Fast-mode Plus Inter-integrated circuit (FMPI2C) interface RM0402
710/1163 RM0402 Rev 6
Bits 31:27 Reserved, must be kept at reset value.
Bit 26 PECBYTE: Packet error checking byte
This bit is set by software, and cleared by hardware when the PEC is transferred, or when a
STOP condition or an Address matched is received, also when PE=0.
0: No PEC transfer.
1: PEC transmission/reception is requested
Note: Writing ‘0’ to this bit has no effect.
This bit has no effect when RELOAD is set.
This bit has no effect is slave mode when SBC=0.
If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 23.3: FMPI2C implementation.
Bit 25 AUTOEND: Automatic end mode (master mode)
This bit is set and cleared by software.
0: software end mode: TC flag is set when NBYTES data are transferred, stretching SCL low.
1: Automatic end mode: a STOP condition is automatically sent when NBYTES data are
transferred.
Note: This bit has no effect in slave mode or when the RELOAD bit is set.
Bit 24 RELOAD: NBYTES reload mode
This bit is set and cleared by software.
0: The transfer is completed after the NBYTES data transfer (STOP or RESTART follows).
1: The transfer is not completed after the NBYTES data transfer (NBYTES is reloaded). TCR
flag is set when NBYTES data are transferred, stretching SCL low.
Bits 23:16 NBYTES[7:0]: Number of bytes
The number of bytes to be transmitted/received is programmed there. This field is don’t care
in slave mode with SBC=0.
Note: Changing these bits when the START bit is set is not allowed.
Bit 15 NACK: NACK generation (slave mode)
The bit is set by software, cleared by hardware when the NACK is sent, or when a STOP
condition or an Address matched is received, or when PE=0.
0: an ACK is sent after current received byte.
1: a NACK is sent after current received byte.
Note: Writing ‘0’ to this bit has no effect.
This bit is used in slave mode only: in master receiver mode, NACK is automatically
generated after last byte preceding STOP or RESTART condition, whatever the NACK
bit value.
When an overrun occurs in slave receiver NOSTRETCH mode, a NACK is
automatically generated whatever the NACK bit value.
When hardware PEC checking is enabled (PECBYTE=1), the PEC acknowledge value
does not depend on the NACK value.
Bit 14 STOP: Stop generation (master mode)
The bit is set by software, cleared by hardware when a STOP condition is detected, or when
PE = 0.
In Master Mode:
0: No Stop generation.
1: Stop generation after current byte transfer.
Note: Writing ‘0’ to this bit has no effect.
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