4 ; unsigned char __fastcall__ revers (unsigned char onoff)
12 ldy INVFLG ; Stash old value
13 and #$FF ; Test for any bit
14 beq normal ; Nothing set
15 lda #~$3F ; Not Inverse
16 normal: eor #$FF ; Xor Normal
18 tya ; What was the old value?
19 eor #$FF ; Normal = $FF, Inverse = $3F