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tms320c6748 - are gpio pulls disabled automatically when config as output

Perry Frogge
Intellectual 370 points

gpio pullup/downs are configured in banks, so within that bank, the gpio can be an input or an output. So when configured as an output, is the pull disabled even though the bit is set to enable pulls for the bank.  I don't wan to drive an output low and have a DC current path thru internal pullup. I scowered data sheets and don't see this info.

thanks

Perry

  • 0
    TI__Expert 4760 points

    Hi Perry,

    The internal Pull-up/Pull-down functionality can be set through SYSCFG1 registers

    1. PUPD_ENA Pull-up/Pull-down Enable Register
    2. PUPD_SEL Pull-up/Pull-down Selection Register

    You need to specify the pin group CP [0...31] in which you’re going to use the Pull-up/Pull-down functionality

    GPIO peripheral provides dedicated general-purpose pins that can be configured as either inputs or Output .You don’t have control over Pull-up/Pull-down selection in the GPIO peripheral registers.

    That is already set in the SYSCFG1 registers regardless of the GPIO direction ( Input/output) set in the direction register .So, the Pull-up/Pull-down functionality remains the same as we set in the SYSCFG1 register, if you don’t want that option you need to disable it the PUPD_ENA resister.

    Regards

    Antony

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  • 0 in reply to Antony Samsunil
    Intellectual 370 points

    Thanks for reply, I am familiar with those registers, but i don't understand how they relate to my question, I was expecting a yes or no answer.

    Is there any logic in the chip  detects a gpio is configured as an output and overrides the PUPD_ENA register bit,   if not , then I think I will have a DC path when I have a pullup turned on and the GPIO driving a 0 out. 

    thanks

  • 0 in reply to Perry Frogge
    Intellectual 370 points

    FYI to those out there trying for very low power,  the pulls remain on when the gpio is configured as an output.  I had a bank of 8 gpios set to drive 0's.  When I disabled the pullups on that bank the current dropped 0.5vmA on the 12v supply to my board. Likely close 1.5mA on 3.3v supply.