User:Ddribin/PPU Sandbox: Difference between revisions
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=== Bit 7 - NMIE<nowiki>:</nowiki> NMI Enable === | |||
Setting NMI to one causes an NMI to be generated at the start of the vertical blanking interval | Setting NMI to one causes an NMI to be generated at the start of the vertical blanking interval | ||
=== Bit 6 - MSE<nowiki>:</nowiki> Master/Slave Enable === | |||
Has no effect on the NES. | Has no effect on the NES. | ||
=== Bit 5 - SSZ<nowiki>:</nowiki> Sprite Size === | |||
0: 8x8; 1: 8x16 | 0: 8x8; 1: 8x16 | ||
=== Bit 4 - BPT<nowiki>:</nowiki> Background Pattern Table === | |||
Background pattern table address (0: $0000; 1: $1000) | Background pattern table address (0: $0000; 1: $1000) | ||
=== Bit 3 - SPT<nowiki>:</nowiki> Sprite Pattern Table === | |||
Sprite pattern table address for 8x8 sprites (0: $0000; 1: $1000) | Sprite pattern table address for 8x8 sprites (0: $0000; 1: $1000) | ||
=== Bit 2 - VDN<nowiki>:</nowiki> VRAM Increment Down === | |||
VRAM address increment per CPU read/write of PPUDATA (0: increment by 1, going across; 1: increment by 32, going 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<nowiki>:</nowiki> Base Nametable Address 1 and 0 === | |||
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Revision as of 14:31, 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
| 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)
