AN1713/0803

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AN1713

APPLICATION NOTE

SMBus SLAVE DRIVER FOR ST7 I2C PERIPHERAL

by Microcontroller Division Applications

INTRODUCTION

The goal of this application note is to implement the SMBus slave protocol using ST7 I2C. The

software of this application performs all SMBus bus protocols mentioned in SMBus v1.1. The

device chosen here is ST72F264 which has multi-master I2C capability.

The program described in this application note is in C language. The driver is compatible with

Metrowerks and Cosmic compilers.

1 CHARACTERISTICS

The main characteristics of this SMBus slave driver are:

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SMBus bus protocols: Quick command, Send/ Receive Byte, Write/ Read Byte, Write/ Read

Word, Write/ Read Block, Process Call Word/ Block

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Slave SMBus addressing

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CRC-8 Packet Error Checking

For more details please refer to the SMBus specification v1.1.

2 SMBus

The System Management Bus (SMBus) is a two-wire interface through which various system

component chips can communicate with each other and with the rest of the system. It is based

on the principles of operation of I2C.

2.1 Similarities of SMBus and I2C

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2 wire bus protocol (1 Clk, 1 Data)

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Master-slave communication, Master provides clock

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Multi master capability

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SMBus data format similar to I2C 7-bit addressing format.

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