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159 lines
5.9 KiB
ArmAsm
159 lines
5.9 KiB
ArmAsm
;
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; Written by Groepaz/Hitmen <groepaz@gmx.net>
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; Cleanup by Ullrich von Bassewitz <uz@cc65.org>
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;
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.export ppuinit
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.export paletteinit, paldata
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.include "nes.inc"
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;+---------+----------------------------------------------------------+
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;| $2000 | PPU Control Register #1 (W) |
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;| | |
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;| | D7: Execute NMI on VBlank |
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;| | 0 = Disabled |
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;| | 1 = Enabled |
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;| | D6: PPU Master/Slave Selection --+ |
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;| | 0 = Master +-- UNUSED |
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;| | 1 = Slave --+ |
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;| | D5: Sprite Size |
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;| | 0 = 8x8 |
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;| | 1 = 8x16 |
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;| | D4: Background Pattern Table Address |
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;| | 0 = $0000 (VRAM) |
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;| | 1 = $1000 (VRAM) |
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;| | D3: Sprite Pattern Table Address |
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;| | 0 = $0000 (VRAM) |
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;| | 1 = $1000 (VRAM) |
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;| | D2: PPU Address Increment |
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;| | 0 = Increment by 1 |
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;| | 1 = Increment by 32 |
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;| | D1-D0: Name Table Address |
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;| | 00 = $2000 (VRAM) |
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;| | 01 = $2400 (VRAM) |
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;| | 10 = $2800 (VRAM) |
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;| | 11 = $2C00 (VRAM) |
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;+---------+----------------------------------------------------------+
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;+---------+----------------------------------------------------------+
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;| $2001 | PPU Control Register #2 (W) |
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;| | |
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;| | D7-D5: Full Background Colour (when D0 == 1) |
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;| | 000 = None +------------+ |
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;| | 001 = Green | NOTE: Do not use more |
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;| | 010 = Blue | than one type |
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;| | 100 = Red +------------+ |
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;| | D7-D5: Colour Intensity (when D0 == 0) |
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;| | 000 = None +--+ |
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;| | 001 = Intensify green | NOTE: Do not use more |
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;| | 010 = Intensify blue | than one type |
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;| | 100 = Intensify red +--+ |
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;| | D4: Sprite Visibility |
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;| | 0 = Sprites not displayed |
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;| | 1 = Sprites visible |
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;| | D3: Background Visibility |
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;| | 0 = Background not displayed |
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;| | 1 = Background visible |
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;| | D2: Sprite Clipping |
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;| | 0 = Sprites invisible in left 8-pixel column |
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;| | 1 = No clipping |
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;| | D1: Background Clipping |
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;| | 0 = BG invisible in left 8-pixel column |
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;| | 1 = No clipping |
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;| | D0: Display Type |
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;| | 0 = Colour display |
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;| | 1 = Monochrome display |
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;+---------+----------------------------------------------------------+
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;-----------------------------------------------------------------------------
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.segment "ONCE"
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.proc ppuinit
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lda #%10101000
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sta PPU_CTRL1
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lda #%00011110
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sta PPU_CTRL2
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; Wait for vblank
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@wait: lda PPU_STATUS
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bpl @wait
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; reset scrolling
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lda #0
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sta PPU_VRAM_ADDR1
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sta PPU_VRAM_ADDR1
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; Make all sprites invisible
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lda #$00
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ldy #$f0
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sta PPU_SPR_ADDR
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ldx #$40
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@loop: sty PPU_SPR_IO
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sta PPU_SPR_IO
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sta PPU_SPR_IO
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sty PPU_SPR_IO
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dex
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bne @loop
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rts
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.endproc
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;-----------------------------------------------------------------------------
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.proc paletteinit
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; Wait for v-blank
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@wait: lda PPU_STATUS
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bpl @wait
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lda #$3F
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sta PPU_VRAM_ADDR2
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lda #$00
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sta PPU_VRAM_ADDR2
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ldx #0
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@loop: lda paldata,x
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sta PPU_VRAM_IO
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inx
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cpx #(16*2)
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bne @loop
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rts
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.endproc
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;-----------------------------------------------------------------------------
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.rodata
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paldata:
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.repeat 2
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.byte $0f ; 0 black
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.byte $14 ; 4 violet
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.byte $3b ; 3 cyan
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.byte $3d ; 1 white
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.byte $38 ; 7 yellow
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.byte $2d ; b dark grey
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.byte $22 ; e light blue
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.byte $04 ; 2 red
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.byte $18 ; 8 orange
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.byte $08 ; 9 brown
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.byte $35 ; a light red
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.byte $01 ; 6 blue
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.byte $10 ; c middle grey
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.byte $2b ; d light green
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.byte $3d ; f light gray
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.byte $1a ; 5 green
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.endrepeat
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