ST7263BEx datasheet(110/186 Pages) STMICROELECTRONICS

110 / 186 page

On-chip peripherals

ST7263Bxx

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Doc ID 7516 Rev 8

Mode selection

The interface can operate in the four following modes:

●

Slave transmitter/receiver

●

Master transmitter/receiver

By default, it operates in slave mode.

The interface automatically switches from slave to master after it generates a START

condition and from master to slave in case of arbitration loss or a STOP generation, allowing

then Multi-Master capability.

Communication flow

In Master mode, it initiates a data transfer and generates the clock signal. A serial data

transfer always begins with a start condition and ends with a stop condition. Both start and

stop conditions are generated in master mode by software.

In Slave mode, the interface is capable of recognizing its own address (7-bit), and the

General Call address. The General Call address detection may be enabled or disabled by

software.

Data and addresses are transferred as 8-bit bytes, MSB first. The first byte following the

start condition is the address byte; it is always transmitted in Master mode.

A 9th clock pulse follows the 8 clock cycles of a byte transfer, during which the receiver must

send an acknowledge bit to the transmitter. Refer to Figure 46.

Figure 46.

I²C bus protocol

Acknowledge may be enabled and disabled by software.

The I²C interface address and/or general call address can be selected by software.

The speed of the I²C interface may be selected between Standard (up to 100 kHz) and Fast

I²C (up to 400 kHz).

SDA/SCL line control

Transmitter mode: the interface holds the clock line low before transmission to wait for the

microcontroller to write the byte in the Data register.

Receiver mode: the interface holds the clock line low after reception to wait for the

microcontroller to read the byte in the Data register.

The SCL frequency (FSCL) is controlled by a programmable clock divider which depends on

the I²C bus mode.

When the I²C cell is enabled, the SDA and SCL ports must be configured as floating inputs.

In this case, the value of the external pull-up resistor used depends on the application.

SCL

SDA

MSB

ACK

STOP

START

CONDITION

VR02119B

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