private void initOpCodes()
{
// ----------------------------------------------------------------------------------------------
// reinitialize OpCode table for additional 4 Z80 prefixes - none, CB, DD, ED, FD
// - combinations DD, FD, CB
m_OpCodes = new OperationCode[0x100 * 7];
m_dictOpCodePrefix = new Dictionary <int, int>(6);
m_dictOpCodePrefix.Add(0xCB, 0x100);
m_dictOpCodePrefix.Add(0xDD, 0x200);
m_dictOpCodePrefix.Add(0xED, 0x300);
m_dictOpCodePrefix.Add(0xFD, 0x400);
m_dictOpCodePrefix.Add(0xDDCB, 0x500);
m_dictOpCodePrefix.Add(0xFDCB, 0x600);
// ----------------------------------------------------------------------------------------------
// OpCode initialization (ordered according to Zilog Z80 CPU Specifications by Sean Young)
initOpCodes8BitLoadGroup(); // 8 bit Load group
initOpCodes16BitLoadGroup(); // 16 bit Load group
initOpCodesExchangeGroup(); // Exchange group
initOpCodesBlockTransferGroup(); // Block Transfer group
initOpCodesSearchGroup(); // Search group
initOpCodes8BitArithLogGroup(); // 8 bit Arithmetic & Logical group
initOpCodes16BitArithLogGroup(); // 16 bit Arithmetic & Logical group
initOpCodesJumpGroup(); // Jump group
initOpCodesCallAndReturnGroup(); // Call and Return group
initOpCodesGenPurposeArithGroup(); // General Purpose Arithmetic group
initOpCodesRotateAndShiftGroup(); // Rotate and Shift group
initOpCodesCPUControlGroup(); // CPU control group
initOpCodesBITManipulationGroup(); // Bit Manipulation group
initOpCodesInputAndOutputGroup(); // Input and Output group
}
public void emulateCycle()
{
if (m_Interrupt != InterruptSignal.None)
{
m_State = CPUState.interrupt;
}
switch (m_State)
{
case CPUState.fetchopcode:
m_PC_Start = m_PC;
m_Cycle = 1;
m_ExtraCycles = false;
m_byteDisplacement = 0;
m_OpCodePrefix = 0;
m_OpCodeIndex = getNextMemByte();
m_oc = m_OpCodes[m_OpCodeIndex];
int iIndexOffset = 0;
if (m_OpCodeIndex == 0xCB || // evaluate prefix
m_OpCodeIndex == 0xDD ||
m_OpCodeIndex == 0xED ||
m_OpCodeIndex == 0xFD)
{
m_OpCodePrefix = m_OpCodeIndex;
iIndexOffset = m_dictOpCodePrefix[m_OpCodePrefix];
m_OpCodeIndex = getNextMemByte();
if (m_OpCodeIndex == 0xCB) // DD CB or FD CB combination
{
m_OpCodePrefix <<= 8;
m_OpCodePrefix |= m_OpCodeIndex;
iIndexOffset = m_dictOpCodePrefix[m_OpCodePrefix];
m_byteDisplacement = getNextMemByte(); // contains displacement before OpCode
m_OpCodeIndex = getNextMemByte();
}
m_oc = m_OpCodes[iIndexOffset + m_OpCodeIndex];
}
// check if OpCode is defined
if (String.IsNullOrEmpty(m_oc.OpCode) || m_oc.executeOperation == null)
{
string sMessage;
if (m_OpCodePrefix > 0)
{
sMessage = String.Format("PC {0:X4} : OpCode {1:X2} {2:X2} unknown!!!",
m_PC_Start, (byte)m_OpCodePrefix, (byte)m_OpCodeIndex);
}
else
{
sMessage = String.Format("PC {0:X4} : OpCode {1:X2} unknown!!!",
m_PC_Start, (byte)m_OpCodeIndex);
}
throw new NotImplementedException(sMessage);
}
#if CPU_TRACE
m_ei.Counter++;
m_ei.PC = m_PC_Start;
m_ei.Bytes = "";
if (m_OpCodePrefix != 0)
{
m_ei.Bytes += String.Format("{0:X2} ", m_OpCodePrefix);
}
m_ei.Bytes += String.Format("{0:X2} ", m_OpCodeIndex);
m_ei.OpCode = m_oc.OpCode;
m_ei.Op1 = "";
m_ei.Op2 = "";
#endif
// increase R register (only bits 6-0)
m_reg_R = (byte)((m_reg_R & 0x80) | ((m_reg_R + 1) & 0x7F));
// set for next processing state
m_wordValue = 0;
m_byteValue = 0;
#if NO_CYCLE_FILLUP
m_MaxCycles = m_PC - m_PC_Start;
#else
m_MaxCycles = m_oc.Cycles;
#endif
m_State = CPUState.addressing;
break;
case CPUState.interrupt: // interrupt
switch (m_Interrupt)
{
case InterruptSignal.NMI:
// perform a RST 66h
m_reg_SP -= 2;;
writeMemWord(m_reg_SP, m_PC);
m_PC = 0x0066;
m_State = CPUState.fetchopcode;
m_Interrupt = InterruptSignal.None;
break;
case InterruptSignal.IRQ:
switch (m_IM)
{
case 0:
// TODO Z80 implement IM 0
throw new NotImplementedException("Z80 IM 0 not implemented!");
case 1: // IM 1 - perform a RST 38h
m_reg_SP -= 2;;
writeMemWord(m_reg_SP, m_PC);
m_PC = 0x0038;
m_State = CPUState.fetchopcode;
m_Interrupt = InterruptSignal.None;
break;
case 2: // IM 2 - jump to interrupt vector
m_reg_SP -= 2;;
writeMemWord(m_reg_SP, m_PC);
m_PC = m_reg_I;
m_State = CPUState.fetchopcode;
m_Interrupt = InterruptSignal.None;
break;
}
break;
}
break;
case CPUState.addressing: // addressing
m_Cycle++;
m_oc.executeAddressing();
break;
case CPUState.operation:
if (m_Cycle >= m_MaxCycles) // emulate cycle exactness by making operation effective on last cycle
{
m_oc.executeOperation();
if (m_Cycle < m_MaxCycles)
{
m_Cycle++; // operation executed induced another cycle (e.g. branch operations)
}
else
{
m_State = CPUState.fetchopcode; // operation finished -> get next opcode
}
#if CPU_TRACE
//if (m_PC_Start == 0x188) { m_TraceActive = true; m_ei.Counter = 1; }
//if (m_PC_Start == 0x18B) m_TraceActive = false;
if (m_State == CPUState.fetchopcode && m_TraceActive)
{
StringBuilder sb = new StringBuilder();
if ((m_ei.Counter % 20) == 1)
{
sb.Clear();
sb.Append("PC-- ");
sb.Append("----------- OpCo Op1,Op2---|");
sb.Append("A F B C D E H L ");
//sb.Append("A' F' B' C' D' E' H' L' ");
sb.Append("IX IY SP I R |");
sb.Append("SZ5H3vNC|");
sb.Append("Disassembly Check---|");
sb.Append("STACK ---------------");
Debug.WriteLine(sb.ToString());
}
sb.Clear();
sb.AppendFormat("{0:X4} ", m_ei.PC);
sb.Append(m_ei.Bytes.PadRight(12));
sb.Append(m_ei.OpCode.PadRight(5));
if (!String.IsNullOrEmpty(m_ei.Op1) && !String.IsNullOrEmpty(m_ei.Op2))
{
sb.Append((m_ei.Op1 + "," + m_ei.Op2).PadRight(10));
}
else
{
sb.Append((m_ei.Op1 + m_ei.Op2).PadRight(10));
}
sb.Append("|");
sb.AppendFormat("{0:X2} ", m_reg_A);
sb.AppendFormat("{0:X2} ", Flags);
sb.AppendFormat("{0:X2} ", m_reg_B);
sb.AppendFormat("{0:X2} ", m_reg_C);
sb.AppendFormat("{0:X2} ", m_reg_D);
sb.AppendFormat("{0:X2} ", m_reg_E);
sb.AppendFormat("{0:X2} ", m_reg_H);
sb.AppendFormat("{0:X2} ", m_reg_L);
//sb.AppendFormat("{0:X2} ", m_reg_A_Alt);
//sb.AppendFormat("{0:X2} ", m_reg_Flags_Alt);
//sb.AppendFormat("{0:X2} ", m_reg_B_Alt);
//sb.AppendFormat("{0:X2} ", m_reg_C_Alt);
//sb.AppendFormat("{0:X2} ", m_reg_D_Alt);
//sb.AppendFormat("{0:X2} ", m_reg_E_Alt);
//sb.AppendFormat("{0:X2} ", m_reg_H_Alt);
//sb.AppendFormat("{0:X2} ", m_reg_L_Alt);
sb.AppendFormat("{0:X4} ", m_reg_IX);
sb.AppendFormat("{0:X4} ", m_reg_IY);
sb.AppendFormat("{0:X4} ", m_reg_SP);
sb.AppendFormat("{0:X2} ", m_reg_I);
sb.AppendFormat("{0:X2} ", m_reg_R);
sb.Append("|");
sb.Append(Convert.ToString(Flags, 2).PadLeft(8, '0'));
sb.Append("|");
string strDisassemblyCheck = m_dis.Disassemble(() => readMemByte(m_ei.PC++));
sb.Append(strDisassemblyCheck.PadRight(20));
sb.Append("|");
for (int spDump = m_reg_SP; spDump <= m_reg_SP + 5; spDump++)
{
sb.AppendFormat("{0:X2} ", readMemByte((UInt16)spDump));
}
Debug.WriteLine(sb.ToString());
sb = null;
}
#endif
}
else
{
m_Cycle++;
}
break;
}
}
private StringBuilder m_sbDebug; // build operations debug string
#endif
public MOS6502() : base()
{
// initialize OpCode table
// reference see http://homepage.ntlworld.com/cyborgsystems/CS_Main/6502/6502.htm
m_OpCodes[0x00] = new OperationCode("BRK", 1, 7, _ADDR_IMP, _BRK);
m_OpCodes[0x01] = new OperationCode("ORA", 2, 6, _ADDR_INDX_1, _ORA);
m_OpCodes[0x05] = new OperationCode("ORA", 2, 3, _ADDR_ZP, _ORA);
m_OpCodes[0x06] = new OperationCode("ASL", 2, 5, _ADDR_ZP, _ASL);
m_OpCodes[0x08] = new OperationCode("PHP", 1, 3, _ADDR_IMP, _PHP);
m_OpCodes[0x09] = new OperationCode("ORA", 2, 2, _ADDR_IMM, _ORA);
m_OpCodes[0x0a] = new OperationCode("ASL", 1, 2, _ADDR_ACC, _ASL);
m_OpCodes[0x0d] = new OperationCode("ORA", 3, 4, _ADDR_ABS, _ORA);
m_OpCodes[0x0e] = new OperationCode("ASL", 3, 6, _ADDR_ABS, _ASL);
m_OpCodes[0x10] = new OperationCode("BPL", 2, 2, _ADDR_REL_1, _BPL);
m_OpCodes[0x11] = new OperationCode("ORA", 2, 5, _ADDR_INDY_1, _ORA);
m_OpCodes[0x15] = new OperationCode("ORA", 2, 4, _ADDR_ZPX_1, _ORA);
m_OpCodes[0x16] = new OperationCode("ASL", 2, 6, _ADDR_ZPX_1, _ASL);
m_OpCodes[0x18] = new OperationCode("CLC", 1, 2, _ADDR_IMP, _CLC);
m_OpCodes[0x19] = new OperationCode("ORA", 3, 4, _ADDR_ABSY_1, _ORA);
m_OpCodes[0x1d] = new OperationCode("ORA", 3, 4, _ADDR_ABSX_1, _ORA);
m_OpCodes[0x1e] = new OperationCode("ASL", 3, 7, _ADDR_ABSX_1, _ASL);
m_OpCodes[0x20] = new OperationCode("JSR", 3, 6, _ADDR_ABS, _JSR);
m_OpCodes[0x21] = new OperationCode("AND", 2, 6, _ADDR_INDX_1, _AND);
m_OpCodes[0x24] = new OperationCode("BIT", 2, 3, _ADDR_ZP, _BIT);
m_OpCodes[0x25] = new OperationCode("AND", 2, 3, _ADDR_ZP, _AND);
m_OpCodes[0x26] = new OperationCode("ROL", 2, 5, _ADDR_ZP, _ROL);
m_OpCodes[0x28] = new OperationCode("PLP", 1, 4, _ADDR_IMP, _PLP);
m_OpCodes[0x29] = new OperationCode("AND", 2, 2, _ADDR_IMM, _AND);
m_OpCodes[0x2a] = new OperationCode("ROL", 1, 2, _ADDR_ACC, _ROL);
m_OpCodes[0x2c] = new OperationCode("BIT", 3, 4, _ADDR_ABS, _BIT);
m_OpCodes[0x2d] = new OperationCode("AND", 3, 4, _ADDR_ABS, _AND);
m_OpCodes[0x2e] = new OperationCode("ROL", 3, 6, _ADDR_ABS, _ROL);
m_OpCodes[0x30] = new OperationCode("BMI", 2, 2, _ADDR_REL_1, _BMI);
m_OpCodes[0x31] = new OperationCode("AND", 2, 5, _ADDR_INDY_1, _AND);
m_OpCodes[0x35] = new OperationCode("AND", 2, 4, _ADDR_ZPX_1, _AND);
m_OpCodes[0x36] = new OperationCode("ROL", 2, 6, _ADDR_ZPX_1, _ROL);
m_OpCodes[0x38] = new OperationCode("SEC", 1, 2, _ADDR_IMP, _SEC);
m_OpCodes[0x39] = new OperationCode("AND", 3, 4, _ADDR_ABSY_1, _AND);
m_OpCodes[0x3d] = new OperationCode("AND", 3, 4, _ADDR_ABSX_1, _AND);
m_OpCodes[0x3e] = new OperationCode("ROL", 3, 7, _ADDR_ABSX_1, _ROL);
m_OpCodes[0x40] = new OperationCode("RTI", 1, 6, _ADDR_IMP, _RTI);
m_OpCodes[0x41] = new OperationCode("EOR", 2, 6, _ADDR_INDX_1, _EOR);
m_OpCodes[0x45] = new OperationCode("EOR", 2, 3, _ADDR_ZP, _EOR);
m_OpCodes[0x46] = new OperationCode("LSR", 2, 5, _ADDR_ZP, _LSR);
m_OpCodes[0x48] = new OperationCode("PHA", 1, 3, _ADDR_IMP, _PHA);
m_OpCodes[0x49] = new OperationCode("EOR", 2, 2, _ADDR_IMM, _EOR);
m_OpCodes[0x4a] = new OperationCode("LSR", 1, 2, _ADDR_ACC, _LSR);
m_OpCodes[0x4c] = new OperationCode("JMP", 3, 3, _ADDR_ABS, _JMP);
m_OpCodes[0x4d] = new OperationCode("EOR", 3, 4, _ADDR_ABS, _EOR);
m_OpCodes[0x4e] = new OperationCode("LSR", 3, 6, _ADDR_ABS, _LSR);
m_OpCodes[0x50] = new OperationCode("BVC", 2, 2, _ADDR_REL_1, _BVC);
m_OpCodes[0x51] = new OperationCode("EOR", 2, 5, _ADDR_INDY_1, _EOR);
m_OpCodes[0x55] = new OperationCode("EOR", 2, 4, _ADDR_ZPX_1, _EOR);
m_OpCodes[0x56] = new OperationCode("LSR", 2, 6, _ADDR_ZPX_1, _LSR);
m_OpCodes[0x58] = new OperationCode("CLI", 1, 2, _ADDR_IMP, _CLI);
m_OpCodes[0x59] = new OperationCode("EOR", 3, 4, _ADDR_ABSY_1, _EOR);
m_OpCodes[0x5d] = new OperationCode("EOR", 3, 4, _ADDR_ABSX_1, _EOR);
m_OpCodes[0x5e] = new OperationCode("LSR", 3, 7, _ADDR_ABSX_1, _LSR);
m_OpCodes[0x60] = new OperationCode("RTS", 1, 6, _ADDR_IMP, _RTS);
m_OpCodes[0x61] = new OperationCode("ADC", 2, 6, _ADDR_INDX_1, _ADC);
m_OpCodes[0x65] = new OperationCode("ADC", 2, 3, _ADDR_ZP, _ADC);
m_OpCodes[0x66] = new OperationCode("ROR", 2, 5, _ADDR_ZP, _ROR);
m_OpCodes[0x68] = new OperationCode("PLA", 1, 4, _ADDR_IMP, _PLA);
m_OpCodes[0x69] = new OperationCode("ADC", 2, 2, _ADDR_IMM, _ADC);
m_OpCodes[0x6a] = new OperationCode("ROR", 1, 2, _ADDR_ACC, _ROR);
m_OpCodes[0x6c] = new OperationCode("JMP", 3, 5, _ADDR_IND_1, _JMP);
m_OpCodes[0x6d] = new OperationCode("ADC", 3, 4, _ADDR_ABS, _ADC);
m_OpCodes[0x6e] = new OperationCode("ROR", 3, 6, _ADDR_ABS, _ROR);
m_OpCodes[0x70] = new OperationCode("BVS", 2, 2, _ADDR_REL_1, _BVS);
m_OpCodes[0x71] = new OperationCode("ADC", 2, 5, _ADDR_INDY_1, _ADC);
m_OpCodes[0x75] = new OperationCode("ADC", 2, 4, _ADDR_ZPX_1, _ADC);
m_OpCodes[0x76] = new OperationCode("ROR", 2, 6, _ADDR_ZPX_1, _ROR);
m_OpCodes[0x78] = new OperationCode("SEI", 1, 2, _ADDR_IMP, _SEI);
m_OpCodes[0x79] = new OperationCode("ADC", 3, 4, _ADDR_ABSY_1, _ADC);
m_OpCodes[0x7d] = new OperationCode("ADC", 3, 4, _ADDR_ABSX_1, _ADC);
m_OpCodes[0x7e] = new OperationCode("ROR", 3, 7, _ADDR_ABSX_1, _ROR);
m_OpCodes[0x81] = new OperationCode("STA", 2, 6, _ADDR_INDX_1, _STA);
m_OpCodes[0x84] = new OperationCode("STY", 2, 3, _ADDR_ZP, _STY);
m_OpCodes[0x85] = new OperationCode("STA", 2, 3, _ADDR_ZP, _STA);
m_OpCodes[0x86] = new OperationCode("STX", 2, 3, _ADDR_ZP, _STX);
m_OpCodes[0x88] = new OperationCode("DEY", 1, 2, _ADDR_IMP, _DEY);
m_OpCodes[0x8a] = new OperationCode("TXA", 1, 2, _ADDR_IMP, _TXA);
m_OpCodes[0x8c] = new OperationCode("STY", 3, 4, _ADDR_ABS, _STY);
m_OpCodes[0x8d] = new OperationCode("STA", 3, 4, _ADDR_ABS, _STA);
m_OpCodes[0x8e] = new OperationCode("STX", 3, 4, _ADDR_ABS, _STX);
m_OpCodes[0x90] = new OperationCode("BCC", 2, 2, _ADDR_REL_1, _BCC);
m_OpCodes[0x91] = new OperationCode("STA", 2, 6, _ADDR_INDY_1, _STA);
m_OpCodes[0x94] = new OperationCode("STY", 2, 4, _ADDR_ZPX_1, _STY);
m_OpCodes[0x95] = new OperationCode("STA", 2, 4, _ADDR_ZPX_1, _STA);
m_OpCodes[0x96] = new OperationCode("STX", 2, 4, _ADDR_ZPY_1, _STX);
m_OpCodes[0x98] = new OperationCode("TYA", 1, 2, _ADDR_IMP, _TYA);
m_OpCodes[0x99] = new OperationCode("STA", 3, 5, _ADDR_ABSY_1, _STA);
m_OpCodes[0x9a] = new OperationCode("TXS", 1, 2, _ADDR_IMP, _TXS);
m_OpCodes[0x9d] = new OperationCode("STA", 3, 5, _ADDR_ABSX_1, _STA);
m_OpCodes[0xa0] = new OperationCode("LDY", 2, 2, _ADDR_IMM, _LDY);
m_OpCodes[0xa1] = new OperationCode("LDA", 2, 6, _ADDR_INDX_1, _LDA);
m_OpCodes[0xa2] = new OperationCode("LDX", 2, 2, _ADDR_IMM, _LDX);
m_OpCodes[0xa4] = new OperationCode("LDY", 2, 3, _ADDR_ZP, _LDY);
m_OpCodes[0xa5] = new OperationCode("LDA", 2, 3, _ADDR_ZP, _LDA);
m_OpCodes[0xa6] = new OperationCode("LDX", 2, 3, _ADDR_ZP, _LDX);
m_OpCodes[0xa8] = new OperationCode("TAY", 1, 2, _ADDR_IMP, _TAY);
m_OpCodes[0xa9] = new OperationCode("LDA", 2, 2, _ADDR_IMM, _LDA);
m_OpCodes[0xaa] = new OperationCode("TAX", 1, 2, _ADDR_IMP, _TAX);
m_OpCodes[0xac] = new OperationCode("LDY", 3, 4, _ADDR_ABS, _LDY);
m_OpCodes[0xad] = new OperationCode("LDA", 3, 4, _ADDR_ABS, _LDA);
m_OpCodes[0xae] = new OperationCode("LDX", 3, 4, _ADDR_ABS, _LDX);
m_OpCodes[0xB0] = new OperationCode("BCS", 2, 2, _ADDR_REL_1, _BCS);
m_OpCodes[0xb1] = new OperationCode("LDA", 2, 5, _ADDR_INDY_1, _LDA);
m_OpCodes[0xb4] = new OperationCode("LDY", 2, 4, _ADDR_ZPX_1, _LDY);
m_OpCodes[0xb5] = new OperationCode("LDA", 2, 4, _ADDR_ZPX_1, _LDA);
m_OpCodes[0xb6] = new OperationCode("LDX", 2, 4, _ADDR_ZPY_1, _LDX);
m_OpCodes[0xb8] = new OperationCode("CLV", 1, 2, _ADDR_IMP, _CLV);
m_OpCodes[0xb9] = new OperationCode("LDA", 3, 4, _ADDR_ABSY_1, _LDA);
m_OpCodes[0xba] = new OperationCode("TSX", 1, 2, _ADDR_IMP, _TSX);
m_OpCodes[0xbc] = new OperationCode("LDY", 3, 4, _ADDR_ABSX_1, _LDY);
m_OpCodes[0xbd] = new OperationCode("LDA", 3, 4, _ADDR_ABSX_1, _LDA);
m_OpCodes[0xbe] = new OperationCode("LDX", 3, 4, _ADDR_ABSY_1, _LDX);
m_OpCodes[0xc0] = new OperationCode("CPY", 2, 2, _ADDR_IMM, _CPY);
m_OpCodes[0xc1] = new OperationCode("CMP", 2, 6, _ADDR_INDX_1, _CMP);
m_OpCodes[0xc4] = new OperationCode("CPY", 2, 3, _ADDR_ZP, _CPY);
m_OpCodes[0xc5] = new OperationCode("CMP", 2, 3, _ADDR_ZP, _CMP);
m_OpCodes[0xc6] = new OperationCode("DEC", 2, 5, _ADDR_ZP, _DEC);
m_OpCodes[0xc8] = new OperationCode("INY", 1, 2, _ADDR_IMP, _INY);
m_OpCodes[0xc9] = new OperationCode("CMP", 2, 2, _ADDR_IMM, _CMP);
m_OpCodes[0xca] = new OperationCode("DEX", 1, 2, _ADDR_IMP, _DEX);
m_OpCodes[0xcc] = new OperationCode("CPY", 3, 4, _ADDR_ABS, _CPY);
m_OpCodes[0xcd] = new OperationCode("CMP", 3, 4, _ADDR_ABS, _CMP);
m_OpCodes[0xce] = new OperationCode("DEC", 3, 6, _ADDR_ABS, _DEC);
m_OpCodes[0xD0] = new OperationCode("BNE", 2, 2, _ADDR_REL_1, _BNE);
m_OpCodes[0xd1] = new OperationCode("CMP", 2, 5, _ADDR_INDY_1, _CMP);
m_OpCodes[0xd5] = new OperationCode("CMP", 2, 4, _ADDR_ZPX_1, _CMP);
m_OpCodes[0xd6] = new OperationCode("DEC", 2, 6, _ADDR_ZPX_1, _DEC);
m_OpCodes[0xd8] = new OperationCode("CLD", 1, 2, _ADDR_IMP, _CLD);
m_OpCodes[0xd9] = new OperationCode("CMP", 3, 4, _ADDR_ABSY_1, _CMP);
m_OpCodes[0xdd] = new OperationCode("CMP", 3, 4, _ADDR_ABSX_1, _CMP);
m_OpCodes[0xde] = new OperationCode("DEC", 3, 7, _ADDR_ABSX_1, _DEC);
m_OpCodes[0xe0] = new OperationCode("CPX", 2, 2, _ADDR_IMM, _CPX);
m_OpCodes[0xe1] = new OperationCode("SBC", 2, 6, _ADDR_INDX_1, _SBC);
m_OpCodes[0xe4] = new OperationCode("CPX", 2, 3, _ADDR_ZP, _CPX);
m_OpCodes[0xe5] = new OperationCode("SBC", 2, 3, _ADDR_ZP, _SBC);
m_OpCodes[0xe6] = new OperationCode("INC", 2, 5, _ADDR_ZP, _INC);
m_OpCodes[0xe8] = new OperationCode("INX", 1, 2, _ADDR_IMP, _INX);
m_OpCodes[0xe9] = new OperationCode("SBC", 2, 2, _ADDR_IMM, _SBC);
m_OpCodes[0xea] = new OperationCode("NOP", 1, 2, _ADDR_IMP, _NOP);
m_OpCodes[0xec] = new OperationCode("CPX", 3, 4, _ADDR_ABS, _CPX);
m_OpCodes[0xed] = new OperationCode("SBC", 3, 4, _ADDR_ABS, _SBC);
m_OpCodes[0xee] = new OperationCode("INC", 3, 6, _ADDR_ABS, _INC);
m_OpCodes[0xF0] = new OperationCode("BEQ", 2, 2, _ADDR_REL_1, _BEQ);
m_OpCodes[0xf1] = new OperationCode("SBC", 2, 5, _ADDR_INDY_1, _SBC);
m_OpCodes[0xf5] = new OperationCode("SBC", 2, 4, _ADDR_ZPX_1, _SBC);
m_OpCodes[0xf6] = new OperationCode("INC", 2, 6, _ADDR_ZPX_1, _INC);
m_OpCodes[0xf8] = new OperationCode("SED", 1, 2, _ADDR_IMP, _SED);
m_OpCodes[0xf9] = new OperationCode("SBC", 3, 4, _ADDR_ABSY_1, _SBC);
m_OpCodes[0xfd] = new OperationCode("SBC", 3, 4, _ADDR_ABSX_1, _SBC);
m_OpCodes[0xfe] = new OperationCode("INC", 3, 7, _ADDR_ABSX_1, _INC);
}
protected CPUState m_State; // current state of the CPU
public CPU8Bit() : base()
{
m_PC = 0x0000; // Program counter starts at $0
m_OpCodes = new OperationCode[0x100];
}
public void emulateCycle()
{
switch (m_State)
{
case CPUState.fetchopcode:
// check and process Interrupt (only when in OpCode fetch)
if (m_Interrupt)
{
m_MaxCycles = 7;
m_Cycle = 1;
m_address = 0;
m_addr = Addressing._not_set_;
m_OperandValue = 0;
m_State = CPUState.interrupt;
break;
}
// save current PC for debugging / tracing
m_PC_Start = m_PC;
// get the next byte and then move the program counter forward
byte opCode = getNextMemByte();
// get from OpCode table
m_oc = m_OpCodes[opCode];
// check if OpCode is defined
if (String.IsNullOrEmpty(m_oc.OpCode) || m_oc.executeOperation == null || m_oc.executeAddressing == null)
{
string sMessage = String.Format("PC {0:X4} : OpCode {1:X2} unknown!!!", m_PC_Start, opCode);
throw new NotImplementedException(sMessage);
}
#if CPU_TRACE
m_sbDebug = new StringBuilder();
m_sbDebug.AppendFormat("{0:X4}:{1:X2} {2} ", m_PC_Start, opCode, m_oc.OpCode);
#endif
m_MaxCycles = m_oc.Cycles;
m_Cycle = 1;
m_address = 0;
m_addr = Addressing._not_set_;
m_OperandValue = 0;
m_State = CPUState.addressing;
break;
case CPUState.addressing: // addressing
m_oc.executeAddressing();
m_Cycle++;
break;
case CPUState.operation:
if (m_Cycle == m_MaxCycles) // emulate cycle exactness by making operation effective on last cycle
{
m_oc.executeOperation();
if (m_Cycle < m_MaxCycles)
{
m_Cycle++; // operation executed induced another cycle (e.g. branch operations)
}
else
{
m_State = CPUState.fetchopcode; // operation finished -> get next opcode
#if CPU_TRACE
m_sbDebug.AppendFormat("\tPC:{0:X4} A:{1:X2} X:{2:X2} Y:{3:X2} SP:{4:X4} |{5}| STACK: {6:X2} {7:X2} {8:X2} {9:X2}",
m_PC,
m_reg_A,
m_reg_X,
m_reg_Y,
Reg_SP,
StatusString,
m_ram[m_StackPtr - m_ramOffset],
m_ram[m_StackPtr + 1 - m_ramOffset],
m_ram[m_StackPtr + 2 - m_ramOffset],
m_ram[m_StackPtr + 3 - m_ramOffset]);
Debug.WriteLine(m_sbDebug.ToString());
#endif
}
}
else
{
m_Cycle++;
}
break;
case CPUState.interrupt:
if (m_Cycle == m_MaxCycles) // emulate cycle exactness by making operation effective on last cycle
{
push_stack((byte)(m_PC >> 8));
push_stack((byte)m_PC);
push_stack(m_reg_SR);
Flag_I = true;
m_PC = readMemWord(0xFFFE); // fetch IRQ vector
m_State = CPUState.fetchopcode;
m_Interrupt = false;
}
else
{
m_Cycle++;
}
break;
}
}