// --------------------
// --- INSTRUCTIONS ---
// --------------------
/// <summary>
/// Add with carry
/// </summary>
/// <param name="step">Step.</param>
private void ADC(StepInfo step)
{
byte a = this.a;
byte b = memory.Read(step.address);
byte c = this.c;
int sum = a + b + c;
this.a = (byte)sum;
SetZN(this.a);
if (sum > 0xFF)
{
this.c = 1;
}
else
{
this.c = 0;
}
if (((a ^ b) & 0x80) == 0 && ((a ^ this.a) & 0x80) != 0)
{
v = 1;
}
else
{
v = 0;
}
}
/// <summary>
/// Subtract with carry flag
/// </summary>
/// <param name="step">Step.</param>
private void SBC(StepInfo step)
{
byte a = this.a;
byte b = memory.Read(step.address);
byte c = this.c;
int sum = a - b - (1 - c);
this.a = (byte)sum;
SetZN(this.a);
if (sum >= 0)
{
c = 1;
}
else
{
c = 0;
}
if (((a ^ b) & 0x80) != 0 && ((a ^ this.a) & 0x80) != 0)
{
v = 1;
}
else
{
v = 0;
}
}
/// <summary>
/// Prints out the instruction
/// </summary>
private void LogInstruction(byte opCode, StepInfo step)
{
byte bytes = INSTRUCTION_SIZES [opCode];
string name = INSTRUCITON_NAMES [opCode];
string w0 = memory.Read((UInt16)(step.pc - 1)).ToString("X2");
string w1 = memory.Read(step.pc).ToString("X2");
string w2 = memory.Read((UInt16)(step.pc + 1)).ToString("X2");
if (bytes < 2)
{
w1 = " ";
}
if (bytes < 3)
{
w2 = " ";
}
string logString = string.Format("{0} {1} {2} {3} {4} {5,28} A:{6} X:{7} Y:{8} P:{9} SP:{10} CYC:{11}",
(step.pc - 1).ToString("X4"), w0, w1, w2, name, "",
a.ToString("X2"), x.ToString("X2"), y.ToString("X2"), GetFlags().ToString("X2"), sp.ToString("X2"), (cycles * 3) % 341);
console.Log(logString);
/*
* fmt.Printf(
* "%4X %s %s %s %s %28s"+
* "A:%02X X:%02X Y:%02X P:%02X SP:%02X CYC:%3d\n",
* cpu.PC, w0, w1, w2, name, "",
* cpu.A, cpu.X, cpu.Y, cpu.Flags(), cpu.SP, (cpu.Cycles*3)%341)
* }
*/
}
/// <summary>
/// Break (force interrupt)
/// </summary>
/// <param name="step">Step.</param>
private void BRK(StepInfo step)
{
Push16(pc);
PHP(step);
SEI(step);
pc = Read16(0xFFFE);
}
/// <summary>
/// Branch if overflow clear
/// </summary>
/// <param name="step">Step.</param>
private void BVC(StepInfo step)
{
if (v == 0)
{
pc = step.address;
AddBranchCycles(step);
}
}
/// <summary>
/// Increment memory
/// </summary>
/// <param name="step">Step.</param>
private void INC(StepInfo step)
{
byte value = (byte)(memory.Read(step.address) + 1);
memory.Write(step.address, value);
SetZN(value);
}
/// <summary>
/// Branch if minus
/// </summary>
/// <param name="step">Step.</param>
private void BMI(StepInfo step)
{
if (n != 0)
{
pc = step.address;
AddBranchCycles(step);
}
}
/// <summary>
/// Adds a cycle for branching and adds another cycle if the branch jumps
/// to a new page.
/// </summary>
/// <param name="info">Step Info.</param>
private void AddBranchCycles(StepInfo info)
{
++cycles;
if (PagesDiffer(info.pc, info.address))
{
++cycles;
}
}
/// <summary>
/// Bit test
/// </summary>
/// <param name="step">Step.</param>
private void BIT(StepInfo step)
{
byte value = memory.Read(step.address);
v = (byte)((value >> 6) & 1);
SetZ((byte)(value & a));
SetN(value);
}
/// <summary>
/// Logical shift right
/// </summary>
/// <param name="step">Step.</param>
private void LSR(StepInfo step)
{
if (step.mode == AddressMode.Accumulator)
{
c = (byte)(a & 1);
a = (byte)(a >> 1);
SetZN(a);
}
else
{
byte value = memory.Read(step.address);
c = (byte)(value & 1);
value = (byte)(value >> 1);
memory.Write(step.address, value);
SetZN(value);
}
}
/// <summary>
/// Rotate right
/// </summary>
/// <param name="step">Step.</param>
private void ROR(StepInfo step)
{
byte c = this.c;
if (step.mode == AddressMode.Accumulator)
{
this.c = (byte)(a & 1);
a = (byte)((a >> 1) | (c << 7));
SetZN(a);
}
else
{
byte value = memory.Read(step.address);
this.c = (byte)(value & 1);
value = (byte)((value >> 1) | (c << 7));
memory.Write(step.address, value);
SetZN(value);
}
}
public int Step()
{
// If we are stalling, stall for a cycle
if (stall > 0)
{
--stall;
return(1);
}
UInt64 startCycles = cycles;
HandleInterrupt();
byte opCode = memory.Read(pc);
AddressMode mode = (AddressMode)INSTRUCTION_MODES [opCode];
AddressInfo info = GetAddress(mode);
pc += INSTRUCTION_SIZES [opCode];
cycles += INSTRUCTION_CYCLES [opCode];
if (info.pageCrossed)
{
cycles += INSTRUCTION_PAGE_CYCLES [opCode];
}
StepInfo step = new StepInfo {
address = info.address,
pc = pc,
mode = mode
};
#if UNITY_EDITOR
LogInstruction(opCode, step);
#endif
table [opCode] (step);
return((int)(cycles - startCycles));
}
/// <summary>
/// Transfer x to stack pointer
/// </summary>
/// <param name="step">Step.</param>
private void TXS(StepInfo step)
{
sp = x;
}
private void ANC(StepInfo step)
{
}
private void XAA(StepInfo step)
{
}
private void TAS(StepInfo step)
{
}
private void AHX(StepInfo step)
{
}
/// <summary>
/// Transfer x to accumulator
/// </summary>
/// <param name="step">Step.</param>
private void TXA(StepInfo step)
{
a = x;
SetZN(a);
}
private void ARR(StepInfo step)
{
}
private void RRA(StepInfo step)
{
}
private void KIL(StepInfo step)
{
}
private void ISC(StepInfo step)
{
}
private void DCP(StepInfo step)
{
}
private void AXS(StepInfo step)
{
}
/// <summary>
/// Logical AND
/// </summary>
/// <param name="step">Step.</param>
private void AND(StepInfo step)
{
a = (byte)(a & memory.Read(step.address));
SetZN(a);
}
private void SHY(StepInfo step)
{
}
private void SLO(StepInfo step)
{
}
private void SRE(StepInfo step)
{
}
private void SAX(StepInfo step)
{
}
/// <summary>
/// Transfer Y to accumulator
/// </summary>
/// <param name="step">Step.</param>
private void TYA(StepInfo step)
{
a = y;
SetZN(a);
}