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cc65/libsrc/apple2/revers.s
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378 B
ArmAsm

;;
;; Kevin Ruland
;;
;; unsigned char __fastcall__ revers (unsigned char onoff)
;;
.export _revers
.include "apple2.inc"
_revers:
ldy TEXTTYP ; Stash old value
and #$FF ; Test for any bit
bne reverse ; Nothing set
lda #$FF
reverse:
ora #$3F
sta TEXTTYP
tya ; What was the old value?
eor #$FF ; Normal = $FF, Reverse = $3F
beq L2
lda #01
L2:
rts