mirror of
https://github.com/MoleskiCoder/EightBit.git
synced 2024-08-30 03:29:01 +00:00
233 lines
4.5 KiB
C++
233 lines
4.5 KiB
C++
#pragma once
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#include <Memory.h>
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#include <Processor.h>
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namespace EightBit {
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class Bus : public Memory {
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public:
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enum CartridgeType {
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ROM = 0,
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ROM_MBC1 = 1,
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ROM_MBC1_RAM = 2,
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ROM_MBC1_RAM_BATTERY = 3,
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};
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enum {
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TotalLineCount = 154,
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RomPageSize = 0x4000
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};
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enum {
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BASE = 0xFF00,
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// Port/Mode Registers
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P1 = 0x0,
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SB = 0x1,
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SC = 0x2,
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DIV = 0x4,
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TIMA = 0x5,
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TMA = 0x6,
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TAC = 0x7,
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// Interrupt Flags
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IF = 0xF,
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IE = 0xFF,
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// LCD Display Registers
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LCDC = 0x40,
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STAT = 0x41,
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SCY = 0x42,
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SCX = 0x43,
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LY = 0x44,
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LYC = 0x45,
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DMA = 0x46,
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BGP = 0x47,
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OBP0 = 0x48,
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OBP1 = 0x49,
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WY = 0x4A,
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WX = 0x4B,
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// Sound Registers
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NR10 = 0x10,
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NR11 = 0x11,
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NR12 = 0x12,
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NR13 = 0x13,
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NR14 = 0x14,
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NR21 = 0x16,
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NR22 = 0x17,
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NR23 = 0x18,
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NR24 = 0x19,
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NR30 = 0x1A,
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NR31 = 0x1B,
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NR32 = 0x1C,
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NR33 = 0x1D,
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NR34 = 0x1E,
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NR41 = 0x20,
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NR42 = 0x21,
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NR43 = 0x22,
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NR44 = 0x23,
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NR50 = 0x24,
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NR51 = 0x25,
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NR52 = 0x26,
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WPRAM_START = 0x30,
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WPRAM_END = 0x3F,
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// Boot rom control
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BOOT_DISABLE = 0x50,
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};
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// IF and IE flags
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enum Interrupts {
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VerticalBlank = Processor::Bit0, // VBLANK
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DisplayControlStatus = Processor::Bit1, // LCDC Status
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TimerOverflow = Processor::Bit2, // Timer Overflow
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SerialTransfer = Processor::Bit3, // Serial Transfer
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Keypad = Processor::Bit3 // Hi-Lo of P10-P13
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};
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enum LcdcControl {
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DisplayBackground = Processor::Bit0,
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ObjectEnable = Processor::Bit1,
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ObjectBlockCompositionSelection = Processor::Bit2,
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BackgroundCodeAreaSelection = Processor::Bit3,
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BackgroundCharacterDataSelection = Processor::Bit4,
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WindowEnable = Processor::Bit5,
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WindowCodeAreaSelection = Processor::Bit6,
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LcdEnable = Processor::Bit7
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};
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enum LcdStatusMode {
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CpuAccessAllowed = 0b00,
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VerticalBlankingPeriod = 0b01,
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SearchingOamRam = 0b10,
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TransferringDataToLcd = 0b11
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};
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Bus();
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void reset();
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virtual void clear() override;
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void triggerInterrupt(int cause) {
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pokeRegister(IF, peekRegister(IF) | cause);
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}
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void writeRegister(int offset, uint8_t content) {
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Memory::write(BASE + offset, content);
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}
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void pokeRegister(int offset, uint8_t content) {
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poke(BASE + offset, content);
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}
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uint8_t readRegister(int offset) {
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return Memory::read(BASE + offset);
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}
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uint8_t peekRegister(int offset) {
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return peek(BASE + offset);
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}
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void checkTimers(int cycles);
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int timerClockTicks() {
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switch (timerClock()) {
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case 0b00:
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return 1024; // 4.096 Khz
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case 0b01:
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return 16; // 262.144 Khz
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case 0b10:
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return 64; // 65.536 Khz
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case 0b11:
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return 256; // 16.384 Khz
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default:
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__assume(0);
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}
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throw std::domain_error("Invalid timer clock specification");
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}
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int timerClock() {
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return peekRegister(TAC) & Processor::Mask2;
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}
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bool timerEnabled() {
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return !timerDisabled();
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}
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bool timerDisabled() {
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return (peekRegister(TAC) & Processor::Bit2) == 0;
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}
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void incrementDIV(int cycles) {
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m_divCounter.word += cycles;
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pokeRegister(DIV, m_divCounter.high);
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}
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void incrementTIMA() {
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uint16_t updated = peekRegister(TIMA) + 1;
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if (updated & Processor::Bit8) {
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triggerInterrupt(TimerOverflow);
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updated = peekRegister(TMA);
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}
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pokeRegister(TIMA, updated & Processor::Mask8);
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}
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void incrementLY() {
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pokeRegister(LY, (peekRegister(LY) + 1) % TotalLineCount);
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}
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void resetLY() {
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pokeRegister(LY, 0);
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}
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void disableBootRom() { m_disableBootRom = true; }
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void enableBootRom() { m_disableBootRom = false; }
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void disableGameRom() { m_disableGameRom = true; }
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void enableGameRom() { m_disableGameRom = false; }
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bool bootRomDisabled() const { return m_disableBootRom; }
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bool bootRomEnabled() const { return !bootRomDisabled(); }
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bool gameRomDisabled() const { return m_disableGameRom; }
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bool gameRomEnabled() const { return !gameRomDisabled(); }
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void loadBootRom(const std::string& path);
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void loadGameRom(const std::string& path);
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private:
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std::vector<uint8_t> m_bootRom;
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std::vector<uint8_t> m_gameRom;
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bool m_disableBootRom;
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bool m_disableGameRom;
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bool m_rom;
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bool m_banked;
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bool m_ram;
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bool m_battery;
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bool m_higherRomBank;
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bool m_ramBankSwitching;
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int m_romBank;
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int m_ramBank;
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register16_t m_divCounter;
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int m_timerCounter;
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int m_timerRate;
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void Bus_WrittenByte(const AddressEventArgs& e);
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void checkTimer(int cycles);
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void validateCartridgeType();
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virtual uint8_t& reference(uint16_t address, bool& rom);
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};
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} |