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PPU work

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This commit is contained in:
Souryo 2014-06-17 18:16:49 -04:00
parent 3ad6418726
commit 4341e47e17
3 changed files with 192 additions and 66 deletions
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172
Core/PPU.cpp
View file

@ -24,23 +24,31 @@ bool PPU::CheckFlag(PPUControlFlags flag)
uint8_t PPU::ReadRAM(uint16_t addr)
{
uint8_t returnValue;
switch(GetRegisterID(addr)) {
case PPURegisters::Control:
return (uint8_t)_state.Control;
case PPURegisters::Control2:
return (uint8_t)_state.Control2;
case PPURegisters::Status:
_writeLow = true;
_state.WriteToggle = false;
_flags.IntensifyBlue = false;
UpdateStatusFlag();
return _state.Status;
case PPURegisters::SpriteData:
return _spriteRAM[_state.SpriteRamAddr];
case PPURegisters::VideoMemoryData:
uint8_t returnValue = _memoryReadBuffer;
returnValue = _memoryReadBuffer;
_memoryReadBuffer = _memoryManager->ReadVRAM(_state.VideoRamAddr);
_state.VideoRamAddr += _flags.VerticalWrite ? 32 : 1;
if(_state.VideoRamAddr >= 0x3F00) {
//No buffer for palette
//TODO: Update read buffer when reading palette (See: http://wiki.nesdev.com/w/index.php/PPU_registers#The_PPUDATA_read_buffer_.28post-fetch.29)
return _memoryReadBuffer;
} else {
return returnValue;
}
default:
//other registers are meant to be read-only
break;
}
return 0;
}
@ -59,19 +67,26 @@ void PPU::WriteRAM(uint16_t addr, uint8_t value)
_state.SpriteRamAddr = value;
break;
case PPURegisters::SpriteData:
_spriteRAM[_state.SpriteRamAddr&0xFF] = value;
_spriteRAM[_state.SpriteRamAddr] = value;
_state.SpriteRamAddr++;
break;
case PPURegisters::ScrollOffsets:
_writeLow = !_writeLow;
if(_state.WriteToggle) {
_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0x73E0) | ((value & 0xF8) << 2) | ((value & 0x0F) << 12);
} else {
_state.XScroll = value & 0x07;
_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0x00F8) | (value >> 3);
}
_state.WriteToggle = !_state.WriteToggle;
break;
case PPURegisters::VideoMemoryAddr:
if(_writeLow) {
_state.VideoRamAddr &= 0xFF00;
_state.VideoRamAddr |= value;
if(_state.WriteToggle) {
_state.TmpVideoRamAddr |= (_state.TmpVideoRamAddr & ~0xFF00) | (value & 0x3F) << 8;
_state.VideoRamAddr = _state.TmpVideoRamAddr;
} else {
_state.VideoRamAddr |= value<<8;
_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0x00FF) | value;
}
_writeLow = !_writeLow;
_state.WriteToggle = !_state.WriteToggle;
break;
case PPURegisters::VideoMemoryData:
_memoryManager->WriteVRAM(_state.VideoRamAddr, value);
@ -80,6 +95,11 @@ void PPU::WriteRAM(uint16_t addr, uint8_t value)
}
}
bool PPU::IsRenderingEnabled()
{
return _flags.BackgroundEnabled || _flags.SpritesEnabled;
}
void PPU::UpdateFlags()
{
uint8_t nameTable = (_state.Control & 0x03);
@ -89,6 +109,8 @@ void PPU::UpdateFlags()
case 2: _flags.NameTableAddr = 0x2800; break;
case 3: _flags.NameTableAddr = 0x2C00; break;
}
_state.TmpVideoRamAddr = (_state.TmpVideoRamAddr & ~0xC0000) | (nameTable << 10);
_flags.VerticalWrite = (_state.Control & 0x04) == 0x04;
_flags.SpritePatternAddr = ((_state.Control & 0x08) == 0x08) ? 0x1000 : 0x0000;
_flags.BackgroundPatternAddr = ((_state.Control & 0x10) == 0x10) ? 0x1000 : 0x0000;
@ -113,26 +135,98 @@ void PPU::UpdateStatusFlag()
_statusFlags.VerticalBlank = false;
}
void PPU::Exec()
//Taken from http://wiki.nesdev.com/w/index.php/The_skinny_on_NES_scrolling#Wrapping_around
void PPU::IncVerticalScrolling()
{
uint64_t equivalentCycleCount = CPU::GetCycleCount() * 3;
while(_cycleCount < equivalentCycleCount) {
if(_scanline == -1) {
//Pre-render scanline
uint16_t addr = _state.VideoRamAddr;
if((addr & 0x7000) != 0x7000) {
// if fine Y < 7
addr += 0x1000; // increment fine Y
} else {
// fine Y = 0
addr &= ~0x7000;
int y = (addr & 0x03E0) >> 5; // let y = coarse Y
if(y == 29) {
y = 0; // coarse Y = 0
addr ^= 0x0800; // switch vertical nametable
} else if(y == 31){
y = 0; // coarse Y = 0, nametable not switched
} else {
y += 1; // increment coarse Y
}
addr = (addr & ~0x03E0) | (y << 5); // put coarse Y back into v
}
_state.VideoRamAddr = addr;
}
//Taken from http://wiki.nesdev.com/w/index.php/The_skinny_on_NES_scrolling#Wrapping_around
void PPU::IncHorizontalScrolling()
{
//Increase coarse X scrolling value.
//When the value is 31, wrap around to 0 and switch nametable
uint16_t addr = _state.VideoRamAddr;
if((addr & 0x001F) == 31) {
addr &= ~0x001F;
addr ^= 0x0400; // switch horizontal nametable
} else {
addr += 1;
}
_state.VideoRamAddr = addr;
}
//Take from http://wiki.nesdev.com/w/index.php/The_skinny_on_NES_scrolling#Tile_and_attribute_fetching
uint16_t PPU::GetTileAddr()
{
return 0x2000 | (_state.VideoRamAddr & 0x0FFF);
}
//Take from http://wiki.nesdev.com/w/index.php/The_skinny_on_NES_scrolling#Tile_and_attribute_fetching
uint16_t PPU::GetAttributeAddr()
{
return 0x23C0 | (_state.VideoRamAddr & 0x0C00) | ((_state.VideoRamAddr >> 4) & 0x38) | ((_state.VideoRamAddr >> 2) & 0x07);
}
void PPU::UpdateScrolling()
{
//For pre-render scanline & all visible scanlines
if(_cycle == 256) {
IncVerticalScrolling();
} else if(_cycle == 257) {
//copy horizontal scrolling value from t
_state.VideoRamAddr = (_state.VideoRamAddr & ~0x041F) | (_state.TmpVideoRamAddr & 0x041F);
} else if((_cycle % 8 == 0 && _cycle < 256) || _cycle == 328 || _cycle == 336) {
IncHorizontalScrolling();
}
}
void PPU::ProcessPrerenderScanline()
{
if(IsRenderingEnabled()) {
UpdateScrolling();
}
if(_cycle == 1) {
_statusFlags.SpriteOverflow = false;
_statusFlags.Sprite0Hit = false;
_statusFlags.VerticalBlank = false;
} else if(_cycle == 304) {
// Copy scroll latch into VRAMADDR register
/*if(_flags.BackgroundEnabled || _flags.SpritesEnabled) {
//p->registers.vramAddress = p->registers.vramLatch;
}*/
} else if(_cycle >= 280 && _cycle <= 304) {
if(IsRenderingEnabled()) {
//copy vertical scrolling value from t
_state.VideoRamAddr = (_state.VideoRamAddr & ~0x7BF0) | (_state.TmpVideoRamAddr & 0x7BF0);
}
} else if(_cycle == 339 && _flags.BackgroundEnabled && (_frameCount % 2 == 1)) {
//Skip a cycle for odd frames, if background drawing is enabled
_cycle++;
}
} else if(_scanline < 240) {
}
void PPU::ProcessVisibleScanline()
{
if(IsRenderingEnabled()) {
UpdateScrolling();
}
if(_cycle == 254) {
if(_flags.BackgroundEnabled) {
//Ppu_renderTileRow(p);
@ -146,8 +240,10 @@ void PPU::Exec()
//Ppu_updateEndScanlineRegisters(p);
}
}
} else if(_scanline == 241) {
//Start of VBlank
}
void PPU::BeginVBlank()
{
if(_cycle == 1) {
_statusFlags.VerticalBlank = true;
/*if(!_suppressVBlank) {
@ -158,18 +254,32 @@ void PPU::Exec()
if(_flags.VBlank) {
CPU::SetNMIFlag();
}
/*if(_flags.VBlank && !_suppressNMI) {
VBlankInterrupt();
}*/
//Ppu_raster(p);
}
} else if(_scanline == 260) {
//End of VBlank
}
void PPU::EndVBlank()
{
if(_cycle == 340) {
_frameCount++;
}
}
void PPU::Exec()
{
bool renderingEnabled = IsRenderingEnabled();
uint64_t equivalentCycleCount = CPU::GetCycleCount() * 3;
while(_cycleCount < equivalentCycleCount) {
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++;

25
Core/PPU.h
View file

@ -48,6 +48,9 @@ struct PPUState
uint8_t Status;
uint8_t SpriteRamAddr;
uint16_t VideoRamAddr;
uint8_t XScroll;
uint16_t TmpVideoRamAddr;
bool WriteToggle;
};
class PPU : public IMemoryHandler
@ -67,15 +70,27 @@ class PPU : public IMemoryHandler
uint16_t _cycle = 0;
uint32_t _frameCount = 0;
bool _writeLow = false;
PPUControlFlags _flags;
PPUStatusFlags _statusFlags;
void PPU::UpdateStatusFlag();
void UpdateStatusFlag();
void PPU::UpdateFlags();
bool PPU::CheckFlag(PPUControlFlags flag);
void UpdateFlags();
bool CheckFlag(PPUControlFlags flag);
bool IsRenderingEnabled();
void IncVerticalScrolling();
void IncHorizontalScrolling();
uint16_t GetTileAddr();
uint16_t GetAttributeAddr();
void UpdateScrolling();
void ProcessPrerenderScanline();
void ProcessVisibleScanline();
void BeginVBlank();
void EndVBlank();
PPURegisters GetRegisterID(uint16_t addr)
{

1
Core/stdafx.h
View file

@ -14,6 +14,7 @@
#include <memory>
#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <memory>