git.sur5r.net Git - cc65/blob - libsrc/nes/ppu.s

   1 ;
   2 ; Written by Groepaz/Hitmen <groepaz@gmx.net>
   3 ; Cleanup by Ullrich von Bassewitz <uz@cc65.org>
   4 ;
   5
   6         .export ppuinit
   7         .export paletteinit, paldata
   8
   9         .include "nes.inc"
  10
  11 ;+---------+----------------------------------------------------------+
  12 ;|  $2000  | PPU Control Register #1 (W)                              |
  13 ;|         |                                                          |
  14 ;|         |    D7: Execute NMI on VBlank                             |
  15 ;|         |           0 = Disabled                                   |
  16 ;|         |           1 = Enabled                                    |
  17 ;|         |    D6: PPU Master/Slave Selection --+                    |
  18 ;|         |           0 = Master                +-- UNUSED           |
  19 ;|         |           1 = Slave               --+                    |
  20 ;|         |    D5: Sprite Size                                       |
  21 ;|         |           0 = 8x8                                        |
  22 ;|         |           1 = 8x16                                       |
  23 ;|         |    D4: Background Pattern Table Address                  |
  24 ;|         |           0 = $0000 (VRAM)                               |
  25 ;|         |           1 = $1000 (VRAM)                               |
  26 ;|         |    D3: Sprite Pattern Table Address                      |
  27 ;|         |           0 = $0000 (VRAM)                               |
  28 ;|         |           1 = $1000 (VRAM)                               |
  29 ;|         |    D2: PPU Address Increment                             |
  30 ;|         |           0 = Increment by 1                             |
  31 ;|         |           1 = Increment by 32                            |
  32 ;|         | D1-D0: Name Table Address                                |
  33 ;|         |         00 = $2000 (VRAM)                                |
  34 ;|         |         01 = $2400 (VRAM)                                |
  35 ;|         |         10 = $2800 (VRAM)                                |
  36 ;|         |         11 = $2C00 (VRAM)                                |
  37 ;+---------+----------------------------------------------------------+
  38 ;+---------+----------------------------------------------------------+
  39 ;|  $2001  | PPU Control Register #2 (W)                              |
  40 ;|         |                                                          |
  41 ;|         | D7-D5: Full Background Colour (when D0 == 1)             |
  42 ;|         |         000 = None  +------------+                       |
  43 ;|         |         001 = Green              | NOTE: Do not use more |
  44 ;|         |         010 = Blue               |       than one type   |
  45 ;|         |         100 = Red   +------------+                       |
  46 ;|         | D7-D5: Colour Intensity (when D0 == 0)                   |
  47 ;|         |         000 = None            +--+                       |
  48 ;|         |         001 = Intensify green    | NOTE: Do not use more |
  49 ;|         |         010 = Intensify blue     |       than one type   |
  50 ;|         |         100 = Intensify red   +--+                       |
  51 ;|         |    D4: Sprite Visibility                                 |
  52 ;|         |           0 = Sprites not displayed                      |
  53 ;|         |           1 = Sprites visible                            |
  54 ;|         |    D3: Background Visibility                             |
  55 ;|         |           0 = Background not displayed                   |
  56 ;|         |           1 = Background visible                         |
  57 ;|         |    D2: Sprite Clipping                                   |
  58 ;|         |           0 = Sprites invisible in left 8-pixel column   |
  59 ;|         |           1 = No clipping                                |
  60 ;|         |    D1: Background Clipping                               |
  61 ;|         |           0 = BG invisible in left 8-pixel column        |
  62 ;|         |           1 = No clipping                                |
  63 ;|         |    D0: Display Type                                      |
  64 ;|         |           0 = Colour display                             |
  65 ;|         |           1 = Monochrome display                         |
  66 ;+---------+----------------------------------------------------------+
  67
  68
  69 ;-----------------------------------------------------------------------------
  70
  71 .segment        "ONCE"
  72
  73 .proc   ppuinit
  74
  75         lda     #%10101000
  76         sta     PPU_CTRL1
  77
  78         lda     #%00011110
  79         sta     PPU_CTRL2
  80
  81 ; Wait for vblank
  82
  83 @wait:  lda     PPU_STATUS
  84         bpl     @wait
  85
  86 ; reset scrolling
  87
  88         lda     #0
  89         sta     PPU_VRAM_ADDR1
  90         sta     PPU_VRAM_ADDR1
  91
  92 ; Make all sprites invisible
  93
  94         lda     #$00
  95         ldy     #$f0
  96         sta     PPU_SPR_ADDR
  97         ldx     #$40
  98 @loop:  sty     PPU_SPR_IO
  99         sta     PPU_SPR_IO
 100         sta     PPU_SPR_IO
 101         sty     PPU_SPR_IO
 102         dex
 103         bne     @loop
 104
 105         rts
 106
 107 .endproc
 108
 109 ;-----------------------------------------------------------------------------
 110
 111 .proc   paletteinit
 112
 113 ; Wait for v-blank
 114 @wait:  lda     PPU_STATUS
 115         bpl     @wait
 116
 117         lda     #$3F
 118         sta     PPU_VRAM_ADDR2
 119         lda     #$00
 120         sta     PPU_VRAM_ADDR2
 121
 122         ldx     #0
 123 @loop:  lda     paldata,x
 124         sta     PPU_VRAM_IO
 125         inx
 126         cpx     #(16*2)
 127         bne     @loop
 128
 129         rts
 130
 131 .endproc
 132
 133 ;-----------------------------------------------------------------------------
 134
 135 .rodata
 136
 137 paldata:
 138         .repeat 2
 139         .byte   $0f     ; 0 black
 140         .byte   $14     ; 4 violett
 141         .byte   $3b     ; 3 cyan
 142         .byte   $3d     ; 1 white
 143
 144         .byte   $38     ; 7 yellow
 145         .byte   $2d     ; b dark grey
 146         .byte   $22     ; e light blue
 147         .byte   $04     ; 2 red
 148
 149         .byte   $18     ; 8 orange
 150         .byte   $08     ; 9 brown
 151         .byte   $35     ; a light red
 152         .byte   $01     ; 6 blue
 153
 154         .byte   $10     ; c middle grey
 155         .byte   $2b     ; d light green
 156         .byte   $3d     ; f light gray
 157         .byte   $1a     ; 5 green
 158         .endrepeat