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RM0401 Rev 3 565/771

RM0401 Fast-mode Plus Inter-integrated circuit (FMPI2C) interface

591

Figure 202. Transfer bus diagrams for SMBus slave transmitter (SBC=1)

SMBus Slave receiver

When the FMPI2C is used in SMBus mode, SBC must be programmed to ‘1’ in order to

allow the PEC checking at the end of the programmed number of data bytes. In order to

allow the ACK control of each byte, the reload mode must be selected (RELOAD=1). Refer

to Slave Byte Control mode on page 538 for more details.

In order to check the PEC byte, the RELOAD bit must be cleared and the PECBYTE bit

must be set. In this case, after NBYTES-1 data have been received, the next received byte

is compared with the internal FMPI2C_PECR register content. A NACK is automatically

generated if the comparison does not match, and an ACK is automatically generated if the

comparison matches, whatever the ACK bit value. Once the PEC byte is received, it is

copied into the FMPI2C_RXDR register like any other data, and the RXNE flag is set.

In the case of a PEC mismatch, the PECERR flag is set and an interrupt is generated if the

ERRIE bit is set in the FMPI2C_CR1 register.

If no ACK software control is needed, the user can program PECBYTE=1 and, in the same

write operation, program NBYTES with the number of bytes to be received in a continuous

flow. After NBYTES-1 are received, the next received byte is checked as being the PEC.

Caution: The PECBYTE bit has no effect when the RELOAD bit is set.

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ST STM32F410 User Manual

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