ST STM32F102 Series Reference Manual page 604

Inter-integrated circuit (I
Bit 3 ADD10: 10-bit header sent (Master mode)
0: No ADD10 event occurred.
1: Master has sent first address byte (header).
– Set by hardware when the master has sent the first byte in 10-bit address mode.
– Cleared by software reading the SR1 register followed by a write in the DR register of the second
address byte, or by hardware when PE=0.
Note:
ADD10 bit is not set after a NACK reception
Bit 2 BTF: Byte Transfer Finished.
0: Data Byte transfer not done
1: Data Byte transfer succeeded
– Set by hardware when NOSTRETCH=0 and:
– In reception when a new byte is received (including ACK pulse) and DR has not been read yet
(RxNE=1).
– In transmission when a new byte should be sent and DR has not been written yet (TxE=1).
– Cleared by software reading SR1 followed by either a read or write in the DR register or by
hardware after a start or a stop condition in transmission or when PE=0.
Note:
The BTF bit is not set after a NACK reception
The BTF bit is not set if next byte to be transmitted is the PEC (TRA=1 in I2C_SR2 register and
PEC=1 in I2C_CR1 register)
Bit 1 ADDR: Address sent (master mode)/matched (slave mode)
This bit is cleared by software reading SR1 register followed reading SR2, or by hardware when
PE=0.
Address Matched (Slave)
0: Address mismatched or not received.
1: Received address matched.
– Set by hardware as soon as the received slave address matched with the OAR registers content
or a general call or a SMBus Device Default Address or SMBus Host or SMBus Alert is
recognized. (when enabled depending on configuration).
Address Sent (Master)
0: No end of address transmission
1: End of address transmission
– For 10-bit addressing, the bit is set after the ACK of the 2nd byte.
– For 7-bit addressing, the bit is set after the ACK of the byte.
Note:
ADDR is not set after a NACK reception
Bit 0 SB: Start Bit (Master mode).
0: No Start condition
1: Start condition generated.
– Set when a Start condition generated.
– Cleared by software by reading the SR1 register followed by writing the DR register, or by
hardware when PE=0
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C) interface RM0008