/// <summary>
/// ExA1 - SKNP Vx
/// Skip next instruction if key with the value of Vx is not pressed.
/// Checks the keyboard, and if the key corresponding to the value of Vx is currently in the up position,
/// PC is increased by 2.
/// </summary>
/// <param name="machineState">
/// The machine State.
/// </param>
public void SkipNextInstructionIfRegisterNotEqualsKeyPressed(IMachineState machineState)
{
if (!machineState.Keys[machineState.VRegisters[machineState.XRegisterFromCurrentOpcode]])
{
machineState.IncreaseProgramCounter();
}
}
/// <summary>
/// 9xy0 - SNE Vx, Vy
/// Skip next instruction if Vx != Vy.
/// The values of Vx and Vy are compared, and if they are not equal, the program counter is increased by 2.
/// </summary>
/// <param name="machineState">
/// The machine State.
/// </param>
public void SkipNextInstructionIfRegisterNotEqualsRegister(IMachineState machineState)
{
if (machineState.VRegisters[machineState.XRegisterFromCurrentOpcode]
!= machineState.VRegisters[machineState.YRegisterFromCurrentOpcode])
{
machineState.IncreaseProgramCounter();
}
}
/// <summary>
/// 4xkk - SNE Vx, byte
/// Skip next instruction if Vx != kk.
/// The interpreter compares register Vx to kk, and if they are not equal, increments the program counter by 2.
/// </summary>
/// <param name="machineState">
/// The machine State.
/// </param>
public void SkipNextInstructionIfRegisterNotEqualsImmediate(IMachineState machineState)
{
if (machineState.VRegisters[machineState.XRegisterFromCurrentOpcode]
!= (machineState.CurrentOpcode & 0x00FF))
{
machineState.IncreaseProgramCounter();
}
}