private bool checkSignals()
{
if (RST) // RESET
{
RESET();
refresh(); //+1T
FX = OPFX.NONE;
XFX = OPXFX.NONE;
HALTED = false;
IFF1 = false;
IFF2 = false;
IM = 0; // ?
regs.PC = 0;
regs.IR = 0;
//regs.SP = 0xFFFF; //?
//regs.AF = 0xFFFF; //?
Tact += 4 - 1; // total should be 3T?
return true;
}
else if (NMI)
{
// 10T (4, 3, 3)
if (HALTED) // workaround for Z80 snapshot halt issue + comfortable debugging
regs.PC++;
NMIACK_M1();
Tact += 3;
refresh();
IFF1 = false;
HALTED = false;
regs.SP--;
WRMEM(regs.SP, (byte)(regs.PC >> 8));
Tact += 3;
regs.SP--;
WRMEM(regs.SP, (byte)(regs.PC & 0xFF));
regs.PC = 0x0066;
Tact += 3;
return true;
}
else if (INT && (!BINT) && IFF1)
{
// IM0: ?13T (?,?,?)
// IM1: 13T (?,?,?)
// IM2: ?19T (?,?,?,?)
if (HALTED) // workaround for Z80 snapshot halt issue + comfortable debugging
regs.PC++;
INTACK_M1();
// M1: 7T = interrupt acknowledgement; SP--
regs.SP--;
//if (HALTED) ??
// Tact += 2;
Tact += 4 + 2;
refresh();
RzxCounter--; // fix because INTAK should not be calculated
IFF1 = false;
IFF2 = false;
HALTED = false;
WRMEM(regs.SP, (byte)(regs.PC >> 8)); // M2: 3T write PCH; SP--
regs.SP--;
Tact += 3;
WRMEM(regs.SP, (byte)(regs.PC & 0xFF)); // M3: 3T write PCL
Tact += 3;
if (IM == 0) // IM 0: execute instruction taken from BUS with timing T+2???
{
regs.MW = 0x0038; // workaround: just execute #FF
}
else if (IM == 1) // IM 1: execute #FF with timing T+2 (11+2=13T)
{
regs.MW = 0x0038;
}
else // IM 2: VH=reg.I; VL=BUS; PC=[V]
{
ushort adr = (ushort)((regs.IR & 0xFF00) | BUS);
regs.MW = RDMEM(adr); // M4: 3T read VL
Tact += 3;
regs.MW += (ushort)(RDMEM(++adr) * 0x100); // M5: 3T read VH, PC=V
Tact += 3;
}
regs.PC = regs.MW;
return true;
}
return false;
}
public void ExecCycle()
{
byte cmd = 0;
if (XFX == OPXFX.NONE && FX == OPFX.NONE)
{
if (checkSignals())
return;
cmd = RDMEM_M1(regs.PC);
}
else
{
if (checkSignals())
return;
cmd = RDMEM(regs.PC);
}
Tact += 3;
regs.PC++;
if (XFX == OPXFX.CB)
{
BINT = false;
ExecCB(cmd);
XFX = OPXFX.NONE;
FX = OPFX.NONE;
}
else if (XFX == OPXFX.ED)
{
refresh();
BINT = false;
ExecED(cmd);
XFX = OPXFX.NONE;
FX = OPFX.NONE;
}
else if (cmd == 0xDD)
{
refresh();
FX = OPFX.IX;
BINT = true;
}
else if (cmd == 0xFD)
{
refresh();
FX = OPFX.IY;
BINT = true;
}
else if (cmd == 0xCB)
{
refresh();
XFX = OPXFX.CB;
BINT = true;
}
else if (cmd == 0xED)
{
refresh();
XFX = OPXFX.ED;
BINT = true;
}
else
{
refresh();
BINT = false;
ExecDirect(cmd);
FX = OPFX.NONE;
}
}