Fixed and improved some pce comments.

[cc65] / libsrc / pce / revers.s

diff --git a/libsrc/pce/revers.s b/libsrc/pce/revers.s
index d1358a52be188937af71f2c858cf46c0d1d5e0d6..b31ff150c306e32800589374ed3529f45a7900f4 100644 (file)
--- a/libsrc/pce/revers.s
+++ b/libsrc/pce/revers.s
@@ -1,5 +1,24 @@
+;
+; Ullrich von Bassewitz, 07.08.1998
+;
+; unsigned char revers (unsigned char onoff);
+;
 
-    .export _revers
-_revers:
-    lda #0
-    rts     
+        .export         _revers
+
+        .include        "extzp.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