1
0
mirror of https://github.com/cc65/cc65.git synced 2024-10-31 20:06:11 +00:00
cc65/libsrc/atmos/revers.s

38 lines
949 B
ArmAsm
Raw Normal View History

;
; Ullrich von Bassewitz, 07.08.1998
;
; unsigned char revers (unsigned char onoff);
;
.export _revers
.export rvs
; ------------------------------------------------------------------------
;
.code
.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
; ------------------------------------------------------------------------
;
.bss
rvs: .res 1