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 void BIT(OpcodeContainer container, ushort address)
{
var value = CPU.ReadByteAt(address);
CPU.IsOverflowed = (value & 0x40) != 0;
CPU.IsNegative = (value & 0x80) != 0;
CPU.IsZero = (value & CPU.Registers.A) == 0;
}
public void AND(OpcodeContainer container, ushort address)
{
var value = CPU.ReadByteAt(address);
var newValue = CPU.Registers.A & value;
this.WriteByteToRegister(CPU.Registers.A, (byte)newValue, S: true, Z: true);
//this.HandlePageBoundaryCrossed(container, isSamePage);
}
public void ORA(OpcodeContainer container, ushort address)
{
var value = CPU.ReadByteAt(address);
CPU.Registers.A.Write((byte)(CPU.Registers.A | value));
this.HandleNegative(CPU.Registers.A);
this.HandleZero(CPU.Registers.A);
// this.HandlePageBoundaryCrossed(container, isSamePage);
}
public static string GetAddressAsString(MOS6502 CPU, OpcodeContainer container)
{
if (container.Name == "RTS")
{
return("");
}
switch (container.AddressingMode)
{
case AddressingModes.Implied:
return("");
case AddressingModes.Accumulator:
return("A");
case AddressingModes.Indirect:
return($"(${intermediateAddress:X4}) @ ${address:X4}");
case AddressingModes.IndirectYWrite:
case AddressingModes.IndirectY:
return($"(${intermediateAddress:X2}),Y @ ${address:X4}");
case AddressingModes.IndirectX:
return($"(${intermediateAddress:X2},X) @ ${address:X4}");
case AddressingModes.ZeroPage:
return($"${address:X2}");
case AddressingModes.ZeroPageX:
return($"${intermediateAddress:X2},X @ ${address:X2}");
case AddressingModes.ZeroPageY:
return($"${intermediateAddress:X2},Y @ ${address:X2}");
case AddressingModes.AbsoluteY:
return($"${intermediateAddress:X4},Y @ ${address:X4}");
case AddressingModes.AbsoluteX:
case AddressingModes.AbsoluteXWrite:
return($"${intermediateAddress:X4},X @ ${address:X4}");
case AddressingModes.Absolute:
return($"${address:X4}");
case AddressingModes.Immediate:
return($"#${operandValue:X2}");
default:
return($"0x{address:X4}");
}
}
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);
}
public void ROR(OpcodeContainer container, ushort address)
{
switch (container !.AddressingMode)
{
