/// <summary>
/// Constructor
/// </summary>
/// <param name="prgRom"></param>
/// <param name="chrRom"></param>
/// <param name="mirroring"></param>
public NROM(byte[] prgRom, byte[] chrRom, enumNametableMirroring mirroring = enumNametableMirroring.Horizontal)
{
NametableMirroring = mirroring;
//Assign first 16k of ROM
Array.Copy(prgRom, 0, _prgRom, 0, prgRom.Length);
//If it's less than 16k, just mirror it to the second bank
if (prgRom.Length <= 0x4000)
{
Array.Copy(prgRom, 0, _prgRom, 0x4000, prgRom.Length);
}
//Setup PPU ROM
if (chrRom != null)
{
Array.Copy(chrRom, 0, _chrRom, 0, chrRom.Length);
}
}
/// <summary>
/// Loads the specified iNES ROM
/// </summary>
/// <param name="ROM">Byte Array containing the desired iNES ROM to load</param>
/// <returns>TRUE if load was successful</returns>
public bool LoadROM(byte[] ROM)
{
//Header is 16 bytes
//PRG Rom starts right after, unless there's a 512 byte trainer (indicated by flags)
var prgROMOffset = 16;
//_header == "NES<EOF>"
if (BitConverter.ToInt32(ROM, 0) != 0x1A53454E)
{
throw new Exception("Invalid ROM Header");
}
//Setup Memory
_prgRomBanks = ROM[4];
var prgROMSize = _prgRomBanks * 16384;
_prgRom = new byte[prgROMSize];
_logger.Info($"PRG ROM Size: {prgROMSize}");
_chrRomBanks = ROM[5];
var chrROMSize = _chrRomBanks * 8192; //0 denotes default 8k
if (ROM[5] == 0)
{
_chrRom = new byte[8192];
UsesCHRRAM = true;
}
else
{
_chrRom = new byte[chrROMSize];
}
_logger.Info($"CHR ROM Size: {chrROMSize}");
//Set Flags6
Flags6 = ROM[6];
//Move PGR ROM Start if Trainer Present
if (Flags6.IsFlagSet(Byte6Flags.TrainerPresent))
{
prgROMOffset += 512;
}
//Set Initial Mirroring Mode
_nametableMirroring = Flags6.IsFlagSet(Byte6Flags.VerticalMirroring) ? enumNametableMirroring.Vertical : enumNametableMirroring.Horizontal;
//Set Flags7
Flags7 = ROM[7];
var prgRAMSize = ROM[8] == 0 ? 8192 : ROM[8] * 8192; //0 denoted default 8k
_prgRam = new byte[prgRAMSize];
//Load PRG ROM
Array.Copy(ROM, prgROMOffset, _prgRom, 0, prgROMSize);
//Load CHR ROM
Array.Copy(ROM, prgROMOffset + prgROMSize, _chrRom, 0, chrROMSize);
//Load Proper Mapper
var mapperNumber = Flags7 & 0xF0 | (Flags6 >> 4 & 0xF);
switch (mapperNumber)
{
case 0:
MemoryMapper = new NROM(_prgRom, _chrRom, _nametableMirroring);
break;
case 1:
MemoryMapper = new MMC1(_prgRomBanks, _chrRom, _prgRom, UsesCHRRAM, false, _nametableMirroring);
break;
case 2:
MemoryMapper = new UxROM(_prgRom, _prgRomBanks, _chrRom, _nametableMirroring);
break;
case 3:
MemoryMapper = new CNROM(_prgRom, _prgRomBanks, _chrRom, _nametableMirroring);
break;
default:
throw new Exception($"Unsupported Mapper: {mapperNumber}");
}
return(true);
}
