Figure 218. Transfer Sequence Diagram For Slave Transmitter - ST STM32F205 series Reference Manual

RM0033
7-bit slave transmitter
S Address
10-bit slave transmitter
S Header
Legend: S= Start, S
EVx= Event (with interrupt if ITEVFEN=1)
EV1: ADDR=1, cleared by reading SR1 followed by reading SR2
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 SR1 register.
1. The EV1 and EV3_1 events stretch SCL low until the end of the corresponding software sequence.
2. The 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 ITEVFEN 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 a read from the
I2C_DR register, stretching SCL low (see

Figure 218. Transfer sequence diagram for slave transmitter

A Data1
EV1 EV3-1 EV3
A Address A
EV1
S Header A
r
= Repeated Start, P= Stop, A= Acknowledge, NA= Non-acknowledge,
r
RM0033 Rev 8
Inter-integrated circuit (I2C) interface
A Data2 A
EV3 EV3
Data1
EV1 EV3_1 EV3
Figure 219 Transfer sequencing).
DataN NA P
.....
EV3-2
A .... DataN NA P
EV3 EV3-2
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