enums and RTC work

more MBC3 work
MBC3 work
2026-03-18 01:09:03 -07:00 · 2026-03-17 01:46:28 -07:00 · 2026-03-16 23:44:38 -07:00
6 changed files with 110 additions and 84 deletions
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,7 +19,11 @@ add_executable(GameBoy++ src/main.cpp
        src/testing.hpp
        src/joypad.cpp
 )
+target_compile_options(GameBoy++ PRIVATE -O2)
 target_link_libraries(GameBoy++ ${SDL2_LIBRARIES})
+target_compile_options(GameBoy++ PRIVATE
+    $<$<CONFIG:Release>:-O2>
+)

 if(CMAKE_EXPORT_COMPILE_COMMANDS)
  add_custom_target(copy_compile_commands ALL
--- a/src/addressSpace.hpp
+++ b/src/addressSpace.hpp
@@ -43,7 +43,6 @@ public:
    Byte TAC = 0xF8;
    // interrupt flag and enable
    Byte IF = 0xE1;
-    ;
    // Sound registers
    Byte NR10;
    Byte NR11;
@@ -93,8 +92,7 @@ public:
  void loadGame(const std::string &filename);

  void determineMBCInfo();
-  bool MBCWrite(Word address);
-  Byte *MBCRead(Word address);
+  Byte *MBCWrite(Word address);
  // prevents seg faults when programs with no MBC try to write to ROM
  Byte dummyVal = 0;

@@ -104,7 +102,7 @@ public:
  void loadRomBank();
  void createRamBank();
  void loadRamBank();
-  MBCType MBC = {};
+  MBCType_enum MBC = {};
  uint32_t romSize = 0;
  uint32_t romBanks = 0;
  uint32_t externalRamSize = 0;
@@ -114,10 +112,11 @@ public:
  void dmaTransfer();

  // MBC registers
-  // Selected ROM Bank = (Secondary Bank << 5) + ROM Bank
+  // Selected ROM Bank in MBC1 = (Secondary Bank << 5) + ROM Bank
  Byte selectedRomBank = 0;
  Byte romBankRegister = 0x00;
-  // 2 bit register acts as secondary rom bank register or ram bank number
+  // 2 bit register acts as secondary rom bank register or ram bank number in
+  // MBC1
  Byte twoBitBankRegister = 0x0;
  Byte selectedExternalRamBank = 0;
  Byte romRamSelect = 0x00;
@@ -129,6 +128,13 @@ public:
  // MBC3
  Byte latchClockData = 0x00;
  Byte ramBankRTCRegister = 0x00;
+  // RTC registers
+  enabledRTCRegister_enum enabledRTCRegister = NONE;
+  Byte RTCSeconds = 0x0;
+  Byte RTCMinutes = 0x0;
+  Byte RTCHours = 0x0;
+  Byte RTCDayLower = 0x0;
+  Byte RTCDayHigher = 0x0;

  void setTesting(bool state);

@@ -138,34 +144,47 @@ public:
      return testRam[address];
    if (address < 0x0100 && bootromLoaded)
      return bootrom[address];
-    if (address < 0x4000)
+    else if (address < 0x4000)
      return memoryLayout.romBank0[address];
-    if (address < 0x8000)
+    else if (address < 0x8000)
      return memoryLayout.romBankSwitch[address - 0x4000];
-    if (address < 0xA000)
+    else if (address < 0xA000)
      return memoryLayout.vram[address - 0x8000];
-    if (address < 0xC000) {
+    else if (address < 0xC000) {
+      if (enabledRTCRegister != NONE) {
+        switch (enabledRTCRegister) {
+        case RTCS:
+          return RTCSeconds;
+        case RTCM:
+          return RTCMinutes;
+        case RTCH:
+          return RTCHours;
+        case RTCDL:
+          return RTCDayLower;
+        case RTCDH:
+          return RTCDayHigher;
+        }
+      }
      if (externalRamSize == 0)
        return 0xFF;
      // MBC2 echos 15 times and only stores lower 4 bits
-      if (MBC == MBC2 || MBC == MBC2Battery)
+      else if (MBC == MBC2 || MBC == MBC2Battery)
        return memoryLayout.externalRam[(address - 0xA000) & 0x01FF] | 0xF0;
-      return memoryLayout.externalRam[address - 0xA000];
-    }
-    if (address < 0xD000)
+      else
+        return memoryLayout.externalRam[address - 0xA000];
+    } else if (address < 0xD000)
      return memoryLayout.memoryBank1[address - 0xC000];
-    if (address < 0xE000)
+    else if (address < 0xE000)
      return memoryLayout.memoryBank2[address - 0xD000];
-    if (address < 0xFE00)
+    else if (address < 0xFE00)
      return memoryLayout.memoryBank1[address - 0xE000];
-    if (address < 0xFEA0)
+    else if (address < 0xFEA0)
      return memoryLayout.oam[address - 0xFE00];
-    if (address < 0xFF00) {
+    else if (address < 0xFF00) {
      if ((memoryLayout.STAT & 0x03) == 2 || (memoryLayout.STAT & 0x03) == 3)
        return 0xFF;
      return 0x00;
-    }
-    if (address < 0xFF80)
+    } else if (address < 0xFF80)
      switch (address) {
      case 0xFF00:
        return memoryLayout.JOYP;
@@ -235,8 +254,6 @@ public:
      case 0xFF43:
        return memoryLayout.SCX;
      case 0xFF44:
-        // for debugging only
-        // return 0x90;
        return memoryLayout.LY;
      case 0xFF45:
        return memoryLayout.LYC;
@@ -258,7 +275,7 @@ public:
        }
        return 0xFF;
      }
-    if (address < 0xFFFF)
+    else if (address < 0xFFFF)
      return memoryLayout.specialRam[address - 0xFF80];
    // 0xFFFF
    return memoryLayout.IE;
@@ -269,28 +286,27 @@ public:
    dummyVal = 0xFF;
    if (testing)
      return testRam[address];
-    if (address < 0x0100 && bootromLoaded)
+    else if (address < 0x0100 && bootromLoaded)
      return bootrom[address];
-    if (address < 0x8000)
-      return (*MBCRead(address));
-    if (address < 0xA000)
+    else if (address < 0x8000)
+      return (*MBCWrite(address));
+    else if (address < 0xA000)
      return memoryLayout.vram[address - 0x8000];
-    if (address < 0xC000) {
+    else if (address < 0xC000) {
      if (externalRamSize == 0)
        return dummyVal;
      return memoryLayout.externalRam[address - 0xA000];
-    }
-    if (address < 0xD000)
+    } else if (address < 0xD000)
      return memoryLayout.memoryBank1[address - 0xC000];
-    if (address < 0xE000)
+    else if (address < 0xE000)
      return memoryLayout.memoryBank2[address - 0xD000];
-    if (address < 0xFE00)
+    else if (address < 0xFE00)
      return memoryLayout.memoryBank1[address - 0xE000];
-    if (address < 0xFEA0)
+    else if (address < 0xFEA0)
      return memoryLayout.oam[address - 0xFE00];
-    if (address < 0xFF00)
+    else if (address < 0xFF00)
      return memoryLayout.notUsable[address - 0xFEA0];
-    if (address < 0xFF80)
+    else if (address < 0xFF80)
      switch (address) {
      case 0xFF00:
        return memoryLayout.JOYP;
@@ -384,7 +400,7 @@ public:
        }
        return dummyVal;
      }
-    if (address < 0xFFFF)
+    else if (address < 0xFFFF)
      return memoryLayout.specialRam[address - 0xFF80];
    // 0xFFFF
    return memoryLayout.IE;
--- a/src/defines.hpp
+++ b/src/defines.hpp
@@ -79,7 +79,7 @@ struct Input {
  bool SELECT = false;
 };

-enum MBCType {
+enum MBCType_enum {
  romOnly = 0x00,
  MBC1 = 0x01,
  MBC1Ram = 0x02,
@@ -111,7 +111,7 @@ enum MBCType {
  HuC1RamBattery = 0xFF
 };

-enum PPUMode {
+enum PPUMode_enum {
  mode0, // Horizontal Blank (Mode 0): No access to video RAM, occurs during
         // horizontal blanking period.
  mode1, // Vertical Blank (Mode 1): No access to video RAM, occurs during
@@ -122,4 +122,12 @@ enum PPUMode {
         // pixel transfer to the screen.
 };

+enum enabledRTCRegister_enum {
+  NONE = 0x00,
+  RTCS = 0x08,
+  RTCM = 0x09,
+  RTCH = 0x0A,
+  RTCDL = 0x0B,
+  RTCDH = 0x0C
+};
 #endif
--- a/src/gameboy.hpp
+++ b/src/gameboy.hpp
@@ -50,7 +50,7 @@ class GameBoy {
  AddressSpace addressSpace;
  const AddressSpace &readOnlyAddressSpace = addressSpace;

-  PPUMode currentMode = PPUMode::mode0;
+  PPUMode_enum currentMode = PPUMode_enum::mode0;
  Byte windowLineCounter = 0;
  int16_t cyclesUntilDMATransfer = 160;

@@ -86,7 +86,7 @@ class GameBoy {
  void SDL2present();

  void checkPPUMode();
-  void setPPUMode(PPUMode mode);
+  void setPPUMode(PPUMode_enum mode);
  uint64_t cyclesSinceLastScanline() const;
  uint64_t cyclesSinceLastRefresh() const;

--- a/src/mbc.cpp
+++ b/src/mbc.cpp
@@ -1,7 +1,8 @@
 #include "addressSpace.hpp"
+#include "defines.hpp"

 void AddressSpace::determineMBCInfo() {
-  MBC = static_cast<MBCType>(memoryLayout.romBank0[0x147]);
+  MBC = static_cast<MBCType_enum>(memoryLayout.romBank0[0x147]);
  romSize = 32768 * (1 << memoryLayout.romBank0[0x147]);
  romBanks = 1 << (memoryLayout.romBank0[0x147] + 1);

@@ -35,13 +36,7 @@ void AddressSpace::determineMBCInfo() {
  }
 }

-bool AddressSpace::MBCWrite(const Word address) {
-  if (address <= 0x7FFF)
-    return true;
-  return false;
-}
-
-Byte *AddressSpace::MBCRead(const Word address) {
+Byte *AddressSpace::MBCWrite(const Word address) {
  if (MBC == MBC1) {
    if (address <= 0x1FFF)
      return &ramEnable;
@@ -51,8 +46,7 @@ Byte *AddressSpace::MBCRead(const Word address) {
      return &twoBitBankRegister;
    if (address <= 0x7FFF)
      return &romRamSelect;
-  }
-  if (MBC == MBC1Ram || MBC == MBC1RamBattery) {
+  } else if (MBC == MBC1Ram || MBC == MBC1RamBattery) {
    if (address <= 0x1FFF)
      return &ramEnable;
    // bits 0-4
@@ -63,14 +57,24 @@ Byte *AddressSpace::MBCRead(const Word address) {
    }
    if (address <= 0x7FFF)
      return &romRamSelect;
-  }
-  if (MBC == MBC2 || MBC == MBC2Battery) {
+  } else if (MBC == MBC2 || MBC == MBC2Battery) {
    if (address <= 0x3FFF) {
      if (address & 0x0100)
        return &romBankRegister;
      else
        return &ramEnable;
    }
+  } else if (MBC == MBC3 || MBC == MBC3TimerBattery) {
+    if (address <= 0x1FFF)
+      return &ramEnable;
+  } else if (MBC == MBC3Ram || MBC == MBC3RamBattery ||
+             MBC == MBC3TimerRamBattery) {
+    if (address <= 0x1FFF)
+      return &ramEnable;
+    if (address <= 0x3FFF)
+      return &romBankRegister;
+    if (address <= 0x5FFF)
+      return &ramBankRTCRegister;
  }
  return &dummyVal;
 }
@@ -127,41 +131,35 @@ void AddressSpace::MBCUpdate() {
    loadRamBank();
  } else if (MBC == MBC2 || MBC == MBC2Battery) {
    selectedRomBank = romBankRegister & 0x0F;
+    selectedExternalRamBank = 0;
+
    loadRomBank();
    loadRamBank();
  } else if (MBC == MBC3 || MBC == MBC3TimerBattery) {
-    romBankRegister &= 0b11111;
-    twoBitBankRegister &= 0b11;
+    selectedRomBank = romBankRegister & 0x7F;
+    selectedExternalRamBank = 0;

-    // 512 KiB can only have 8KiB of ram
-    if (romSize >= 524288) {
-      if (romBankRegister == 0)
-        selectedRomBank = (twoBitBankRegister << 5) + 1;
-      selectedRomBank = (twoBitBankRegister << 5) + romBankRegister;
-    } else {
-      if (romBankRegister == 0)
-        selectedRomBank = 1;
+    if (MBC == MBC3TimerBattery) {
+      if(ramBankRTCRegister >= 0x8 && ramBankRTCRegister <= 0xC)
+        enabledRTCRegister = static_cast<enabledRTCRegister_enum>(ramBankRTCRegister);
      else
-        selectedRomBank = romBankRegister;
+        enabledRTCRegister = NONE;
    }
+    loadRomBank();
+    loadRamBank();
  } else if (MBC == MBC3Ram || MBC == MBC3RamBattery ||
             MBC == MBC3TimerRamBattery) {
-    romBankRegister &= 0b11111;
-    twoBitBankRegister &= 0b11;
+    selectedRomBank = romBankRegister & 0x7F;
+    selectedExternalRamBank = ramBankRTCRegister & 0b11;

-    // 512 KiB can only have 8KiB of ram
-    if (romSize >= 524288) {
-      if (romBankRegister == 0)
-        selectedRomBank = (twoBitBankRegister << 5) + 1;
-      selectedRomBank = (twoBitBankRegister << 5) + romBankRegister;
-      selectedExternalRamBank = 0;
-    } else {
-      if (romBankRegister == 0)
-        selectedRomBank = 1;
+    if (MBC == MBC3TimerRamBattery) {
+      if(ramBankRTCRegister >= 0x8 && ramBankRTCRegister <= 0xC)
+        enabledRTCRegister = static_cast<enabledRTCRegister_enum>(ramBankRTCRegister);
      else
-        selectedRomBank = romBankRegister;
-      selectedExternalRamBank = twoBitBankRegister;
+        enabledRTCRegister = NONE;
    }
+    loadRomBank();
+    loadRamBank();
  }
 }

--- a/src/ppu.cpp
+++ b/src/ppu.cpp
@@ -46,9 +46,9 @@ void GameBoy::ppuUpdate() {
      readOnlyAddressSpace.memoryLayout.STAT & (1 << 5);
  const bool previousInterruptLine = statInteruptLine;

-  if (currentMode == PPUMode::mode0 && hBlankInterruptEnabled ||
-      currentMode == PPUMode::mode3 && drawingInterruptEnabled ||
-      currentMode == PPUMode::mode2 && oamInterruptEnabled) {
+  if (currentMode == PPUMode_enum::mode0 && hBlankInterruptEnabled ||
+      currentMode == PPUMode_enum::mode3 && drawingInterruptEnabled ||
+      currentMode == PPUMode_enum::mode2 && oamInterruptEnabled) {
    statInteruptLine = true;
  } else {
    statInteruptLine = false;
@@ -84,13 +84,13 @@ void GameBoy::checkPPUMode() {
    break;
  case 2:
    if (cyclesSinceScanline > MODE2_DURATION) {
-      setPPUMode(PPUMode::mode3);
+      setPPUMode(PPUMode_enum::mode3);
    }
    break;
  case 3:
    if (cyclesSinceScanline > MODE2_DURATION + MODE3_MIN_DURATION) {
      drawLine();
-      setPPUMode(PPUMode::mode0);
+      setPPUMode(PPUMode_enum::mode0);
    }
    break;
  }
@@ -98,14 +98,14 @@ void GameBoy::checkPPUMode() {

 void GameBoy::incLY() {
  addressSpace.memoryLayout.LY += 1;
-  setPPUMode(PPUMode::mode2);
+  setPPUMode(PPUMode_enum::mode2);
  if (addressSpace.memoryLayout.LY > SCANLINES_PER_FRAME - 1) {
    addressSpace.memoryLayout.LY = 0;
    windowLineCounter = 0;
  } else if (addressSpace.memoryLayout.LY == 144) {
    // VBlank Period
    SDL2present();
-    setPPUMode(PPUMode::mode1);
+    setPPUMode(PPUMode_enum::mode1);
    addressSpace.memoryLayout.IF |= 0x1;
  }
 }
@@ -120,7 +120,7 @@ uint64_t GameBoy::cyclesSinceLastRefresh() const {
  return difference;
 }

-void GameBoy::setPPUMode(const PPUMode mode) {
+void GameBoy::setPPUMode(const PPUMode_enum mode) {
  switch (mode) {
  case mode0:
    addressSpace.memoryLayout.STAT &= ~0x03;
Author	SHA1	Message	Date
YayIguess	c242fb7574	enums and RTC work	2026-03-18 01:09:03 -07:00
YayIguess	80e23312de	more MBC3 work	2026-03-17 01:46:28 -07:00
YayIguess	037ba0c76d	MBC3 work	2026-03-16 23:44:38 -07:00