http://www.tienza.es/crux/src/www.jwz.org/xscreensaver/xscreensaver-5.05.tar.gz

[xscreensaver] / hacks / images / m6502 / keftal.asm

diff --git a/hacks/images/m6502/keftal.asm b/hacks/images/m6502/keftal.asm
new file mode 100644 (file)
index 0000000..efb2982
--- /dev/null
+++ b/hacks/images/m6502/keftal.asm
@@ -0,0 +1,82 @@
+; awfully slow.. be patient
+
+init:
+  ldx #0
+  stx $0
+  inx
+  stx $2
+  stx $3
+  inx
+  stx $1
+
+loop:
+  lda $2
+  cmp #$20
+  bne notIncF2
+  inc $3
+  lda #0
+  sta $2
+notIncF2:
+  inc $2
+
+; CALCULATE START
+
+  lda $2
+  sta $f1
+  lda $2
+  sta $f2
+  jsr multiply
+
+  lda $f4
+  sta $f8
+
+  lda $3
+  sta $f1
+  lda $3
+  sta $f2
+  jsr multiply
+
+; CALCULATE STOP
+
+  lda $f4
+  clc
+  adc $f8
+
+  lsr
+  lsr
+  lsr
+  lsr
+  lsr
+  ldx #0
+  sta ($0,x)
+  inc $0
+  lda $0
+  cmp #$00
+  bne notNextY
+  inc $1
+  lda $1
+  cmp #6
+  beq exit
+notNextY:
+  jmp loop
+exit:
+  rts
+
+multiply:
+  lda #0
+  sta $f4
+  sta $f5
+  ldx #8
+a:asl $f4
+  rol $f5
+  asl $f2
+  bcc b
+  clc
+  lda $f4
+  adc $f1
+  sta $f4
+  bcc b
+  inc $f5
+b:dex
+  bne a
+  rts 
\ No newline at end of file