; Atari 7800 image viewer -- programs MARIA, then holds.
;
; MARIA DMAs the display-list list (DLL), the per-line display lists (DLs) and the
; bitmap straight out of cartridge ROM, so the viewer only loads MARIA's colour
; registers, points it at the DLL, turns DMA on, and loops.  MARIA registers live
; in zero page ($20-$3F).
;
; #defines from viewer/assemble.py --
;   SCRIPT   address of the colour register script -- (reg, value) byte pairs
;            written as $0000+reg = value, terminated by $FF
;   DLL      address of the display-list list

        * = $4000

reset:
        sei
        cld
        ldx #$ff
        txs
        lda #$00
        sta $3c                 ; CTRL = 0 -- DMA off while we set up

        ; ---- load MARIA colour registers from the script ----
        ldx #$00
sloop:
        lda SCRIPT,x
        cmp #$ff
        beq sdone
        tay                     ; Y = MARIA register ($20..$3F)
        inx
        lda SCRIPT,x
        sta $0000,y
        inx
        jmp sloop
sdone:
        ; ---- point MARIA at the display-list list ----
        lda #>DLL
        sta $2c                 ; DPPH
        lda #<DLL
        sta $30                 ; DPPL

        ; ---- enable DMA (160A, no DLI) ----
        lda #$40
        sta $3c                 ; CTRL

loop:
        jmp loop                ; the packer fills the reset vectors at $FFFA