AN1042/0803

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AN1042

APPLICATION NOTE

ST7 ROUTINE FOR I2C SLAVE MODE MANAGEMENT

by Microcontroller Division Application Team

INTRODUCTION

The goal of this application note is to present a useful example of communication using the

I2C peripheral of the ST7. The ST7 microcontroller is used as a slave and can communicate

with any master. This slave, through the I2C interface, receives data bytes from the master im-

plementing error management and returns them. This application has been realized with a

ST72264,7-bit, general call and 10-bit addressing mode.

1 ST7 I2C INTERFACE

The ST7 I2C peripheral allows multi master and slave communication with bus error manage-

ment. In this application, only the single slave mode is used (with error management).

The I2C synchronous communication needs only two signals: SCL (Serial clock line) and SDA

(Serial data line). The corresponding port pins have to be configured as floating inputs (here

PA4 and PA6).

Please refer to the ST7 datasheet for more details.

1.1 COMMUNICATION SPEED

The ST7 I2C peripheral allows to communicate at different speeds. It is able to work in

standard and fast I2C modes up to 400kHz.

It’s the master which imposes the communication speed. For more details, please refer to the

AN971.

1.2 START, STOP CONDITION AND ACKNOWLEDGE GENERATION

The Start and Stop conditions are sent by the master.

An Acknowledge is sent after an address or a data byte is received when the ACK bit is set in

the Control register (CR).

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