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;
; Ullrich von Bassewitz, 07.08.1998
;
; unsigned char revers (unsigned char onoff);
;
.include "atari.inc"
.export _revers
.export _revflag
_revers:
ldx #$00 ; Assume revers off
tay ; Test onoff
beq L1 ; Jump if off
ldx #$80 ; Load on value
L1: ldy #$00 ; Assume old value is zero
lda _revflag ; Load old value
stx _revflag ; Set new value
beq L2 ; Jump if old value zero
iny ; Make old value = 1
L2: ldx #$00 ; Load high byte of result
tya ; Load low byte, set CC
rts
.bss
_revflag:
.res 1
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