RM0090: Reference manual - STMicroelectronics

Inter-integrated circuit (I 2 C) interface RM0090
SDA
SCL
SMBA
Noise
filter
Noise
filter
1. SMBA is an optional signal in SMBus mode. This signal is not applicable if SMBus is disabled.
25.3.2 I 2 C slave mode
Data
control
Clock
control
Clock control
Register (CCR)
Control registers
(CR1&CR2)
Status registers
(SR1&SR2)
By default the I 2 C interface operates in Slave mode. To switch from default Slave mode to
Master mode a Start condition generation is needed.
The peripheral input clock must be programmed in the I2C_CR2 register in order to
generate correct timings. The peripheral input clock frequency must be at least:
● 2 MHz in Standard mode
● 4 MHz in Fast mode
As soon as a start condition is detected, the address is received from the SDA line and sent
to the shift register. Then it is compared with the address of the interface (OAR1) and with
OAR2 (if ENDUAL=1) or the General Call address (if ENGC = 1).
Note: In 10-bit addressing mode, the comparison includes the header sequence (11110xx0),
where xx denotes the two most significant bits of the address.
707/1416 Doc ID 018909 Rev 3
Data register
Data shift register
Comparator
Own address register
Dual address register
Interrupts
PEC register
Control
logic
PEC calculation
DMA requests & ACK
MS30035V1