// // Copyright (c) Adrian Conlon. All rights reserved. // namespace M6502 { using EightBit; public class MOS6502(Bus bus) : Core(bus) { #region Core instruction dispatching protected override bool MaybeExecute() { if (base.MaybeExecute()) { return true; } var cycles = this.Cycles; switch (this.OpCode) { case 0x02: this.SwallowRead(); this.JAM(); break; // *JAM case 0x03: this.IndexedIndirectX(); this.SLO(); break; // *SLO (indexed indirect X) case 0x04: this.ZeroPage(); NOP(); break; // *NOP (zero page) case 0x07: this.ZeroPage(); this.SLO(); break; // *SLO (zero page) case 0x0b: this.Immediate(); this.ANC(); break; // *ANC (immediate) case 0x0c: this.Absolute(); NOP(); break; // *NOP (absolute) case 0x0f: this.Absolute(); this.SLO(); break; // *SLO (absolute) case 0x12: this.SwallowRead(); this.JAM(); break; // *JAM case 0x13: this.IndirectIndexedYAddress(); this.FixupRead(); this.SLO(); break; // *SLO (indirect indexed Y) case 0x14: this.ZeroPageX(); NOP(); break; // *NOP (zero page, X) case 0x17: this.ZeroPageX(); this.SLO(); break; // *SLO (zero page, X) case 0x1a: this.SwallowRead(); NOP(); break; // *NOP (implied) case 0x1b: this.AbsoluteYAddress(); this.FixupRead(); this.SLO(); break; // *SLO (absolute, Y) case 0x1c: this.AbsoluteXAddress(); this.MaybeFixupRead(); NOP(); break; // *NOP (absolute, X) case 0x1e: this.AbsoluteXAddress(); this.FixupRead(); this.ASL(); break; // ASL (absolute, X) case 0x1f: this.AbsoluteXAddress(); this.FixupRead(); this.SLO(); break; // *SLO (absolute, X) case 0x22: this.SwallowRead(); this.JAM(); break; // *JAM case 0x23: this.IndexedIndirectX(); this.RLA(); break; // *RLA (indexed indirect X) case 0x27: this.ZeroPage(); this.RLA(); break; // *RLA (zero page) case 0x2b: this.Immediate(); this.ANC(); break; // *ANC (immediate) case 0x2f: this.Absolute(); this.RLA(); break; // *RLA (absolute) case 0x32: this.SwallowRead(); this.JAM(); break; // *JAM case 0x33: this.IndirectIndexedYAddress(); this.FixupRead(); this.RLA(); break; // *RLA (indirect indexed Y) case 0x34: this.ZeroPageX(); NOP(); break; // *NOP (zero page, X) case 0x37: this.ZeroPageX(); this.RLA(); break; // *RLA (zero page, X) case 0x3a: this.SwallowRead(); NOP(); break; // *NOP (implied) case 0x3b: this.AbsoluteYAddress(); this.FixupRead(); this.RLA(); break; // *RLA (absolute, Y) case 0x3c: this.AbsoluteXAddress(); this.MaybeFixupRead(); NOP(); break; // *NOP (absolute, X) case 0x3e: this.AbsoluteXAddress(); this.FixupRead(); this.ROL(); break; // ROL (absolute, X) case 0x3f: this.AbsoluteXAddress(); this.FixupRead(); this.RLA(); break; // *RLA (absolute, X) case 0x42: this.SwallowRead(); this.JAM(); break; // *JAM case 0x43: this.IndexedIndirectX(); this.SRE(); break; // *SRE (indexed indirect X) case 0x47: this.ZeroPage(); this.SRE(); break; // *SRE (zero page) case 0x4b: this.Immediate(); this.ASR(); break; // *ASR (immediate) case 0x4f: this.Absolute(); this.SRE(); break; // *SRE (absolute) case 0x52: this.SwallowRead(); this.JAM(); break; // *JAM case 0x53: this.IndirectIndexedYAddress(); this.FixupRead(); this.SRE(); break; // *SRE (indirect indexed Y) case 0x57: this.ZeroPageX(); this.SRE(); break; // *SRE (zero page, X) case 0x5a: this.SwallowRead(); NOP(); break; // *NOP (implied) case 0x5b: this.AbsoluteYAddress(); this.FixupRead(); this.SRE(); break; // *SRE (absolute, Y) case 0x5c: this.AbsoluteXAddress(); this.MaybeFixupRead(); NOP(); break; // *NOP (absolute, X) case 0x5e: this.AbsoluteXAddress(); this.FixupRead(); this.LSR(); break; // LSR (absolute, X) case 0x5f: this.AbsoluteXAddress(); this.FixupRead(); this.SRE(); break; // *SRE (absolute, X) case 0x62: this.SwallowRead(); this.JAM(); break; // *JAM case 0x63: this.IndexedIndirectX(); this.RRA(); break; // *RRA (indexed indirect X) case 0x64: this.ZeroPage(); NOP(); break; // *NOP (zero page) case 0x67: this.ZeroPage(); this.RRA(); break; // *RRA (zero page) case 0x6b: this.Immediate(); this.ARR(); break; // *ARR (immediate) case 0x6f: this.Absolute(); this.RRA(); break; // *RRA (absolute) case 0x72: this.SwallowRead(); this.JAM(); break; // *JAM case 0x73: this.IndirectIndexedYAddress(); this.FixupRead(); this.RRA(); break; // *RRA (indirect indexed Y) case 0x74: this.ZeroPageX(); NOP(); break; // *NOP (zero page, X) case 0x77: this.ZeroPageX(); this.RRA(); break; // *RRA (zero page, X) case 0x7a: this.SwallowRead(); NOP(); break; // *NOP (implied) case 0x7b: this.AbsoluteYAddress(); this.FixupRead(); this.RRA(); break; // *RRA (absolute, Y) case 0x7c: this.AbsoluteXAddress(); this.MaybeFixupRead(); NOP(); break; // *NOP (absolute, X) case 0x7e: this.AbsoluteXAddress(); this.FixupRead(); this.ROR(); break; // ROR (absolute, X) case 0x7f: this.AbsoluteXAddress(); this.FixupRead(); this.RRA(); break; // *RRA (absolute, X) case 0x80: this.Immediate(); NOP(); break; // *NOP (immediate) case 0x83: this.IndexedIndirectXAddress(); this.SAX(); break; // *SAX (indexed indirect X) case 0x87: this.ZeroPageAddress(); this.SAX(); break; // *SAX (zero page) case 0x89: this.Immediate(); NOP(); break; // *NOP (immediate) case 0x8b: this.Immediate(); this.ANE(); break; // *ANE (immediate) case 0x8f: this.AbsoluteAddress(); this.SAX(); break; // *SAX (absolute) case 0x92: this.SwallowRead(); this.JAM(); break; // *JAM case 0x93: this.IndirectIndexedYAddress(); this.Fixup(); this.SHA(); break; // *SHA (indirect indexed, Y) case 0x97: this.ZeroPageYAddress(); this.SAX(); break; // *SAX (zero page, Y) case 0x9b: this.AbsoluteYAddress(); this.Fixup(); this.TAS(); break; // *TAS (absolute, Y) case 0x9c: this.AbsoluteXAddress(); this.Fixup(); this.SYA(); break; // *SYA (absolute, X) case 0x9e: this.AbsoluteYAddress(); this.Fixup(); this.SXA(); break; // *SXA (absolute, Y) case 0x9f: this.AbsoluteYAddress(); this.Fixup(); this.SHA(); break; // *SHA (absolute, Y) case 0xa3: this.IndexedIndirectX(); this.LAX(); break; // *LAX (indexed indirect X) case 0xa7: this.ZeroPage(); this.LAX(); break; // *LAX (zero page) case 0xab: this.Immediate(); this.ATX(); break; // *ATX (immediate) case 0xaf: this.Absolute(); this.LAX(); break; // *LAX (absolute) case 0xb2: this.SwallowRead(); this.JAM(); break; // *JAM case 0xb3: this.IndirectIndexedY(); this.LAX(); break; // *LAX (indirect indexed Y) case 0xb7: this.ZeroPageY(); this.LAX(); break; // *LAX (zero page, Y) case 0xbb: this.AbsoluteYAddress(); this.MaybeFixupRead(); this.LAS(); break; // *LAS (absolute, Y) case 0xbf: this.AbsoluteY(); this.LAX(); break; // *LAX (absolute, Y) case 0xc3: this.IndexedIndirectX(); this.DCP(); break; // *DCP (indexed indirect X) case 0xc7: this.ZeroPage(); this.DCP(); break; // *DCP (zero page) case 0xcb: this.Immediate(); this.AXS(); break; // *AXS (immediate) case 0xcf: this.Absolute(); this.DCP(); break; // *DCP (absolute) case 0xd2: this.SwallowRead(); this.JAM(); break; // *JAM case 0xd3: this.IndirectIndexedYAddress(); this.FixupRead(); this.DCP(); break; // *DCP (indirect indexed Y) case 0xd7: this.ZeroPageX(); this.DCP(); break; // *DCP (zero page, X) case 0xda: this.SwallowRead(); NOP(); break; // *NOP (implied) case 0xdb: this.AbsoluteYAddress(); this.FixupRead(); this.DCP(); break; // *DCP (absolute, Y) case 0xdc: this.AbsoluteXAddress(); this.MaybeFixupRead(); NOP(); break; // *NOP (absolute, X) case 0xdf: this.AbsoluteXAddress(); this.FixupRead(); this.DCP(); break; // *DCP (absolute, X) case 0xe3: this.IndexedIndirectX(); this.ISB(); break; // *ISB (indexed indirect X) case 0xe7: this.ZeroPage(); this.ISB(); break; // *ISB (zero page) case 0xeb: this.Immediate(); this.SBC(); break; // *SBC (immediate) case 0xef: this.Absolute(); this.ISB(); break; // *ISB (absolute) case 0xf2: this.SwallowRead(); this.JAM(); break; // *JAM case 0xf3: this.IndirectIndexedYAddress(); this.FixupRead(); this.ISB(); break; // *ISB (indirect indexed Y) case 0xf7: this.ZeroPageX(); this.ISB(); break; // *ISB (zero page, X) case 0xfa: this.SwallowRead(); NOP(); break; // *NOP (implied) case 0xfb: this.AbsoluteYAddress(); this.FixupRead(); this.ISB(); break; // *ISB (absolute, Y) case 0xfc: this.AbsoluteXAddress(); this.MaybeFixupRead(); NOP(); break; // *NOP (absolute, X) case 0xff: this.AbsoluteXAddress(); this.FixupRead(); this.ISB(); break; // *ISB (absolute, X) } return cycles != this.Cycles; } #endregion #region Bus/Memory Access protected override void ModifyWrite(byte data) { // The read will have already taken place... this.MemoryWrite(); // Modify cycle this.MemoryWrite(data); // Write cycle } #endregion #region Addressing modes protected override void IndirectAddress() { this.AbsoluteAddress(); this.GetAddressPaged(); } #region Address page fixup protected override void Fixup() { this.MemoryRead(); this.Bus.Address.High = this.FixedPage; } protected override void FixupBranch(sbyte relative) { this.NoteFixedAddress(this.PC.Joined + relative); this.MaybeFixup(); } #endregion #endregion #region Instruction implementations #region Undocumented instructions #region Undocumented instructions with BCD effects protected virtual void ARR() { if (this.Denary != 0) this.DecimalARR(); else this.BinaryARR(); } private byte CoreARR() { this.A &= this.Bus.Data; var unshiftedA = this.A; this.RORA(); this.SetFlag(StatusBits.VF, OverflowTest((byte)(this.A ^ this.A << 1))); return unshiftedA; } private void DecimalARR() { // With thanks to https://github.com/TomHarte/CLK // What a very strange instruction ARR is... var unshiftedA = this.CoreARR(); if (LowerNibble(unshiftedA) + (unshiftedA & 0x1) > 5) this.A = (byte)(LowerNibble((byte)(this.A + 6)) | HigherNibble(this.A)); this.SetFlag(StatusBits.CF, HigherNibble(unshiftedA) + (unshiftedA & 0x10) > 0x50); if (this.Carry != 0) this.A += 0x60; } protected void BinaryARR() { this.CoreARR(); this.SetFlag(StatusBits.CF, OverflowTest(this.A)); } #endregion #region Undocumented instructions with fixup effects private void StoreFixupEffect(byte data) { var mask = (byte)(this.UnfixedPage + 1); // base_hi + 1, always var updated = (byte)(data & mask); if (this.Fixed) { this.Bus.Address.High = updated; } this.MemoryWrite(updated); } private void SHA() => this.StoreFixupEffect((byte)(this.A & this.X)); private void SYA() => this.StoreFixupEffect(this.Y); private void SXA() => this.StoreFixupEffect(this.X); #endregion private void SAX() => this.MemoryWrite((byte)(this.A & this.X)); private void LAX() { this.LDA(); this.LDX(); } private void ANC() { this.AND(); this.SetFlag(StatusBits.CF, NegativeTest(this.A)); } private void AXS() { this.X = this.Through(this.BinarySUB((byte)(this.A & this.X))); this.ResetFlag(StatusBits.CF, this.Intermediate.High); } private void JAM() { this.MemoryRead(0xff, 0xff); this.Bus.Address.Low = 0xfe; this.MemoryRead(); this.MemoryRead(); this.Bus.Address.Low = 0xff; this.MemoryRead(); this.MemoryRead(); this.MemoryRead(); this.MemoryRead(); this.MemoryRead(); this.MemoryRead(); } private void TAS() { this.S = (byte)(this.A & this.X); this.SHA(); } private void LAS() => this.A = this.X = this.S = this.Through(this.Bus.Data & this.S); private void ANE() => this.A = this.Through((this.A | 0xee) & this.X & this.Bus.Data); private void ATX() => this.A = this.X = this.Through((this.A | 0xee) & this.Bus.Data); private void ASR() { this.AND(); this.LSRA(); } private void ISB() { this.INC(); this.SBC(); } private void RLA() { this.ROL(); this.AND(); } private void RRA() { this.ROR(); this.ADC(); } private void SLO() { this.ASL(); this.ORA(); } private void SRE() { this.LSR(); this.EOR(); } private void DCP() { this.DEC(); this.CMP(); } #endregion #region Processor variations protected override byte BinaryADC(byte data) { var result = base.BinaryADC(data); this.AdjustNZ(result); return result; } protected override byte BinarySUB(byte operand, int borrow = 0) { var result = base.BinarySUB(operand, borrow); this.AdjustNZ(result); return result; } protected override byte DecimalSUB(byte operand, int borrow) { var result = base.DecimalSUB(operand, borrow); this.AdjustNZ(this.Intermediate.Low); return result; } #endregion #endregion } }