[PARPORT] Cannot write to parport data register

From: Guenther Sohler (guenther.sohler@newlogic.com)
Date: Tue Mar 26 2002 - 06:05:54 EST

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    Hallo Group,

    I wanted to connect a LCD Display to my parallel port and test it a
    little bit, but then I realized that i was not longer able to
    handle the bits in the parport by writing to 0x378.
    Handling the bits of 0x37a worked fine
    Its very strange.
    I can only achieving the data to be on the pins if i INSTANTLY write to
    If I dont do, there are random values at the pins in parbort connector
    sub25 2-9 (bits 0-7)
    I connected a led to bit0 and found out, that the bit always goes to 0
    when my program terminates.
    I have seen that the bit very often changes the state especially during
    scanf input and during booting the computer and booting linux
    I have tried for different io port adresses 0x378 and 0x278. I have
    tried different modi in the bios(SPP, EPP, ECP) and I even tried
    to change the mode by writing to the extended control register(0x378
    I am sure that no system services are running any more(especially not
    So I dont have any Idea whats going wrong.

    Please also reply to my email

    Thankx, rds Guenther

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