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micro I/o lines

Discussion in 'General Electronics Discussion' started by Rajinder, Dec 16, 2016.

  1. Rajinder

    Rajinder

    402
    7
    Jan 30, 2016
    Hi all,
    I need to understand micro I/o lines for a PIC 18F.
    If I put a 10k pull up on a pin, and configure the pin as a input. It will read high. But if the same pin is set to an output, what happens? Also can I drive this low even though it has a pull up, by this I mean using the internal FET or open collector transistor inside the micro?
    Best regards
    Raj
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    Unless something else pulls it (harder) to ground.

    The output takes the state you set it unless the pull up resistor has such a low value that the microcontroller can't pull it low. in addition, when you set the output to a low state current will flow through the resistor.

    Yes. If the output is open collector then this is the only way to get a high level on the output.
     
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