Ports and Interfaces > Parallel Port

Pin 4 goes high automatically when one of the status pins connected to the GND!

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Jan Axelson:
Use Output only if possible, otherwise bidirectional.

Rightia:
I set it to Bi-Directional and I still have the problem!
When I close the switch of the pin 13, the pin 04 goes high automatically!


                220 ohms    LED
Pin 04 -------^^^------|>|------|
                                              |
                           switch          |
Pin 13 ----------------/ ----------|
                                              |
                                              |
Pin 25 ----------------------------|

Jan Axelson:
Have you written zero to pin 4?

Rightia:
Yes, and before I press the switch, the LED is off.

Jan Axelson:
In bidirectional mode, S4 is XFlag, which goes high to indicate support for using the data lines as inputs. It looks like the port driver is responding on detecting XFlag's going low.

If you set the port to output-only in the BIOS, you can still use the status bits for inputs and the driver won't try to negotiate other modes. That's what I would try next.

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