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AM2432: Unused Pin

Mari Tsunoda
Expert 5726 points

Part Number: AM2432

Hi Team,

My customer has a question as below.

I found the TI's engineer's comment as below
 "All enabled input buffers must be pulled below its VILSS potential or pulled above its VIHSS potential as defined in the respective Electrical Characteristics section of the datasheet. "
URL:
https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1086028/faq-am2432-am2x---boot-pins-pull-down-up-requirements?tisearch=e2e-sitesearch&keymatch=QSPI%2520boot%25201S-1S-4S#


If I set RXACTIVE bit to 0 in the PADCONFIG register(Input buffer disabled), is pullup or pulldown register not needed?
Which selection is preferred to non-used pin? (No connection to the all on PWB)
1, disable input buffer(RXACTIVE=0)
2, enable output buffer(TXDIS=0) and select GPIO and output Hi or Low.
3, setup pulldown or pullup with PADCONFIG register.

Best regards,

Mari Tsunoda

  • 0
    TI__Mastermind 25403 points

    Hey Mari,

    In general,

    Disable Input Buffer (RXACTIVE=0) - Ensures spurious noise/signals aren't interpreted at the pad.

    Disable Output Buffer (TXDIS=1) - Ensures no signals are driven by the pad (this could become a source of noise on other unused signals)

    As far as the pull configuration of a non-used pin, it is often dependent on the default functionality of that pin. For a pin such as the JTAG TRSTn, enabling the internal pull down resistor is recommended to ensure the TAP controller remains in reset. It may seem redundant somewhat redundant with the input buffer disabled, but it is recommended to ensure proper operation. Customers should review this on a per-pin basis to determine the best pull configuration to ensure proper operation regardless of possible noise/signals that may accidentally be seen at the pin.

    Please let us know if this addresses your customers questions/concerns.

    Best Regards,

    Zackary Fleenor

  • 0 in reply to Fleenor
    TI__Expert 5726 points

    Hi Zack,

    I received the follow-up question below:

    We should set TXDIS=1 to disable output buffer. Is that right?
    example：TX_DIS bit Description on TRM Table 5-105 TX_DIS Description
    Driver Disable
    0h - Driver is enabled
    1h - Driver is disabled

    Disable Output Buffer (TXDIS=1) for unused pin setting. right?

    Best regards,

    Mari

  • +1 in reply to Mari Tsunoda
    TI__Mastermind 25403 points

    Hey Mari,

    Statement is correct:

    Driver Disable
    0h - Driver is enabled
    1h - Driver is disabled

    Disable Output Buffer (TXDIS=1)

    I have updated original reply to reflect.

    Best Regards,

    Zackary Fleenor