Inter-integrated circuit (I2C) interface UM0306
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Bit 10
AF: Acknowledge Failure.
0: No acknowledge failure
1: Acknowledge failure
– Set by hardware when no acknowledge is returned.
– Cleared by software writing 0, or by hardware when PE=0.
Bit 9
ARLO: Arbitration Lost (master mode)
0: No Arbitration Lost detected
1: Arbitration Lost detected
Set by hardware when the interface loses the arbitration of the bus to another
master
– Cleared by software writing 0, or by hardware when PE=0.
After an ARLO event the interface switches back automatically to Slave mode
(M/SL=0).
Note:
In SMBUS, the arbitration on the data in slave mode occurs only during the data
phase, or the acknowledge transmission (not on the address acknowledge).
Bit 8
BERR: Bus Error
0: No misplaced Start or Stop condition
1: Misplaced Start or Stop condition
– Set by hardware when the interface detects a misplaced Start or Stop condition
– Cleared by software writing 0, or by hardware when PE=0.
Bit 7
TxE: Data Register Empty (transmitters)
0: Data register not empty
1: Data register empty
– Set when DR is empty in transmission. TxE is not set during address phase.
– Cleared by software writing to the DR register or by hardware after a start or a
stop condition or when PE=0.
TxE is not set if either a NACK is received, or if next byte to be transmitted is PEC (PEC=1)
Bit 6
RxNE: Data Register not Empty (receivers).
0: Data register empty
1: Data register not empty
– Set when data register is not empty in receiver mode. RxNE is not set during
address phase.
– Cleared by software reading or writing the DR register or by hardware when
PE=0.
RxNE is not set in case of ARLO event.
Bit 5 Reserved, forced by hardware to 0.
Bit 4
STOPF: Stop detection (Slave mode)
0: No Stop condition detected
1: Stop condition detected
– Set by hardware when a Stop condition is detected on the bus by the slave
after an acknowledge (if ACK=1).
– Cleared by software reading the SR1 register followed by a write in the CR1
register, or by hardware when PE=0
Note:
The STOPF bit is not set after a NACK reception
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