  sta (temp_ptr_z),y
  lda (temp_ptr_y),y ; copy colour
  sta (temp_ptr_w),y
  dey
  bpl @scroll_one_char
  cpx scroll_region_end         ; last line?
  bne @scroll_one_line         ; no -> go on
  jsr erase_line_by_vector       ; del last line
  
  rts
  

scroll_down_scrollregion:
  ldx scroll_region_end     ; get last line
@scroll_one_line:
  jsr set_line_vectors
  lda temp_ptr_x ; screen line
  ldy temp_ptr_x+1
  sta temp_ptr_z
  sty temp_ptr_z+1
  lda temp_ptr_y ; colour line
  ldy