EightBit/LR35902/inc/GameBoyBus.h
Adrian Conlon 44ff68d6f3 First part of gb linux port.
Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
2017-10-02 16:47:05 +01:00

343 lines
8.8 KiB
C++

#pragma once
#include <array>
#include <tuple>
#include <Rom.h>
#include <Ram.h>
#include <Bus.h>
#include <Processor.h>
#include <Signal.h>
namespace EightBit {
namespace GameBoy {
class Bus : public EightBit::Bus {
public:
enum CartridgeType {
ROM = 0,
ROM_MBC1 = 1,
ROM_MBC1_RAM = 2,
ROM_MBC1_RAM_BATTERY = 3,
};
enum {
CyclesPerSecond = 4 * 1024 * 1024,
FramesPerSecond = 60,
CyclesPerFrame = CyclesPerSecond / FramesPerSecond,
TotalLineCount = 154,
CyclesPerLine = CyclesPerFrame / TotalLineCount,
RomPageSize = 0x4000
};
enum {
BASE = 0xFF00,
// Port/Mode Registers
P1 = 0x0, // R/W Mask5
SB = 0x1, // R/W Mask8
SC = 0x2, // R/W Bit7 | Bit0
// Timer control
DIV = 0x4, // R/W Mask8
TIMA = 0x5, // R/W Mask8
TMA = 0x6, // R/W Mask8
TAC = 0x7, // R/W Mask3
// Interrupt Flags
IF = 0xF, // R/W Mask5
IE = 0xFF, // R/W Mask5
// Sound Registers
NR10 = 0x10, // R/W Mask7
NR11 = 0x11, // R/W Bit7 | Bit6
NR12 = 0x12, // R/W Mask8
NR13 = 0x13, // W 0
NR14 = 0x14, // R/W Bit6
NR21 = 0x16, // R/W Bit7 | Bit6
NR22 = 0x17, // R/W Mask8
NR23 = 0x18, // W 0
NR24 = 0x19, // R/W Bit6
NR30 = 0x1A, // R/W Bit7
NR31 = 0x1B, // R/W Mask8
NR32 = 0x1C, // R/W Bit6 | Bit5
NR33 = 0x1D, // W 0
NR34 = 0x1E, // R/W Bit6
NR41 = 0x20, // R/W Mask6
NR42 = 0x21, // R/W Mask8
NR43 = 0x22, // R/W Mask8
NR44 = 0x23, // R/W Bit6
NR50 = 0x24, // R/W Mask8
NR51 = 0x25, // R/W Mask8
NR52 = 0x26, // R/W Mask8 Mask8
WAVE_PATTERN_RAM_START = 0x30,
WAVE_PATTERN_RAM_END = 0x3F,
// LCD Display Registers
LCDC = 0x40, // R/W Mask8
STAT = 0x41, // R/W Mask7
SCY = 0x42, // R/W Mask8
SCX = 0x43, // R/W Mask8
LY = 0x44, // R Mask8 zeroed
LYC = 0x45, // R/W Mask8
DMA = 0x46, // W 0
BGP = 0x47, // R/W Mask8
OBP0 = 0x48, // R/W Mask8
OBP1 = 0x49, // R/W Mask8
WY = 0x4A, // R/W Mask8
WX = 0x4B, // R/W Mask8
// Boot rom control
BOOT_DISABLE = 0x50,
};
// IF and IE flags
enum Interrupts {
VerticalBlank = Processor::Bit0, // VBLANK
DisplayControlStatus = Processor::Bit1, // LCDC Status
TimerOverflow = Processor::Bit2, // Timer Overflow
SerialTransfer = Processor::Bit3, // Serial Transfer
KeypadPressed = Processor::Bit4 // Hi-Lo transition of P10-P13
};
enum LcdcControl {
DisplayBackground = Processor::Bit0,
ObjectEnable = Processor::Bit1,
ObjectBlockCompositionSelection = Processor::Bit2,
BackgroundCodeAreaSelection = Processor::Bit3,
BackgroundCharacterDataSelection = Processor::Bit4,
WindowEnable = Processor::Bit5,
WindowCodeAreaSelection = Processor::Bit6,
LcdEnable = Processor::Bit7
};
enum LcdStatusMode {
HBlank = 0b00,
VBlank = 0b01,
SearchingOamRam = 0b10,
TransferringDataToLcd = 0b11
};
Bus();
Signal<int> DisplayStatusModeUpdated;
void reset();
void triggerInterrupt(int cause) {
pokeRegister(IF, peekRegister(IF) | cause);
}
void writeRegister(int offset, uint8_t content) {
write(BASE + offset, content);
}
void pokeRegister(int offset, uint8_t content) {
poke(BASE + offset, content);
}
uint8_t readRegister(int offset) {
return read(BASE + offset);
}
uint8_t peekRegister(int offset) {
return peek(BASE + offset);
}
void checkTimers(int cycles);
int timerClockTicks() {
switch (timerClock()) {
case 0b00:
return 1024; // 4.096 Khz
case 0b01:
return 16; // 262.144 Khz
case 0b10:
return 64; // 65.536 Khz
case 0b11:
return 256; // 16.384 Khz
default:
UNREACHABLE;
}
throw std::domain_error("Invalid timer clock specification");
}
int timerClock() {
return peekRegister(TAC) & Processor::Mask2;
}
bool timerEnabled() {
return !timerDisabled();
}
bool timerDisabled() {
return (peekRegister(TAC) & Processor::Bit2) == 0;
}
void incrementDIV(int cycles) {
m_divCounter.word += cycles;
pokeRegister(DIV, m_divCounter.high);
}
void incrementTIMA() {
uint16_t updated = peekRegister(TIMA) + 1;
if (updated & Processor::Bit8) {
triggerInterrupt(TimerOverflow);
updated = peekRegister(TMA);
}
pokeRegister(TIMA, updated & Processor::Mask8);
}
void incrementLY() {
pokeRegister(LY, (peekRegister(LY) + 1) % TotalLineCount);
}
void resetLY() {
pokeRegister(LY, 0);
}
void transferDma() {
if (m_dmaTransferActive) {
m_oamRam.poke(m_dmaAddress.low, peek(m_dmaAddress.word));
m_dmaTransferActive = ++m_dmaAddress.low < 0xa0;
}
}
void updateLcdStatusMode(int mode) {
const auto current = m_ioPorts.peek(STAT) & ~Processor::Mask2;
m_ioPorts.poke(STAT, current | mode);
DisplayStatusModeUpdated.fire(mode);
}
void disableBootRom() { m_disableBootRom = true; }
void enableBootRom() { m_disableBootRom = false; }
void disableGameRom() { m_disableGameRom = true; }
void enableGameRom() { m_disableGameRom = false; }
bool bootRomDisabled() const { return m_disableBootRom; }
bool bootRomEnabled() const { return !bootRomDisabled(); }
bool gameRomDisabled() const { return m_disableGameRom; }
bool gameRomEnabled() const { return !gameRomDisabled(); }
void loadBootRom(const std::string& path);
void loadGameRom(const std::string& path);
void pressRight() { m_p14 = m_p10 = false; triggerKeypadInterrupt(); }
void releaseRight() { m_p14 = m_p10 = true; }
void pressLeft() { m_p14 = m_p11 = false, triggerKeypadInterrupt(); }
void releaseLeft() { m_p14 = m_p11 = true; }
void pressUp() { m_p14 = m_p12 = false, triggerKeypadInterrupt(); }
void releaseUp() { m_p14 = m_p12 = true; }
void pressDown() { m_p14 = m_p13 = false, triggerKeypadInterrupt(); }
void releaseDown() { m_p14 = m_p13 = true; }
void pressA() { m_p15 = m_p10 = false, triggerKeypadInterrupt(); }
void releaseA() { m_p15 = m_p10 = true; }
void pressB() { m_p15 = m_p11 = false, triggerKeypadInterrupt(); }
void releaseB() { m_p15 = m_p11 = true; }
void pressSelect() { m_p15 = m_p12 = false, triggerKeypadInterrupt(); }
void releaseSelect() { m_p15 = m_p12 = true; }
void pressStart() { m_p15 = m_p13 = false, triggerKeypadInterrupt(); }
void releaseStart() { m_p15 = m_p13 = true; }
protected:
virtual uint8_t& reference(uint16_t address, bool& rom) {
rom = true;
if ((address < 0x100) && bootRomEnabled())
return m_bootRom.reference(address);
if ((address < 0x4000) && gameRomEnabled())
return m_gameRomBanks[0].reference(address);
if ((address < 0x8000) && gameRomEnabled())
return m_gameRomBanks[m_romBank].reference(address - 0x4000);
rom = false;
if (address < 0xa000)
return m_videoRam.reference(address - 0x8000);
if (address < 0xc000)
return m_ramBanks.size() == 0 ? rom = true, placeDATA(0xff) : m_ramBanks[m_ramBank].reference(address - 0xa000);
if (address < 0xe000)
return m_lowInternalRam.reference(address - 0xc000);
if (address < 0xfe00)
return m_lowInternalRam.reference(address - 0xe000); // Low internal RAM mirror
if (address < 0xfea0)
return m_oamRam.reference(address - 0xfe00);
if (address < 0xff00)
return rom = true, placeDATA(0xff);
if (address < 0xff80)
return m_ioPorts.reference(address - 0xff00);
return m_highInternalRam.reference(address - 0xff80);
}
private:
Rom m_bootRom; // 0x0000 - 0x00ff
std::vector<Rom> m_gameRomBanks; // 0x0000 - 0x3fff, 0x4000 - 0x7fff (switchable)
Ram m_videoRam; // 0x8000 - 0x9fff
std::vector<Ram> m_ramBanks; // 0xa000 - 0xbfff (switchable)
Ram m_lowInternalRam; // 0xc000 - 0xdfff (mirrored at 0xe000)
Ram m_oamRam; // 0xfe00 - 0xfe9f
Ram m_ioPorts; // 0xff00 - 0xff7f
Ram m_highInternalRam; // 0xff80 - 0xffff
bool m_disableBootRom;
bool m_disableGameRom;
bool m_rom;
bool m_banked;
bool m_ram;
bool m_battery;
bool m_higherRomBank;
bool m_ramBankSwitching;
int m_romBank;
int m_ramBank;
register16_t m_divCounter;
int m_timerCounter;
int m_timerRate;
register16_t m_dmaAddress;
bool m_dmaTransferActive;
bool m_scanP15;
bool m_scanP14;
bool m_p15; // misc keys
bool m_p14; // direction keys
bool m_p13; // down/start
bool m_p12; // up/select
bool m_p11; // left/b
bool m_p10; // right/a
void checkTimer(int cycles);
void validateCartridgeType();
void mask(uint16_t address, uint8_t masking) {
poke(address, peek(address) | ~masking);
}
void mask(uint8_t masking) {
mask(ADDRESS().word, masking);
}
void triggerKeypadInterrupt() {
triggerInterrupt(Interrupts::KeypadPressed);
}
void Bus_WrittenByte(uint16_t address);
void Bus_ReadingByte(uint16_t address);
};
}
}