Re: Assembler in C

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From: Sergio Masci (sergio@xcprod.com)
Date: Thu 07 Jun 2001 - 05:53:29 IDT


Only a guess (reasonably educated one), but I think this might be a runtime
error. It may be a problem with other drivers interfering between the
register setup and the register read / write (really depends on the
drivers). Try disabling interrupts while you access the vga registers.

Regards
Sergio
PS check the code below, I've maked it with changes!

> I'm compiling as follows:
>
> gcc -O2 ck.c -DSHOW=1 libvgagl.a libvga.a ckn.o -o cks
>
> It appears that no I/O writes or reads are taking place.  The output from:
>

    // not sure about the actuall name of the disable / enable functions,
you'll
    // have to look that up
    _disable();

>     outb( 0x14, 0x3D6 );                // Select XR14
>

    // problem maybe occuring here!!!

>     stat    = inb( 0x3D7 ) & 0x8F;      // Enable VSYNC, Retrace, and
HSYNC

    // or here

>     outb( stat | 0x50, 0x3D7 );

    _enable();

>     fprintf( report, "stat is %0X\n", stat );
>
> is always 0.  Are the compiler switches I need?


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