// // Copyright (c) Adrian Conlon. All rights reserved. // namespace EightBit { public class M6502(Bus bus) : M6502Core(bus) { #region Core instruction dispatching protected override bool MaybeExecute() { if (base.MaybeExecute()) { return true; } var cycles = this.Cycles; switch (this.OpCode) { case 0x02: this.Jam(); break; // *JAM case 0x03: this.IndexedIndirectXRead(); this.SLO(); break; // *SLO (indexed indirect X) case 0x04: this.ZeroPageRead(); break; // *NOP (zero page) case 0x07: this.ZeroPageRead(); this.SLO(); break; // *SLO (zero page) case 0x0b: this.ImmediateRead(); this.ANC(); break; // *ANC (immediate) case 0x0c: this.AbsoluteRead(); break; // *NOP (absolute) case 0x0f: this.AbsoluteRead(); this.SLO(); break; // *SLO (absolute) case 0x12: this.Jam(); break; // *JAM case 0x13: this.IndirectIndexedYAddress(); this.FixupRead(); this.SLO(); break; // *SLO (indirect indexed Y) case 0x14: this.ZeroPageXRead(); break; // *NOP (zero page, X) case 0x17: this.ZeroPageXRead(); this.SLO(); break; // *SLO (zero page, X) case 0x1a: this.SwallowRead(); break; // *NOP (implied) case 0x1b: this.AbsoluteYAddress(); this.FixupRead(); this.SLO(); break; // *SLO (absolute, Y) case 0x1c: this.AbsoluteXAddress(); this.MaybeFixupRead(); break; // *NOP (absolute, X) case 0x1f: this.AbsoluteXAddress(); this.FixupRead(); this.SLO(); break; // *SLO (absolute, X) case 0x22: this.Jam(); break; // *JAM case 0x23: this.IndexedIndirectXRead(); this.RLA(); ; break; // *RLA (indexed indirect X) case 0x27: this.ZeroPageRead(); this.RLA(); ; break; // *RLA (zero page) case 0x2b: this.ImmediateRead(); this.ANC(); break; // *ANC (immediate) case 0x2f: this.AbsoluteRead(); this.RLA(); break; // *RLA (absolute) case 0x32: this.Jam(); break; // *JAM case 0x33: this.IndirectIndexedYAddress(); this.FixupRead(); this.RLA(); break; // *RLA (indirect indexed Y) case 0x34: this.ZeroPageXRead(); break; // *NOP (zero page, X) case 0x37: this.ZeroPageXRead(); this.RLA(); ; break; // *RLA (zero page, X) case 0x3a: this.SwallowRead(); break; // *NOP (implied) case 0x3b: this.AbsoluteYAddress(); this.FixupRead(); this.RLA(); break; // *RLA (absolute, Y) case 0x3c: this.AbsoluteXAddress(); this.MaybeFixupRead(); break; // *NOP (absolute, X) case 0x3f: this.AbsoluteXAddress(); this.FixupRead(); this.RLA(); break; // *RLA (absolute, X) case 0x42: this.Jam(); break; // *JAM case 0x43: this.IndexedIndirectXRead(); this.SRE(); break; // *SRE (indexed indirect X) case 0x47: this.ZeroPageRead(); this.SRE(); break; // *SRE (zero page) case 0x4b: this.ImmediateRead(); this.ASR(); break; // *ASR (immediate) case 0x4f: this.AbsoluteRead(); this.SRE(); break; // *SRE (absolute) case 0x52: this.Jam(); break; // *JAM case 0x53: this.IndirectIndexedYAddress(); this.FixupRead(); this.SRE(); break; // *SRE (indirect indexed Y) case 0x57: this.ZeroPageXRead(); this.SRE(); break; // *SRE (zero page, X) case 0x5a: this.SwallowRead(); break; // *NOP (implied) case 0x5b: this.AbsoluteYAddress(); this.FixupRead(); this.SRE(); break; // *SRE (absolute, Y) case 0x5c: this.AbsoluteXAddress(); this.MaybeFixupRead(); break; // *NOP (absolute, X) case 0x5f: this.AbsoluteXAddress(); this.FixupRead(); this.SRE(); break; // *SRE (absolute, X) case 0x62: this.Jam(); break; // *JAM case 0x63: this.IndexedIndirectXRead(); this.RRA(); break; // *RRA (indexed indirect X) case 0x64: this.ZeroPageRead(); break; // *NOP (zero page) case 0x67: this.ZeroPageRead(); this.RRA(); break; // *RRA (zero page) case 0x6b: this.ImmediateRead(); this.ARR(); break; // *ARR (immediate) case 0x6f: this.AbsoluteRead(); this.RRA(); break; // *RRA (absolute) case 0x72: this.Jam(); break; // *JAM case 0x73: this.IndirectIndexedYAddress(); this.FixupRead(); this.RRA(); break; // *RRA (indirect indexed Y) case 0x74: this.ZeroPageXRead(); break; // *NOP (zero page, X) case 0x77: this.ZeroPageXRead(); this.RRA(); break; // *RRA (zero page, X) case 0x7a: this.SwallowRead(); break; // *NOP (implied) case 0x7b: this.AbsoluteYAddress(); this.FixupRead(); this.RRA(); break; // *RRA (absolute, Y) case 0x7c: this.AbsoluteXAddress(); this.MaybeFixupRead(); break; // *NOP (absolute, X) case 0x7f: this.AbsoluteXAddress(); this.FixupRead(); this.RRA(); break; // *RRA (absolute, X) case 0x80: this.ImmediateRead(); break; // *NOP (immediate) case 0x83: this.IndexedIndirectXAddress(); this.MemoryWrite((byte)(this.A & this.X)); break; // *SAX (indexed indirect X) case 0x87: this.ZeroPageAddress(); this.MemoryWrite((byte)(this.A & this.X)); break; // *SAX (zero page) case 0x89: this.ImmediateRead(); break; // *NOP (immediate) case 0x8b: this.ImmediateRead(); this.ANE(); break; // *ANE (immediate) case 0x8f: this.AbsoluteAddress(); this.MemoryWrite((byte)(this.A & this.X)); break; // *SAX (absolute) case 0x92: this.Jam(); break; // *JAM case 0x93: this.IndirectIndexedYAddress(); this.Fixup(); this.SHA(); break; // *SHA (indirect indexed, Y) case 0x97: this.ZeroPageYAddress(); this.MemoryWrite((byte)(this.A & this.X)); 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.IndexedIndirectXRead(); this.A = this.X = this.Through(); break; // *LAX (indexed indirect X) case 0xa7: this.ZeroPageRead(); this.A = this.X = this.Through(); break; // *LAX (zero page) case 0xab: this.ImmediateRead(); this.ATX(); break; // *ATX (immediate) case 0xaf: this.AbsoluteRead(); this.A = this.X = this.Through(); break; // *LAX (absolute) case 0xb2: this.Jam(); break; // *JAM case 0xb3: this.IndirectIndexedYRead(); this.A = this.X = this.Through(); break; // *LAX (indirect indexed Y) case 0xb7: this.ZeroPageYRead(); this.A = this.X = this.Through(); break; // *LAX (zero page, Y) case 0xbb: this.AbsoluteYAddress(); this.MaybeFixup(); this.LAS(); break; // *LAS (absolute, Y) case 0xbf: this.AbsoluteYRead(); this.A = this.X = this.Through(); break; // *LAX (absolute, Y) case 0xc3: this.IndexedIndirectXRead(); this.DCP(); break; // *DCP (indexed indirect X) case 0xc7: this.ZeroPageRead(); this.DCP(); break; // *DCP (zero page) case 0xcb: this.ImmediateRead(); this.AXS(); break; // *AXS (immediate) case 0xcf: this.AbsoluteRead(); this.DCP(); break; // *DCP (absolute) case 0xd2: this.Jam(); break; // *JAM case 0xd3: this.IndirectIndexedYAddress(); this.FixupRead(); this.DCP(); break; // *DCP (indirect indexed Y) case 0xd7: this.ZeroPageXRead(); this.DCP(); break; // *DCP (zero page, X) case 0xda: this.SwallowRead(); break; // *NOP (implied) case 0xdb: this.AbsoluteYAddress(); this.FixupRead(); this.DCP(); break; // *DCP (absolute, Y) case 0xdc: this.AbsoluteXAddress(); this.MaybeFixupRead(); break; // *NOP (absolute, X) case 0xdf: this.AbsoluteXAddress(); this.FixupRead(); this.DCP(); break; // *DCP (absolute, X) case 0xe3: this.IndexedIndirectXRead(); this.ISB(); break; // *ISB (indexed indirect X) case 0xe7: this.ZeroPageRead(); this.ISB(); break; // *ISB (zero page) case 0xeb: this.ImmediateRead(); this.SBC(); break; // *SBC (immediate) case 0xef: this.AbsoluteRead(); this.ISB(); break; // *ISB (absolute) case 0xf2: this.Jam(); break; // *JAM case 0xf3: this.IndirectIndexedYAddress(); this.FixupRead(); this.ISB(); break; // *ISB (indirect indexed Y) case 0xf7: this.ZeroPageXRead(); this.ISB(); break; // *ISB (zero page, X) case 0xfa: this.SwallowRead(); break; // *NOP (implied) case 0xfb: this.AbsoluteYAddress(); this.FixupRead(); this.ISB(); break; // *ISB (absolute, Y) case 0xfc: this.AbsoluteXAddress(); this.MaybeFixupRead(); 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.Word + relative); this.MaybeFixup(); } #endregion #endregion #region Instruction implementations #region Undocumented instructions #region Undocumented instructions with BCD effects private void ARR() { var value = this.Bus.Data; if (this.DecimalMasked != 0) this.ARR_d(value); else this.ARR_b(value); } private void ARR_d(byte value) { // With thanks to https://github.com/TomHarte/CLK // What a very strange instruction ARR is... this.A &= value; var unshiftedA = this.A; this.A = this.Through((this.A >> 1) | (this.Carry << 7)); this.SetFlag(StatusBits.VF, OverflowTest((byte)(this.A ^ (this.A << 1)))); 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; } private void ARR_b(byte value) { this.A &= value; this.A = this.Through((this.A >> 1) | (this.Carry << 7)); this.SetFlag(StatusBits.CF, OverflowTest(this.A)); this.SetFlag(StatusBits.VF, OverflowTest((byte)(this.A ^ (this.A << 1)))); } #endregion #region Undocumented instructions with fixup effects private void StoreFixupEffect(byte data) { ////var fixedAddress = (byte)(this.Bus.Address.High + 1); //var fixedAddress = this.FixedPage + 1; //var updated = (byte)(data & fixedAddress); //if (this.Fixed) //{ // this.Bus.Address.High = updated; //} //this.MemoryWrite(updated); byte updated; if (this.Fixed) { updated = (byte)(data & this.FixedPage); this.Bus.Address.High = updated; } else { updated = (byte)(data & this.UnfixedPage); 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 ANC() { this.AndR(); 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.Bus.Address.Assign(this.PC); this.MemoryRead(); 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.MemoryRead() & 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.AndR(); this.A = this.LSR(this.A); } private void ISB() { this.ModifyWrite(this.INC()); this.SBC(); } private void RLA() { this.ModifyWrite(this.ROL()); this.AndR(); } private void RRA() { this.ModifyWrite(this.ROR()); this.ADC(); } private void SLO() { this.ModifyWrite(this.ASL()); this.OrR(); } private void SRE() { this.ModifyWrite(this.LSR()); this.EorR(); } private void DCP() { this.ModifyWrite(this.DEC()); this.CMP(this.A); } #endregion #endregion } }