mp #$c0
  bcc :+
  jmp end_plot_char   ; no output
; --- $a0-$bf ---   C=(latin-1) chars
:       
  cmp #$a0
  bcc :+
  sbc #$40    ; SC = PET - $40
  jmp @check_for_reverse
; --- $80-$9f ---   - illegal -
:       
  cmp #$80
  bcc :+
  jmp end_plot_char   ; no output
; --- $60-$7f ---  kapital letters        
:
  cmp #$60
  bcc :+
  sbc #$20    ; SC = PET - $20
  jmp @check_for_reverse
; --- $40-$5f ---  small letters
:
  cmp #$40
  bcc :+        
  sbc #$40    ; SC = PET - $40
  j