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Update revers.s

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Stefan 2019-11-19 19:23:31 +01:00 committed by Oliver Schmidt
parent 2c34723a97
commit eeefd10f8f
1 changed files with 1 additions and 27 deletions
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28
libsrc/c16/revers.s
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@ -1,27 +1 @@
;
; Ullrich von Bassewitz, 07.08.1998
;
; unsigned char revers (unsigned char onoff);
;
.export _revers
.include "plus4.inc"
.proc _revers
ldx #$00 ; Assume revers off
tay ; Test onoff
beq L1 ; Jump if off
ldx #$80 ; Load on value
ldy #$00 ; Assume old value is zero
L1: lda RVS ; Load old value
stx RVS ; 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
.endproc
.include "../plus4/revers.s"