private void HandleINT()
{
// TODO: Check if INT is supposed to be able to fire during this push and other memory operations
var opcode = AcknowledgeInterrupt();
if (Registers.InterruptMode == Z80InterruptMode.External)
{
var instr = InstructionDecoder.DecodeNextInstruction(this, opcode);
instr.Execute(this, instr.InstructionBytes);
}
else if (Registers.InterruptMode == Z80InterruptMode.FixedAddress)
{
PushWord(Registers.PC);
Registers.PC = 0x38;
}
else if (Registers.InterruptMode == Z80InterruptMode.Vectorized)
{
var upper = Registers.I;
var lower = opcode;
var addr = Utilities.LETo16Bit(lower, upper);
PushWord(Registers.PC);
var jumpAddr = ReadWord(addr);
Registers.PC = jumpAddr;
}
}
public List <DisassembledInstruction> Disassemble(ushort address)
{
Registers.PC = address;
var instructions = new List <DisassembledInstruction>();
DisassembledInstruction instruction;
do
{
instruction = InstructionDecoder.DecodeNextInstruction(this);
instructions.Add(instruction);
} while (!instruction.ControlInstruction);
return(instructions);
}
public void ExecuteNextInstruction()
{
if (Registers.PC == 0)
{
throw new InvalidOperationException("Hit address 0");
}
if (Registers.PC == 5)
{
// Handle CP/M syscalls
switch (Registers.C)
{
case 2:
{
var inputByte = Registers.E;
var outputChar = Encoding.ASCII.GetString(new[] { inputByte })[0];
Console.Write(outputChar);
break;
}
case 9:
{
var strAddress = Registers.DE;
var inputBytes = new List <byte>();
byte inputByte;
_cycleCount += 3;
while ((inputByte = ReadMemory(strAddress)) != '$')
{
_cycleCount += 3;
inputBytes.Add(inputByte);
strAddress++;
}
var outputChar = Encoding.ASCII.GetString(inputBytes.ToArray());
Console.Write(outputChar);
break;
}
default:
// throw new NotImplementedException($"Unimplemented syscall {Registers.C}");
break;
}
FetchOpcode();
_cycleCount += Z80Instructions.RET(this, null);
}
var instruction = InstructionDecoder.DecodeNextInstruction(this);
var beforeCount = _cycleCount;
_cycleCount += instruction.Execute(this, instruction.InstructionBytes);
if (_cycleCount != ControlLines.SystemClock.Ticks)
{
throw new InvalidOperationException($"Cycle mismatch when executing instruction {instruction.Mnemonic} - expected {_cycleCount - beforeCount} but got {ControlLines.SystemClock.Ticks - beforeCount} cycles");
}
if (Registers.IFF1 && ControlLines.INT.Value == TristateWireState.LogicLow)
{
HandleINT();
}
}
