/// <summary>
/// Reads the value of a 16bit shadow register
/// </summary>
/// <param name="register"></param>
/// <returns></returns>
public ushort Read(Reg16Shadow register)
{
var highOrderByte = default(byte);
var lowOrderByte = default(byte);
switch (register)
{
case Reg16Shadow.AF:
highOrderByte = A2;
lowOrderByte = F2;
break;
case Reg16Shadow.BC:
highOrderByte = B2;
lowOrderByte = C2;
break;
case Reg16Shadow.DE:
highOrderByte = D2;
lowOrderByte = E2;
break;
case Reg16Shadow.HL:
highOrderByte = H2;
lowOrderByte = L2;
break;
default:
throw new Exception("Unknown register " + register);
}
return(MakeWord(highOrderByte, lowOrderByte));
}
/// <summary>
/// Sets the value into a 16bit shadow register
/// </summary>
/// <param name="register"></param>
/// <param name="word"></param>
public void Set(Reg16Shadow register, ushort word)
{
var(highOrderByte, lowOrderByte) = word.Split();
switch (register)
{
case Reg16Shadow.AF:
A2 = highOrderByte;
F2 = lowOrderByte;
break;
case Reg16Shadow.BC:
B2 = highOrderByte;
C2 = lowOrderByte;
break;
case Reg16Shadow.DE:
D2 = highOrderByte;
E2 = lowOrderByte;
break;
case Reg16Shadow.HL:
H2 = highOrderByte;
L2 = lowOrderByte;
break;
default:
throw new Exception("Unknown register " + register);
}
}
public void IsShouldBePossibleToWriteAndReadFromEvery16BitShadowRegister(Reg16Shadow register)
{
var ANY_VALUE = (ushort)0xABCD;
var machine = new Machine();
machine.Registers.Set(register, ANY_VALUE);
Assert.Equal(ANY_VALUE, machine.Registers.Read(register));
}
public void EXShouldErrorIfGivenAnyShadowRegisterOtherThanAF(Reg16Shadow register)
{
var machine = new Machine();
machine.Registers.Set(Reg16.AF, 0x1000);
machine.Registers.Set(register, 0x2000);
var exception = Record.Exception(() => machine.EX(Reg16.AF, register));
Assert.IsType(typeof(System.InvalidOperationException), exception);
}
public void EXXShouldSwapARegisterWithItsShadow(Reg16 register, Reg16Shadow shadow)
{
var machine = new Machine();
machine.Registers.Set(register, 0xAAAA);
machine.Registers.Set(shadow, 0xBBBB);
machine.EXX();
Assert.Equal(0xAAAA, machine.Registers.Read(shadow));
Assert.Equal(0xBBBB, machine.Registers.Read(register));
}
/// <summary>
/// Usage: Exchanges the register AF with its shadow register
/// Flags: Yes as this is the F register
/// </summary>
/// <param name="operand1"></param>
/// <param name="operand2"></param>
public void EX(Reg16 operand1, Reg16Shadow operand2)
{
if (operand1 != Reg16.AF)
{
throw new InvalidOperationException("The only register supported is AF");
}
if (operand2 != Reg16Shadow.AF)
{
throw new InvalidOperationException("The only shadow register supported is AF");
}
var valueForOperand1 = this.Registers.Read(operand1);
var valueForOperand2 = this.Registers.Read(operand2);
this.Registers.Set(operand2, valueForOperand1);
this.Registers.Set(operand1, valueForOperand2);
}