Programmer Power Tools/Programmer Power Tools.iso/progjrn/pj_vga.arc/VGA62-L3.ASM

Assembly Source File | 1988-02-18 | 4KB | 198 lines

Code from "Yet Another VGA Write Mode" by Michael Abrash, PJ,
Volume 6.2.  Copyright 1987 Michael Abrash
;
; *** Listing 3 ***
;
; Program to illustrate flipping from bit-mapped graphics mode to
; text mode and back without losing any of the graphics bit-map.
;
; Assembled with MASM 5.0, linked with MS-LINK 3.60.
;
; By Michael Abrash 11/8/87
;
Stack    segment    para stack 'STACK'
    db    512 dup(0)
Stack    ends

GRAPHICS_SEGMENT equ    0a000h    ;mode 10 bit-map segment
TEXT_SEGMENT    equ    0b800h    ;mode 3 bit-map segment
SC_INDEX    equ    3c4h    ;Sequence Controller Index register
MAP_MASK    equ    2    ;index of Map Mask register
GC_INDEX    equ    3ceh    ;Graphics Controller Index register
READ_MAP    equ    4    ;index of Read Map register

Data    segment    para common 'DATA'

GStrikeAnyKeyMsg0    label    byte
    db    0dh, 0ah, 'Graphics mode', 0dh, 0ah
    db    'Strike any key to continue...', 0dh, 0ah, '$'

GStrikeAnyKeyMsg1    label    byte
    db    0dh, 0ah, 'Graphics mode again', 0dh, 0ah
    db    'Strike any key to continue...', 0dh, 0ah, '$'

TStrikeAnyKeyMsg    label    byte
    db    0dh, 0ah, 'Text mode', 0dh, 0ah
    db    'Strike any key to continue...', 0dh, 0ah, '$'

Plane2Save    db    2000h dup (?)    ;save area for plane 2 data
                    ; where font gets loaded
CharAttSave    db    4000 dup (?)    ;save area for memory wiped
                    ; out by character/attribute
                    ; data in text mode
Data    ends

Code    segment    para public 'CODE'
    assume    cs:Code, ds:Data
Start    proc    near
    mov    ax,10h
    int    10h        ;select video mode 10h (640x350)
;
; Fill the graphics bit-map with a colored pattern.
;
    cld
    mov    ax,GRAPHICS_SEGMENT
    mov    es,ax
    mov    ah,3        ;initial fill pattern
    mov    cx,4        ;four planes to fill
    mov    dx,SC_INDEX
    mov    al,MAP_MASK
    out    dx,al        ;leave the SC Index pointing to the
    inc    dx        ; Map Mask register

FillBitMap:
    mov    al,10h
    shr    al,cl        ;generate map mask for this plane
    out    dx,al        ;set map mask for this plane
    sub    di,di        ;start at offset 0
    mov    al,ah        ;get the fill pattern
    push    cx        ;preserve plane count
    mov    cx,8000h    ;fill 32K words
    rep stosw        ;do fill for this plane
    pop    cx        ;get back plane count
    shl    ah,1
    shl    ah,1
    loop    FillBitMap
;
; Put up "strike any key" message.
;
    mov    ax,Data
    mov    ds,ax
    mov    dx,offset GStrikeAnyKeyMsg0
    mov    ah,9
    int    21h
;
; Wait for a key.
;
    mov    ah,01h
    int    21h
;
; Save the 8K of plane 2 that will be used by the font.
;
    mov    dx,GC_INDEX
    mov    al,READ_MAP
    out    dx,al
    inc    dx
    mov    al,2
    out    dx,al        ;set up to read from plane 2
    mov    ax,Data
    mov    es,ax
    mov    ax,GRAPHICS_SEGMENT
    mov    ds,ax
    sub    si,si
    mov    di,offset Plane2Save
    mov    cx,2000h/2    ;save 8K (length of default font)
    rep movsw
;
; Go to text mode without clearing display memory.
;
    mov    ax,083h
    int    10h
;
; Save the text mode bit-map.
;
    mov    ax,Data
    mov    es,ax
    mov    ax,TEXT_SEGMENT
    mov    ds,ax
    sub    si,si
    mov    di,offset CharAttSave
    mov    cx,4000/2    ;length of one text screen in words
    rep movsw
;
; Fill the text mode screen with dots and put up "strike any key"
; message.
;
    mov    ax,TEXT_SEGMENT
    mov    es,ax
    sub    di,di
    mov    al,'.'        ;fill character
    mov    ah,7        ;fill attribute
    mov    cx,4000/2    ;length of one text screen in words
    rep stosw
    mov    ax,Data
    mov    ds,ax
    mov    dx,offset TStrikeAnyKeyMsg
    mov    ah,9
    int    21h
;
; Wait for a key.
;
    mov    ah,01h
    int    21h
;
; Restore the text mode screen to the state it was in on entering
; text mode.
;
    mov    ax,Data
    mov    ds,ax
    mov    ax,TEXT_SEGMENT
    mov    es,ax
    mov    si,offset CharAttSave
    sub    di,di
    mov    cx,4000/2    ;length of one text screen in words
    rep movsw
;
; Return to mode 10h without clearing display memory.
;
    mov    ax,90h
    int    10h
;
; Restore the portion of plane 2 that was wiped out by the font.
;
    mov    dx,SC_INDEX
    mov    al,MAP_MASK
    out    dx,al
    inc    dx
    mov    al,4
    out    dx,al        ;set up to write to plane 2
    mov    ax,Data
    mov    ds,ax
    mov    ax,GRAPHICS_SEGMENT
    mov    es,ax
    mov    si,offset Plane2Save
    sub    di,di
    mov    cx,2000h/2    ;restore 8K (length of default font)
    rep movsw
;
; Put up "strike any key" message.
;
    mov    ax,Data
    mov    ds,ax
    mov    dx,offset GStrikeAnyKeyMsg1
    mov    ah,9
    int    21h
;
; Wait for a key before returning to text mode and ending.
;
    mov    ah,01h
    int    21h
    mov    ax,03h
    int    10h
    mov    ah,4ch
    int    21h
Start    endp
Code    ends
    end    Start