TCA9534A: To check whether the command is received correctly

Hello Takao,

"Does this device have the function to send signal automatically to inform about the I/O register command from I2C being received correcly?"

After sending an address, on 9th clock cycle the device should pull down on SDA to tell you it has Acknowledged the address is correct. After sending the register address on the device, you should see the acknowledge again (9th clock cycle after the device register address). After writing to a register, following the byte sent there should also be an acknowledge. This should inform you the data was written to the register correctly.

You can see an example of this on page 21 on figure 29 of the datasheet below:

"to check whether the I2C command to set I/O port is delivered correctly, should we read register condition after sending command?"

If you receive the Ack from the slave device, it really should have been written to correctly. If for some reason you do not think that is the case or just want to double check, you can re-initiate a start condition on the SDA line and read from the slave address and the register you wrote to previously.

An example of how the read process should go is on page 22/23. Figure 31 shows the process of writing to an address then reading the address which was previously written to:

Thanks,

-Bobby