Category : Files from Magazines
Archive   : PJ-EGA.ZIP
Filename : PJ4-L2.ASM

 
Output of file : PJ4-L2.ASM contained in archive : PJ-EGA.ZIP
; Listing 2.
; Program to illustrate operation of set/reset circuitry to force
; setting of memory that already contains data.
; Assembled with MASM 4.0, linked with LINK 3.51.
; By Michael Abrash, 4/26/87.
;
stack segment para stack 'STACK'
db 512 dup(?)
stack ends
;
EGA_VIDEO_SEGMENT equ 0a000h ;EGA display memory segment
;
; EGA register equates.
;
TS_INDEX equ 3c4h ;TS index register
TS_MAP_MASK equ 2 ;TS map mask register
GC_INDEX equ 3ceh ;GC index register
GC_SET_RESET equ 0 ;GC set/reset register
GC_ENABLE_SET_RESET equ 1 ;GC enable set/reset register
;
; Macro to set indexed register INDEX of TS chip to SETTING.
;
SETTS macro INDEX, SETTING
mov dx,TS_INDEX
mov al,INDEX
out dx,al
inc dx
mov al,SETTING
out dx,al
dec dx
endm
;
; Macro to set indexed register INDEX of GC chip to SETTING.
;
SETGC macro INDEX, SETTING
mov dx,GC_INDEX
mov al,INDEX
out dx,al
inc dx
mov al,SETTING
out dx,al
dec dx
endm
;
cseg segment para public 'CODE'
assume cs:cseg
start proc near
;
; Select 640x350 graphics mode.
;
mov ax,010h
int 10h
;
mov ax,EGA_VIDEO_SEGMENT
mov es,ax ;point to video memory
;
; Draw 18 10-scan-line high horizontal bars in green, 10 scan lines apart.
;
SETTS TS_MAP_MASK,02h ;map mask setting enables only
; plane 1, the green plane
sub di,di ;start at beginning of video memory
mov al,0ffh
mov bp,18 ;# bars to draw
HorzBarLoop:
mov cx,80*10 ;# bytes per horizontal bar
rep stosb ;draw bar
add di,80*10 ;point to start of next bar
dec bp
jnz HorzBarLoop
;
; Fill screen with blue, using set/reset to force plane 0 to 1's and all
; other plane to 0's.
;
SETTS TS_MAP_MASK,0fh ;must set map mask to enable all
; planes, so set/reset values can
; be written to memory
SETGC GC_ENABLE_SET_RESET,0fh ;CPU data to all planes will be
; replaced by set/reset value
SETGC GC_SET_RESET,01h ;set/reset value is 0ffh for plane 0
; (the blue plane) and 0 for other
; planes
sub di,di
mov cx,80*350 ;# bytes per screen
mov al,0ffh ;since set/reset is enabled for all
; planes, the CPU data is ignored-
; only the act of writing is
; important
rep stosb ;perform fill (affects all planes)
;
; Turn off set/reset.
;
SETGC GC_ENABLE_SET_RESET,0
;
; Exit to DOS.
;
mov ah,4ch
int 21h
start endp
cseg ends
end start



  3 Responses to “Category : Files from Magazines
Archive   : PJ-EGA.ZIP
Filename : PJ4-L2.ASM

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

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