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38 lines
564 B
ArmAsm
38 lines
564 B
ArmAsm
; hposn_low, hposn_high will each be filled with $C0 bytes
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; based on routine by John Brooks
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; posted on comp.sys.apple2 on 2018-07-11
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; https://groups.google.com/d/msg/comp.sys.apple2/v2HOfHOmeNQ/zD76fJg_BAAJ
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; clobbers A,X
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; preserves Y
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; vmw note: version I was using based on applesoft HPOSN was ~64 bytes
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; this one is 37 bytes
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build_tables:
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ldx #0
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btmi:
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txa
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and #$F8
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bpl btpl1
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ora #5
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btpl1:
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asl
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bpl btpl2
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ora #5
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btpl2:
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asl
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asl
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sta hposn_low, X
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txa
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and #7
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rol
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asl hposn_low, X
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rol
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ora #$20
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sta hposn_high, X
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inx
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cpx #$C0
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bne btmi
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rts
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