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TCA6416A: TCA6416A Configured as all Outputs after Power-Up

Chris Raynolds
Prodigy 60 points
Part Number: TCA6416A


Although the TCA6416A specification states that the configuration registers come out of power up as all high, indicating all pins are configured as inputs, this is NOT the case. After power up a read using the IIC bus of the configuration registers at command byte 0x6 and 0x7 returns all lows, indicating all pins are configured as outputs. Please, does anyone have any information regarding this contradiction? Thank You ChrisR

  • 0
    TI__Guru 62920 points
    Hi Chris,

    The device is supposed to initialize itself with the correct default register values automatically once it becomes fully powered. However, there are some requirements on the VCC ramp profile in order to make sure this power-on-reset process works as intended. These requirements are given in Section 10.1 of the datasheet beginning on page 29. Can you please confirm that you are operating within these requirements?

    Also, sorry for the basic question, but could you also confirm that you are able to read non-zero values from other registers or that write/read operations can work? I just want to make sure there isn't some other hardware issue at play here.

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Prodigy 60 points

    Hello Max, Thank you so much for this response. I am working with a Xilinx ZCU102 evaluation board, and both the power pins are tied to the same 3.3V source, so there is no sequencing of supplies, hence the problem, and reset is just tied high with not even an RC for a reset. I have confirmed that momentarily grounding the reset pin gives the default configuration expected, all GPIOs configured as inputs, all high. And yes I have confirmed that right after power on:

    input registers@ 0x0 and 0x1 are both reading 0xFF

    output registers@ 0x2 and 0x3 are both reading 0xFF

    polarity inversion registers@ 0x4 and 0x5 are both reading 0x00

    configuration registers@ 0x6 and 0x7 are both reading 0x00

    And that right after a momentary reset all the registers read their correct defaults.

    Many thanks, this ticket can be closed, or if I can provide more information from the hardware in the lab, please let me be of assistance. Thanks Chris Raynolds

  • 0 in reply to Chris Raynolds
    TI__Guru 62920 points
    Thanks for the update! I'm glad things are making sense now. Please just let us know if you encounter any more issues with this device in the future.

    Max