Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hpda!hpcupt1!hprnd!pyt
From: pyt@hprnd.HP.COM (Pierre-Yves Thoulon)
Newsgroups: comp.sys.ibm.pc
Subject: Re: VGA and Bit Mask Register: HEEEEEELP !
Message-ID: <1040011@hprnd.HP.COM>
Date: 7 Mar 89 18:36:15 GMT
References: <1040010@hprnd.HP.COM>
Organization: HP Roseville Networks Division
Lines: 33

OK ! as usual, every time I post something to notes, I find the answer
by myself the day after... The solution is that I forgot to load the
internal VGA latch before doing the modify/write. The full stuff is
below:


#define START	(char far *)0xa0000000
#define END	(char far *)0xa0009600
void main(void)
{
	union REGS regs;
	char far *Address;
>>>>>>	char Dummy;

	regs.h.ah = 0;
	regs.h.al = 0x12;
	int86(0x10, &regs, &regs);	/* set display mode 0x12 */

	outp(0x3ce, 5);	/* Mode register */
	outp(0x3cf, 2); /* Write Mode 2 */

	outp(0x3ce, 8); /* Bit Mask register */
	outp(0x3cf, 0); /* all bits masked */

	for (Address=START; Address < END; Address++)
	{
>>>>>>>>	Dummy = *Address; /* dummy read */
		*Address = 4;	/* paint pixel Red */
	}
	
	pause();
	reset();
}