User:Ddribin/PPU Sandbox: Difference between revisions

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


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; Bit 7 - INB<nowiki>:</nowiki> Intensify Blues
=== Bit 7 - INB<nowiki>:</nowiki> Intensify Blues ===


; Bit 6 - ING<nowiki>:</nowiki> Intensify Greens
=== Bit 6 - ING<nowiki>:</nowiki> Intensify Greens ===


; Bit 5 - INR<nowiki>:</nowiki> Intensify Reds
=== Bit 5 - INR<nowiki>:</nowiki> Intensify Reds ===


; Bit 4 - SRE<nowiki>:</nowiki> Sprite Render Enable
=== Bit 4 - SRE<nowiki>:</nowiki> Sprite Render Enable ===


; Bit 3 - BRE<nowiki>:</nowiki> Background Render Enable
=== Bit 3 - BRE<nowiki>:</nowiki> Background Render Enable ===


; Bit 2 - SCD<nowiki>:</nowiki> Sprite Clip Disable
=== Bit 2 - SCD<nowiki>:</nowiki> Sprite Clip Disable ===


; Bit 1 - BCD<nowiki>:</nowiki> Background Clip Disable
=== Bit 1 - BCD<nowiki>:</nowiki> Background Clip Disable ===
 
; Bit 0 - GRYE<nowiki>:</nowiki> Grayscale Enable


=== Bit 0 - GRYE<nowiki>:</nowiki> Grayscale Enable ===


== PPUSTATUS ==
== PPUSTATUS ==

Revision as of 14:40, 26 December 2009

PPU Register Overview

Address Register Name (Alt. Name?) Function
$2000 PPUCTRL PPUCR PPU Control Register
$2001 PPUMASK PPUMR PPU Mask Register
$2002 PPUSTATUS PPUSR PPU Status Register
$2003 OAMADDR OAMAR OAM Address Register
$2004 OAMDATA OAMDR OAM Data Register
$2005 PPUSCROLL PPUSCR PPU Scroll Register
$2006 PPUADDR PPUAR PPU Address Register
$2007 PPUDATA PPUDR PPU Data Register
$4014 OAMDMA OAMDMA OAM DMA

PPUCTRL: PPU Control Register

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 NMI 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)

PPUMASK: PPU Mask Register

Bit 7 6 5 4 3 2 1 0
$2001 INB ING INR SRE BRE SCD BCD GRYE
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

Bit 6 - ING: Intensify Greens

Bit 5 - INR: Intensify Reds

Bit 4 - SRE: Sprite Render Enable

Bit 3 - BRE: Background Render Enable

Bit 2 - SCD: Sprite Clip Disable

Bit 1 - BCD: Background Clip Disable

Bit 0 - GRYE: Grayscale Enable

PPUSTATUS

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
        ppuctrl := $2000
        ppumask := $2001
        ppustatus := $2002
        oamaddr := $2003
        oamdata := $2004
        ppuscroll := $2005
        ppuaddr := $2006
        ppuaddr := $2007
        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_gry = bit2mask(0)

        ppustatus_vbl = bit2mask(7)
        ppustatus_s0h = bit2mask(6)
        ppustatus_sov = bit2mask(5)