0000        09          .TITLE "GTIADLI 4/30/82 by Craig Chamberlain"›››››GTIADLI 4/30/82 by Craig Chamberlain› ››0000        10          .PAGE          ›            11 ;›            12 ;necessary operating system and hardware equates›            13 ;›026F        14 GPRIOR   =    $026F          ;GTIA priority control (shadow)›D01A        15 COLBK    =    $D01A          ;background color register›D01B        16 PRIOR    =    $D01B          ;GTIA priority control (hardware)›D40A        17 WSYNC    =    $D40A          ;horizontal blank synchronization›            18 ;›            19 ;›0000        20          *=   $0600     ›            21 ;›            22 ;this service routine for the display list interrupt›            23 ;can be placed anywhere in RAM, and was placed on page six›            24 ;only for purposes of demonstration›            25 ;›            26 ;begin interrupt service routine code›            27 ;›            28 ;save contents of accumulator›            29 ;›0600 48     30          PHA            ›            31 ;›            32 ;get the multicolor player, fifth player, and priority bits›            33 ;›0601 AD6F02 34          LDA  GPRIOR    ›            35 ;›            36 ;force the GTIA mode select bits to zero but save the other bits›0604 293F   37          AND  #$3F      ›            38 ;›            39 ;wait until next scan line for a nice clean change›            40 ;›0606 8D0AD4 41          STA  WSYNC     ›            42 ;›            43 ;change hardware register until VBLANK›            44 ;›0609 8D1BD0 45          STA  PRIOR     ›            46 ;›            47 ;reset COLOR4 to zero (for modes 9 and 11)›060C A900   48          LDA  #$00      ›060E 8D1AD0 49          STA  COLBK     ›            50 ;›            51 ;restore accumulator›            52 ;›0611 68     53          PLA            ›            54 ;›            55 ;return from the display list interrupt›            56 ;›0612 40     57          RTI            ›            58 ;›            59 ;end of interrupt service routine›            60 ;›››››GTIADLI 4/30/82 by Craig Chamberlain› ››=026F GPRIOR        =D01A COLBK         =D01B PRIOR         =D40A WSYNC         ›››››