RE: [PARPORT] inb (problems)

From: Samuel Ace Winchenbach (
Date: Fri Apr 07 2000 - 07:40:33 EDT

  • Next message: Tim Waugh: "RE: [PARPORT] inb (problems)"

    >Some implementations don't allow reads from the control port though.

    I can read from the control port in Windows 98 S.E.

    Also I know I can tie the control port directly to ground. I am an
    electrical engineering major at University and we have gone over the
    internal workings of the parallel port. The dangerous thing to do is set a
    pin low and then put +5 volts on the pin (without anything resisting the
    current). What happens is the Open-Collector transistor inside tries to
    sink too much current and with a small puff of smoke your parallel port
    stops working. :) Pulling the line low is a different story. Internally
    there is a 4.7 Kohm pull up resistor. This prevents too much current from

    Still, I have learned in my class that you can read from the control port
    (which works in windows, and seeing it is based on hardware... I would not
    think that this would be different in windows!) So I am rather confused.

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