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Antic Magazine 1982 June
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Antic_June_1982_Vol_1_No_2.atr
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2021-01-30
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;¢; Listing #2¢; by Stan Ockers¢; for ANTIC The ATARI Resource¢; a Vertical Blank Interrupt routine¢; call from BASIC A=USR(1536)¢;¢ ORG $600 ; page six location¢ PLA ; ignore parameter count¢ LDY #$0A ; lo-byte VBI routine¢ LDX #$06 ; hi-byte VBI routine¢ LDA #07 ; deferred VBI¢ JMP $E45C ; O.S. inserts VBI¢VBI LDA #00 ; zero ?¢ CMP $D0 ; move flag plyr 0¢ BEQ SKP ; forget plyr 0¢ INC $CE ; one space right¢ LDX $CE ; update¢ STX $D000 ; horiz pos. plyr 0¢SKP CMP $D1 ; mov flag 1 0 ?¢ BEQ OUT ; yes forget p1yr 1¢ DEC $CF ; one space left¢ LDX $CF ; update¢ STX $D001 ; horiz pos. plyr I¢OUT JMP $E462 ; VBI exit thru O.S.¢