User:Ddribin/PPU Sandbox: Difference between revisions

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|-
|-
! $2000
! $2000
| NMI || MSS || SSZ || BPT || SPT || VDN || NTA1 || NTA0
| NMIE || MSE || SSZ || BPT || SPT || VDN || NTA1 || NTA0
|-
|-
! Read/Write
! Read/Write
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|}
|}


; Bit 7 - NMI<nowiki>:</nowiki> NMI Enable
; 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 - MSS<nowiki>:</nowiki> Master/Slave Enable
; Bit 6 - MSE<nowiki>:</nowiki> Master/Slave Enable
Has no effect on the NES.
Has no effect on the NES.


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|-
|-
! $2001
! $2001
| INB || ING || INR || SPR || BGR || SPC || BGC || GRY
| INB || ING || INR || SRE || BRE || SCD || BCD || GRY
|-
|-
! Read/Write
! Read/Write
Line 81: Line 81:
; Bit 5 - INR<nowiki>:</nowiki> Intensify Reds
; Bit 5 - INR<nowiki>:</nowiki> Intensify Reds


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


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


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


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


; Bit 0 - GRY<nowiki>:</nowiki> Grayscale Enable
; Bit 0 - GRY<nowiki>:</nowiki> Grayscale Enable
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         ppumask        := $2001
         ppumask        := $2001


         ppuctrl_nmi = bit2mask(7)
         ppuctrl_nmie = bit2mask(7)
         ppuctrl_mss = bit2mask(6)
         ppuctrl_mse = bit2mask(6)
         ppuctrl_ssz = bit2mask(5)
         ppuctrl_ssz = bit2mask(5)
         ppuctrl_bpt = bit2mask(4)
         ppuctrl_bpt = bit2mask(4)
Line 118: Line 118:
         ppumask_ing = bit2mask(6)
         ppumask_ing = bit2mask(6)
         ppumask_inr = bit2mask(5)
         ppumask_inr = bit2mask(5)
         ppumask_spr = bit2mask(4)
         ppumask_sre = bit2mask(4)
         ppumask_bgr = bit2mask(3)
         ppumask_bre = bit2mask(3)
         ppumask_spc = bit2mask(2)
         ppumask_scd = bit2mask(2)
         ppumask_bgc = bit2mask(1)
         ppumask_bcd = bit2mask(1)
         ppumask_gry = bit2mask(0)
         ppumask_gry = bit2mask(0)
</pre>
</pre>

Revision as of 04:07, 26 December 2009

PPU Register Overview

Address Register Function
$2000 PPUCTRL PPU Control Register
$2001 PPUMASK PPU Mask Register
$2002 PPUSTATUS PPU Status Register

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 X X X X X X X X
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
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)

PPUSTATUS - The PPU Status Register

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

CA65 Definitions

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

        ;; PPU Registers
        ppuctrl         := $2000
        ppumask         := $2001

        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)
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