PROGRAM LISTING: 87-10/GRAPHDLI.M65

0100 ;GRAPHICS 8/9 DEMO, SOURCE
0110 ;BY PAUL LAY
0120 ;(FROM PAGE 6 MAGAZINE, ENGLAND)
0130 PRIOR = $D01B
0140 WSYNC = $D40A
0150     *=  $0600
0160     PHA 
0170     TXA 
0180     PHA 
0190     TYA 
0200     PHA 
0210     LDA #$00
0220     LDY #$40
0230     LDX #$A0    ; Loop over
0240 ;                 160 scans
0250 LOOP
0260     STA WSYNC
0270     STA PRIOR   ; Disable GTIA
0280     CPX #$A0
0290     BEQ SKIP1   ; First LMS ?
0300 ;
0310     NOP 
0320 SKIP1
0330     CPX #$42    ; Second LMS ?
0340     BEQ SKIP2
0350 ;
0360     STA $CB     ; Three cycle
0370 ;                 delay !
0380 SKIP2
0390     STA $CB     ; Three cycle
0400 ;                 delay !
0410     NOP 
0420     NOP 
0430     NOP 
0440     NOP 
0450     STY PRIOR   ; Enable GTIA #9
0460     DEX 
0470     BNE LOOP
0480 ;
0490     STA WSYNC
0500     STA PRIOR   ; Disable GTIA
0510     PLA 
0520     TAY 
0530     PLA 
0540     TAX 
0550     PLA 
0560     RTI