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TCA9546A: I2C access during #RESET=Low

K.Yaita
Guru 29690 points
Part Number: TCA9546A

Hi Team,

Does TCA9546A send NACK if I2C access is occured even when #RESET pin is Low?

Best Regards,
Yaita / Japan disty

  • 0
    TI__Guru 60112 points
    Yaita-san,

    When the RESET pin is pulled low all the channels are deselected and the I2C state machine resets. Because of this there should be no acknowledge bit present when the device is resetting. Are you holding the RESET pin low for an extended period of time?

    Regards,
  • 0 in reply to Eric Hackett
    Guru 29690 points

    Hi Eric-san,

    I apologize my question is unclear.
    There is another I2C slave device (yellow) that is connected to the same I2C bus of TCA9546A like the following in my customer's system.



    I heard if a master device access to yellow device during #RESET pin of TCA9546A is low, master couldn't access yellow device.
    On the other hand, the master could access to yellow device during #RESET pin of TCA9546A is high.

    My customer coudn't see waveforms of SDA and SCL in this situation however wants to know if TCA9546A pulls SDA or SCL low when #RESET is low.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 17205 points

    Hello Yaita-san,

    When the TCA9546A is held in reset, all the channels are held in a high impedance state, thus you can still communicate with the SLAVE devices on the "SDA" and "SCL" bus. 

    -Francis Houde