RM0312 datasheet(175/275 Pages) STMICROELECTRONICS

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RM0312

Inter-integrated circuit (I2C) interface

200

Slave transmitter

Following the address reception and after clearing ADDR, the slave sends bytes from the

DR register to the SDA line via the internal shift register.

The slave stretches SCL low until ADDR is cleared and DR filled with the data to be sent

(see Transfer sequencing EV1 EV3 in the following figure).

When the acknowledge pulse is received:

•

The TXE bit is set by hardware with an interrupt if the ITEVTEN and the ITBUFEN bits

are set.

If TXE is set and a data was not written in the DR register before the end of the next data

transmission, the BTF bit is set and the interface waits until BTF is cleared, by reading the

SR1 register and then writing to the DR register, stretching SCL low.

Figure 67. Transfer sequence diagram for slave transmitter

1. Legend:

S= Start, Sr = Repeated Start, P= Stop, A= Acknowledge, NA= Non-acknowledge, EVx = Event (with

interrupt if ITEVTEN=1)

EV1: ADDR =1, cleared by reading SR1 register followed by reading SR3.

EV3-1: TXE=1, shift register empty, data register empty, write Data1 in DR.

EV3: TXE=1, shift register not empty, data register empty, cleared by writing DR.

EV3-2: AF=1, AF is cleared by writing ‘0’ in AF bit of SR2 register.

2. EV1 and EV3-1 events stretch SCL low until the end of the corresponding software sequence.

3. EV3 event stretches SCL low if the software sequence is not completed before the end of the next byte

transmission.

Slave receiver

Following the address reception and after clearing ADDR, the slave receives bytes from the

SDA line into the DR register via the internal shift register. After each byte the interface

generates in sequence:

•

An acknowledge pulse if the ACK bit is set

•

The RXNE bit is set by hardware and an interrupt is generated if the ITEVTEN and

ITBUFEN bit is set.

If RXNE is set and the data in the DR register is not read before the end of the next data

reception, the BTF bit is set and the interface waits until BTF is cleared, by reading the SR1

7-bit slave transmitter

10-bit slave transmitter

S Address

Data1

Data2

.....

DataN

EV1 EV3-1 EV3

EV3

EV3-2

S Header

Address

EV1

Sr Header A

Data1

.... DataN

NA P

EV1 EV3_1

EV3

EV3-2

ai18209

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