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cc65/libsrc/pce/revers.s

24 lines
529 B
ArmAsm

;
; 1998-08-07, Ullrich von Bassewitz
; 2015-11-23, Greg King
;
; unsigned char __fastcall__ revers (unsigned char onoff);
;
.export _revers
.importzp RVS
.proc _revers
cmp #$01 ; False or true?
cla
ror a ; Either $00 or $80
ldy RVS ; Load old value
sta RVS ; Set new value
tya
asl a
rol a ; Either $00 or $01
clx
rts
.endproc