Basic-like GRAPHICS function; not yet implemented; provides the

"graphics memory used" constructor

git-svn-id: svn://svn.cc65.org/cc65/trunk@541 b7a2c559-68d2-44c3-8de9-860c34a00d81

diff --git a/libsrc/atari/graphics.s b/libsrc/atari/graphics.s
new file mode 100644 (file)
index 0000000..2b82207
--- /dev/null
+++ b/libsrc/atari/graphics.s
@@ -0,0 +1,98 @@
+;
+; Christian Groessler, December 2000
+;
+; this file provides an equivalent to the BASIC GRAPHICS function
+;
+; void __fastcall__ graphics(unsigned char mode);
+
+       .export _graphics
+       .constructor    scr_memtop,28
+
+       .import __graphmode_used
+
+       .include        "atari.inc"
+
+       .code
+
+
+.proc  _graphics
+
+       rts             ; not implemented yet!
+
+.endproc
+
+
+; calc. upper memory limit to use
+
+.proc  scr_memtop
+
+       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
+