mirror of https://github.com/cc65/cc65.git
28 lines
771 B
ArmAsm
28 lines
771 B
ArmAsm
;
|
|
; Ullrich von Bassewitz, 07.08.1998
|
|
;
|
|
; unsigned char revers (unsigned char onoff);
|
|
;
|
|
|
|
.export _revers
|
|
|
|
.include "vic20.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
|
|
|