public void Decode_Instruction(String inst, int address)
{
switch (inst)
{
case "HLT":
registers[2] |= 0x2;
break;
case "LOD":
if (registers[1] == 2)
{
registers[0] = (Bus.Get_Values())[0];
}
else
{
registers[0] = mainMemory[registers[1]];
}
break;
case "STR":
if (registers[1] == 1)
{
mainMemory[registers[1]] &= 0x3;
mainMemory[registers[1]] = (UInt16)(((UInt16)registers[0] & 0xC) | mainMemory[registers[1]]);
}
else
{
mainMemory[registers[1]] = (UInt16)registers[0];
}
if (registers[1] < 3)
{
Bus.Update_Bus(mainMemory[2], mainMemory[1], mainMemory[0], 16);
}
break;
case "ADD":
int temp1 = registers[0];
int temp2 = mainMemory[registers[1]];
int result = temp1 + temp2;
result += (registers[2] & 0x1);
registers[0] = result & 0xF;
//Set overflow bit
if (((temp1 & 0x8) == 0x8) && ((temp2 & 0x8) == 0x8) && ((result & 0x8) != 0x8))
{
registers[2] |= 0x8;
registers[2] ^= (result & 0x8);
}
else if (((temp1 & 0x8) != 0x8) && ((temp2 & 0x8) != 0x8) && ((result & 0x8) == 0x8))
{
registers[2] |= 0x8;
registers[2] ^= (result & 0x8);
}
else
{
registers[2] &= 0x7;
registers[2] ^= (result & 0x8);
}
//If there was a carry out
if ((result & 0x10) == 0x10)
{
registers[2] |= 0x1;
}
else
{
registers[2] &= 0xE;
}
break;
case "NOP":
break;
case "NND":
registers[0] &= mainMemory[registers[1]];
registers[0] = ~registers[0];
registers[0] &= 0xF;
break;
case "JMP":
if (registers[0] == 0)
{
registers[3] = registers[1];
}
break;
case "CXA":
registers[0] = registers[2];
break;
default:
registers[2] |= 0x2;
break;
}
}
