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TUSB1044: I2C NACK condition

Kazuki Kuramochi
Expert 8330 points
Part Number: TUSB1044

Hello Expert,

I have question regarding I2C communication with TUSB1044.
I'd like to know about when TUSB1044 return NACK signal on I2C.

I think this will return NACK when received wrong slave address and wrong command(e.g. receive unsupported register).
Is there other condition that will cause NACK return? For example, Does reserved register access cause NACK? 

I'm looking forward to hearing back from you.


Best regards,
Kazuki Kuramochi

  • 0
    TI__Guru** 104520 points

    There are five conditions that lead to the generation of a NACK:

    1. No receiver is present on the bus with the transmitted address so there is no device to respond with an acknowledge.

    2. The receiver is unable to receive or transmit because it is performing some real-time function and is not ready to start communication with the master.

    3. During the transfer, the receiver gets data or commands that it does not understand.

    4. During the transfer, the receiver cannot receive any more data bytes.

    5. A master-receiver must signal the end of the transfer to the slave transmitter.

  • 0 in reply to Brian Zhou
    TI__Expert 8330 points

    Hello Brian-san,

    Sorry for my late reply and thank you for your swift support.

    I think you showed situation is general condition with I2C communication of asserting NACK by receiver side.
    Then, I'd like to know about the detail of 3. and 4. condition with TUSB1044.

    Is there possibility of causing 3. and 4. condition with TUSB1044.
    And should we do any specific procedure with TUSB1044 for preventing condition of 3. and 4.?(e.g. add some wait before sending next command for avoiding the risk of happening case 3.)


    Best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Guru** 104520 points

    3 or 4 do not happen often, normally happened for a wrong address or conflict address, did you check that ?

  • 0 in reply to Brian Zhou
    TI__Expert 8330 points

    Hello Brian-san,

    We don't observed NACK but we want to prepare for this situation just in case.

    So I'd like to know about what status will cause NACK response.
    You said case 3 and 4 probably won't happen.
    But if there is case of causing NACK regarding case 3 and 4 even if it is rare case.

    Do you know the specific case or condition which cause NACK regarding case 3 and 4 with TUSB1044?


    Best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Guru** 104520 points

    we haven't see any case for 3 or 4 with TUSB1044 yet

  • 0 in reply to Brian Zhou
    TI__Expert 8330 points

    I understood.

    Thank you.