; Commodore PET screen viewer (6502).  Copies PAGES*256 bytes of precomputed
; screen codes from DATA into the PET screen RAM at $8000, then loops.  The PET
; video hardware continuously displays $8000 as text, so the picture stays up.
;
; #defines from viewer/assemble.py --  DATA = source address, PAGES = 256-byte
; pages to copy (4 for 40-col / 1000 bytes, 8 for 80-col / 2000 bytes).

        * = $0420

src = $fb
dst = $fd

start:
        lda #<DATA
        sta src
        lda #>DATA
        sta src+1
        lda #$00
        sta dst
        lda #$80
        sta dst+1               ; dest = $8000 (screen RAM)
        ldx #PAGES
        ldy #$00
cp:
        lda (src),y
        sta (dst),y
        iny
        bne cp
        inc src+1
        inc dst+1
        dex
        bne cp
hang:
        jmp hang