public static ushort GetZeroPage(MOS6502 CPU)
{
var pc = CPU.ReadNextByte();
CPU.IncrementPC();
return(pc);
}
public static ushort GetAbsolute(MOS6502 CPU)
{
var nextShort = CPU.ReadNextShort();
CPU.IncrementPC(2);
return(nextShort);
}
public static ushort GetAbsoluteX(MOS6502 CPU)
{
intermediateAddress = CPU.ReadNextShort();
var nextShort = (ushort)(intermediateAddress + CPU.Registers.X);
CPU.IncrementPC(2);
return(nextShort);
}
public static ushort GetImmediate(MOS6502 CPU)
{
var pc = CPU.Registers.PC.Read();
operandValue = CPU.ReadNextByte(isCycle: false);
CPU.IncrementPC();
return(pc);
}
public static ushort GetZeroPageY(MOS6502 CPU)
{
intermediateAddress = CPU.ReadNextByte();
var address = (ushort)(intermediateAddress + CPU.Registers.Y);
address &= 0xFF;
CPU.CycleFinished();
CPU.IncrementPC();
return(address);
}
public static ushort GetIndirectX(MOS6502 CPU)
{
var incompleteXAddress = CPU.ReadNextByte();
CPU.IncrementPC();
var intermediateAddress = (byte)(incompleteXAddress + CPU.Registers.X);
return(intermediateAddress == 0xFF
? (ushort)(CPU.ReadByteAt(0xFF) | CPU.ReadByteAt(0x00) << 8)
: CPU.ReadShortAt(intermediateAddress));
}
public static ushort GetIndirectYWrite(MOS6502 CPU)
{
intermediateAddress = CPU.ReadNextByte();
CPU.IncrementPC();
var baseAddress = intermediateAddress == 0xFF
? (ushort)(CPU.ReadByteAt(0xFF) | CPU.ReadByteAt(0x00) << 8)
: CPU.ReadShortAt((ushort)intermediateAddress);
CPU.CycleFinished();
return((ushort)(baseAddress + CPU.Registers.Y));
}
public static ushort GetIndirectY(MOS6502 CPU)
{
intermediateAddress = CPU.ReadNextByte();
CPU.IncrementPC();
var baseAddress = intermediateAddress == 0xFF
? (ushort)(CPU.ReadByteAt(0xFF) | CPU.ReadByteAt(0x00) << 8)
: CPU.ReadShortAt((ushort)intermediateAddress);
var finalAddress = (ushort)(baseAddress + CPU.Registers.Y);
if (AddressingMode.NotSamePage(baseAddress, CPU.Registers.Y))
{
CPU.CycleFinished();
}
return(finalAddress);
}