#include "nes/cpu.hh" #include "nes/ppu.hh" #include "nes/controller.hh" #include "nes/mapper.hh" #include "nes/util/snapshot.hh" namespace nes { cpu::cpu(ppu& ppu, mapper& mapper, controller& controller_1, controller& controller_2) : ppu_{ ppu } , mapper_{ mapper } , controller_1_{ controller_1 } , controller_2_{ controller_2 } { registers_.pc = read16(address{ 0xFFFC }); } auto cpu::build_snapshot(snapshot& snapshot) -> void { snapshot.cpu_cycle = current_cycles_; snapshot.ram = std::vector(std::begin(ram_), std::end(ram_)); snapshot.registers.pc = registers_.pc; snapshot.registers.sp = registers_.sp; snapshot.registers.a = registers_.a; snapshot.registers.x = registers_.x; snapshot.registers.y = registers_.y; snapshot.registers.p = registers_.p; snapshot.registers.c = registers_.c; snapshot.registers.z = registers_.z; snapshot.registers.i = registers_.i; snapshot.registers.d = registers_.d; snapshot.registers.b = registers_.b; snapshot.registers.v = registers_.v; snapshot.registers.n = registers_.n; } auto cpu::stall_cycles(cycle_count const count) -> void { current_cycles_ += count; } auto cpu::trigger_nmi() -> void { nmi_pending_ = true; } auto cpu::step() -> void { // See https://www.nesdev.org/wiki/CPU_unofficial_opcodes #ifdef NES_ENABLE_PPU if (nmi_pending_) { execute_interrupt(address{ 0xFFFA }); nmi_pending_ = false; } #endif auto const opcode = advance_pc8(); switch (opcode) { case 0x00: run_brk(); break; case 0x01: run_ora(); break; case 0x02: run_stp(); break; case 0x03: run_slo(); break; case 0x04: run_nop(); break; case 0x05: run_ora(); break; case 0x06: run_asl(); break; case 0x07: run_slo(); break; case 0x08: run_php(); break; case 0x09: run_ora(); break; case 0x0A: run_asl(); break; case 0x0B: run_anc(); break; case 0x0C: run_nop(); break; case 0x0D: run_ora(); break; case 0x0E: run_asl(); break; case 0x0F: run_slo(); break; case 0x10: run_bpl(); break; case 0x11: run_ora(); break; case 0x12: run_stp(); break; case 0x13: run_slo(); break; case 0x14: run_nop(); break; case 0x15: run_ora(); break; case 0x16: run_asl(); break; case 0x17: run_slo(); break; case 0x18: run_clc(); break; case 0x19: run_ora(); break; case 0x1A: run_nop(); break; case 0x1B: run_slo(); break; case 0x1C: run_nop(); break; case 0x1D: run_ora(); break; case 0x1E: run_asl(); break; case 0x1F: run_slo(); break; case 0x20: run_jsr(); break; case 0x21: run_and(); break; case 0x22: run_stp(); break; case 0x23: run_rla(); break; case 0x24: run_bit(); break; case 0x25: run_and(); break; case 0x26: run_rol(); break; case 0x27: run_rla(); break; case 0x28: run_plp(); break; case 0x29: run_and(); break; case 0x2A: run_rol(); break; case 0x2B: run_anc(); break; case 0x2C: run_bit(); break; case 0x2D: run_and(); break; case 0x2E: run_rol(); break; case 0x2F: run_rla(); break; case 0x30: run_bmi(); break; case 0x31: run_and(); break; case 0x32: run_stp(); break; case 0x33: run_rla(); break; case 0x34: run_nop(); break; case 0x35: run_and(); break; case 0x36: run_rol(); break; case 0x37: run_rla(); break; case 0x38: run_sec(); break; case 0x39: run_and(); break; case 0x3A: run_nop(); break; case 0x3B: run_rla(); break; case 0x3C: run_nop(); break; case 0x3D: run_and(); break; case 0x3E: run_rol(); break; case 0x3F: run_rla(); break; case 0x40: run_rti(); break; case 0x41: run_eor(); break; case 0x42: run_stp(); break; case 0x43: run_sre(); break; case 0x44: run_nop(); break; case 0x45: run_eor(); break; case 0x46: run_lsr(); break; case 0x47: run_sre(); break; case 0x48: run_pha(); break; case 0x49: run_eor(); break; case 0x4A: run_lsr(); break; case 0x4B: run_alr(); break; case 0x4C: run_jmp(); break; case 0x4D: run_eor(); break; case 0x4E: run_lsr(); break; case 0x4F: run_sre(); break; case 0x50: run_bvc(); break; case 0x51: run_eor(); break; case 0x52: run_stp(); break; case 0x53: run_sre(); break; case 0x54: run_nop(); break; case 0x55: run_eor(); break; case 0x56: run_lsr(); break; case 0x57: run_sre(); break; case 0x58: run_cli(); break; case 0x59: run_eor(); break; case 0x5A: run_nop(); break; case 0x5B: run_sre(); break; case 0x5C: run_nop(); break; case 0x5D: run_eor(); break; case 0x5E: run_lsr(); break; case 0x5F: run_sre(); break; case 0x60: run_rts(); break; case 0x61: run_adc(); break; case 0x62: run_stp(); break; case 0x63: run_rra(); break; case 0x64: run_nop(); break; case 0x65: run_adc(); break; case 0x66: run_ror(); break; case 0x67: run_rra(); break; case 0x68: run_pla(); break; case 0x69: run_adc(); break; case 0x6A: run_ror(); break; case 0x6B: run_arr(); break; case 0x6C: run_jmp(); break; case 0x6D: run_adc(); break; case 0x6E: run_ror(); break; case 0x6F: run_rra(); break; case 0x70: run_bvs(); break; case 0x71: run_adc(); break; case 0x72: run_stp(); break; case 0x73: run_rra(); break; case 0x74: run_nop(); break; case 0x75: run_adc(); break; case 0x76: run_ror(); break; case 0x77: run_rra(); break; case 0x78: run_sei(); break; case 0x79: run_adc(); break; case 0x7A: run_nop(); break; case 0x7B: run_rra(); break; case 0x7C: run_nop(); break; case 0x7D: run_adc(); break; case 0x7E: run_ror(); break; case 0x7F: run_rra(); break; case 0x80: run_nop(); break; case 0x81: run_sta(); break; case 0x82: run_nop(); break; case 0x83: run_sax(); break; case 0x84: run_sty(); break; case 0x85: run_sta(); break; case 0x86: run_stx(); break; case 0x87: run_sax(); break; case 0x88: run_dey(); break; case 0x89: run_nop(); break; case 0x8A: run_txa(); break; case 0x8B: run_xaa(); break; case 0x8C: run_sty(); break; case 0x8D: run_sta(); break; case 0x8E: run_stx(); break; case 0x8F: run_sax(); break; case 0x90: run_bcc(); break; case 0x91: run_sta(); break; case 0x92: run_stp(); break; case 0x93: run_ahx(); break; case 0x94: run_sty(); break; case 0x95: run_sta(); break; case 0x96: run_stx(); break; case 0x97: run_sax(); break; case 0x98: run_tya(); break; case 0x99: run_sta(); break; case 0x9A: run_txs(); break; case 0x9B: run_tas(); break; case 0x9C: run_shy(); break; case 0x9D: run_sta(); break; case 0x9E: run_shx(); break; case 0x9F: run_ahx(); break; case 0xA0: run_ldy(); break; case 0xA1: run_lda(); break; case 0xA2: run_ldx(); break; case 0xA3: run_lax(); break; case 0xA4: run_ldy(); break; case 0xA5: run_lda(); break; case 0xA6: run_ldx(); break; case 0xA7: run_lax(); break; case 0xA8: run_tay(); break; case 0xA9: run_lda(); break; case 0xAA: run_tax(); break; case 0xAB: run_lax(); break; case 0xAC: run_ldy(); break; case 0xAD: run_lda(); break; case 0xAE: run_ldx(); break; case 0xAF: run_lax(); break; case 0xB0: run_bcs(); break; case 0xB1: run_lda(); break; case 0xB2: run_stp(); break; case 0xB3: run_lax(); break; case 0xB4: run_ldy(); break; case 0xB5: run_lda(); break; case 0xB6: run_ldx(); break; case 0xB7: run_lax(); break; case 0xB8: run_clv(); break; case 0xB9: run_lda(); break; case 0xBA: run_tsx(); break; case 0xBB: run_las(); break; case 0xBC: run_ldy(); break; case 0xBD: run_lda(); break; case 0xBE: run_ldx(); break; case 0xBF: run_lax(); break; case 0xC0: run_cpy(); break; case 0xC1: run_cmp(); break; case 0xC2: run_nop(); break; case 0xC3: run_dcp(); break; case 0xC4: run_cpy(); break; case 0xC5: run_cmp(); break; case 0xC6: run_dec(); break; case 0xC7: run_dcp(); break; case 0xC8: run_iny(); break; case 0xC9: run_cmp(); break; case 0xCA: run_dex(); break; case 0xCB: run_axs(); break; case 0xCC: run_cpy(); break; case 0xCD: run_cmp(); break; case 0xCE: run_dec(); break; case 0xCF: run_dcp(); break; case 0xD0: run_bne(); break; case 0xD1: run_cmp(); break; case 0xD2: run_stp(); break; case 0xD3: run_dcp(); break; case 0xD4: run_nop(); break; case 0xD5: run_cmp(); break; case 0xD6: run_dec(); break; case 0xD7: run_dcp(); break; case 0xD8: run_cld(); break; case 0xD9: run_cmp(); break; case 0xDA: run_nop(); break; case 0xDB: run_dcp(); break; case 0xDC: run_nop(); break; case 0xDD: run_cmp(); break; case 0xDE: run_dec(); break; case 0xDF: run_dcp(); break; case 0xE0: run_cpx(); break; case 0xE1: run_sbc(); break; case 0xE2: run_nop(); break; case 0xE3: run_isc(); break; case 0xE4: run_cpx(); break; case 0xE5: run_sbc(); break; case 0xE6: run_inc(); break; case 0xE7: run_isc(); break; case 0xE8: run_inx(); break; case 0xE9: run_sbc(); break; case 0xEA: run_nop(); break; case 0xEB: run_sbc(); break; case 0xEC: run_cpx(); break; case 0xED: run_sbc(); break; case 0xEE: run_inc(); break; case 0xEF: run_isc(); break; case 0xF0: run_beq(); break; case 0xF1: run_sbc(); break; case 0xF2: run_stp(); break; case 0xF3: run_isc(); break; case 0xF4: run_nop(); break; case 0xF5: run_sbc(); break; case 0xF6: run_inc(); break; case 0xF7: run_isc(); break; case 0xF8: run_sed(); break; case 0xF9: run_sbc(); break; case 0xFA: run_nop(); break; case 0xFB: run_isc(); break; case 0xFC: run_nop(); break; case 0xFD: run_sbc(); break; case 0xFE: run_inc(); break; case 0xFF: run_isc(); break; default: std::abort(); } } // ----------------------------------------------------------------------------------------------------------------- // Instructions // ----------------------------------------------------------------------------------------------------------------- template auto cpu::run_brk() -> void { // BRK: Break fetch_operand(); execute_interrupt(address{ 0xFFFE }); } template auto cpu::run_ora() -> void { // ORA: Logical Inclusive OR auto operand = fetch_operand(); eval_ora(operand.read()); current_cycles_ += operand.get_cycles(); } auto cpu::run_stp() -> void { // TODO: Proper STP handling std::abort(); } template auto cpu::run_slo() -> void { // SLO: ASL + ORA auto operand = fetch_operand(force_page_crossing::yes); auto const tmp = eval_asl(operand.read()); operand.write(tmp); eval_ora(tmp); current_cycles_ += operand.get_cycles() + cycle_count::from_cpu(2); } template auto cpu::run_nop() -> void { // NOP: NOP auto operand = fetch_operand(); current_cycles_ += operand.get_cycles(); } auto cpu::run_nop() -> void { // NOP: NOP current_cycles_ += cycle_count::from_cpu(2); } auto cpu::run_php() -> void { // PHP: Push Processor Status eval_php(); current_cycles_ += cycle_count::from_cpu(3); } template auto cpu::run_asl() -> void { // ASL: Arithmetic Shift Left auto operand = fetch_operand(); operand.write(eval_asl(operand.read())); current_cycles_ += shift_cycle_count(); } template auto cpu::run_anc() -> void { // ANC: AND #i + copy N to C auto operand = fetch_operand(); eval_and(operand.read()); registers_.c = registers_.n; current_cycles_ += operand.get_cycles(); } template auto cpu::run_bpl() -> void { // BPL: Break If Positive branch(!registers_.n); } auto cpu::run_clc() -> void { // CLC: Clear Carry Flag registers_.c = false; current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_jsr() -> void { // JSR: Jump to Subroutine static_assert(Mode == addressing_mode::absolute, "JSR only supports absolute addressing."); push_stack16(registers_.pc + 1); auto operand = fetch_operand(); registers_.pc = operand.get_address().get_absolute(); current_cycles_ += cycle_count::from_cpu(6); } template auto cpu::run_and() -> void { // AND: Logical AND auto operand = fetch_operand(); eval_and(operand.read()); current_cycles_ += operand.get_cycles(); } template auto cpu::run_rla() -> void { // RLA: ROL + AND auto operand = fetch_operand(force_page_crossing::yes); auto const tmp = eval_rol(operand.read()); operand.write(tmp); eval_and(tmp); current_cycles_ += operand.get_cycles() + cycle_count::from_cpu(2); } template auto cpu::run_bit() -> void { // BIT: Bit Test auto operand = fetch_operand(); auto const arg = operand.read(); auto const res = (registers_.a & arg) != 0; registers_.z = res == 0; registers_.v = (arg & 0x40) != 0; registers_.n = (arg & 0x80) != 0; current_cycles_ += operand.get_cycles(); } template auto cpu::run_rol() -> void { // ROR: Rotate Left auto operand = fetch_operand(); auto const result = eval_rol(operand.read()); operand.write(result); current_cycles_ += shift_cycle_count(); } auto cpu::run_plp() -> void { // PLP: Pull Processor Status eval_plp(); current_cycles_ += cycle_count::from_cpu(4); } template auto cpu::run_bmi() -> void { branch(registers_.n); } auto cpu::run_sec() -> void { // SEC: Set Carry Flag registers_.c = true; current_cycles_ += cycle_count::from_cpu(2); } auto cpu::run_rti() -> void { // RTI: Return From Interrupt eval_plp(); registers_.pc = pop_stack16(); current_cycles_ += cycle_count::from_cpu(6); } template auto cpu::run_eor() -> void { // EOR: Exclusive OR auto operand = fetch_operand(); eval_eor(operand.read()); current_cycles_ += operand.get_cycles(); } template auto cpu::run_sre() -> void { // SRE: LSR + EOR auto operand = fetch_operand(force_page_crossing::yes); auto const tmp = eval_lsr(operand.read()); operand.write(tmp); eval_eor(tmp); current_cycles_ += operand.get_cycles() + cycle_count::from_cpu(2); } template auto cpu::run_lsr() -> void { // LSR: Logical Shift Right auto operand = fetch_operand(); auto const old_val = operand.read(); auto const new_val = static_cast(old_val >> 1); operand.write(new_val); registers_.c = (old_val & 0x1) != 0; update_zn(new_val); current_cycles_ += shift_cycle_count(); } template auto cpu::run_alr() -> void { // ALR: AND #i + LSR A auto operand = fetch_operand(); eval_and(operand.read()); registers_.a = eval_lsr(registers_.a); current_cycles_ += operand.get_cycles(); } auto cpu::run_pha() -> void { // PHA: Push Accumulator push_stack8(registers_.a); current_cycles_ += cycle_count::from_cpu(3); } template auto cpu::run_jmp() -> void { // JMP: Jump auto operand = fetch_operand(); registers_.pc = operand.get_address().get_absolute(); current_cycles_ += jump_cycle_count(); } template auto cpu::run_bvc() -> void { // BVC: Branch If Overflow Clear branch(!registers_.v); } auto cpu::run_cli() -> void { // CLI: Clear Interrupt Disable registers_.i = false; current_cycles_ += cycle_count::from_cpu(2); } auto cpu::run_rts() -> void { // RTS: Return from Subroutine auto const addr = address{ pop_stack16() } + 1; registers_.pc = addr.get_absolute(); current_cycles_ += cycle_count::from_cpu(6); } template auto cpu::run_adc() -> void { // ADC: Add With Carry auto operand = fetch_operand(); eval_adc(operand.read()); current_cycles_ += operand.get_cycles(); } template auto cpu::run_rra() -> void { // RRA: ROR + ADC auto operand = fetch_operand(force_page_crossing::yes); auto const tmp = eval_ror(operand.read()); operand.write(tmp); eval_adc(tmp); current_cycles_ += operand.get_cycles() + cycle_count::from_cpu(2); } template auto cpu::run_ror() -> void { // ROR: Rotate Right auto operand = fetch_operand(); auto const result = eval_ror(operand.read()); operand.write(result); current_cycles_ += shift_cycle_count(); } template auto cpu::run_arr() -> void { // ARR: AND #i + ROR A but with different flags // TODO std::abort(); } auto cpu::run_pla() -> void { // PLA: Pull Accumulator registers_.a = pop_stack8(); update_zn(registers_.a); current_cycles_ += cycle_count::from_cpu(4); } template auto cpu::run_bvs() -> void { // BVS: Branch If Overflow Set branch(registers_.v); } auto cpu::run_sei() -> void { // SEI: Set Interrupt Disable registers_.i = true; current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_sta() -> void { // STA: Store Accumulator auto operand = fetch_operand(force_page_crossing::yes); operand.write(registers_.a); current_cycles_ += operand.get_cycles(); } template auto cpu::run_ahx() -> void { // AHX: ??? // TODO std::abort(); } template auto cpu::run_sax() -> void { // SAX: AND A X auto operand = fetch_operand(); auto const result = static_cast(registers_.a & registers_.x); operand.write(result); current_cycles_ += operand.get_cycles(); } template auto cpu::run_sty() -> void { // STX: Store Y auto operand = fetch_operand(); operand.write(registers_.y); current_cycles_ += operand.get_cycles(); } template auto cpu::run_stx() -> void { // STX: Store X auto operand = fetch_operand(); operand.write(registers_.x); current_cycles_ += operand.get_cycles(); } auto cpu::run_dey() -> void { // DEY: Decrement Y Register registers_.y -= 1; update_zn(registers_.y); current_cycles_ += cycle_count::from_cpu(2); } auto cpu::run_txa() -> void { // TXA: Transfer X to Accumulator registers_.a = registers_.x; update_zn(registers_.a); current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_xaa() -> void { // XAA: Depends on analog behavior. run_stp(); } template auto cpu::run_bcc() -> void { // BCC: Branch If Carry Clear branch(!registers_.c); } auto cpu::run_tya() -> void { // TYA: Transfer Y to Accumulator registers_.a = registers_.y; update_zn(registers_.a); current_cycles_ += cycle_count::from_cpu(2); } auto cpu::run_txs() -> void { // TXS: Transfer X to Stack Pointer registers_.sp = registers_.x; current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_tas() -> void { // TAS: ??? // TODO std::abort(); } template auto cpu::run_shy() -> void { // SHY: ??? // TODO std::abort(); } template auto cpu::run_shx() -> void { // SHY: ??? // TODO std::abort(); } template auto cpu::run_ldy() -> void { // LDY: Load Y Register auto operand = fetch_operand(); registers_.y = operand.read(); update_zn(registers_.y); current_cycles_ += operand.get_cycles(); } template auto cpu::run_lda() -> void { // LDA: Load Accumulator auto operand = fetch_operand(); registers_.a = operand.read(); update_zn(registers_.a); current_cycles_ += operand.get_cycles(); } template auto cpu::run_ldx() -> void { // LDX: Load X Register auto operand = fetch_operand(); registers_.x = operand.read(); update_zn(registers_.x); current_cycles_ += operand.get_cycles(); } template auto cpu::run_lax() -> void { // LAX: LDA + TAX auto operand = fetch_operand(); registers_.x = registers_.a = operand.read(); update_zn(registers_.a); current_cycles_ += operand.get_cycles(); } auto cpu::run_tay() -> void { // TAY: Transfer Accumulator to Y registers_.y = registers_.a; update_zn(registers_.y); current_cycles_ += cycle_count::from_cpu(2); } auto cpu::run_tax() -> void { // TAX: Transfer Accumulator to X registers_.x = registers_.a; update_zn(registers_.x); current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_bcs() -> void { // BCS: Branch If Carry Set branch(registers_.c); } auto cpu::run_clv() -> void { // CLV: Clear Overflow Flag registers_.v = false; current_cycles_ += cycle_count::from_cpu(2); } auto cpu::run_tsx() -> void { // TSX: Transfer Stack Pointer to X registers_.x = registers_.sp; update_zn(registers_.x); current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_las() -> void { // LAS: ??? // TODO std::abort(); } template auto cpu::run_cpy() -> void { // CPY: Compare Y Register auto operand = fetch_operand(); eval_cmp(registers_.y, operand.read()); current_cycles_ += operand.get_cycles(); } template auto cpu::run_axs() -> void { // AXS: Set X to ((A AND X) - #value without borrow), updates NZC // TODO std::abort(); } template auto cpu::run_cmp() -> void { // CMP: Compare auto operand = fetch_operand(); eval_cmp(registers_.a, operand.read()); current_cycles_ += operand.get_cycles(); } template auto cpu::run_dcp() -> void { // DCP: DEC + CMP auto operand = fetch_operand(force_page_crossing::yes); auto const tmp = static_cast(operand.read() - 1); operand.write(tmp); eval_cmp(registers_.a, tmp); current_cycles_ += operand.get_cycles() + cycle_count::from_cpu(2); } template auto cpu::run_dec() -> void { // DEC: Decrement Memory auto operand = fetch_operand(); auto const old_val = read8(operand.get_address()); auto const new_val = static_cast(old_val - 1); write8(operand.get_address(), new_val); update_zn(new_val); current_cycles_ += inc_dec_cycle_count(); } auto cpu::run_iny() -> void { // INY: Increment Y registers_.y += 1; update_zn(registers_.y); current_cycles_ += cycle_count::from_cpu(2); } auto cpu::run_dex() -> void { // DEX: Decrement X Register registers_.x -= 1; update_zn(registers_.x); current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_bne() -> void { // BNE: Branch If Not Equal branch(!registers_.z); } auto cpu::run_cld() -> void { // CLD: Clear Decimal Mode registers_.d = false; current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_cpx() -> void { // CPX: Compare X Register auto operand = fetch_operand(); eval_cmp(registers_.x, operand.read()); current_cycles_ += operand.get_cycles(); } template auto cpu::run_sbc() -> void { // SBC: Subtract With Carry auto operand = fetch_operand(); eval_adc(~operand.read()); current_cycles_ += operand.get_cycles(); } template auto cpu::run_isc() -> void { // ISC: INC + SBC auto operand = fetch_operand(force_page_crossing::yes); auto const tmp = static_cast(operand.read() + 1); operand.write(tmp); eval_adc(~tmp); current_cycles_ += operand.get_cycles() + cycle_count::from_cpu(2); } template auto cpu::run_inc() -> void { // INC: Increment Memory auto operand = fetch_operand(); auto const old_val = read8(operand.get_address()); auto const new_val = static_cast(old_val + 1); write8(operand.get_address(), new_val); update_zn(new_val); current_cycles_ += inc_dec_cycle_count(); } auto cpu::run_inx() -> void { // INX: Increment X registers_.x += 1; update_zn(registers_.x); current_cycles_ += cycle_count::from_cpu(2); } template auto cpu::run_beq() -> void { // BEQ: Branch If Equal branch(registers_.z); } auto cpu::run_sed() -> void { // SED: Set Decimal Flag registers_.d = true; current_cycles_ += cycle_count::from_cpu(2); } // ----------------------------------------------------------------------------------------------------------------- // Helpers // ----------------------------------------------------------------------------------------------------------------- auto cpu::advance_pc8() -> std::uint8_t { auto const val = read8(address{ registers_.pc }); registers_.pc += 1; return val; } auto cpu::advance_pc16() -> std::uint16_t { auto const val = read16(address{ registers_.pc }); registers_.pc += 2; return val; } auto cpu::push_stack8(std::uint8_t const value) -> void { write8(stack_offset + registers_.sp, value); registers_.sp -= 1; } auto cpu::push_stack16(std::uint16_t const value) -> void { auto const low = static_cast(value >> 0 & 0xFF); auto const high = static_cast(value >> 8 & 0xFF); push_stack8(high); push_stack8(low); } auto cpu::pop_stack8() -> std::uint8_t { registers_.sp += 1; return read8(stack_offset + registers_.sp); } auto cpu::pop_stack16() -> std::uint16_t { auto const low = pop_stack8(); auto const high = pop_stack8(); return static_cast((high << 8) | (low << 0)); } auto cpu::update_zn(std::uint8_t const value) -> void { registers_.z = value == 0; registers_.n = (value & 0x80) != 0; } template auto cpu::branch(bool const condition) -> void { static_assert(Mode == addressing_mode::relative, "Branch should only be used with relative operands."); auto operand = fetch_operand(); if (condition) { registers_.pc = operand.get_address().get_absolute(); current_cycles_ += operand.get_cycles(); } else { current_cycles_ += cycle_count::from_cpu(2); } } auto cpu::execute_interrupt(address const vector) -> void { push_stack16(registers_.pc); eval_php(); registers_.pc = read16(vector); registers_.i = true; current_cycles_ += cycle_count::from_cpu(7); } auto cpu::eval_ror(std::uint8_t const arg) -> std::uint8_t { auto const res = static_cast((registers_.c << 7) | (arg >> 1)); registers_.c = (arg & 0x1) != 0; update_zn(res); return res; } auto cpu::eval_rol(std::uint8_t const arg) -> std::uint8_t { auto const res = static_cast((arg << 1) | (registers_.c ? 1 : 0)); registers_.c = (arg & 0x80) != 0; update_zn(res); return res; } auto cpu::eval_asl(std::uint8_t const arg) -> std::uint8_t { auto const new_val = static_cast(arg << 1); registers_.c = (arg & 0x80) != 0; update_zn(new_val); return new_val; } auto cpu::eval_lsr(std::uint8_t const arg) -> std::uint8_t { auto const new_val = static_cast(arg >> 1); registers_.c = (arg & 0x01) != 0; update_zn(new_val); return new_val; } auto cpu::eval_adc(std::uint8_t const arg) -> void { auto const old_val = registers_.a; auto const tmp = old_val + arg + (registers_.c ? 1 : 0); auto const new_val = static_cast(tmp); registers_.a = new_val; registers_.c = tmp > 0xFF; registers_.v = ((old_val ^ arg) & 0x80) == 0 && ((old_val ^ new_val) & 0x80) != 0; update_zn(registers_.a); } auto cpu::eval_and(std::uint8_t const arg) -> void { registers_.a &= arg; update_zn(registers_.a); } auto cpu::eval_ora(std::uint8_t const arg) -> void { registers_.a |= arg; update_zn(registers_.a); } auto cpu::eval_eor(std::uint8_t const arg) -> void { registers_.a ^= arg; update_zn(registers_.a); } auto cpu::eval_cmp(std::uint8_t const a, std::uint8_t const b) -> void { update_zn(a - b); registers_.c = a >= b; } auto cpu::eval_plp() -> void { // Ignore bits 4 and 5 registers_.p = (pop_stack8() & 0b11001111) | (registers_.p & 0b00110000); } auto cpu::eval_php() -> void { // Always set bits 4 and 5. push_stack8(registers_.p | 0b00110000); } // ----------------------------------------------------------------------------------------------------------------- // Operands // ----------------------------------------------------------------------------------------------------------------- // // See: https://www.nesdev.org/wiki/CPU_addressing_modes // template auto cpu::fetch_operand(force_page_crossing const force_page_crossing) -> operand { auto addr = address{}; auto cycles = cycle_count{}; switch (Mode) { case addressing_mode::immediate: static_assert(Mode != addressing_mode::immediate); case addressing_mode::accumulator: static_assert(Mode != addressing_mode::accumulator); case addressing_mode::zero_page: { addr = address{ advance_pc8() }; cycles = cycle_count::from_cpu(3); break; } case addressing_mode::absolute: { addr = address{ advance_pc16() }; cycles = cycle_count::from_cpu(4); break; } case addressing_mode::relative: { auto const offset = static_cast(advance_pc8()); auto const base = address{ registers_.pc }; addr = address{ static_cast(registers_.pc + offset) }; auto const page_crossing = base.get_page() != addr.get_page() || force_page_crossing == force_page_crossing::yes; cycles = cycle_count::from_cpu(page_crossing ? 4 : 3); break; } case addressing_mode::indirect: { auto const arg = address{ advance_pc16() }; // Account for buggy indirect read: https://www.nesdev.org/wiki/Errata addr = arg.get_offset() == 0xFF ? address{ read8(address{ arg.get_page(), 0x00 }), read8(arg) } : address{ read16(arg) }; cycles = cycle_count::from_cpu(6); break; } case addressing_mode::zero_page_indexed_x: { // PEEK((arg + X) % 256) addr = address{ 0x00, static_cast(advance_pc8() + registers_.x) }; cycles = cycle_count::from_cpu(4); break; } case addressing_mode::zero_page_indexed_y: { // PEEK((arg + Y) % 256) addr = address{ 0x00, static_cast(advance_pc8() + registers_.y) }; cycles = cycle_count::from_cpu(4); break; } case addressing_mode::absolute_indexed_x: { // PEEK(arg + X) auto const arg = address{ advance_pc16() }; addr = arg + registers_.x; auto const page_crossing = addr.get_page() != arg.get_page() || force_page_crossing == force_page_crossing::yes; cycles = cycle_count::from_cpu(page_crossing ? 5 : 4); break; } case addressing_mode::absolute_indexed_y: { // PEEK(arg + Y) auto const arg = address{ advance_pc16() }; addr = arg + registers_.y; auto const page_crossing = addr.get_page() != arg.get_page() || force_page_crossing == force_page_crossing::yes; cycles = cycle_count::from_cpu(page_crossing ? 5 : 4); break; } case addressing_mode::indexed_indirect: { // PEEK(PEEK((arg + X) % 256) + PEEK((arg + X + 1) % 256) * 256) auto const arg = advance_pc8(); auto const page = read8(address{ 0x00, static_cast(arg + registers_.x + 1) }); auto const offset = read8(address{ 0x00, static_cast(arg + registers_.x) }); addr = address{ page, offset }; cycles = cycle_count::from_cpu(6); break; } case addressing_mode::indirect_indexed: { // PEEK(PEEK(arg) + PEEK((arg + 1) % 256) * 256 + Y) auto const arg = advance_pc8(); auto const page = read8(address{ 0x00, static_cast(arg + 1) }); auto const offset = read8(address{ 0x00, static_cast(arg) }); auto const base = address{ page, offset }; addr = base + registers_.y; auto const page_crossing = addr.get_page() != base.get_page() || force_page_crossing == force_page_crossing::yes; cycles = cycle_count::from_cpu(page_crossing ? 6 : 5); break; } } return operand{ *this, addr, cycles }; } template<> auto cpu::fetch_operand(force_page_crossing) -> operand { return operand{ *this }; } template<> auto cpu::fetch_operand(force_page_crossing) -> operand { return operand{ advance_pc8() }; } // ----------------------------------------------------------------------------------------------------------------- // Memory Access // ----------------------------------------------------------------------------------------------------------------- // // See: https://www.nesdev.org/wiki/CPU_memory_map // auto cpu::read8(address const addr) -> std::uint8_t { if (addr <= address{ 0x1FFF }) { return ram_[addr.get_absolute() % ram_size]; } if (addr <= address{ 0x3FFF }) { #ifdef NES_ENABLE_PPU switch (addr.get_absolute() % 8) { case 0: return ppu_.read_latch(); case 1: return ppu_.read_latch(); case 2: return ppu_.read_ppustatus(); case 3: return ppu_.read_latch(); case 4: return ppu_.read_oamdata(); case 5: return ppu_.read_latch(); case 6: return ppu_.read_latch(); case 7: return ppu_.read_ppudata(); default: return 0x0; } #else return 0x0; #endif } if (addr <= address{ 0x4013 }) { return 0x0; } // TODO: APU registers #ifdef NES_ENABLE_PPU if (addr == address{ 0x4014 }) { return ppu_.read_latch(); } #else if (addr == address{ 0x4014 }) { return 0x0; } #endif if (addr == address{ 0x4015 }) { return 0x0; } // TODO: APU registers if (addr == address{ 0x4016 }) { return controller_1_.read(); } if (addr == address{ 0x4017 }) { return controller_2_.read(); } if (addr <= address{ 0x401F }) { return 0x0; } return mapper_.read_cpu(addr); } auto cpu::read16(address const addr) -> std::uint16_t { auto const low = read8(addr + 0); auto const high = read8(addr + 1); return static_cast((high << 8) | (low << 0)); } auto cpu::write8(address const addr, std::uint8_t const value) -> void { if (addr <= address{ 0x1FFF }) { ram_[addr.get_absolute() % ram_size] = value; return; } if (addr <= address{ 0x3FFF }) { #ifdef NES_ENABLE_PPU switch (addr.get_absolute() % 8) { case 0: ppu_.write_ppuctrl(value); return; case 1: ppu_.write_ppumask(value); return; case 2: ppu_.write_latch(value); return; case 3: ppu_.write_oamaddr(value); return; case 4: ppu_.write_oamdata(value); return; case 5: ppu_.write_ppuscroll(value); return; case 6: ppu_.write_ppuaddr(value); return; case 7: ppu_.write_ppudata(value); return; default: return; } #else return; #endif } if (addr <= address{ 0x4013 }) { return; } // TODO: APU registers #ifdef NES_ENABLE_PPU if (addr == address{ 0x4014 }) { ppu_.write_oamdma(value); return; } #else if (addr == address{ 0x4014 }) { return; } #endif if (addr == address{ 0x4015 }) { return; } // TODO: APU registers if (addr == address{ 0x4016 }) { controller_1_.write(value); return; } if (addr == address{ 0x4017 }) { controller_2_.write(value); return; } if (addr <= address{ 0x401F }) { return; } mapper_.write_cpu(addr, value); } auto cpu::write16(address const addr, std::uint16_t const value) -> void { auto const low = static_cast(value >> 0 & 0xFF); auto const high = static_cast(value >> 8 & 0xFF); write8(addr + 0, low); write8(addr + 1, high); } } // namespace nes