ST STM32F405 Reference Manual page 869

RM0090
Bits 15:8 PEC[7:0] Packet error checking register
Bit 7 DUALF: Dual flag (Slave mode)
– Cleared by hardware after a Stop condition or repeated Start condition, or when PE=0.
Bit 6 SMBHOST: SMBus host header (Slave mode)
– Cleared by hardware after a Stop condition or repeated Start condition, or when PE=0.
Bit 5 SMBDEFAULT: SMBus device default address (Slave mode)
– Cleared by hardware after a Stop condition or repeated Start condition, or when PE=0.
Bit 4 GENCALL: General call address (Slave mode)
– Cleared by hardware after a Stop condition or repeated Start condition, or when PE=0.
Bit 3 Reserved, must be kept at reset value
Bit 2 TRA: Transmitter/receiver
Bit 1 BUSY: Bus busy
– Set by hardware on detection of SDA or SCL low
– cleared by hardware on detection of a Stop condition.
Bit 0 MSL: Master/slave
– Set by hardware as soon as the interface is in Master mode (SB=1).
– Cleared by hardware after detecting a Stop condition on the bus or a loss of arbitration
Note: Reading I2C_SR2 after reading I2C_SR1 clears the ADDR flag, even if the ADDR flag was
set after reading I2C_SR1. Consequently, I2C_SR2 must be read only when ADDR is found
set in I2C_SR1 or when the STOPF bit is cleared.
This register contains the internal PEC when ENPEC=1.
0: Received address matched with OAR1
1: Received address matched with OAR2
0: No SMBus Host address
1: SMBus Host address received when SMBTYPE=1 and ENARP=1.
0: No SMBus Device Default address
1: SMBus Device Default address received when ENARP=1
0: No General Call
1: General Call Address received when ENGC=1
0: Data bytes received
1: Data bytes transmitted
This bit is set depending on the R/W bit of the address byte, at the end of total address
phase.
It is also cleared by hardware after detection of Stop condition (STOPF=1), repeated Start
condition, loss of bus arbitration (ARLO=1), or when PE=0.
0: No communication on the bus
1: Communication ongoing on the bus
It indicates a communication in progress on the bus. This information is still updated when
the interface is disabled (PE=0).
0: Slave Mode
1: Master Mode
(ARLO=1), or by hardware when PE=0.
Inter-integrated circuit (I2C) interface
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