ST72325AR7-Auto datasheet(171/243 Pages) STMICROELECTRONICS

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ST72325xxx-Auto

I2C bus interface (I2C)

Doc ID 13770 Rev 3

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16.7.3

I2C status register 2 (SR2)

1M/SL

Master/Slave

This bit is set by hardware as soon as the interface is in Master mode (writing

START = 1). It is cleared by hardware after detecting a Stop condition on the bus or

a loss of arbitration (ARLO = 1). It is also cleared when the interface is disabled

(PE = 0).

0: Slave mode

1: Master mode

0SB

Start bit (Master mode)

This bit is set by hardware as soon as the Start condition is generated (following a

write START = 1). An interrupt is generated if ITE = 1. It is cleared by software

reading SR1 register followed by writing the address byte in DR register. It is also

cleared by hardware when the interface is disabled (PE = 0).

0: No Start condition

1: Start condition generated

Table 85.

SR1 register description (continued)

Bit

Name

Function

SR2

Reset value: 0000 0000 (00h)

543

Reserved

STOPF

ARLO

BERR

GCAL

RORORO

Table 86.

SR2 register description

Bit

Name

Function

7:5

Reserved. Forced to 0 by hardware.

4AF

Acknowledge failure

This bit is set by hardware when no acknowledge is returned. An interrupt is

generated if ITE = 1. It is cleared by software reading SR2 register or by hardware

when the interface is disabled (PE = 0).

The SCL line is not held low while AF = 1 but by other flags (SB or BTF) that are set

at the same time.

0: No acknowledge failure

1: Acknowledge failure

Note: When an AF event occurs, the SCL line is not held low; however, the SDA line

can remain low if the last bits transmitted are all 0. It is then necessary to release

both lines by software.

3STOPF

Stop detection (Slave mode)

This bit is set by hardware when a Stop condition is detected on the bus after an

acknowledge (if ACK = 1). An interrupt is generated if ITE = 1. It is cleared by

software reading SR2 register or by hardware when the interface is disabled

(PE = 0).

The SCL line is not held low while STOPF = 1.

0: No Stop condition detected

1: Stop condition detected

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