[6]=1

diate

bit-1

bit-0

1 1 1

FC

RD

Bit-7

Bit-6

Bit-5

Bit-4

Bit-3

Bit-2

Bit-1

Bit-0

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TABLE 7: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1

ADDRESS

REG

READ/

WRITE

BIT-7

BIT-6

BIT-5

BIT-4

BIT-3

BIT-2

BIT-1

BIT-0

COMMENT

A2-A0

NAME

Baud Rate Generator Divisor

0 0 0

0 0 1

DREV

DVID

RD

Bit-7

0

Bit-6

0

Bit-5

0

Bit-4

0

Bit-3

1

Bit-2

0

Bit-1

0

Bit-0 LCR[7] = 1

LCR≠0xBF

1

DLL= 0x00

DLM= 0x00

0 0 0

0 0 1

DLL RD/WR

DLM RD/WR

Bit-7

Bit-6

Bit-5

Bit-4

Bit-3

Bit-2

Bit-1

Bit-0 LCR[7] = 1

LCR≠0xBF

Bit-0

DLD[7:6]

0 1 0

DLD RD/WR BRG

Enable 4X Mode 8X Mode

Bit-3

Bit-2

Bit-1

Bit-0 LCR[7] = 1

LCR≠0xBF

select Indepen-

dent

BRG

EFR[4] = 1

Enhanced Registers

0 0 0

0 0 1

FC

RD

Bit-7

Bit-6

Bit-5

Bit-4

Bit-3

Bit-2

invert

Bit-1

RTS

Bit-0

TRIG

WR

FCTR RD/WR RX/TX

select

Swap

SCR

trigger

mode

bit-1

trigger

mode

RS485

interrupt RX IR delay

mode

RTS

delay

bit-0

bit-1

bit-0

0 1 0

EFR RD/WR

Auto

CTS#

Enable Enable

Auto

RTS#

Special

Char

Select

Enable

Soft-

ware

Flow

Cntl

Soft-

ware

Flow

Cntl

Soft-

ware

Flow

Cntl

Soft-

ware

Flow

IER [7:4],

ISR [5:4],

FCR[5:3],

MCR[7:5],

DLD

LCR=0XBF

Cntl

Bit-2

Bit-1

Bit-0

Bit-3

1 0 0

1 0 1

1 1 0

1 1 1

XON1 RD/WR

XON2 RD/WR

XOFF1 RD/WR

XOFF2 RD/WR

Bit-7

Bit-6

Bit-5

Bit-4

Bit-3

Bit-2

Bit-1

Bit-0

4.0 INTERNAL REGISTER DESCRIPTIONS

4.1 Receive Holding Register (RHR) - Read- Only

SEE”RECEIVER” ON PAGE 14.

4.2 Transmit Holding Register (THR) - Write-Only

SEE”TRANSMITTER” ON PAGE 13.

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1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

4.3

Interrupt Enable Register (IER) - Read/Write

The Interrupt Enable Register (IER) masks the interrupts from receive data ready, transmit empty, line status

and modem status registers. These interrupts are reported in the Interrupt Status Register (ISR).

4.3.1

IER versus Receive FIFO Interrupt Mode Operation

When the receive FIFO (FCR BIT-0 = 1) and receive interrupts (IER BIT-0 = 1) are enabled, the RHR interrupts

(see ISR bits 2 and 3) status will reflect the following:

A. The receive data available interrupts are issued to the host when the FIFO has reached the programmed

trigger level. It will be cleared when the FIFO drops below the programmed trigger level.

B. FIFO level will be reflected in the ISR register when the FIFO trigger level is reached. Both the ISR register

status bit and the interrupt will be cleared when the FIFO drops below the trigger level.

C. The receive data ready bit (LSR BIT-0) is set as soon as a character is transferred from the shift register to

the receive FIFO. It is reset when the FIFO is empty.

4.3.2

IER versus Receive/Transmit FIFO Polled Mode Operation

When FCR BIT-0 equals a logic 1 for FIFO enable; resetting IER bits 0-3 enables the XR16M770 in the FIFO

polled mode of operation. Since the receiver and transmitter have separate bits in the LSR either or both can

be used in the polled mode by selecting respective transmit or receive control bit(s).

A. LSR BIT-0 indicates there is data in RHR or RX FIFO.

B. LSR BIT-1 indicates an overrun error has occurred and that data in the FIFO may not be valid.

C. LSR BIT 2-4 provides the type of receive data errors encountered for the data byte in RHR, if any.

D. LSR BIT-5 indicates THR is empty.

E. LSR BIT-6 indicates when both the transmit FIFO and TSR are empty.

F. LSR BIT-7 indicates a data error in at least one character in the RX FIFO.

IER[0]: RHR Interrupt Enable

The receive data ready interrupt will be issued when RHR has a data character in the non-FIFO mode or when

the receive FIFO has reached the programmed trigger level in the FIFO mode.

Logic 0 = Disable the receive data ready interrupt (default).

Logic 1 = Enable the receiver data ready interrupt.

IER[1]: THR Interrupt Enable

This bit enables the Transmit Ready interrupt which is issued whenever the THR becomes empty in the non-

FIFO mode or when data in the FIFO falls below the programmed trigger level in the FIFO mode. If the THR is

empty when this bit is enabled, an interrupt will be generated.

Logic 0 = Disable Transmit Ready interrupt (default).

Logic 1 = Enable Transmit Ready interrupt.

IER[2]: Receive Line Status Interrupt Enable

If any of the LSR register bits 1, 2, 3 or 4 is a logic 1, it will generate an interrupt to inform the host controller

about the error status of the current data byte in FIFO. LSR bit-1 generates an interrupt immediately when an

overrun occurs. LSR bits 2-4 generate an interrupt when the character in the RHR has an error. However,

when EMSR bit-6 changes to 1 (default is 0), LSR bit 2-4 generate an interrupt when the character is received

in the RX FIFO. Please refer to “Section 4.12, Enhanced Mode Select Register (EMSR) - Write-only” on

page 36.

• Logic 0 = Disable the receiver line status interrupt (default).

• Logic 1 = Enable the receiver line status interrupt.

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IER[3]: Modem Status Interrupt Enable

• Logic 0 = Disable the modem status register interrupt (default).

• Logic 1 = Enable the modem status register interrupt.

IER[4]: Sleep Mode Enable (requires EFR[4] = 1)

• Logic 0 = Disable Sleep Mode (default).

• Logic 1 = Enable Sleep Mode. See Sleep Mode section for further details.

IER[5]: Xoff Interrupt Enable (requires EFR[4]=1)

• Logic 0 = Disable the software flow control, receive Xoff interrupt. (default)

• Logic 1 = Enable the software flow control, receive Xoff interrupt. See Software Flow Control section for

details.

IER[6]: RTS# Output Interrupt Enable (requires EFR[4]=1)

• Logic 0 = Disable the RTS# interrupt (default).

• Logic 1 = Enable the RTS# interrupt. The UART issues an interrupt when the RTS# pin makes a transition

from LOW to HIGH (if enabled by EFR bit-6).

IER[7]: CTS# Input Interrupt Enable (requires EFR[4]=1)

• Logic 0 = Disable the CTS# interrupt (default).

• Logic 1 = Enable the CTS# interrupt. The UART issues an interrupt when CTS# pin makes a transition from

LOW to HIGH (if enabled by EFR bit-7).

4.4

Interrupt Status Register (ISR) - Read-Only

The UART provides multiple levels of prioritized interrupts to minimize external software interaction. The

Interrupt Status Register (ISR) provides the user with six interrupt status bits. Performing a read cycle on the

ISR will give the user the current highest pending interrupt level to be serviced, others are queued up to be

serviced next. No other interrupts are acknowledged until the pending interrupt is serviced. The Interrupt

Source Table, Table 8, shows the data values (bit 0-5) for the interrupt priority levels and the interrupt sources

associated with each of these interrupt levels.

4.4.1

Interrupt Generation:

• LSR is by any of the LSR bits 1, 2, 3 and 4.

• RXRDY is by RX trigger level.

• RXRDY Time-out is by a 4-char plus 12 bits delay timer.

• TXRDY is by TX trigger level or TX FIFO empty.

• MSR is by any of the MSR bits 0, 1, 2 and 3.

• Receive Xon/Xoff/Special character is by detection of a Xon, Xoff or Special character.

• CTS# is when the remote transmitter toggles the input pin (from LOW to HIGH) during auto CTS flow control.

• RTS# is when its receiver toggles the output pin (from LOW to HIGH) during auto RTS flow control.

• Wakeup interrupt is generated when the M770 wakes up from the sleep mode.

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1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

4.4.2

Interrupt Clearing:

• LSR interrupt is cleared by a read to the LSR register.

• RXRDY interrupt is cleared by reading data until FIFO falls below the trigger level.

• RXRDY Time-out interrupt is cleared by reading RHR.

• TXRDY interrupt is cleared by a read to the ISR register or writing to THR.

• MSR interrupt is cleared by a read to the MSR register.

• Xon or Xoff interrupt is cleared by a read to the ISR register. See EMSR[7].

• Special character interrupt is cleared by a read to ISR register or after next character is received. See

EMSR[7].

• RTS# and CTS# flow control interrupts are cleared by a read to the MSR register.

• Wakeup interrupt is cleared by a read to ISR register.

]

TABLE 8: INTERRUPT SOURCE AND PRIORITY LEVEL

PRIORITY

ISR REGISTER STATUS BITS

SOURCE OF INTERRUPT

LEVEL

BIT-5

BIT-4

BIT-3

BIT-2

BIT-1

BIT-0

1

2

3

4

5

6

7

-

0

1

0

1

0

1

0

1

0

1

0

1

0

1

LSR (Receiver Line Status Register)

RXRDY (Receive Data Time-out)

RXRDY (Received Data Ready)

TXRDY (Transmit Ready)

MSR (Modem Status Register)

RXRDY (Received Xon, Xoff or Special character)

CTS#, RTS# change of state

None (default) or Wakeup interrupt

ISR[0]: Interrupt Status

• Logic 0 = An interrupt is pending and the ISR contents may be used as a pointer to the appropriate interrupt

service routine.

• Logic 1 = No interrupt pending (default condition).

ISR[3:1]: Interrupt Status

These bits indicate the source for a pending interrupt at interrupt priority levels (See Interrupt Source Table 8).

ISR[4]: Interrupt Status (requires EFR bit-4 = 1)

This bit is enabled when EFR bit-4 is set to a logic 1. ISR bit-4 indicates that the receiver detected a data match

of the Xoff, Xon or special character(s).

ISR[5]: Interrupt Status (requires EFR bit-4 = 1)

ISR bit-5 indicates that CTS# or RTS# has changed state from LOW to HIGH.

ISR[7:6]: FIFO Enable Status

These bits are set to a logic 0 when the FIFOs are disabled. They are set to a logic 1 when the FIFOs are

enabled.

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4.5

FIFO Control Register (FCR) - Write-Only

This register is used to enable the FIFOs, clear the FIFOs, set the transmit/receive FIFO trigger levels, and

enable the wake up interrupt. They are defined as follows:

FCR[0]: TX and RX FIFO Enable

• Logic 0 = Disable the transmit and receive FIFO (default).

• Logic 1 = Enable the transmit and receive FIFOs. This bit must be set to logic 1 when other FCR bits are

written or they will not be programmed.

FCR[1]: RX FIFO Reset

This bit is only active when FCR bit-0 is a ‘1’.

• Logic 0 = No receive FIFO reset (default)

• Logic 1 = Reset the receive FIFO pointers and FIFO level counter logic (the receive shift register is not

cleared or altered). This bit will return to a logic 0 after resetting the FIFO.

FCR[2]: TX FIFO Reset

This bit is only active when FCR bit-0 is a ‘1’.

• Logic 0 = No transmit FIFO reset (default).

• Logic 1 = Reset the transmit FIFO pointers and FIFO level counter logic (the transmit shift register is not

cleared or altered). This bit will return to a logic 0 after resetting the FIFO.

FCR[3]: Enable wake up interrupt (requires EFR bit-4 = 1)

• Logic 0 = Disable the wake up interrupt (default).

• Logic 1 = Enable the wake up interrupt.

Please refer to “Section 2.17.3, Wake-up Interrupt” on page 21.

FCR[5:4]: Transmit FIFO Trigger Select (requires EFR bit-4 = 1)

These 2 bits set the trigger level for the transmit FIFO. The UART will issue a transmit interrupt when the

number of characters in the FIFO falls below the selected trigger level, or when it gets empty in case that the

FIFO did not get filled over the trigger level on last re-load. Table 9 below shows the selections. Note that the

receiver and the transmitter cannot use different trigger tables. Whichever selection is made last applies to

both the RX and TX side.

FCR[7:6]: Receive FIFO Trigger Select

These 2 bits are used to set the trigger level for the receive FIFO. The UART will issue a receive interrupt when

the number of the characters in the FIFO crosses the trigger level. Table 9 shows the complete selections.

Note that the receiver and the transmitter cannot use different trigger tables. Whichever selection is made last

applies to both the RX and TX side.

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REV. 1.0.2

TABLE 9: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION

TRANSMIT

TRIGGER FCTR FCTR

FCR

BIT-7

FCR

BIT-6

FCR

BIT-5

FCR

BIT-4

RECEIVE

TRIGGER LEVEL

TRIGGER

LEVEL

COMPATIBILITY

TABLE

BIT-5

BIT-4

Table-A

0

1 (default)

16C550, 16C2550,

16C2552, 16C554,

16C580

0

1

0

1

0

1

1 (default)

4

8

14

Table-B

Table-C

Table-D

0

1

0

1

0

1

0

1

0

1

16

8

16C650A

24

30

0

1

0

1

0

1

8

16

24

28

0

1

0

1

0

1

8

16C654

16

32

56

0

1

0

1

0

1

8

16

56

60

X

Programmable Programmable 16L2752, 16C2850,

16C2852, 16C850,

16C854, 16C864

via TRG

register.

FCTR[7] = 0.

FCTR[7] = 1.

4.6

Line Control Register (LCR) - Read/Write

The Line Control Register is used to specify the asynchronous data communication format. The word or

character length, the number of stop bits, and the parity are selected by writing the appropriate bits in this

register.

LCR[1:0]: TX and RX Word Length Select

These two bits specify the word length to be transmitted or received.

BIT-1

BIT-0

WORD LENGTH

0

1

0

1

0

1

5 (default)

6

7

8

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LCR[2]: TX and RX Stop-bit Length Select

The length of stop bit is specified by this bit in conjunction with the programmed word length.

STOP BIT LENGTH

(BIT TIME(S))

WORD

LENGTH

BIT-2

0

1

5,6,7,8

5

1 (default)

1-1/2

2

6,7,8

LCR[3]: TX and RX Parity Select

Parity or no parity can be selected via this bit. The parity bit is a simple way used in communications for data

integrity check. See Table 10 for parity selection summary below.

• Logic 0 = No parity.

• Logic 1 = A parity bit is generated during the transmission while the receiver checks for parity error of the

data character received.

LCR[4]: TX and RX Parity Select

If the parity bit is enabled with LCR bit-3 set to a logic 1, LCR BIT-4 selects the even or odd parity format.

• Logic 0 = ODD Parity is generated by forcing an odd number of logic 1’s in the transmitted character. The

receiver must be programmed to check the same format (default).

• Logic 1 = EVEN Parity is generated by forcing an even number of logic 1’s in the transmitted character. The

receiver must be programmed to check the same format.

LCR[5]: TX and RX Parity Select

If the parity bit is enabled, LCR BIT-5 selects the forced parity format.

• LCR BIT-5 = logic 0, parity is not forced (default).

• LCR BIT-5 = logic 1 and LCR BIT-4 = logic 0, parity bit is forced to a logical 1 for the transmit and receive

data.

• LCR BIT-5 = logic 1 and LCR BIT-4 = logic 1, parity bit is forced to a logical 0 for the transmit and receive

data.

TABLE 10: PARITY SELECTION

LCR BIT-5 LCR BIT-4 LCR BIT-3

PARITY SELECTION

No parity

X

0

1

X

0

1

0

1

0

1

Odd parity

Even parity

Force parity to mark, HIGH

Forced parity to space, LOW

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LCR[6]: Transmit Break Enable

REV. 1.0.2

When enabled, the Break control bit causes a break condition to be transmitted (the TX output is forced to a

“space’, logic 0, state). This condition remains, until disabled by setting LCR bit-6 to a logic 0.

• Logic 0 = No TX break condition. (default)

• Logic 1 = Forces the transmitter output (TX) to a “space”, logic 0, for alerting the remote receiver of a line

break condition.

LCR[7]: Baud Rate Divisors Enable

Baud rate generator divisor (DLL/DLM/DLD) enable.

• Logic 0 = Data registers are selected. (default)

• Logic 1 = Divisor latch registers are selected.

4.7

Modem Control Register (MCR) or General Purpose Outputs Control - Read/Write

The MCR register is used for controlling the serial/modem interface signals or general purpose inputs/outputs.

MCR[0]: DTR# Output

The DTR# pin is a modem control output. If the modem interface is not used, this output may be used as a

general purpose output.

• Logic 0 = Force DTR# output HIGH (default).

• Logic 1 = Force DTR# output LOW.

MCR[1]: RTS# Output

The RTS# pin is a modem control output and may be used for automatic hardware flow control by enabled by

EFR bit-6. If the modem interface is not used, this output may be used as a general purpose output.

• Logic 0 = Force RTS# output HIGH (default).

• Logic 1 = Force RTS# output LOW. It is required to start Auto RTS Flow Control.

MCR[2]: Reserved

OP1# is not available as an output pin on the M770. But it is available for use during Internal Loopback Mode.

In the Loopback Mode, this bit is used to write the state of the modem RI# interface signal.

MCR[3]: INT Output Enable

Enable or disable INT outputs to become active or in three-state. This bit is also used to control the OP2#

signal during internal loopback mode.

• Logic 0 = INT output disabled (three state) in the 16 mode (default). During internal loopback mode, OP2# is

HIGH.

• Logic 1 = INT output enabled (active) in the 16 mode. During internal loopback mode, OP2# is LOW.

TABLE 11: INT OUTPUT MODES

MCR

INT OUTPUT IN 16 MODE

BIT-3

0

1

Three-State

Active

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MCR[4]: Internal Loopback Enable

• Logic 0 = Disable loopback mode (default).

• Logic 1 = Enable local loopback mode, see loopback section and Figure 14.

MCR[5]: Xon-Any Enable (requires EFR bit-4 = 1)

• Logic 0 = Disable Xon-Any function (for 16C550 compatibility, default).

• Logic 1 = Enable Xon-Any function. In this mode, any RX character received will resume transmit operation.

The RX character will be loaded into the RX FIFO , unless the RX character is an Xon or Xoff character and

the M770 is programmed to use the Xon/Xoff flow control.

MCR[6]: Infrared Encoder/Decoder Enable (requires EFR bit-4 = 1)

• Logic 0 = Enable the standard modem receive and transmit input/output interface. (Default)

• Logic 1 = Enable infrared IrDA receive and transmit inputs/outputs. The TX/RX output/input are routed to the

infrared encoder/decoder. The data input and output levels conform to the IrDA infrared interface

requirement. The RX FIFO may need to be flushed upon enable. While in this mode, the infrared TX output

will be LOW during idle data conditions.

MCR[7]: Clock Prescaler Select (requires EFR bit-4 = 1)

• Logic 0 = Divide by one. The input clock from the crystal or external clock is fed directly to the Programmable

Baud Rate Generator without further modification, i.e., divide by one (default).

• Logic 1 = Divide by four. The prescaler divides the input clock from the crystal or external clock by four and

feeds it to the Programmable Baud Rate Generator, hence, data rates become one forth.

4.8

Line Status Register (LSR) - Read Only

This register provides the status of data transfers between the UART and the host. If IER bit-2 is enabled, LSR

bit 1 will generate an interrupt immediately and LSR bits 2-4 will generate an interrupt when a character with an

error is in the RHR.

LSR[0]: Receive Data Ready Indicator

• Logic 0 = No data in receive holding register or FIFO (default).

• Logic 1 = Data has been received and is saved in the receive holding register or FIFO.

LSR[1]: Receiver Overrun Flag

• Logic 0 = No overrun error (default).

• Logic 1 = Overrun error. A data overrun error condition occurred in the receive shift register. This happens

when additional data arrives while the FIFO is full. In this case the previous data in the receive shift register

is overwritten. Note that under this condition the data byte in the receive shift register is not transferred into

the FIFO, therefore the data in the FIFO is not corrupted by the error.

LSR[2]: Receive Data Parity Error Tag

• Logic 0 = No parity error (default).

• Logic 1 = Parity error. The receive character in RHR does not have correct parity information and is suspect.

This error is associated with the character available for reading in RHR.

LSR[3]: Receive Data Framing Error Tag

• Logic 0 = No framing error (default).

• Logic 1 = Framing error. The receive character did not have a valid stop bit(s). This error is associated with

the character available for reading in RHR.

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LSR[4]: Receive Break Tag

REV. 1.0.2

• Logic 0 = No break condition (default).

• Logic 1 = The receiver received a break signal (RX was LOW for at least one character frame time). In the

FIFO mode, only one break character is loaded into the FIFO. The break indication remains until the RX

input returns to the idle condition, “mark” or HIGH.

LSR[5]: Transmit Holding Register Empty Flag

This bit is the Transmit Holding Register Empty indicator. The THR bit is set to a logic 1 when the last data byte

is transferred from the transmit holding register to the transmit shift register. The bit is reset to logic 0

concurrently with the data loading to the transmit holding register by the host. In the FIFO mode this bit is set

when the transmit FIFO is empty, it is cleared when the transmit FIFO contains at least 1 byte.

LSR[6]: THR and TSR Empty Flag

This bit is set to a logic 1 whenever the transmitter goes idle. It is set to logic 0 whenever either the THR or

TSR contains a data character. In the FIFO mode this bit is set to a logic 1 whenever the transmit FIFO and

transmit shift register are both empty.

LSR[7]: Receive FIFO Data Error Flag

• Logic 0 = No FIFO error (default).

• Logic 1 = A global indicator for the sum of all error bits in the RX FIFO. At least one parity error, framing error

or break indication is in the FIFO data. This bit clears when there is no more error(s) in any of the bytes in the

RX FIFO.

4.9

Modem Status Register (MSR) - Read Only

This register provides the current state of the modem interface input signals. Lower four bits of this register are

used to indicate the changed information. These bits are set to a logic 1 whenever a signal from the modem

changes state. These bits may be used for general purpose inputs when they are not used with modem

signals. Reading the higher four bits shows the status of the modem signals.

MSR[0]: Delta CTS# Input Flag

• Logic 0 = No change on CTS# input (default).

• Logic 1 = The CTS# input has changed state since the last time it was monitored. A modem status interrupt

will be generated if MSR interrupt is enabled (IER bit-3).

MSR[1]: Delta DSR# Input Flag

• Logic 0 = No change on DSR# input (default).

• Logic 1 = The DSR# input has changed state since the last time it was monitored. A modem status interrupt

will be generated if MSR interrupt is enabled (IER bit-3).

MSR[2]: Delta RI# Input Flag

• Logic 0 = No change on RI# input (default).

• Logic 1 = The RI# input has changed from LOW to HIGH, ending of the ringing signal. A modem status

interrupt will be generated if MSR interrupt is enabled (IER bit-3).

MSR[3]: Delta CD# Input Flag

• Logic 0 = No change on CD# input (default).

• Logic 1 = Indicates that the CD# input has changed state since the last time it was monitored. A modem

status interrupt will be generated if MSR interrupt is enabled (IER bit-3).

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MSR[4]: CTS Input Status

CTS# pin may function as automatic hardware flow control signal input if it is enabled and selected by Auto

CTS (EFR bit-7). Auto CTS Flow Control allows starting and stopping of local data transmissions based on the

modem CTS# signal. A HIGH on the CTS# pin will stop UART transmitter as soon as the current character has

finished transmission, and a LOW will resume data transmission. Normally MSR bit-4 bit is the complement of

the CTS# input. However in the loopback mode, this bit is equivalent to the RTS# bit in the MCR register. The

CTS# input may be used as a general purpose input when the modem interface is not used.

MSR[5]: DSR Input Status

Normally this bit is the complement of the DSR# input. In the loopback mode, this bit is equivalent to the DTR#

bit in the MCR register. The DSR# input may be used as a general purpose input when the modem interface is

not used.

MSR[6]: RI Input Status

Normally this bit is the complement of the RI# input. In the loopback mode this bit is equivalent to bit-2 in the

MCR register. The RI# input may be used as a general purpose input when the modem interface is not used.

MSR[7]: CD Input Status

Normally this bit is the complement of the CD# input. In the loopback mode this bit is equivalent to bit-3 in the

MCR register. The CD# input may be used as a general purpose input when the modem interface is not used.

4.10 Modem Status Register (MSR) - Write Only

This register provides the advanced features of XR16M770. Lower four bits of this register are reserved.

Writing to the higher four bits enables additional functions.

MSR[3:0]: Reserved

MSR[4]: Enable/Disable Transmitter (Requires EFR[4] = 1)

• Logic 0 = Enable Transmitter (default).

• Logic 1 = Disable Transmitter.

MSR[5]: Enable/Disable Receiver (Requires EFR[4] = 1)

• Logic 0 = Enable Receiver (default).

• Logic 1 = Disable Receiver.

MSR[6]: Enable/Disable 9-bit mode (Requires EFR[4] = 1)

For the 9-bit mode information, See ”Section 2.15, Normal Multidrop Mode” on page 18.

• Logic 0 = Normal 8-bit mode (default).

• Logic 1 = Enable 9-bit or Multidrop mode.

MSR[7]: Enable/Disable fast IR mode (Requires EFR[4] = 1)

The M770 supports the new fast IR transmission with data rate up to 1.152 Mbps.

• Logic 0 = IrDA version 1.0, 3/16 pulse ratio, data rate up to 115.2 Kbps (default).

• Logic 1 = IrDA version 1.1, 1/4 pulse ratio, data rate up to 1.152 Mbps. For more IR mode information, please

See ”Section 2.16, Infrared Mode” on page 19.

4.11 Scratch Pad Register (SPR) - Read/Write

This is a 8-bit general purpose register for the user to store temporary data. The content of this register is

preserved during sleep mode but becomes 0xFF (default) after a reset or a power off-on cycle.

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XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

4.12 Enhanced Mode Select Register (EMSR) - Write-only

This register replaces SPR (during a Write) and is accessible only when FCTR[6] = 1.

EMSR[1:0]: Receive/Transmit FIFO Level Count

REV. 1.0.2

When Scratchpad Swap (FCTR[6]) is asserted, EMSR bits 1-0 controls what mode the FIFO Level Counter is

operating in.

TABLE 12: SCRATCHPAD SWAP SELECTION

FCTR[6] EMSR[1] EMSR[0]

Scratchpad is

0

1

X

0

1

X

0

1

Scratchpad

RX FIFO Level Counter Mode

TX FIFO Level Counter Mode

Alternate RX/TX FIFO Counter Mode

During Alternate RX/TX FIFO Level Counter Mode, the first value read after EMSR bits 1-0 have been

asserted will always be the RX FIFO Level Counter. The second value read will correspond with the TX FIFO

Level Counter. The next value will be the RX FIFO Level Counter again, then the TX FIFO Level Counter and

so on and so forth.

EMSR[2]: Send TX Immediately

• Logic 0 = Do not send TX immediately (default).

• Logic 1 = Send TX immediately. When FIFO is enabled and this bit is set, the next data will be to the TX shift

register. Thus, the data will be sent out immediately instead of queuing in the FIFO. Every time, only 1 byte

will be send out. Once this byte has been sent out, the EMSR[2] will go back to 0 automatically. If more than

1 byte will be sent out, EMSR[2] needs to be set to 1 for each byte.

EMSR[3]: Invert RTS in RS485 mode

• Logic 0 = RTS# output is a logic 0 during TX and a logic 1 during RX (default).

• Logic 1 = RTS# output is a logic 1 during TX and a logic 0 during RX.

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XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

EMSR[5:4]: Extended RTS Hysteresis

TABLE 13: AUTO RTS HYSTERESIS

RTS#

HYSTERESIS

(CHARACTERS)

EMSR

BIT-5

EMSR

BIT-4

FCTR

BIT-1

FCTR

BIT-0

0

1

0

1

0

1

0

±4

±6

±8

0

1

0

1

0

1

0

1

±8

±16

±24

±32

1

0

1

0

1

0

1

±40

±44

±48

±52

1

0

1

0

1

0

1

±12

±20

±28

±36

EMSR[6]: LSR Interrupt Mode

• Logic 0 = LSR Interrupt Delayed (default). LSR bits 2, 3, and 4 will generate an interrupt when the character

with the error is in the RHR.

• Logic 1 = LSR Interrupt Immediate. LSR bits 2, 3, and 4 will generate an interrupt as soon as the character is

received into the FIFO.

EMSR[7]: Xoff/Special character Interrupt Mode Select

This bit selects how the Xoff and Special character interrupt is cleared. The XON interrupt can only be cleared

by reading the ISR register.

• Logic 0 = Xoff interrupt is cleared by either reading ISR register or when an XON character is received.

Special character interrupt is cleared by either reading ISR register or when next character is received.

(default).

• Logic 1 = Xoff/Special character interrupt can only be cleared by reading the ISR register.

4.13 Baud Rate Generator Registers (DLL, DLM and DLD) - Read/Write

These registers make-up the value of the baud rate divisor. The M770 has different DLL, DLM and DLD for

transmitter and receiver. It provides more convenience for the transmitter and receiver to transmit data with

different rate. The M770 uses DLD[7:6] to select TX or RX. Then it provides DLD[5:0] to select the sampling

frequency and fractional baud rate divisor. The concatenation of the contents of DLM and DLL gives the 16-bit

divisor value. The value is added to DLD[3:0]/16 to achieve the fractional baud rate divisor. DLD must be

enabled via EFR bit-4 before it can be accessed. See Table 14 below and See ”Section 2.7, Programmable

Baud Rate Generator with Fractional Divisor” on page 11.

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XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

DLD[5:4]: Sampling Rate Select

REV. 1.0.2

These bits select the data sampling rate. By default, the data sampling rate is 16X. The maximum data rate will

double if the 8X mode is selected and will quadruple if the 4X mode is selected. See Table 14 below.

TABLE 14: SAMPLING RATE SELECT

DLD[5]

DLD[4]

SAMPLING RATE

0

1

0

1

X

16X

8X

4X

DLD[6]: Independent BRG enable

• Logic 0 = The Transmitter and Receiver uses the same Baud Rate Generator. (default).

• Logic 1 = The Transmitter and Receiver uses different Baud Rate Generators. Use DLD[7] for selecting

which baud rate generator to configure.

DLD[7]: BRG select

When DLD[6] = 1, this bit selects whether the values written to DLL, DLM and DLD[5:0] will be for the Transmit

Baud Rate Generator or the Receive Baud Rate Generator. When DLD[6] = 0 (same Baud Rate Generator

used for both TX and RX), this bit must be a logic 0 to properly write to the appropriate DLL, DLM and

DLD[5:0]. .

TABLE 15: BRG SELECT

DLD[7]

DLD[6]

BRG

0

Transmitter and Receiver uses same BRG.

Writing to DLL, DLM and DLD[5:0] configures the BRG for both the TX and RX.

0

1

0

Transmitter and Receiver uses different BRGs.

Writing to DLL, DLM and DLD[5:0] configures the BRG for TX.

Transmitter and Receiver uses different BRGs.

Writing to DLL, DLM and DLD[5:0] configures the BRG for RX.

Transmitter and Receiver uses same BRG.

Writing to DLL, DLM and DLD[5:0] has no effect on BRG used by the TX and RX.

4.14 Trigger Level Register (TRG) - Write-Only

User Programmable Transmit/Receive Trigger Level Register.

TRG[7:0]: Trigger Level Register

These bits are used to program desired trigger levels when trigger Table-D is selected. FCTR bit-7 selects

between programming the RX Trigger Level (a logic 0) and the TX Trigger Level (a logic 1).

4.15 RX/TX FIFO Level Count Register (FC) - Read-Only

This register replaces SPR (during a read) and is accessible when FCTR[6] = 1. This register is also

accessible when LCR = 0xBF. It is suggested to read the FIFO Level Count Register at the Scratchpad

Register location when FCTR bit-6 = 1. See Table 12.

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XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

FC[7:0]: RX/TX FIFO Level Count

Receive/Transmit FIFO Level Count. Number of characters in Receiver FIFO (FCTR[7] = 0) or Transmitter

FIFO (FCTR[7] = 1) can be read via this register. Reading this register is not recommended when transmitting

or receiving data.

4.16 Feature Control Register (FCTR) - Read/Write

FCTR[1:0]: RTS Hysteresis

User selectable RTS# hysteresis levels for hardware flow control application. After reset, these bits are set to

“0” to select the next trigger level for hardware flow control. See Table 13 for more details.

FCTR[2]: IrDa RX Inversion

• Logic 0 = Select RX input as encoded IrDa data (Idle state will be LOW).

• Logic 1 = Select RX input as inverted encoded IrDa data (Idle state will be HIGH).

FCTR[3]: Auto RS-485 Direction Control

• Logic 0 = Standard ST16C550 mode. Transmitter generates an interrupt when transmit holding register

becomes empty and transmit shift register is shifting data out.

• Logic 1 = Enable Auto RS485 Direction Control function. The direction control signal, RTS# pin, changes its

output logic state from LOW to HIGH one bit time after the last stop bit of the last character is shifted out.

Also, the Transmit interrupt generation is delayed until the transmitter shift register becomes empty. The

RTS# output pin will automatically return to a LOW when a data byte is loaded into the TX FIFO. However,

RTS# behavior can be inverted by setting EMSR[3] = 1.

FCTR[5:4]: Transmit/Receive Trigger Table Select

See Table 16 for more details.

TABLE 16: TRIGGER TABLE SELECT

FCTR

BIT-5

FCTR

BIT-4

TABLE

0

1

0

1

0

1

Table-A (TX/RX)

Table-B (TX/RX)

Table-C (TX/RX)

Table-D (TX/RX)

FCTR[6]: Scratchpad Swap

• Logic 0 = Scratch Pad register is selected as general read and write register. ST16C550 compatible mode.

• Logic 1 = FIFO Count register (Read-Only), Enhanced Mode Select Register (Write-Only). Number of

characters in transmit or receive FIFO can be read via scratch pad register when this bit is set. Enhanced

Mode Select Register is selected when it is written into.

FCTR[7]: Programmable Trigger Register Select

• Logic 0 = Registers TRG and FC selected for RX.

• Logic 1 = Registers TRG and FC selected for TX.

4.17 Enhanced Feature Register (EFR) - Read/Write

Enhanced features are enabled or disabled using this register. Bit 0-3 provide single or dual consecutive

character software flow control selection (see Table 17). When the Xon1 and Xon2 and Xoff1 and Xoff2 modes

are selected, the double 8-bit words are concatenated into two sequential characters. Caution: note that

whenever changing the TX or RX flow control bits, always reset all bits back to logic 0 (disable) before

programming a new setting.

39

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

EFR[3:0]: Software Flow Control Select

REV. 1.0.2

Single character and dual sequential characters software flow control is supported. Combinations of software

flow control can be selected by programming these bits.

TABLE 17: SOFTWARE FLOW CONTROL FUNCTIONS

EFR BIT-3

CONT-3

EFR BIT-2

CONT-2

EFR BIT-1

CONT-1

EFR BIT-0

CONT-0

TRANSMIT AND RECEIVE SOFTWARE FLOW CONTROL

0

1

0

1

X

1

0

1

X

0

X

0

1

0

1

0

X

0

No TX and RX flow control (default and reset)

No transmit flow control

Transmit Xon1, Xoff1

Transmit Xon2, Xoff2

Transmit Xon1 and Xon2, Xoff1 and Xoff2

No receive flow control

0

Receiver compares Xon1, Xoff1

Receiver compares Xon2, Xoff2

1

Transmit Xon1, Xoff1

Receiver compares Xon1 or Xon2, Xoff1 or Xoff2

0

1

0

1

0

1

Transmit Xon2, Xoff2

Receiver compares Xon1 or Xon2, Xoff1 or Xoff2

Transmit Xon1 and Xon2, Xoff1 and Xoff2,

Receiver compares Xon1 and Xon2, Xoff1 and Xoff2

No transmit flow control,

Receiver compares Xon1 and Xon2, Xoff1 and Xoff2

EFR[4]: Enhanced Function Bits Enable

Enhanced function control bit. This bit enables IER bits 4-7, ISR bits 4-5, FCR bits 3-5, MCR bits 5-7, and DLD

to be modified. After modifying any enhanced bits, EFR bit-4 can be set to a logic 0 to latch the new values.

This feature prevents legacy software from altering or overwriting the enhanced functions once set. Normally, it

is recommended to leave it enabled, logic 1.

• Logic 0 = modification disable/latch enhanced features. IER bits 4-7, ISR bits 4-5, FCR bits 3-5, MCR bits 5-

7, and DLD are saved to retain the user settings. After a reset, the IER bits 4-7, ISR bits 4-5, FCR bits 3-5,

and MCR bits 5-7, and DLD are set to a logic 0 to be compatible with ST16C550 mode (default).

• Logic 1 = Enables the EFR[3:0] register bits to be modified by the user.

EFR[5]: Special Character Detect Enable

• Logic 0 = Special Character Detect Disabled (default).

• Logic 1 = Special Character Detect Enabled. The UART compares each incoming receive character with

data in Xoff-2 register. If a match exists, the receive data will be transferred to FIFO and ISR bit-4 will be set

to indicate detection of the special character. Bit-0 corresponds with the LSB bit of the receive character. If

flow control is set for comparing Xon1, Xoff1 (EFR [1:0]= ‘10’) then flow control and special character work

normally. However, if flow control is set for comparing Xon2, Xoff2 (EFR[1:0]= ‘01’) then flow control works

normally, but Xoff2 will not go to the FIFO, and will generate an Xoff interrupt and a special character

interrupt, if enabled via IER bit-5.

40

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

EFR[6]: Auto RTS Flow Control Enable

RTS# output may be used for hardware flow control by setting EFR bit-6 to logic 1. When Auto RTS is

selected, an interrupt will be generated when the receive FIFO is filled to the programmed trigger level and

RTS de-asserts HIGH at the next upper trigger level/hysteresis level. RTS# will return LOW when FIFO data

falls below the next lower trigger level/hysteresis level. The RTS# output must be asserted (LOW) before the

auto RTS can take effect. RTS# pin will function as a general purpose output when hardware flow control is

disabled.

• Logic 0 = Automatic RTS flow control is disabled (default).

• Logic 1 = Enable Automatic RTS flow control.

EFR[7]: Auto CTS Flow Control Enable

Automatic CTS Flow Control.

• Logic 0 = Automatic CTS flow control is disabled (default).

• Logic 1 = Enable Automatic CTS flow control. Data transmission stops when CTS# input de-asserts to logic

1. Data transmission resumes when CTS# returns to a logic 0.

4.18 Software Flow Control Registers (XOFF1, XOFF2, XON1, XON2) - Read/Write

These registers are used as the programmable software flow control characters xoff1, xoff2, xon1, and xon2.

For more details, see Table 5. The xoff2 is also used as auto address detect register when the auto 9-bit mode

enabled. See ”Section 2.15.1, Auto Address Detection” on page 19.

41

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

TABLE 18: UART RESET CONDITIONS

REGISTERS

RESET STATE

DLM, DLL

DLM = 0x00 and DLL = 0x01. Only resets to these val-

ues during a power up. They do not reset when the

Reset Pin is asserted.

(Both TX and RX)

DLD

RHR

THR

IER

Bits 7-0 = 0x00

Bits 7-0 = 0xXX

Bits 7-0 = 0x00

Bits 7-0 = 0x01

Bits 7-0 = 0x00

Bits 7-0 = 0x60

FCR

ISR

LCR

MCR

LSR

MSR

Bits 7-0 =0xX0 (Read-only)

Bits 7-4 = 0000 (Write-only)

SPR

EMSR

FC

Bits 7-0 = 0xFF

Bits 7-0 = 0x00

RESET STATE

HIGH

TRG

FCTR

EFR

XON1

XON2

XOFF1

XOFF2

I/O SIGNALS

TX

RTS#

DTR#

INT

HIGH

Three-State Condition

42

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

ABSOLUTE MAXIMUM RATINGS

Power Supply Range

Voltage at Any Pin

3.6 Volts

GND-0.3 V to 3.6 V

-40^oto +85^oC

Operating Temperature

-65^oto +150^oC

500 mW

Storage Temperature

Package Dissipation

TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: ± 15%)

theta-ja = 33^oC/W, theta-jc = 22^oC/W

Thermal Resistance (32-QFN)

theta-ja = 38^oC/W, theta-jc = 26^oC/W

Thermal Resistance (24-QFN)

theta-ja = 166^oC/W, theta-jc = 98.2^oC/W

Thermal Resistance (25-BGA)

ELECTRICAL CHARACTERISTICS

DC ELECTRICAL CHARACTERISTICS

UNLESS OTHERWISE NOTED: TA = -40^OTO +85^OC, VCC IS 1.62 TO 3.63V

LIMITS

1.8V

LIMITS

2.5V

LIMITS

3.3V

SYMBOL

PARAMETER

UNITS

CONDITIONS

MIN

MAX

MIN

MAX

MIN

MAX

V_ILCKClock Input Low Level

V_IHCKClock Input High Level

-0.3

1.4

0.3

-0.3

2.0

0.4

-0.3

2.4

0.6

V

VCC

0.2

VCC

0.5

VCC

0.7

V_IL

V_IH

V_OL

Input Low Voltage

Input High Voltage

Output Low Voltage

-0.3

1.4

-0.3

1.8

-0.3

2.0

VCC

0.4

V

I_OL= 6 mA

0.4

I_OL= 4 mA

0.4

I_OL= 1.5 mA

V_OH

Output High Voltage

2.0

V

I_OH= -4 mA

I_OH= -2 mA

I_OH= -200 uA

1.8

1.4

I_IL

I_IH

Input Low Leakage Current

Input High Leakage Current

Input Pin Capacitance

±15

5

±15

5

±15

5

uA

pF

C_IN

I_CC

Power Supply Current

1.5

3

2

2.5

15

mA Ext Clk = 5MHz

uA See Test 1

I_SLEEP/Sleep / Power Save Current

I_PWRSV

6

Test 1: The following inputs remain steady at VCC or GND state to minimize Sleep current: A0-A2, D0-D7, IOR#, IOW#,

CS#. Also, RX input must idle at HIGH while asleep. For Power-Save, the UART internally isolates all of these inputs (ex-

cept the modem inputs and Reset pins) therefore eliminating any unnecessary external buffers to keep the inputs steady.

43

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

SEE”POWER-SAVE FEATURE” ON PAGE 21. To achieve minimum power drain, the voltage at any of the inputs of the

M770 should NOT be lower than its VCC supply.

AC ELECTRICAL CHARACTERISTICS

TA = -40^OTO +85^OC, VCC IS 1.62 TO 3.6V, 70 PF LOAD WHERE APPLICABLE

LIMITS

SYMBOL

PARAMETER

1.8V ± 10%

2.5V ± 10%

3.3V ± 10%

UNIT

MIN

MAX

MIN

MAX

MIN

MAX

XTAL1

ECLK

T_ECLK

UART Crystal Frequency

External Clock Frequency

External Clock Time Period

24

30

24

50

24

64

MHz

ns

15

0

9

0

7

0

T_AS

T_AH

Address Setup Time

Address Hold Time

Chip Select Width

IOR# Strobe Width

Read Cycle Delay

Data Access Time

Data Disable Time

IOW# Strobe Width

Write Cycle Delay

Data Setup Time

ns

0

T_CS

90

60

35

T_RD

T_DY

T_RDV

T_DD

T_WR

T_DY

85

25

55

10

30

5

90

30

3

60

15

3

35

10

3

T_DS

T_DH

T_WDO

T_MOD

Data Hold Time

Delay From IOW# To Output

50

Delay To Set Interrupt From MODEM

Input

T_RSI

T_SSI

T_RRI

T_SI

Delay To Reset Interrupt From IOR#

Delay From Stop To Set Interrupt

Delay From IOR# To Reset Interrupt

Delay From Start To Interrupt

50

1

50

1

50

1

ns

Bclk

ns

45

24

45

24

45

24

ns

T_INT

Delay From Initial INT Reset To

Transmit Start

8

Bclk

T_WRI

T_SSR

T_RR

Delay From IOW# To Reset Interrupt

Delay From Stop To Set RXRDY#

Delay From IOR# To Reset RXRDY#

Delay From IOW# To Set TXRDY#

45

1

45

1

45

1

ns

Bclk

ns

45

T_WT

ns

44

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

AC ELECTRICAL CHARACTERISTICS

TA = -40^OTO +85^OC, VCC IS 1.62 TO 3.6V, 70 PF LOAD WHERE APPLICABLE

LIMITS

SYMBOL

PARAMETER

1.8V ± 10%

2.5V ± 10%

3.3V ± 10%

UNIT

MIN

MAX

MIN

MAX

MIN

MAX

T_SRT

Delay From Center of Start To Reset

TXRDY#

8

Bclk

T_RST

Bclk

Reset Pulse Width

Baud Clock

40

16X or 8X or 4X of data rate

40

ns

Hz

FIGURE 15. CLOCK TIMING

CLK

EXTERNAL

CLOCK

OSC

FIGURE 16. MODEM INPUT/OUTPUT TIMING

IO W #

IO W

A c tiv e

T _W

D O

R T S #

D T R #

C h a n g e o f s ta te

C D #

C T S #

D S R #

C h a n g e o f s ta te

T _{M O D}

IN T

A c tiv e

T _{R S I}

IO R #

A c tiv e

T _{M O D}

C h a n g e o f s ta te

R I#

45

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

FIGURE 17. DATA BUS READ TIMING

A0-A2

CS#

Valid Address

T_CS

Valid Address

T_CS

T_AS

T_AH

T_DY

T_RD

IOR#

D0-D7

T_DD

T_RDV

Valid Data

RDTm

FIGURE 18. DATA BUS WRITE TIMING

A0-A2

CS#

Valid Address

T_CS

T_AS

T_AH

T_CS

T_DY

T_WR

IOW#

D0-D7

T_DH

T_DS

Valid Data

16Write

46

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

FIGURE 19. RECEIVE READY & INTERRUPT TIMING [NON-FIFO MODE]

RX

Stop

Bit

Start

Bit

D0:D7

T_SSR

1 Byte

in RHR

INT

T_SSR

Active

Data

Active

Data

Active

Data

RXRDY#

Ready

T_RR

IOR#

(Reading data

out of RHR)

RXNFM

FIGURE 20. TRANSMIT READY & INTERRUPT TIMING [NON-FIFO MODE]

TX

(Unloading)

Stop

Bit

Start

Bit

D0:D7

IER[1]

enabled

ISR is read

INT*

T_WRI

T_SRT

TXRDY#

T_WT

IOW#

(Loading data

into THR)

*INT is cleared when the ISR is read or when data is loaded into the THR.

TXNonFIFO

47

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

FIGURE 21. RECEIVE READY & INTERRUPT TIMING [FIFO MODE]

Start

Bit

RX

S

T

D0:D7

T

D0:D7

T_SSI

D0:D7

S

T

S

D0:D7

T

D0:D7

T

Stop

Bit

RX FIFO drops

below RX

Trigger Level

INT

T_SSR

FIFO

Empties

RX FIFO fills up to RX

Trigger Level or RX Data

Timeout

RXRDY#

First Byte is

Received in

RX FIFO

T_RRI

T_RR

IOR#

(Reading data out

of RX FIFO)

RXINTDMA#

FIGURE 22. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE]

Stop

Bit

Start

Bit

Last Data Byte

Transmitted

TX FIFO

Empty

TX

(Unloading)

T

S

T

D0:D7

T

S

D0:D7

T

S D0:D7

T

D0:D7

T

D0:D7

T

ISR is read

T_SI

IER[1]

enabled

ISR is read

T_SRT

INT*

TX FIFO

Empty

TX FIFO fills up

to trigger level

TX FIFO drops

below trigger level

T_WRI

Data in

TX FIFO

TXRDY#

T_WT

IOW#

(Loading data

into FIFO)

*INT is cleared when the ISR is read or when TX FIFO fills up to the trigger level.

TXDMA#

48

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

PACKAGE DIMENSIONS (24 PIN QFN - 4 X 4 X 0.9 mm)

Note: the actual center pad

is metallic and the size (D2)

is device-dependent with a

typical tolerance of 0.3mm

Note: The control dimension is in millimeter.

INCHES

MILLIMETERS

SYMBOL

MIN

MAX

0.039

0.002

0.010

0.161

0.110

0.012

MIN

0.80

0.00

0.15

3.90

2.50

0.18

MAX

1.00

0.05

0.25

4.10

2.80

0.30

A

A1

A3

D

0.031

0.000

0.006

0.154

0.098

0.007

D2

b

e

0.0197 BSC

0.50 BSC

L

0.014

0.008

0.018

-

0.35

0.20

0.45

-

k

49

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

PACKAGE DIMENSIONS (32 PIN QFN - 5 X 5 X 0.9 mm)

Note: the actual center pad

is metallic and the size (D2)

is device-dependent with a

typical tolerance of 0.3mm

Note: The control dimension is in millimeter.

INCHES

MILLIMETERS

SYMBOL

MIN

MAX

0.039

0.002

0.010

0.201

0.150

0.012

MIN

0.80

0.00

0.15

4.90

3.50

0.18

MAX

1.00

0.05

0.25

5.10

3.80

0.30

A

A1

A3

D

0.031

0.000

0.006

0.193

0.138

0.007

D2

b

e

0.0197 BSC

0.50 BSC

L

0.012

0.008

0.020

-

0.35

0.20

0.45

-

k

50

XR16M770

REV. 1.0.2

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

PACKAGE DIMENSIONS (25 PIN BGA - 3 X 3 X 0.8 mm)

5

4

3

2

1

A1 corner

A

B

C

D

E

D

D1

D

(A1 corner feature is mfger option)

Seating

Plane

b

A2

A

A1

e

Note: The control dimension is the millimeter column

INCHES

MILLIMETERS

SYMBOL

MIN

MAX

0.031

0.007

0.024

0.122

MIN

MAX

0.80

0.19

0.61

3.10

A

A1

A2

D

0.028

0.005

0.022

0.114

0.70

0.13

0.57

2.90

D1

b

0.079 BSC

0.012

0.020 BSC

2.00 BSC

0.50 BSC

0.008

0.20

0.30

e

51

XR16M770

1.62V TO 3.63V HIGH PERFORMANCE UART WITH 64-BYTE FIFO

REV. 1.0.2

REVISION HISTORY

DATE

REVISION

Rev 1.0.0

Rev 1.0.1

Rev 1.0.2

DESCRIPTION

September 2008

February 2009

December 2009

Final Datasheet.

Added 32-QFN pin package on page 2 to replace the grey block.

Corrected "INT pin type".

NOTICE

EXAR Corporation reserves the right to make changes to the products contained in this publication in order to

improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any

circuits described herein, conveys no license under any patent or other right, and makes no representation that

the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration

purposes and may vary depending upon a user’s specific application. While the information in this publication

has been carefully checked; no responsibility, however, is assumed for inaccuracies.

EXAR Corporation does not recommend the use of any of its products in life support applications where the

failure or malfunction of the product can reasonably be expected to cause failure of the life support system or

to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless

EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has

been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately

protected under the circumstances.

Datasheet December 2009.

Send your UART technical inquiry with technical details to hotline: uarttechsupport@exar.com.

Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.

52


型号：	XR16M770IL32-0B-EB
厂家：	EXAR CORPORATION
描述：	EVAL BOARD FOR XR16M770-B 32QFN
文件：	总52页 (文件大小：1091K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

XR16M770IL32-0B-EB [EXAR]

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