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TCAL9539-Q1: I2C communication failure

Leo Ma
Expert 3716 points
Part Number: TCAL9539-Q1
Other Parts Discussed in Thread: TCAL9539

Tool/software:

Hi Expert,

Have a nice day!

Customer use TCAL9539-Q1 and find some issues need your help.

Issue: When the MCU meet I2C communication failure (Such as I2C busy), then the 9539 can’t re-communicate with MCU when they reset the I2C from MCU. The communication can only be rework normally when they do “Power-On Reset” on 9539.

So I have these questions:

Q1: Will the I2C communication failure cause the 9539’s registers locked?

Q2: In DS 8.1: “The device can be reset to its default state by applying a low logic level to the RESET pin, issuing a software reset command, or by cycling power to the device and causing a power-on reset.”

 

Does this will influence external loads’ states? Or just influence internal registers?

 

Q3: In DS 8.3.4 : “When RESET is toggled the input port register is updated to reflect the state of the GPIO pins.”

Why there is only “input port register” to be updated but no “output port register” to be updated? Is it because all I/Os will be set to inputs at reset?

Thanks！

Best Regards,

Leo Ma

  • 0
    TI__Mastermind 48308 points

    Hi Leo,

    Please let me get back to you by noon CST tomorrow. 

    Regards,

    TYler

  • 0
    TI__Mastermind 48308 points

    Hi Leo,

    Leo Ma said:
    Q1: Will the I2C communication failure cause the 9539’s registers locked?

    It sounds like the I2C communication failure is specifically the SDA bus being locked LOW. Therefore, the registers of the TCAL9539 will remain at their set state because I2C write commands can no longer occur on the bus. 

    Leo Ma said:
    Q2: In DS 8.1: “The device can be reset to its default state by applying a low logic level to the RESET pin, issuing a software reset command, or by cycling power to the device and causing a power-on reset.”
    Leo Ma said:
    Does this will influence external loads’ states? Or just influence internal registers?

    The three ways of resetting the device will influence the internal register states which will influence the configuration of the I/O side. The default state of the I/O pins is configured all as INPUTs.

    Leo Ma said:
    Why there is only “input port register” to be updated but no “output port register” to be updated? Is it because all I/Os will be set to inputs at reset?

    This is correct. Upon /RESET command to the I/O expander, the I/O's will all be set to their default state which is high-z inputs at reset. Outputs are no longer configured. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    TI__Expert 3716 points

    Hi Tyler,

    Thanks for confirm.

    Customer sent me more tests results, and I'll move to Email to you for deep discussion.

    Best Regards,

    Leo Ma

  • +1 in reply to Leo Ma
    TI__Mastermind 48308 points

    Hi Leo,

    I saw the email and will respond later today. 

    Regards,

    Tyler