2 ; 1998-08-07, Ullrich von Bassewitz
3 ; 2015-11-23, Greg King
5 ; unsigned char __fastcall__ revers (unsigned char onoff);
13 cmp #$01 ; False or true?
15 ror a ; Either $00 or $80
16 ldy RVS ; Load old value
17 sta RVS ; Set new value
20 rol a ; Either $00 or $01