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();
}
}
public static uint GetInstructionRealAddress(Cpu8086 cpu, Register segmentPrefix, int instruction, int instructionValue, int instructionDisplacement)
{
switch (instruction)
{
case OpCodeManager.ARG_DEREFERENCE:
if (segmentPrefix == Register.Invalid)
{
segmentPrefix = instructionValue == 6 ? Register.SS : Register.DS; // BP needs SS segment
}
var addr = GetInstructionAddress(cpu, instruction, instructionValue, instructionDisplacement);
return(SegmentToAddress(cpu.GetRegister(segmentPrefix), addr));
case OpCodeManager.ARG_MEMORY:
if (segmentPrefix == Register.Invalid)
{
segmentPrefix = Register.DS;
}
var address = GetInstructionAddress(cpu, instruction, instructionValue, instructionDisplacement);
return(SegmentToAddress(cpu.GetRegister(segmentPrefix), address));
default:
throw new NotImplementedException();
}
}
public static ushort GetInstructionAddress(Cpu8086 cpu, int instruction, int instructionValue, int instructionDisplacement)
{
switch (instruction)
{
case OpCodeManager.ARG_DEREFERENCE:
ushort address;
switch (instructionValue)
{
case 0:
address = (ushort)(cpu.GetRegister(Register.BX) + cpu.GetRegister(Register.SI));
break;
case 1:
address = (ushort)(cpu.GetRegister(Register.BX) + cpu.GetRegister(Register.DI));
break;
case 2:
address = (ushort)(cpu.GetRegister(Register.BP) + cpu.GetRegister(Register.SI));
break;
case 3:
address = (ushort)(cpu.GetRegister(Register.BP) + cpu.GetRegister(Register.DI));
break;
case 4:
address = cpu.GetRegister(Register.SI);
break;
case 5:
address = cpu.GetRegister(Register.DI);
break;
case 6:
address = cpu.GetRegister(Register.BP);
break;
case 7:
address = cpu.GetRegister(Register.BX);
break;
default:
throw new NotImplementedException();
}
return((ushort)(address + instructionDisplacement));
case OpCodeManager.ARG_MEMORY:
return((ushort)instructionValue);
default:
throw new NotImplementedException();
}
}
