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INT 10h, 12h (18) Alternate Select EGA
Returns information on the Enhanced Display Adapter (EGA) and allows
the selection of an alternative EGA Print Screen routine.
On entry: AH 12h
BL Subservice
10h - Return EGA information
20h - Select alternative EGA Print Screen
routine
VGA Only:
30h - Set number of scan lines
0-200, 0-350, 2-400
Activates after mode change
31h - AX = 0/1 -> allow/prevent palette load
with new mode
32h - AL = 0/1 -> Video On/Off
33h - AL = 0/1 -> Gray scale summing On/Off
34h - AL = 0/1 -> Scale cursor to font On/Off
35h - Switch betwen adapter and motherboard
video
AL = 0 adapter off, es:dx save state
= 1 motherboard on
= 2 active video off, es:dx save..
= 3 inactive video on, es:dx ..
36h - Turn Screen On / Off
AL = 0/1 -> Screen On/Off
Returns: (for Subservice 10h only):
BH Display mode in effect
00h Color mode (3Dxh address range)
01h Monochrome mode (3Bxh address range)
BL EGA memory
00h 64K
01h 128K
02h 192K
03h 256K
CH Adapter bits
CL Switch setting
--------------------------------------------------------------------------
Notes: The value returned in CL (Switch setting) represents
the DIP switch settings on the EGA. The Adapter bits
(CH) is defined as follows:
Adapter bits (CH)
7 6 5 4 3 2 1 0
x x x x . . . . Unused
. . . . x x . . Reserved
. . , . . . x . FEAT1 (pin 17)
. . . . . . . x FEAT0 (pin 19)
To print the screen contents when the number of rows
changes, use Subservice 20h (Set Alternative Print
Screen) to install a Print Screen routine that will
work correctly with the row change.
See Also:
INT 10h, 11h
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