BL702/704/706 Reference Manual
11.5.8 Enable signal
After the above configurations are completed, write the enable signal register MEN to 1 to automatically start the I2C
transmission process.
When the read-write flag is set to 0, I2C sends data, and the host sends the process:
1. Start bit
2. (1 bit left from device address + 0) + ACK
3. Slave device address + ACK
4. 1 byte data + ACK
5. 1 byte data + ACK
6. Stop bit
When the read / write flag is set to 1, I2C receives data and the host sends the process:
1. Start bit
2. (1 bit left from device address + 0) + ACK
3. Slave device address + ACK
4. Start bit
5. (1 bit left from device address + 1) + ACK
6. 1 byte data + ACK
7. 1 byte data + ACK
8. Stop bit
11.6 FIFO management
The I2C FIFO depth is 2 words. I2C transmission and reception can be divided into RX FIFO and TX FIFO.
The register RFICNT indicates how much data (unit word) needs to be read in the RX FIFO.
The register TFICNT indicates how much space (in Word) is available for writing in the TX FIFO.
I2C FIFO status:
• RX FIFO underflow: When the data in the RX FIFO has been read or is empty, continue to read data from the RX
FIFO, the register RFIU will be set;
• RX FIFO overflow: When I2C receives data until the 2 words of RX FIFO are filled. Without reading the RX FIFO,
I2C receives the data again and the register RFIO will be set;
BL702/704/706 Reference Manual 212/ 375
@2021 Bouffalo Lab
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