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620 lines
18 KiB
C++
620 lines
18 KiB
C++
#include "stdafx.h"
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#include "PPU.h"
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#include "CPU.h"
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IVideoDevice *PPU::VideoDevice = nullptr;
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uint32_t PPU_PALETTE_RGB[] = {
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0x666666, 0x002A88, 0x1412A7, 0x3B00A4, 0x5C007E,
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0x6E0040, 0x6C0600, 0x561D00, 0x333500, 0x0B4800,
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0x005200, 0x004F08, 0x00404D, 0x000000, 0x000000,
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0x000000, 0xADADAD, 0x155FD9, 0x4240FF, 0x7527FE,
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0xA01ACC, 0xB71E7B, 0xB53120, 0x994E00, 0x6B6D00,
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0x388700, 0x0C9300, 0x008F32, 0x007C8D, 0x000000,
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0x000000, 0x000000, 0xFFFEFF, 0x64B0FF, 0x9290FF,
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0xC676FF, 0xF36AFF, 0xFE6ECC, 0xFE8170, 0xEA9E22,
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0xBCBE00, 0x88D800, 0x5CE430, 0x45E082, 0x48CDDE,
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0x4F4F4F, 0x000000, 0x000000, 0xFFFEFF, 0xC0DFFF,
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0xD3D2FF, 0xE8C8FF, 0xFBC2FF, 0xFEC4EA, 0xFECCC5,
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0xF7D8A5, 0xE4E594, 0xCFEF96, 0xBDF4AB, 0xB3F3CC,
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0xB5EBF2, 0xB8B8B8, 0x000000, 0x000000,
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};
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PPU::PPU(MemoryManager *memoryManager)
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{
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_memoryManager = memoryManager;
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_state = {};
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_flags = {};
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_statusFlags = {};
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memset(_spriteRAM, 0xFF, 0x100);
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_outputBuffer = new uint8_t[256 * 240 * 4];
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}
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PPU::~PPU()
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{
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delete[] _outputBuffer;
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}
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bool PPU::CheckFlag(PPUControlFlags flag)
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{
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return false;
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}
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void PPU::UpdateVideoRamAddr()
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{
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if(_scanline >= 239 || !IsRenderingEnabled()) {
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_state.VideoRamAddr += _flags.VerticalWrite ? 32 : 1;
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} else {
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//"During rendering (on the pre-render line and the visible lines 0-239, provided either background or sprite rendering is enabled), "
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//it will update v in an odd way, triggering a coarse X increment and a Y increment simultaneously"
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IncHorizontalScrolling();
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IncVerticalScrolling();
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}
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}
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uint8_t PPU::ReadRAM(uint16_t addr)
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{
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uint8_t returnValue;
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switch(GetRegisterID(addr)) {
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case PPURegisters::Status:
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_state.WriteToggle = false;
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_flags.IntensifyBlue = false;
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UpdateStatusFlag();
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return _state.Status;
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case PPURegisters::SpriteData:
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return _spriteRAM[_state.SpriteRamAddr];
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case PPURegisters::VideoMemoryData:
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returnValue = _memoryReadBuffer;
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_memoryReadBuffer = _memoryManager->ReadVRAM(_state.VideoRamAddr);
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if(_state.VideoRamAddr >= 0x3F00) {
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returnValue = ReadPaletteRAM(_state.VideoRamAddr);
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}
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UpdateVideoRamAddr();
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return returnValue;
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default:
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//other registers are meant to be read-only
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break;
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}
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return 0;
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}
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void PPU::WriteRAM(uint16_t addr, uint8_t value)
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{
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switch(GetRegisterID(addr)) {
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case PPURegisters::Control:
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SetControlRegister(value);
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break;
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case PPURegisters::Mask:
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SetMaskRegister(value);
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break;
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case PPURegisters::SpriteAddr:
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_state.SpriteRamAddr = value;
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break;
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case PPURegisters::SpriteData:
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_spriteRAM[_state.SpriteRamAddr] = value;
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_state.SpriteRamAddr = (_state.SpriteRamAddr + 1) % 0x100;
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break;
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case PPURegisters::ScrollOffsets:
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if(_state.WriteToggle) {
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_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0x73E0) | ((value & 0xF8) << 2) | ((value & 0x07) << 12);
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} else {
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_state.XScroll = value & 0x07;
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_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0x001F) | (value >> 3);
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}
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_state.WriteToggle = !_state.WriteToggle;
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break;
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case PPURegisters::VideoMemoryAddr:
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if(_state.WriteToggle) {
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_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0x00FF) | value;
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_state.VideoRamAddr = _state.TmpVideoRamAddr;
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} else {
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_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0xFF00) | ((value & 0x3F) << 8);
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}
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_state.WriteToggle = !_state.WriteToggle;
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break;
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case PPURegisters::VideoMemoryData:
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if(_state.VideoRamAddr >= 0x3F00) {
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WritePaletteRAM(_state.VideoRamAddr, value);
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} else {
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_memoryManager->WriteVRAM(_state.VideoRamAddr, value);
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}
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UpdateVideoRamAddr();
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break;
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case PPURegisters::SpriteDMA:
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//DMA transfer starts at SpriteRamAddr and wraps around
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for(int i = 0; i < 0x100; i++) {
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_spriteRAM[(_state.SpriteRamAddr+i)&0xFF] = _memoryManager->Read(value*0x100 + i);
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}
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//"the DMA procedure takes 513 CPU cycles (+1 on odd CPU cycles)"
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CPU::IncCycleCount((CPU::GetCycleCount() % 2 == 0) ? 513 : 514);
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break;
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}
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}
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uint8_t PPU::ReadPaletteRAM(uint16_t addr)
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{
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addr &= 0x1F;
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if(addr == 0x10 || addr == 0x14 || addr == 0x18 || addr == 0x1C) {
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addr &= ~0x10;
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}
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return _paletteRAM[addr];
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}
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void PPU::WritePaletteRAM(uint16_t addr, uint8_t value)
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{
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addr &= 0x1F;
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if(addr == 0x10 || addr == 0x14 || addr == 0x18 || addr == 0x1C) {
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addr &= ~0x10;
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}
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_paletteRAM[addr] = value;
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}
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uint32_t PPU::GetBGPaletteEntry(uint32_t paletteOffset, uint32_t pixel)
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{
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if(pixel == 0) {
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return ReadPaletteRAM(0x3F00) % 64;
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} else {
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return ReadPaletteRAM(0x3F00 + paletteOffset + pixel) % 64;
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}
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}
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uint32_t PPU::GetSpritePaletteEntry(uint32_t paletteOffset, uint32_t pixel)
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{
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if(pixel == 0) {
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return ReadPaletteRAM(0x3F00) % 64;
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} else {
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return ReadPaletteRAM(0x3F10 + paletteOffset + pixel) % 64;
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}
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}
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bool PPU::IsRenderingEnabled()
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{
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return _flags.BackgroundEnabled || _flags.SpritesEnabled;
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}
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void PPU::SetControlRegister(uint8_t value)
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{
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_state.Control = value;
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uint8_t nameTable = (_state.Control & 0x03);
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_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0x0C00) | (nameTable << 10);
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_flags.VerticalWrite = (_state.Control & 0x04) == 0x04;
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_flags.SpritePatternAddr = ((_state.Control & 0x08) == 0x08) ? 0x1000 : 0x0000;
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_flags.BackgroundPatternAddr = ((_state.Control & 0x10) == 0x10) ? 0x1000 : 0x0000;
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_flags.LargeSprites = (_state.Control & 0x20) == 0x20;
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bool originalVBlank = _flags.VBlank;
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_flags.VBlank = (_state.Control & 0x80) == 0x80;
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if(!originalVBlank && _flags.VBlank && _statusFlags.VerticalBlank) {
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CPU::SetNMIFlag();
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}
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}
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void PPU::SetMaskRegister(uint8_t value)
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{
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_state.Mask = value;
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_flags.Grayscale = (_state.Mask & 0x01) == 0x01;
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_flags.BackgroundMask = (_state.Mask & 0x02) == 0x02;
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_flags.SpriteMask = (_state.Mask & 0x04) == 0x04;
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_flags.BackgroundEnabled = (_state.Mask & 0x08) == 0x08;
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_flags.SpritesEnabled = (_state.Mask & 0x10) == 0x10;
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_flags.IntensifyRed = (_state.Mask & 0x20) == 0x20;
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_flags.IntensifyGreen = (_state.Mask & 0x40) == 0x40;
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_flags.IntensifyBlue = (_state.Mask & 0x80) == 0x80;
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}
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void PPU::UpdateStatusFlag()
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{
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_state.Status = ((uint8_t)_statusFlags.SpriteOverflow << 5) |
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((uint8_t)_statusFlags.Sprite0Hit << 6) |
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((uint8_t)_statusFlags.VerticalBlank << 7);
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_statusFlags.VerticalBlank = false;
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if(_scanline == 241 && _cycle == 0) {
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_doNotSetVBFlag = true;
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}
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}
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//Taken from http://wiki.nesdev.com/w/index.php/The_skinny_on_NES_scrolling#Wrapping_around
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void PPU::IncVerticalScrolling()
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{
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uint16_t addr = _state.VideoRamAddr;
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if((addr & 0x7000) != 0x7000) {
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// if fine Y < 7
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addr += 0x1000; // increment fine Y
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} else {
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// fine Y = 0
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addr &= ~0x7000;
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int y = (addr & 0x03E0) >> 5; // let y = coarse Y
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if(y == 29) {
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y = 0; // coarse Y = 0
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addr ^= 0x0800; // switch vertical nametable
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} else if(y == 31){
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y = 0; // coarse Y = 0, nametable not switched
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} else {
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y++; // increment coarse Y
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}
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addr = (addr & ~0x03E0) | (y << 5); // put coarse Y back into v
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}
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_state.VideoRamAddr = addr;
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}
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//Taken from http://wiki.nesdev.com/w/index.php/The_skinny_on_NES_scrolling#Wrapping_around
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void PPU::IncHorizontalScrolling()
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{
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//Increase coarse X scrolling value.
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uint16_t addr = _state.VideoRamAddr;
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if((addr & 0x001F) == 31) {
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//When the value is 31, wrap around to 0 and switch nametable
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addr = (addr & ~0x001F) ^ 0x0400;
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} else {
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addr++;
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}
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_state.VideoRamAddr = addr;
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}
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//Take from http://wiki.nesdev.com/w/index.php/The_skinny_on_NES_scrolling#Tile_and_attribute_fetching
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uint16_t PPU::GetNameTableAddr()
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{
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return 0x2000 | (_state.VideoRamAddr & 0x0FFF);
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}
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//Take from http://wiki.nesdev.com/w/index.php/The_skinny_on_NES_scrolling#Tile_and_attribute_fetching
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uint16_t PPU::GetAttributeAddr()
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{
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return 0x23C0 | (_state.VideoRamAddr & 0x0C00) | ((_state.VideoRamAddr >> 4) & 0x38) | ((_state.VideoRamAddr >> 2) & 0x07);
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}
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void PPU::LoadTileInfo()
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{
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_previousTile = _currentTile;
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_currentTile = _nextTile;
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uint16_t tileIndex = _memoryManager->ReadVRAM(GetNameTableAddr());
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uint16_t tileAddr = (tileIndex << 4) | (_state.VideoRamAddr >> 12) | _flags.BackgroundPatternAddr;
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uint16_t shift = ((_state.VideoRamAddr >> 4) & 0x04) | (_state.VideoRamAddr & 0x02);
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_nextTile.PaletteOffset = ((_memoryManager->ReadVRAM(GetAttributeAddr()) >> shift) & 0x03) << 2;
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_nextTile.LowByte = _memoryManager->ReadVRAM(tileAddr);
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_nextTile.HighByte = _memoryManager->ReadVRAM(tileAddr + 8);
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}
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void PPU::LoadSpriteTileInfo(uint8_t spriteIndex)
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{
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uint32_t spriteAddr = spriteIndex * 4;
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uint8_t spriteY = _secondarySpriteRAM[spriteAddr];
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uint8_t tileIndex = _secondarySpriteRAM[spriteAddr+1];
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uint8_t attributes = _secondarySpriteRAM[spriteAddr+2];
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uint8_t spriteX = _secondarySpriteRAM[spriteAddr+3];
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bool backgroundPriority = (attributes & 0x20) == 0x20;
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bool horizontalMirror = (attributes & 0x40) == 0x40;
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bool verticalMirror = (attributes & 0x80) == 0x80;
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if(spriteY < 240) {
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uint16_t tileAddr;
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uint8_t lineOffset;
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if(verticalMirror) {
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lineOffset = (_flags.LargeSprites ? 15 : 7) - (_scanline - spriteY);
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} else {
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lineOffset = _scanline - spriteY;
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}
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if(_flags.LargeSprites) {
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tileAddr = (((tileIndex & 0x01) ? 0x1000 : 0x0000) | ((tileIndex & ~0x01) << 4)) + (lineOffset >= 8 ? lineOffset + 8 : lineOffset);
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} else {
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tileAddr = ((tileIndex << 4) | _flags.SpritePatternAddr) + lineOffset;
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}
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_spriteX[spriteIndex] = spriteX;
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_spriteTiles[spriteIndex].BackgroundPriority = backgroundPriority;
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_spriteTiles[spriteIndex].HorizontalMirror = horizontalMirror;
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_spriteTiles[spriteIndex].PaletteOffset = (attributes & 0x03) << 2;
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_spriteTiles[spriteIndex].LowByte = _memoryManager->ReadVRAM(tileAddr);
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_spriteTiles[spriteIndex].HighByte = _memoryManager->ReadVRAM(tileAddr + 8);
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}
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}
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void PPU::LoadNextTile()
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{
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_state.LowBitShift |= _nextTile.LowByte;
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_state.HighBitShift |= _nextTile.HighByte;
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}
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void PPU::InitializeShiftRegisters()
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{
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_state.LowBitShift = (_currentTile.LowByte << 8) | _nextTile.LowByte;
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_state.HighBitShift = (_currentTile.HighByte << 8) | _nextTile.HighByte;
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}
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void PPU::ShiftTileRegisters()
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{
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_state.LowBitShift <<= 1;
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_state.HighBitShift <<= 1;
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}
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void PPU::DrawPixel()
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{
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//This is called 3.7 million times per second - needs to be as fast as possible.
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uint8_t offset = _state.XScroll;
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bool useBackground = true;
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uint32_t backgroundColor = 0;
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uint32_t spriteColor = 0;
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if(_flags.BackgroundEnabled) {
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backgroundColor = (((_state.LowBitShift << offset) & 0x8000) >> 15) | (((_state.HighBitShift << offset) & 0x8000) >> 14);
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}
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uint8_t i;
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if(_flags.SpritesEnabled) {
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for(i = 0; i < _spriteCount; i++) {
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int32_t shift = -((int32_t)_spriteX[i] - (int32_t)_cycle + 1);
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if(shift >= 0 && shift < 8) {
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if(_spriteTiles[i].HorizontalMirror) {
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spriteColor = ((_spriteTiles[i].LowByte >> shift) & 0x01) | ((_spriteTiles[i].HighByte >> shift) & 0x01) << 1;
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} else {
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spriteColor = ((_spriteTiles[i].LowByte << shift) & 0x80) >> 7 | ((_spriteTiles[i].HighByte << shift) & 0x80) >> 6;
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}
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if(spriteColor != 0) {
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//First sprite without a 00 color, use it.
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break;
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}
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}
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}
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}
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if(_cycle <= 8) {
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if(!_flags.BackgroundMask) {
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//"0: Hide background in leftmost 8 pixels of screen;"
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backgroundColor = 0;
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}
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if(!_flags.SpriteMask) {
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//"0: Hide sprites in leftmost 8 pixels of screen;"
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spriteColor = 0;
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}
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}
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if(spriteColor != 0 && (backgroundColor == 0 || !_spriteTiles[i].BackgroundPriority)) {
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//Check sprite priority
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useBackground = false;
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}
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if(i == 0 && spriteColor != 0 && backgroundColor != 0 && _sprite0Visible && _cycle != 256 && _flags.BackgroundEnabled && _flags.SpritesEnabled) {
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//"The hit condition is basically sprite zero is in range AND the first sprite output unit is outputting a non-zero pixel AND the background drawing unit is outputting a non-zero pixel."
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//"Sprite zero hits do not register at x=255" (cycle 256)
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//"... provided that background and sprite rendering are both enabled"
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//"Should always miss when Y >= 239"
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_statusFlags.Sprite0Hit = true;
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}
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uint32_t pixelColor = 0;
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if(useBackground) {
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// If we're grabbing the pixel from the high part of the shift register, use the previous tile's palette, not the current one
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pixelColor = PPU_PALETTE_RGB[GetBGPaletteEntry(offset + ((_cycle - 1) % 8) < 8 ? _previousTile.PaletteOffset : _currentTile.PaletteOffset, backgroundColor)];
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} else {
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pixelColor = PPU_PALETTE_RGB[GetSpritePaletteEntry(_spriteTiles[i].PaletteOffset, spriteColor)];
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}
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uint32_t bufferPosition = _scanline * 256 + (_cycle - 1);
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((uint32_t*)_outputBuffer)[bufferPosition] = 0xFF000000 | pixelColor;
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//Shift the tile registers to prepare for the next cycle
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ShiftTileRegisters();
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}
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void PPU::ProcessPreVBlankScanline()
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{
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//For pre-render scanline & all visible scanlines
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if(IsRenderingEnabled()) {
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//Update video ram address according to scrolling logic
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if(_cycle == 256) {
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IncVerticalScrolling();
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} else if(_cycle == 257) {
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//copy horizontal scrolling value from t
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_state.VideoRamAddr = (_state.VideoRamAddr & ~0x041F) | (_state.TmpVideoRamAddr & 0x041F);
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} else if((_cycle % 8 == 0 && _cycle > 0 && _cycle < 256) || _cycle == 328 || _cycle == 336) {
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IncHorizontalScrolling();
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}
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}
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if(_cycle >= 257 && _cycle <= 320) {
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//"OAMADDR is set to 0 during each of ticks 257-320 (the sprite tile loading interval) of the pre-render and visible scanlines."
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_state.SpriteRamAddr = 0;
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}
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}
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void PPU::ProcessPrerenderScanline()
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{
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ProcessPreVBlankScanline();
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if(_cycle == 1) {
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_statusFlags.SpriteOverflow = false;
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_statusFlags.Sprite0Hit = false;
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_statusFlags.VerticalBlank = false;
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} else if(_cycle >= 280 && _cycle <= 304) {
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if(IsRenderingEnabled()) {
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//copy vertical scrolling value from t
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_state.VideoRamAddr = (_state.VideoRamAddr & ~0x7BE0) | (_state.TmpVideoRamAddr & 0x7BE0);
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}
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} else if(_cycle == 339 && _flags.BackgroundEnabled && (_frameCount % 2 == 1)) {
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//Skip a cycle for odd frames, if background drawing is enabled
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_cycle = -1;
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_scanline = 0;
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} else if(_cycle == 321 || _cycle == 329) {
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|
LoadTileInfo();
|
|
if(_cycle == 329) {
|
|
InitializeShiftRegisters();
|
|
}
|
|
}
|
|
}
|
|
|
|
void PPU::ProcessVisibleScanline()
|
|
{
|
|
if(_cycle > 0 && _cycle <= 256) {
|
|
if((_cycle - 1) % 8 == 0) {
|
|
//Cycle 1, 9, 17, etc.
|
|
if(_cycle != 1) {
|
|
LoadNextTile();
|
|
}
|
|
LoadTileInfo();
|
|
}
|
|
|
|
DrawPixel();
|
|
|
|
if(IsRenderingEnabled()) {
|
|
CopyOAMData();
|
|
}
|
|
|
|
if(_cycle == 256 && _scanline == 239) {
|
|
//Send frame to GUI once the last pixel has been output
|
|
PPU::VideoDevice->UpdateFrame(_outputBuffer);
|
|
}
|
|
} else if((_cycle - 261) % 8 == 0 && _cycle <= 320) {
|
|
uint32_t spriteIndex = (_cycle - 261) / 8;
|
|
if(spriteIndex < _spriteCount) {
|
|
LoadSpriteTileInfo(spriteIndex);
|
|
}
|
|
} else if(_cycle == 321 || _cycle == 329) {
|
|
LoadTileInfo();
|
|
if(_cycle == 329) {
|
|
InitializeShiftRegisters();
|
|
}
|
|
}
|
|
|
|
ProcessPreVBlankScanline();
|
|
}
|
|
|
|
void PPU::CopyOAMData()
|
|
{
|
|
static uint8_t _buffer = 0;
|
|
static bool _writeData = false;
|
|
static uint32_t _overflowCounter = 0;
|
|
static bool _sprite0Added = true;
|
|
|
|
if(_cycle < 65) {
|
|
//Clear secondary OAM at between cycle 0 and 64
|
|
_secondarySpriteRAM[_cycle >> 1] = 0xFF;
|
|
} else {
|
|
if(_cycle == 65) {
|
|
_overflowCounter = 0;
|
|
_sprite0Added = false;
|
|
_writeData = false;
|
|
_secondaryOAMAddr = 0;
|
|
} else if(_cycle == 256) {
|
|
_sprite0Visible = _sprite0Added;
|
|
_spriteCount = (_secondaryOAMAddr >> 2);
|
|
}
|
|
|
|
if(_cycle & 0x01) {
|
|
//Read a byte from the primary OAM on odd cycles
|
|
_buffer = _spriteRAM[_state.SpriteRamAddr & 0xFF];
|
|
_state.SpriteRamAddr++;
|
|
} else {
|
|
if(!_writeData && _state.SpriteRamAddr < 0x100 && _scanline >= _buffer && _scanline < _buffer + (_flags.LargeSprites ? 16 : 8)) {
|
|
_writeData = true;
|
|
}
|
|
|
|
if(_secondaryOAMAddr < 0x20) {
|
|
//Copy 1 byte to secondary OAM
|
|
_secondarySpriteRAM[_secondaryOAMAddr] = _buffer;
|
|
|
|
if(_writeData) {
|
|
_secondaryOAMAddr++;
|
|
|
|
if(_state.SpriteRamAddr == 0x01) {
|
|
_sprite0Added = true;
|
|
}
|
|
|
|
if((_secondaryOAMAddr & 0x03) == 0) {
|
|
//Done copying
|
|
_writeData = false;
|
|
}
|
|
} else {
|
|
_state.SpriteRamAddr += 3;
|
|
}
|
|
} else {
|
|
//8 sprites have been found, check next sprite for overflow + emulate PPU bug
|
|
//Based on: http://forums.nesdev.com/viewtopic.php?p=85431#p85431
|
|
//Behavior matches: http://forums.nesdev.com/viewtopic.php?p=1387#p1387
|
|
if(!_statusFlags.SpriteOverflow) {
|
|
if(_writeData) {
|
|
//Sprite is visible, consider this to be an overflow
|
|
_statusFlags.SpriteOverflow = true;
|
|
_overflowCounter = 3;
|
|
} else if((_state.SpriteRamAddr & 0x3) != 0) {
|
|
//Sprite isn't on this scanline, trigger sprite evaluation bug
|
|
_state.SpriteRamAddr += 4;
|
|
}
|
|
} else {
|
|
if(_overflowCounter != 0) {
|
|
_overflowCounter--;
|
|
if(_overflowCounter == 0) {
|
|
_state.SpriteRamAddr = (_state.SpriteRamAddr + 3) & 0x0FFC;
|
|
}
|
|
} else {
|
|
_state.SpriteRamAddr = (_state.SpriteRamAddr + 4) & 0x0FFC;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void PPU::BeginVBlank()
|
|
{
|
|
if(_cycle == 1) {
|
|
if(!_doNotSetVBFlag) {
|
|
_statusFlags.VerticalBlank = true;
|
|
if(_flags.VBlank) {
|
|
CPU::SetNMIFlag();
|
|
}
|
|
}
|
|
_doNotSetVBFlag = false;
|
|
}
|
|
}
|
|
|
|
void PPU::EndVBlank()
|
|
{
|
|
if(_cycle == 340) {
|
|
_frameCount++;
|
|
}
|
|
}
|
|
|
|
void PPU::Exec()
|
|
{
|
|
uint64_t equivalentCycleCount = CPU::GetCycleCount() * 3;
|
|
uint32_t gap = (uint32_t)(equivalentCycleCount - _cycleCount);
|
|
_cycleCount += gap;
|
|
while(gap > 0) {
|
|
if(_scanline == -1) {
|
|
ProcessPrerenderScanline();
|
|
} else if(_scanline < 240) {
|
|
ProcessVisibleScanline();
|
|
} else if(_scanline == 241) {
|
|
BeginVBlank();
|
|
} else if(_scanline == 260) {
|
|
EndVBlank();
|
|
}
|
|
|
|
if(_cycle == 340) {
|
|
_cycle = 0;
|
|
_scanline++;
|
|
|
|
if(_scanline == 261) {
|
|
_scanline = -1;
|
|
}
|
|
} else {
|
|
_cycle++;
|
|
}
|
|
|
|
gap--;
|
|
}
|
|
} |