private static byte Read(int address)
{
BUS_RW_P = BUS_RW;
BUS_ADDRESS = address;
BUS_RW = true;
ClockComponents();
if (address < 0x2000)// Internal 2K Work RAM (mirrored to 800h-1FFFh)
{
return(WRAM[address & 0x7FF]);
}
else if (address < 0x4000)
{
#region Internal PPU Registers (mirrored to 2008h-3FFFh)
switch (address & 7)
{
case 2: // $2002
{
ppu_2002_temp = 0;
if (vbl_flag)
{
ppu_2002_temp |= 0x80;
}
if (spr_0Hit)
{
ppu_2002_temp |= 0x40;
}
if (spr_overflow)
{
ppu_2002_temp |= 0x20;
}
vbl_flag_temp = false;
vram_flipflop = false;
// NMI disable effect only at vbl set period (HClock between 1 and 3)
if ((VClock == vbl_vclock_Start) && (HClock <= 3))
{
NMI_Current = (vbl_flag_temp & nmi_enabled);
}
return(ppu_2002_temp);
}
case 4: // $2004
{
ppu_2004_temp = oam_ram[oam_address];
if (VClock < 240 && IsRenderingOn())
{
if (HClock < 64)
{
ppu_2004_temp = 0xFF;
}
else if (HClock < 192)
{
ppu_2004_temp = oam_ram[((HClock - 64) << 1) & 0xFC];
}
else if (HClock < 256)
{
ppu_2004_temp = ((HClock & 1) == 1) ? oam_ram[0xFC] : oam_ram[((HClock - 192) << 1) & 0xFC];
}
else if (HClock < 320)
{
ppu_2004_temp = 0xFF;
}
else
{
ppu_2004_temp = oam_ram[0];
}
}
return(ppu_2004_temp);
}
case 7: // $2007
{
ppu_2007_temp = 0;
if ((vram_address & 0x3F00) == 0x3F00)
{
// The return value should be from the palettes bank
ppu_2007_temp = (byte)(palettes_bank[vram_address & ((vram_address & 0x03) == 0 ? 0x0C : 0x1F)] & grayscale);
// fill buffer from chr or nametables
vram_address_temp_access1 = vram_address & 0x2FFF;
if (vram_address_temp_access1 < 0x2000)
{
reg2007buffer = board.ReadCHR(ref vram_address_temp_access1, false);
}
else
{
reg2007buffer = board.ReadNMT(ref vram_address_temp_access1);
}
}
else
{
ppu_2007_temp = reg2007buffer;
// fill buffer
vram_address_temp_access1 = vram_address & 0x3FFF;
if (vram_address_temp_access1 < 0x2000)
{
reg2007buffer = board.ReadCHR(ref vram_address_temp_access1, false);
}
else if (vram_address_temp_access1 < 0x3F00)
{
reg2007buffer = board.ReadNMT(ref vram_address_temp_access1);
}
else
{
reg2007buffer = palettes_bank[vram_address_temp_access1 & ((vram_address_temp_access1 & 0x03) == 0 ? 0x0C : 0x1F)];
}
}
vram_address = (vram_address + vram_increament) & 0x7FFF;
board.OnPPUAddressUpdate(ref vram_address);
return(ppu_2007_temp);
}
}
#endregion
}
else if (address < 0x4020)
{
#region Internal APU Registers
switch (address)
{
case 0x4015:
{
temp_4015 = 0;
// Channels enable
if (sq1_duration_counter > 0)
{
temp_4015 |= 0x01;
}
if (sq2_duration_counter > 0)
{
temp_4015 |= 0x02;
}
if (trl_duration_counter > 0)
{
temp_4015 |= 0x04;
}
if (noz_duration_counter > 0)
{
temp_4015 |= 0x08;
}
if (dmc_dmaSize > 0)
{
temp_4015 |= 0x10;
}
// IRQ
if (FrameIrqFlag)
{
temp_4015 |= 0x40;
}
if (DeltaIrqOccur)
{
temp_4015 |= 0x80;
}
FrameIrqFlag = false;
IRQFlags &= ~IRQ_APU;
return(temp_4015);
}
case 0x4016:
{
temp_4016 = (byte)(PORT0 & 1);
PORT0 >>= 1;
if (IsZapperConnected)
{
temp_4016 |= zapper.GetData();
}
if (IsVSUnisystem)
{
temp_4016 |= VSUnisystemDIP.GetData4016();
}
return(temp_4016);
}
case 0x4017:
{
temp_4017 = (byte)(PORT1 & 1);
PORT1 >>= 1;
if (IsZapperConnected)
{
temp_4017 |= zapper.GetData();
}
if (IsVSUnisystem)
{
temp_4017 |= VSUnisystemDIP.GetData4017();
}
return(temp_4017);
}
}
#endregion
}
else if (address < 0x6000)// Cartridge Expansion Area almost 8K
{
return(board.ReadEXP(ref address));
}
else if (address < 0x8000)// Cartridge SRAM Area 8K
{
return(board.ReadSRM(ref address));
}
else if (address <= 0xFFFF)// Cartridge PRG-ROM Area 32K
{
return(board.ReadPRG(ref address));
}
// Should not reach here !
return(0);
}
public byte Read(int address)
{
BUS_RW_P = BUS_RW;
BUS_ADDRESS = address;
BUS_RW = true;
#region Clock Components
this.ppu.Clock();
/*
* NMI edge detector polls the status of the NMI line during φ2 of each CPU cycle
* (i.e., during the second half of each cycle)
*/
this.interrupts.PollInterruptStatus();
this.ppu.Clock();
this.ppu.Clock();
if (this.emulator.DoPalAdditionalClock) // In pal system ..
{
this.emulator.palCyc++;
if (this.emulator.palCyc == 5)
{
this.ppu.Clock();
this.emulator.palCyc = 0;
}
}
this.apu.Clock();
this.dma.Clock();
board.OnCPUClock();
#endregion
if (address < 0x2000) // Internal 2K Work RAM (mirrored to 800h-1FFFh)
{
return(WRAM[address & 0x7FF]);
}
else if (address < 0x4000)
{
#region Internal PPU Registers (mirrored to 2008h-3FFFh)
switch (address & 7)
{
case 2: // $2002
{
this.ppu.ppu_2002_temp = 0;
if (this.interrupts.vbl_flag)
{
this.ppu.ppu_2002_temp |= 0x80;
}
if (this.ppu.spr_0Hit)
{
this.ppu.ppu_2002_temp |= 0x40;
}
if (this.ppu.spr_overflow)
{
this.ppu.ppu_2002_temp |= 0x20;
}
this.interrupts.vbl_flag_temp = false;
this.ppu.vram_flipflop = false;
this.interrupts.CheckNMI(); // NMI disable effect only at vbl set period (HClock between 1 and 3)
return(this.ppu.ppu_2002_temp);
}
case 4: // $2004
{
this.ppu.ppu_2004_temp = oam_ram[this.ppu.oam_address];
if (this.ppu.VClock < 240 && this.ppu.IsRenderingOn())
{
if (this.ppu.HClock < 64)
{
this.ppu.ppu_2004_temp = 0xFF;
}
else if (this.ppu.HClock < 192)
{
this.ppu.ppu_2004_temp = oam_ram[((this.ppu.HClock - 64) << 1) & 0xFC];
}
else if (this.ppu.HClock < 256)
{
this.ppu.ppu_2004_temp = ((this.ppu.HClock & 1) == 1) ? oam_ram[0xFC] : oam_ram[((this.ppu.HClock - 192) << 1) & 0xFC];
}
else if (this.ppu.HClock < 320)
{
this.ppu.ppu_2004_temp = 0xFF;
}
else
{
this.ppu.ppu_2004_temp = oam_ram[0];
}
}
return(this.ppu.ppu_2004_temp);
}
case 7: // $2007
{
this.ppu.ppu_2007_temp = 0;
if ((this.ppu.vram_address & 0x3F00) == 0x3F00)
{
// The return value should be from the palettes bank
this.ppu.ppu_2007_temp = (byte)(palettes_bank[this.ppu.vram_address & ((this.ppu.vram_address & 0x03) == 0 ? 0x0C : 0x1F)] & this.ppu.grayscale);
// fill buffer from chr or nametables
this.ppu.vram_address_temp_access1 = this.ppu.vram_address & 0x2FFF;
if (this.ppu.vram_address_temp_access1 < 0x2000)
{
this.ppu.reg2007buffer = board.ReadCHR(ref this.ppu.vram_address_temp_access1, false);
}
else
{
this.ppu.reg2007buffer = board.ReadNMT(ref this.ppu.vram_address_temp_access1);
}
}
else
{
this.ppu.ppu_2007_temp = this.ppu.reg2007buffer;
// fill buffer
this.ppu.vram_address_temp_access1 = this.ppu.vram_address & 0x3FFF;
if (this.ppu.vram_address_temp_access1 < 0x2000)
{
this.ppu.reg2007buffer = board.ReadCHR(ref this.ppu.vram_address_temp_access1, false);
}
else if (this.ppu.vram_address_temp_access1 < 0x3F00)
{
this.ppu.reg2007buffer = board.ReadNMT(ref this.ppu.vram_address_temp_access1);
}
else
{
this.ppu.reg2007buffer = palettes_bank[this.ppu.vram_address_temp_access1 & ((this.ppu.vram_address_temp_access1 & 0x03) == 0 ? 0x0C : 0x1F)];
}
}
this.ppu.vram_address = (this.ppu.vram_address + this.ppu.vram_increament) & 0x7FFF;
board.OnPPUAddressUpdate(ref this.ppu.vram_address);
return(this.ppu.ppu_2007_temp);
}
}
#endregion
}
else if (address < 0x4020)
{
#region Internal APU Registers
switch (address)
{
case 0x4015:
{
temp_4015 = 0;
// Channels enable
if (this.apu.pulse1Channel.Duration_counter > 0)
{
temp_4015 |= 0x01;
}
if (this.apu.pulse2Channel.Duration_counter > 0)
{
temp_4015 |= 0x02;
}
if (this.apu.triangleChannel.Duration_counter > 0)
{
temp_4015 |= 0x04;
}
if (this.apu.noiseChannel.Duration_counter > 0)
{
temp_4015 |= 0x08;
}
if (this.apu.dmcChannel.dmc_dmaSize > 0)
{
temp_4015 |= 0x10;
}
// IRQ
if (this.apu.FrameIrqFlag)
{
temp_4015 |= 0x40;
}
if (this.apu.dmcChannel.DeltaIrqOccur)
{
temp_4015 |= 0x80;
}
this.apu.FrameIrqFlag = false;
Interrupts.IRQFlags &= ~Interrupts.IRQ_APU;
return(temp_4015);
}
case 0x4016:
{
temp_4016 = (byte)(this.input.PORT0 & 1);
this.input.PORT0 >>= 1;
if (this.input.IsZapperConnected)
{
temp_4016 |= this.input.zapper.GetData();
}
if (this.legacy.IsVSUnisystem)
{
temp_4016 |= this.input.VSUnisystemDIP.GetData4016();
}
return(temp_4016);
}
case 0x4017:
{
temp_4017 = (byte)(this.input.PORT1 & 1);
this.input.PORT1 >>= 1;
if (this.input.IsZapperConnected)
{
temp_4017 |= this.input.zapper.GetData();
}
if (this.legacy.IsVSUnisystem)
{
temp_4017 |= this.input.VSUnisystemDIP.GetData4017();
}
return(temp_4017);
}
}
#endregion
}
else if (address < 0x6000) // Cartridge Expansion Area almost 8K
{
return(board.ReadEXP(ref address));
}
else if (address < 0x8000) // Cartridge SRAM Area 8K
{
return(board.ReadSRM(ref address));
}
else if (address <= 0xFFFF) // Cartridge PRG-ROM Area 32K
{
return(board.ReadPRG(ref address));
}
// Should not reach here !
return(0);
}