;; Fill display with $FF

LDA $00 ; Start of display
STO $21 ; Pixel index

; store the $FF that we'll use to fill the screen
LDA $FF
STO $22

@copy-to-display
  LDA ($22) ; A = mem[$22] = $FF
  STO ($21) ; mem[mem[$21]] = A = $FF

; increment pixel index
LDA ($21)
ADD $01
STO $21

; if CF is set, then the display is full and we're done
FHP 0
  JMP @copy-to-display

END