RM0390 Rev 4 705/1328
RM0390 Fast-mode Plus Inter-integrated circuit (FMPI2C) interface
758
Slave Byte Control mode
In order to allow byte ACK control in slave reception mode, Slave Byte Control mode must
be enabled by setting the SBC bit in the FMPI2C_CR1 register. This is required to be
compliant with SMBus standards.
Reload mode must be selected in order to allow byte ACK control in slave reception mode
(RELOAD=1). To get control of each byte, NBYTES must be initialized to 0x1 in the ADDR
interrupt subroutine, and reloaded to 0x1 after each received byte. When the byte is
received, the TCR bit is set, stretching the SCL signal low between the 8th and 9th SCL
pulses. The user can read the data from the FMPI2C_RXDR register, and then decide to
acknowledge it or not by configuring the ACK bit in the FMPI2C_CR2 register. The SCL
stretch is released by programming NBYTES to a non-zero value: the acknowledge or not-
acknowledge is sent and next byte can be received.
NBYTES can be loaded with a value greater than 0x1, and in this case, the reception flow is
continuous during NBYTES data reception.
Note: The SBC bit must be configured when the FMPI2C is disabled, or when the slave is not
addressed, or when ADDR=1.
The RELOAD bit value can be changed when ADDR=1, or when TCR=1.
Caution: Slave Byte Control mode is not compatible with NOSTRETCH mode. Setting SBC when
NOSTRETCH=1 is not allowed.
Figure 247. Slave initialization flowchart
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