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26 lines
603 B
PHP
26 lines
603 B
PHP
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; SetHorizPos - Sets the horizontal position of an object.
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; The X register contains the index of the desired object:
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; X=0: player 0
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; X=1: player 1
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; X=2: missile 0
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; X=3: missile 1
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; X=4: ball
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; NOTE: This version of the routine does a NEWLINE before executing.
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; It does NOT do a HMOVE and HCLR.
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SetHorizPos subroutine
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sec ; set carry flag
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sta WSYNC ; start a new line
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.DivideLoop
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sbc #15 ; subtract 15
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bcs .DivideLoop ; branch until negative
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eor #7 ; calculate fine offset
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asl
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asl
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asl
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asl
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sta HMP0,x ; set fine offset
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sta RESP0,x ; fix coarse position
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rts ; return to caller
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