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James Gregory 2013-12-31 11:38:48 +11:00
commit f658bfbb40
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54
45-04.md
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@ -94,34 +94,36 @@ Listing 45.2, which provides mode set code for 640x400 mode.
**LISTING 45.2 L45-2.C**
/* Mode set routine for VGA 640x400 16-color mode. Tested with
Borland C++ in C compilation mode. */
```c
/* Mode set routine for VGA 640x400 16-color mode. Tested with
Borland C++ in C compilation mode. */
#include <dos.h>
#include <dos.h>
void Set640x400()
{
union REGS regset;
void Set640x400()
{
union REGS regset;
/* First, set to standard 640x350 mode (mode 10h) */
regset.x.ax = 0x0010;
int86(0x10, &regset, &regset);
/* First, set to standard 640x350 mode (mode 10h) */
regset.x.ax = 0x0010;
int86(0x10, &regset, &regset);
/* Modify the sync polarity bits (bits 7 & 6) of the
Miscellaneous Output register (readable at 0x3CC, writable at
0x3C2) to select the 400-scan-line vertical scanning rate */
outp(0x3C2, ((inp(0x3CC) & 0x3F) | 0x40));
/* Modify the sync polarity bits (bits 7 & 6) of the
Miscellaneous Output register (readable at 0x3CC, writable at
0x3C2) to select the 400-scan-line vertical scanning rate */
outp(0x3C2, ((inp(0x3CC) & 0x3F) | 0x40));
/* Now, tweak the registers needed to convert the vertical
timings from 350 to 400 scan lines */
outpw(0x3D4, 0x9C10); /* adjust the Vertical Sync Start register
for 400 scan lines */
outpw(0x3D4, 0x8E11); /* adjust the Vertical Sync End register
for 400 scan lines */
outpw(0x3D4, 0x8F12); /* adjust the Vertical Display End
register for 400 scan lines */
outpw(0x3D4, 0x9615); /* adjust the Vertical Blank Start
register for 400 scan lines */
outpw(0x3D4, 0xB916); /* adjust the Vertical Blank End register
for 400 scan lines */
}
/* Now, tweak the registers needed to convert the vertical
timings from 350 to 400 scan lines */
outpw(0x3D4, 0x9C10); /* adjust the Vertical Sync Start register
for 400 scan lines */
outpw(0x3D4, 0x8E11); /* adjust the Vertical Sync End register
for 400 scan lines */
outpw(0x3D4, 0x8F12); /* adjust the Vertical Display End
register for 400 scan lines */
outpw(0x3D4, 0x9615); /* adjust the Vertical Blank Start
register for 400 scan lines */
outpw(0x3D4, 0xB916); /* adjust the Vertical Blank End register
for 400 scan lines */
}
```