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23 lines
726 B
ArmAsm
23 lines
726 B
ArmAsm
;
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; Ullrich von Bassewitz, 2005-03-28
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;
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; unsigned char __fastcall__ revers (unsigned char onoff)
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;
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.export _revers
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.include "apple2.inc"
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_revers:
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tax ; Test onoff
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beq normal ; If zero, "normal" must be set
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ldx #$3F+1 ; Set "inverse"
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normal: dex ; $00->$FF, $40->$3F
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lda #$00 ; Preload return code for "normal"
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ldy INVFLG ; Load current flag value
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stx INVFLG ; Save new flag value
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bmi :+ ; Jump if current value is $FF (normal)
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lda #$01 ; Return "inverse"
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: ldx #$00
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rts
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