User:Ddribin/PPU Sandbox: Difference between revisions

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! Address !! Name !! (Alt. Names?) !! Function
! Address !! Name !! (Alt. Names?) !! Function
|-
|-
| $2000 || [[#PPUCTRL|PPUCTRL]] || PPUCR PCR ||  PPU Control Register
| $2000 || [[#PPUCR1|PPUCR1]] || PPUCTRL PCR ||  PPU Control Register 1
|-
|-
| $2001 || [[#PPUMASK|PPUMASK]] || PPUMR  PMR || PPU Mask Register
| $2001 || [[#PPUCR1|PPUCR2]] || PPUMASK PPUMR  PMR || PPU Control Register 2
|-
|-
| $2002 || [[#PPUSTATUS|PPUSTATUS]] || PPUSR PSR || PPU Status Register
| $2002 || [[#PPUSR|PPUSR]] || PPUSTATUS PSR || PPU Status Register
|-
|-
| $2003 || OAMADDR || OAMAR OAR || OAM Address Register
| $2003 || OAMAR || OAMADDR OAR || OAM Address Register
|-
|-
| $2004 || OAMDATA || OAMDR  ODR || OAM Data Register
| $2004 || OAMDR || OAMDATA ODR || OAM Data Register
|-
|-
| $2005 || PPUSCROLL || PPUSCR PSCR || PPU Scroll Register
| $2005 || PPUSCR || PPUSCROLL PSCR || PPU Scroll Register
|-  
|-  
| $2006 || PPUADDR || PPUAR PAR || PPU Address Register
| $2006 || PPUAR || PPUADDR PAR || PPU Address Register
|-
|-
| $2007 || PPUDATA || PPUDR PDR || PPU Data Register
| $2007 || PPUDR || PPUDATA PDR || PPU Data Register
|-
|-
| $4014 || OAMDMA || ODMA || OAM DMA
| $4014 || OAMDMA || ODMA || OAM DMA
|}
|}


== <span id="PPUCTRL">PPUCTRL</span>: PPU Control Register ==
== <span id="PPUCR1">PPUCR1</span>: PPU Control Register 1 ==


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|}
|}


== <span id="PPUMASK">PPUMASK</span>: PPU Mask Register ==
== <span id="PPUCR2">PPUCR2</span>: PPU Control Register 2 ==


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=== Bit 1 - BCD<nowiki>:</nowiki> Background Clip Disable ===
=== Bit 1 - BCD<nowiki>:</nowiki> Background Clip Disable ===


Control background in leftmost 8 pixels of screen (0: clip; 1: display).
Control background clipping in leftmost 8 pixels of screen (0: clip; 1: display).


=== Bit 0 - GSE<nowiki>:</nowiki> Grayscale Enable ===
=== Bit 0 - GSE<nowiki>:</nowiki> Grayscale Enable ===
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0: normal color; 1: AND all palette entries with 0x30, effectively producing a monochrome display; note that colour emphasis STILL works when this is on!
0: normal color; 1: AND all palette entries with 0x30, effectively producing a monochrome display; note that colour emphasis STILL works when this is on!


== <span id="PPUSTATUS">PPUSTATUS</span>: PPU Status Register ==
== <span id="PPUSR">PPUSR</span>: PPU Status Register ==


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         ;; PPU Registers
         ;; PPU Registers
         ppuctrl := $2000
         ppucr1 := $2000
         ppumask := $2001
         nmie = bit2mask(7)
         ppustatus := $2002
        mse  = bit2mask(6)
        ssz  = bit2mask(5)
        bpt  = bit2mask(4)
        spt  = bit2mask(3)
        vdn  = bit2mask(2)
        nta1 = bit2mask(1)
        nta0 = bit2mask(0)
 
        nta_2000 = bits2mask(%00, nta0)
        nta_2400 = bits2mask(%01, nta0)
        nta_2800 = bits2mask(%10, nta0)
        nta_2c00 = bits2mask(%11, nta0)
 
        ppucr2 := $2001
         inb = bit2mask(7)
        ing = bit2mask(6)
        inr = bit2mask(5)
        sre = bit2mask(4)
        bre = bit2mask(3)
        scd = bit2mask(2)
        bcd = bit2mask(1)
        gse= bit2mask(0)
 
        ppusr := $2002
        vbl = bit2mask(7)
        s0h = bit2mask(6)
        sov = bit2mask(5)
 
         oamaddr := $2003
         oamaddr := $2003
         oamdata := $2004
         oamdata := $2004
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         ppuaddr := $2007
         ppuaddr := $2007
         oamdma := $4014
         oamdma := $4014
        ppuctrl_nmie = bit2mask(7)
        ppuctrl_mse = bit2mask(6)
        ppuctrl_ssz = bit2mask(5)
        ppuctrl_bpt = bit2mask(4)
        ppuctrl_spt = bit2mask(3)
        ppuctrl_vdn = bit2mask(2)
        ppuctrl_nta1 = bit2mask(1)
        ppuctrl_nta0 = bit2mask(0)
        ppuctrl_nta_2000 = bits2mask(%00, ppuctrl_nta0)
        ppuctrl_nta_2400 = bits2mask(%01, ppuctrl_nta0)
        ppuctrl_nta_2800 = bits2mask(%10, ppuctrl_nta0)
        ppuctrl_nta_2c00 = bits2mask(%11, ppuctrl_nta0)
       
        ppumask_inb = bit2mask(7)
        ppumask_ing = bit2mask(6)
        ppumask_inr = bit2mask(5)
        ppumask_sre = bit2mask(4)
        ppumask_bre = bit2mask(3)
        ppumask_scd = bit2mask(2)
        ppumask_bcd = bit2mask(1)
        ppumask_gse= bit2mask(0)
        ppustatus_vbl = bit2mask(7)
        ppustatus_s0h = bit2mask(6)
        ppustatus_sov = bit2mask(5)
</pre>
</pre>

Latest revision as of 22:09, 5 December 2010

PPU Register Overview

The PPU exposes only eight memory-mapped registers to the CPU. These nominally sit at $2000 through $2007 in the CPU's address space, but because they're incompletely decoded, they're mirrored in every 8 bytes from $2008 through $3FFF, so a write to $3456 is the same as a write to $2006.

PPU Registers
Address Name (Alt. Names?) Function
$2000 PPUCR1 PPUCTRL PCR PPU Control Register 1
$2001 PPUCR2 PPUMASK PPUMR PMR PPU Control Register 2
$2002 PPUSR PPUSTATUS PSR PPU Status Register
$2003 OAMAR OAMADDR OAR OAM Address Register
$2004 OAMDR OAMDATA ODR OAM Data Register
$2005 PPUSCR PPUSCROLL PSCR PPU Scroll Register
$2006 PPUAR PPUADDR PAR PPU Address Register
$2007 PPUDR PPUDATA PDR PPU Data Register
$4014 OAMDMA ODMA OAM DMA

PPUCR1: PPU Control Register 1

Bit 7 6 5 4 3 2 1 0
$2000 NMIE MSE SSZ BPT SPT VDN NTA1 NTA0
Read/Write W W W W W W W W
Initial Value 0 X 0 0 0 0 0 0

Bit 7 - NMIE: NMI Enable

Setting NMIE to one causes an NMI to be generated at the start of the vertical blanking interval.

Bit 6 - MSE: Master/Slave Enable

Has no effect on the NES.

Bit 5 - SSZ: Sprite Size

0: 8x8; 1: 8x16

Bit 4 - BPT: Background Pattern Table

Background pattern table address (0: $0000; 1: $1000)

Bit 3 - SPT: Sprite Pattern Table

Sprite pattern table address for 8x8 sprites (0: $0000; 1: $1000)

Bit 2 - VDN: VRAM Increment Down

VRAM address increment per CPU read/write of PPUDATA (0: increment by 1, going across; 1: increment by 32, going down)

Bits 1, 0 - NTA1 and NTA0: Base Nametable Address 1 and 0

NTA1 NTA0 Base VRAM Address
0 0 $2000 (Nametable 0)
0 1 $2400 (Nametable 1)
1 0 $2800 (Nametable 2)
1 1 $2C00 (Nametable 3)

PPUCR2: PPU Control Register 2

Bit 7 6 5 4 3 2 1 0
$2001 INB ING INR SRE BRE SCD BCD GSE
Read/Write W W W W W W W W
Initial Value 0 0 0 0 0 X X 0

Bit 7 - INB: Intensify Blues

Intensify blues and darken other colors.

Bit 6 - ING: Intensify Greens

Intensify greens and darken other colors.

Bit 5 - INR: Intensify Reds

Intensify reds and darken other colors.

Bit 4 - SRE: Sprite Render Enable

Enable sprite rendering.

Bit 3 - BRE: Background Render Enable

Enable background rendering.

Bit 2 - SCD: Sprite Clip Disable

Control sprite clipping in leftmost 8 pixels of screen (0: clip; 1: display).

Bit 1 - BCD: Background Clip Disable

Control background clipping in leftmost 8 pixels of screen (0: clip; 1: display).

Bit 0 - GSE: Grayscale Enable

0: normal color; 1: AND all palette entries with 0x30, effectively producing a monochrome display; note that colour emphasis STILL works when this is on!

PPUSR: PPU Status Register

Bit 7 6 5 4 3 2 1 0
$2002 VBL S0H SOV --- --- --- --- ---
Read/Write R R R R R R R R
Initial Value X 0 X X X X X X

Bit 7 - VBL: Vertical Blank

Bit 6 - S0H: Sprite 0 Hit

Bit 5 - SOV: Sprite Overflow

Bits 4..0 - Res: Reserved

CA65 Definitions

.define bit2mask(bitnum) (1 << bitnum)
.define bits2mask(bits, bitnum) (bits << bitnum)

        ;; PPU Registers
        ppucr1 := $2000
        nmie = bit2mask(7)
        mse  = bit2mask(6)
        ssz  = bit2mask(5)
        bpt  = bit2mask(4)
        spt  = bit2mask(3)
        vdn  = bit2mask(2)
        nta1 = bit2mask(1)
        nta0 = bit2mask(0)

        nta_2000 = bits2mask(%00, nta0)
        nta_2400 = bits2mask(%01, nta0)
        nta_2800 = bits2mask(%10, nta0)
        nta_2c00 = bits2mask(%11, nta0)

        ppucr2 := $2001
        inb = bit2mask(7)
        ing = bit2mask(6)
        inr = bit2mask(5)
        sre = bit2mask(4)
        bre = bit2mask(3)
        scd = bit2mask(2)
        bcd = bit2mask(1)
        gse= bit2mask(0)

        ppusr := $2002
        vbl = bit2mask(7)
        s0h = bit2mask(6)
        sov = bit2mask(5)

        oamaddr := $2003
        oamdata := $2004
        ppuscroll := $2005
        ppuaddr := $2006
        ppuaddr := $2007
        oamdma := $4014
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