at89c51ac3-s3sim ATMEL Corporation, at89c51ac3-s3sim Datasheet - Page 61

Manufacturer Part Number

at89c51ac3-s3sim

Description

At89c51ac3 Enhanced 8-bit Microcontroller With 64kb Flash Memory

Manufacturer

ATMEL Corporation

Datasheet

1.AT89C51AC3-S3SIM.pdf (140 pages)

Automatic Address

Recognition

4383D–8051–02/08

Figure 33. UART Timing in Mode 1

Figure 34. UART Timing in Modes 2 and 3

The automatic address recognition feature is enabled when the multiprocessor commu-

nication feature is enabled (SM2 bit in SCON register is set).

Implemented in the hardware, automatic address recognition enhances the multiproces-

sor communication feature by allowing the serial port to examine the address of each

incoming command frame. Only when the serial port recognizes its own address will the

receiver set the RI bit in the SCON register to generate an interrupt. This ensures that

the CPU is not interrupted by command frames addressed to other devices.

If necessary, you can enable the automatic address recognition feature in mode 1. In

this configuration, the stop bit takes the place of the ninth data bit. Bit RI is set only when

the received command frame address matches the device’s address and is terminated

by a valid stop bit.

To support automatic address recognition, a device is identified by a given address and

a broadcast address.

Note:

SMOD0=0

SMOD0=1

SMOD0=X

SMOD0=1

The multiprocessor communication and automatic address recognition features cannot

be enabled in mode 0 (i.e. setting SM2 bit in SCON register in mode 0 has no effect).

RXD

Start

bit

Data byte

Ninth

Stop

bit

Stop

bit