Figure 238. I2C Bus Protocol - STMicroelectronics STM32F405 Reference Manual

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RM0090 Inter-integrated circuit (I C) interface
Data and addresses are transferred as 8-bit bytes, MSB first. The first byte(s) following the
start condition contain the address (one in 7-bit mode, two in 10-bit mode). The address is
always transmitted in Master mode.
A 9th clock pulse follows the 8 clock cycles of a byte transfer, during which the receiver must
send an acknowledge bit to the transmitter. Refer to Figure 238.
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Figure 238. I C bus protocol
SDA
ACK
MSB
SCL
1 2 8 9
Stop
Start
condition
condition
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Acknowledge may be enabled or disabled by software. The I C interface addresses (dual
addressing 7-bit/ 10-bit and/or general call address) can be selected by software.
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The block diagram of the I C interface is shown in Figure 239.
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