ST STM32F301 6 Series Reference Manual page 691

RM0366
When the SMBus controller wants to send a RESTART condition after the PEC, the
software mode must be selected (AUTOEND = 0). In this case, once NBYTES[7:0] - 1 are
transmitted, the I2C_PECR register content is transmitted. The TC flag is set after the PEC
transmission, stretching the SCL line low. The RESTART condition must be programmed in
the TC interrupt subroutine.
Caution: The PECBYTE bit has no effect when the RELOAD bit is set.
Example SMBus controller transmitter 2 bytes + PEC, automatic end mode (STOP)
NBYTES
NBYTES
Figure 274. Bus transfer diagrams for SMBus controller transmitter
TXIS TXIS
S Address A
EV1
INIT
TXE
xx
INIT: program target address, program NBYTES = 3, AUTOEND=1, set PECBYTE, set START
EV1: TXIS ISR: wr data1
EV2: TXIS ISR: wr data2
Example SMBus controller transmitter 2 bytes + PEC, software end mode (RESTART)
TXIS TXIS
S Address A data1
EV1
INIT EV2
xx 3
INIT: program target address, program NBYTES = 3, AUTOEND=0, set PECBYTE, set START
EV1: TXIS ISR: wr data1
EV2: TXIS ISR: wr data2
EV3: TC ISR: program target address, program NBYTES = N, set START
Inter-integrated circuit interface (I2C)
data1 A data2 A
EV2
3
A data2 A PEC A
RM0366 Rev 5
legend:
PEC A P
legend:
TC
Rstart Address
EV3
N
transmission
reception
SCL stretch
transmission
reception
SCL stretch
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