.include "validation.a"
      .include "ppu_sync.a"
      
      .default palette = default_palette
      .default tiles = default_tiles

      .code
begin_ppu_test:
      lda   #40
      jsr   delay_msec
      jsr   wait_vbl
      jsr   disable_ppu
      jsr   clear_vram
      jsr   clear_sprites
      rts
      
      .code
default_palette:
      .db   $0f,$01,$02,$39
      .db   $0f,$03,$04,$38
      .db   $0f,$05,$06,$38
      .db   $0f,$11,$12,$38
      
      .db   $0f,$32,$32,$21
      .db   $0f,$32,$32,$32
      .db   $0f,$32,$32,$32
      .db   $0f,$32,$32,$32

      .code
default_tiles:
      .db   $00,$00,$00,$00,$00,$00,$00,$00
      .db   $00,$00,$00,$00,$00,$00,$00,$00

      .db   $ff,$ff,$ff,$ff,$ff,$ff,$ff,$ff
      .db   $ff,$ff,$ff,$ff,$ff,$ff,$ff,$ff

      .db   $f0,$0f,$f0,$0f,$f0,$0f,$f0,$0f
      .db   $f0,$0f,$f0,$0f,$f0,$0f,$f0,$0f
      
      .db   $80,$00,$00,$00,$00,$00,$00,$00
      .db   $80,$00,$00,$00,$00,$00,$00,$00
      
      .db   $81,$00,$00,$00,$00,$00,$00,$81
      .db   $81,$00,$00,$00,$00,$00,$00,$81
      .code

clear_palette:
      jsr   wait_vbl
      lda   #$3f
      jsr   set_vpage
      lda   #$0f
      ldx   #$20
:     sta   $2007
      dex
      bne   -
      rts
      .code

; A = # of tiles
load_tiles:
      asl   a
      asl   a
      asl   a
      asl   a
      tax
      jsr   wait_vbl
      lda   #0
      jsr   set_vpage
      ldy   #0
:     lda   tiles,y
      sta   $2007
      iny
      dex
      bne   -
      rts
      .code
      
load_test_chr:
      jsr   wait_vbl
      lda   #0
      jsr   set_vpage
      ldy   #0
:     lda   tiles,y
      sta   $2007
      iny
      cpy   #$40
      bne   -
      rts
      .code

load_palette:
      lda   #$3f
      jsr   set_vpage
      ldy   #0
:     lda   palette,y
      sta   $2007
      iny
      cpy   #$20
      bne   -
      rts
      .code

load_graphics:
      jsr   wait_vbl
      jsr   load_palette
      jsr   load_test_chr
      jsr   clear_nametable
      rts
      .code

; Find first byte in VRAM which doesn't match A.
; Address is Y * $100 + X
find_changed_vram:
      pha
      lda   #0
      jsr   set_vpage
      bit   $2007
      pla
      ldx   #0
      ldy   #0
:     cmp   $2007
      bne   found
      inx
      bne   -
      iny
      cpy   #$24
      bne   -
found:
      rts