public void LSR(OpcodeContainer container, ushort address)
{
switch (container.AddressingMode)
{
case AddressingModes.Accumulator:
CPU.IsCarry = (CPU.Registers.A & 1) == 1;
CPU.Registers.A.Write((byte)(CPU.Registers.A >> 1));
CPU.IsNegative = false;
this.HandleZero(CPU.Registers.A);
break;
default:
var value = CPU.ReadByteAt(address);
CPU.IsCarry = (value & 1) == 1;
byte shiftedValue = (byte)(value >> 1);
// Spin cycle for the work above.
CPU.CycleFinished();
CPU.WriteByteAt(address, shiftedValue);
CPU.IsNegative = false;
this.HandleZero(shiftedValue);
break;
}
}
public static ushort GetAbsoluteXWrite(MOS6502 CPU)
{
intermediateAddress = CPU.ReadNextShort();
var nextShort = (ushort)(intermediateAddress + CPU.Registers.X);
CPU.IncrementPC(2);
CPU.CycleFinished();
return(nextShort);
}
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 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);
}
public static ushort GetAddressedOperand(MOS6502 CPU, OpcodeContainer container)
{
operandValue = 0;
intermediateAddress = 0;
address = 0;
switch (container.AddressingMode)
{
case AddressingModes.Implied:
address = 0x0000;
CPU.CycleFinished();
break;
case AddressingModes.Accumulator:
address = 0x0000;
CPU.CycleFinished();
break;
case AddressingModes.Immediate:
address = AddressingMode.GetImmediate(CPU);
break;
case AddressingModes.Absolute:
address = AddressingMode.GetAbsolute(CPU);
break;
case AddressingModes.AbsoluteX:
address = AddressingMode.GetAbsoluteX(CPU);
break;
case AddressingModes.AbsoluteXWrite:
address = AddressingMode.GetAbsoluteXWrite(CPU);
break;
case AddressingModes.AbsoluteY:
address = AddressingMode.GetAbsoluteY(CPU);
break;
case AddressingModes.Indirect:
address = AddressingMode.GetIndirect(CPU);
break;
case AddressingModes.IndirectX:
address = AddressingMode.GetIndirectX(CPU);
break;
case AddressingModes.IndirectY:
address = AddressingMode.GetIndirectY(CPU);
break;
case AddressingModes.IndirectYWrite:
address = AddressingMode.GetIndirectYWrite(CPU);
break;
case AddressingModes.ZeroPage:
address = AddressingMode.GetZeroPage(CPU);
break;
case AddressingModes.ZeroPageX:
address = AddressingMode.GetZeroPageX(CPU);
break;
case AddressingModes.ZeroPageY:
address = AddressingMode.GetZeroPageY(CPU);
break;
case AddressingModes.Relative:
address = AddressingMode.GetRelative(CPU);
break;
default:
throw new InvalidOperationException();
}
if (MOS6502.IsDebug)
{
CPU.LastAccessedAddress = AddressingMode.GetAddressAsString(CPU, container);
}
return(address);
}