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TCA9534A: Read from register operation

Takao Yamamoto5
Expert 1690 points
Part Number: TCA9534A

Dear all,

Could you teach me how to operate when I read from register repeatedly?

Should I send R/W command each cycle?

Should I send I/O setting each cycle?

Best regards,

  • 0
    TI__Guru 62910 points
    Hello Yamamoto-san,

    If you wish to read from the same register repeatedly, you should only need to send the command byte once to choose the right register address. After that, the master can initiate a read command by sending the right slave its address with the R/W bit set to 1. Then, it can read data continuously as long as the master ACKs every eight bits and does not send a STOP condition. You can refer to Figure 32 in the datasheet for an example of this.

    Regards,
    Max
  • 0 in reply to Max Robertson
    Expert 1690 points
    Hello Robertson,

    Thank you for your answer.
    Could I check my understanding?

    You said 'Then, it can read data continuously as long as the master ACKs every eight bits and does not send a STOP condition. ' at previous post.

    If I read the same device after sending a STOP condition, must I send the register address? or, can I read by sending only the slave address with the R/W bit set to 1?

    By the way, could you give me some source example of Write/Read if you have?

    Best regards,
  • 0 in reply to Takao Yamamoto5
    TI__Guru 62910 points
    Yamamoto-san,

    Unfortunately we do not have example code to provide, but I can confirm that your understanding is correct. Further, you do not need to re-send the register address even if a STOP condition occurs. You can simply issue another read command to the proper slave address, as you mentioned. Please let me know if this is not clear.

    Best regards,
    Max