diff options
Diffstat (limited to 'src/nes/cpu.cc')
| -rw-r--r-- | src/nes/cpu.cc | 47 |
1 files changed, 36 insertions, 11 deletions
diff --git a/src/nes/cpu.cc b/src/nes/cpu.cc index bb4830f..b488a08 100644 --- a/src/nes/cpu.cc +++ b/src/nes/cpu.cc @@ -3,6 +3,8 @@ #include "nes/controller.hh" #include "nes/mapper.hh" +#define ENABLE_PPU + namespace nes { cpu::cpu(ppu& ppu, mapper& mapper, controller& controller_1, controller& controller_2) @@ -57,14 +59,16 @@ namespace nes if (nmi_pending_) { +#ifdef ENABLE_PPU execute_interrupt(address{ 0xFFFA }); +#endif nmi_pending_ = false; } auto const opcode = advance_pc8(); switch (opcode) { - case 0x00: run_brk(); break; + case 0x00: run_brk<addressing_mode::immediate>(); break; case 0x01: run_ora<addressing_mode::indexed_indirect>(); break; case 0x02: run_stp(); break; case 0x03: run_slo<addressing_mode::indexed_indirect>(); break; @@ -102,7 +106,7 @@ namespace nes case 0x23: run_rla<addressing_mode::indexed_indirect>(); break; case 0x24: run_bit<addressing_mode::zero_page>(); break; case 0x25: run_and<addressing_mode::zero_page>(); break; - case 0x26: run_rol<addressing_mode::accumulator>(); break; + case 0x26: run_rol<addressing_mode::zero_page>(); break; case 0x27: run_rla<addressing_mode::zero_page>(); break; case 0x28: run_plp(); break; case 0x29: run_and<addressing_mode::immediate>(); break; @@ -328,10 +332,12 @@ namespace nes // Instructions // ----------------------------------------------------------------------------------------------------------------- + template<cpu::addressing_mode Mode> auto cpu::run_brk() -> void { - // TODO: Proper BRK handling - std::abort(); + // BRK: Break + fetch_operand<Mode>(); + execute_interrupt(address{ 0xFFFE }); } template<cpu::addressing_mode Mode> @@ -377,8 +383,7 @@ namespace nes auto cpu::run_php() -> void { // PHP: Push Processor Status - // Always set bits 4 and 5. - push_stack8(registers_.p | 0b00110000); + eval_php(); current_cycles_ += cycle_count::from_cpu(3); } @@ -453,7 +458,7 @@ namespace nes auto operand = fetch_operand<Mode>(); auto const arg = operand.read(); auto const res = (registers_.a & arg) != 0; - registers_.z = !res; + registers_.z = res == 0; registers_.v = (arg & 0x40) != 0; registers_.n = (arg & 0x80) != 0; current_cycles_ += operand.get_cycles(); @@ -701,7 +706,7 @@ namespace nes auto cpu::run_xaa() -> void { // XAA: Depends on analog behavior. - run_brk(); + run_stp(); } template<cpu::addressing_mode Mode> @@ -1046,16 +1051,15 @@ namespace nes } } - auto cpu::execute_interrupt(address vector) -> void + auto cpu::execute_interrupt(address const vector) -> void { push_stack16(registers_.pc); - run_php(); + 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<std::uint8_t>((registers_.c << 7) | (arg >> 1)); @@ -1132,6 +1136,11 @@ namespace nes (registers_.p & 0b00110000); } + auto cpu::eval_php() -> void + { + // Always set bits 4 and 5. + push_stack8(registers_.p | 0b00110000); + } // ----------------------------------------------------------------------------------------------------------------- // Operands @@ -1272,6 +1281,7 @@ namespace nes if (addr <= address{ 0x1FFF }) { return ram_[addr.get_absolute() % ram_size]; } if (addr <= address{ 0x3FFF }) { +#ifdef ENABLE_PPU switch (addr.get_absolute() % 8) { case 0: return ppu_.read_latch(); @@ -1284,9 +1294,16 @@ namespace nes case 7: return ppu_.read_ppudata(); default: return 0x0; } +#else + return 0x0; +#endif } if (addr <= address{ 0x4013 }) { return 0x0; } // TODO: APU registers +#ifdef 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(); } @@ -1306,6 +1323,7 @@ namespace nes if (addr <= address{ 0x1FFF }) { ram_[addr.get_absolute() % ram_size] = value; return; } if (addr <= address{ 0x3FFF }) { +#ifdef ENABLE_PPU switch (addr.get_absolute() % 8) { case 0: ppu_.write_ppuctrl(value); return; @@ -1318,9 +1336,16 @@ namespace nes case 7: ppu_.write_ppudata(value); return; default: return; } +#else + return; +#endif } if (addr <= address{ 0x4013 }) { return; } // TODO: APU registers +#ifdef 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; } |