public void ExecuteRet()
{
var sp = (ushort)Registers.SP;
var newPC = NumberUtils.CreateShort(ReadFromMemoryInternal(sp), ReadFromMemoryInternal((ushort)(sp + 1)));
Registers.PC = (ushort)newPC;
Registers.SP += 2;
}
private int AcceptPendingInterrupt()
{
if (executionContext.IsEiOrDiInstruction)
{
return(0);
}
if (NmiInterruptPending)
{
IsHalted = false;
Registers.IFF1 = 0;
this.ExecuteCall(NmiServiceRoutine);
return(11);
}
if (!InterruptsEnabled)
{
return(0);
}
var activeIntSource = InterruptSources.FirstOrDefault(s => s.IntLineIsActive);
if (activeIntSource == null)
{
return(0);
}
Registers.IFF1 = 0;
Registers.IFF2 = 0;
IsHalted = false;
switch (InterruptMode)
{
case 0:
var opcode = activeIntSource.ValueOnDataBus.GetValueOrDefault(0xFF);
InstructionExecutor.Execute(opcode);
return(13);
case 1:
InstructionExecutor.Execute(RST38h_opcode);
return(13);
case 2:
var pointerAddress = NumberUtils.CreateShort(
lowByte: activeIntSource.ValueOnDataBus.GetValueOrDefault(0xFF),
highByte: Registers.I);
var callAddress = NumberUtils.CreateShort(
lowByte: Memory[pointerAddress],
highByte: Memory[pointerAddress.Inc()]);
this.ExecuteCall(callAddress.ToUShort());
return(19);
}
return(0);
}
private short ReadShortFromMemory(ushort address)
{
return(NumberUtils.CreateShort(
ProcessorAgent.ReadFromMemory(address),
ProcessorAgent.ReadFromMemory((ushort)(address + 1))));
}
private short FetchWord()
{
return(NumberUtils.CreateShort(
lowByte: ProcessorAgent.FetchNextOpcode(),
highByte: ProcessorAgent.FetchNextOpcode()));
}