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cc65/libsrc/atari/graphics.s

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;
; Christian Groessler, December 2000
;
; this file provides an equivalent to the BASIC GRAPHICS function
;
; void __fastcall__ graphics(unsigned char mode);
.export _graphics
.constructor initscrmem,28
.import __graphmode_used
.include "atari.inc"
.code
.proc _graphics
rts ; not implemented yet!
.endproc
; calc. upper memory limit to use
.proc initscrmem
lda __graphmode_used
beq ignore ; mode 0 doesn't need adjustment
cmp #32
bcs ignore ; invalid value
asl a
tay
lda APPMHI
sec
sbc grmemusage,y
sta APPMHI
lda APPMHI+1
sbc grmemusage+1,y
sta APPMHI+1
ignore: rts
.endproc
.rodata
; memory usage of the different graphics modes (0-31)
; values < 0 of "bytes needed" are mappped to 0
; bytes needed ; mode ; val. of MEMTOP
grmemusage:
.word 0 ; 0 ; 39967
.word 0 ;-318 ; 1 ; 40285
.word 0 ;-568 ; 2 ; 40535
.word 0 ;-558 ; 3 ; 40525
.word 0 ;-298 ; 4 ; 40265
.word 182 ; 5 ; 39785
.word 1182 ; 6 ; 38785
.word 3198 ; 7 ; 36769
.word 7120 ; 8 ; 32847
.word 7146 ; 9 ; 32821
.word 7146 ; 10 ; 32821
.word 7146 ; 11 ; 32821
.word 162 ; 12 ; 39805
.word 0 ;-328 ; 13 ; 40295
.word 3278 ; 14 ; 36689
.word 7120 ; 15 ; 32847
.word 0 ; 16 ; 39967
.word 0 ;-320 ; 17 ; 40287
.word 0 ;-572 ; 18 ; 40539
.word 0 ;-560 ; 19 ; 40527
.word 0 ;-296 ; 20 ; 40263
.word 184 ; 21 ; 39783
.word 1192 ; 22 ; 38775
.word 3208 ; 23 ; 36759
.word 7146 ; 24 ; 32821
.word 7146 ; 25 ; 32821
.word 7146 ; 26 ; 32821
.word 7146 ; 27 ; 32821
.word 160 ; 28 ; 39807
.word 0 ;-332 ; 29 ; 40299
.word 3304 ; 30 ; 36663
.word 7146 ; 31 ; 32821
; the program used to get these values (Atari BASIC):
; 100 FILE=0
; 110 IF FILE=1 THEN OPEN #1,8,0,"D:FREEMEM.OUT"
; 120 IF FILE<>1 THEN OPEN #1,8,0,"E:"
; 200 DIM G(32)
; 210 FOR I=0 TO 32:GRAPHICS I:GOSUB 1000:G(I)=VAL:NEXT I
; 220 GRAPHICS 0
; 230 FOR I=0 TO 31:PRINT #1;I;":",G(I);" - ";G(0)-G(I):NEXT I
; 240 CLOSE #1
; 999 END
; 1000 VAL=PEEK(741)+256*PEEK(742)
; 1010 RETURN