DocID024597 Rev 3 1117/1693
RM0351 Inter-integrated circuit (I2C) interface
1177
35.4.6 Data transfer
The data transfer is managed through transmit and receive data registers and a shift
register.
Reception
The SDA input fills the shift register. After the 8th SCL pulse (when the complete data byte is
received), the shift register is copied into I2C_RXDR register if it is empty (RXNE=0). If
RXNE=1, meaning that the previous received data byte has not yet been read, the SCL line
is stretched low until I2C_RXDR is read. The stretch is inserted between the 8th and 9th
SCL pulse (before the Acknowledge pulse).
Figure 356. Data reception
XX
3HIFTREGISTER
DATA
DATA
XX DATA
28.%
!#+PULSE
DATA DATA
!#+PULSE
XX
)#?28$2
RDDATARDDATA
3#,
LEGEND
3#,
STRETCH
-36
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