aboutsummaryrefslogtreecommitdiff
path: root/conio/revers.s
blob: a04a96932541331d2d74f9deccc15051958e6f7d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
;
; Ullrich von Bassewitz, 07.08.1998

; modified version for taipan, which doesn't actually
; call revers() any more. only _revflag is needed, see
; rvs_on() and rvs_off() in console.s.

;
; unsigned char revers (unsigned char onoff);
;
        .include "atari.inc"
        
;        .export         _revers
        .export         _revflag

;_revers:
;        ldx     #$00            ; Assume revers off
;        tay                     ; Test onoff
;        beq     L1              ; Jump if off
;        ldx     #$80            ; Load on value
;L1:     ldy     #$00            ; Assume old value is zero
;        lda     _revflag        ; Load old value
;        stx     _revflag        ; 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

        .bss

_revflag:
        .res    1