ushort IInstructionFetcher.FetchU16()
{
var value = _cpu.ReadU16(InstructionHelper.SegmentToAddress(
_cpu.GetRegister(Register.CS),
(ushort)(_cpu.GetRegister(Register.IP) + _fetched)));
_fetched += 2;
return(value);
}
public static ushort GetInstructionValue(Cpu8086 cpu, OpCodeManager.OpCodeFlag flag, Register segmentPrefix, int instruction, int instructionValue, int instructionDisplacement)
{
switch (instruction)
{
case (int)Register.AX:
case (int)Register.CX:
case (int)Register.DX:
case (int)Register.BX:
case (int)Register.SP:
case (int)Register.BP:
case (int)Register.SI:
case (int)Register.DI:
case (int)Register.IP:
case (int)Register.CS:
case (int)Register.DS:
case (int)Register.ES:
case (int)Register.SS:
return(cpu.GetRegister((Register)instruction));
case OpCodeManager.ARG_BYTE_REGISTER:
return(cpu.GetRegisterU8((Register)instructionValue));
case OpCodeManager.ARG_DEREFERENCE:
case OpCodeManager.ARG_MEMORY:
var address = GetInstructionRealAddress(cpu, segmentPrefix, instruction, instructionValue, instructionDisplacement);
return(flag.Has(OpCodeManager.OpCodeFlag.Size8) ? cpu.ReadU8(address) : cpu.ReadU16(address));
case OpCodeManager.ARG_CONSTANT:
return((ushort)instructionValue);
default:
throw new NotImplementedException();
}
}
