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mmu.cpp
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mmu.cpp
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// GB Enhanced+ Copyright Daniel Baxter 2015
// Licensed under the GPLv2
// See LICENSE.txt for full license text
// File : mmu.cpp
// Date : May 09, 2015
// Description : Game Boy (Color) memory manager unit
//
// Handles reading and writing bytes to memory locations
// Used to switch ROM and RAM banks
// Also loads ROM and BIOS files
#include <filesystem>
#include "mmu.h"
#include "common/util.h"
/****** MMU Constructor ******/
DMG_MMU::DMG_MMU()
{
reset();
}
/****** MMU Deconstructor ******/
DMG_MMU::~DMG_MMU()
{
//Always clean up external camera pic from SRAM before saving
if(cart.mbc_type == GB_CAMERA)
{
for(u32 x = 0; x < cart.cam_buffer.size(); x++) { random_access_bank[0][0x100 + x] = 0x0; }
}
save_backup(config::save_file);
memory_map.clear();
std::cout<<"MMU::Shutdown\n";
}
/****** MMU Reset ******/
void DMG_MMU::reset()
{
//Remap ROM when resetting GB Memory Cartridge
if((config::cart_type == DMG_GBMEM) && (cart.flash_stat == 0xF0)) { gb_mem_remap(); }
//If ROM has already been remapped for GB Memory Cartridge, do nothing
if((config::cart_type == DMG_GBMEM) && (cart.flash_stat == 0x40)) { }
//Otherwise, clear memory map as usual
else
{
memory_map.clear();
memory_map.resize(0x10000, 0);
}
rom_bank = 1;
ram_bank = 0;
wram_bank = 1;
vram_bank = 0;
bank_bits = 0;
bank_mode = 0;
ram_banking_enabled = false;
in_bios = config::use_bios;
bios_type = 1;
bios_size = 0x100;
cart.rom_size = 0;
cart.ram_size = 0;
cart.mbc_type = ROM_ONLY;
cart.battery = false;
cart.ram = false;
cart.multicart = ((config::cart_type == DMG_MBC1M) || (config::cart_type == DMG_MMM01));
cart.sonar = (config::cart_type == DMG_MBC1S);
cart.rumble = false;
cart.rtc = false;
cart.rtc_enabled = false;
cart.rtc_latch_1 = cart.rtc_latch_2 = 0xFF;
if(cart.flash_stat != 0x40) { cart.flash_cnt = 0x0; }
cart.flash_cmd = 0;
if(cart.flash_stat != 0x40) { cart.flash_stat = 0x6; }
if(cart.flash_stat != 0x40) { cart.flash_io_bank = 0; }
cart.flash_get_id = false;
for(int x = 0; x < 5; x++)
{
cart.latch_reg[x] = 0;
cart.rtc_reg[x] = 0;
}
cart.rtc_timestamp = 0;
cart.idle = false;
cart.internal_value = cart.internal_state = cart.cs = cart.sk = cart.buffer_length = cart.command_code = cart.addr = cart.buffer = 0;
for(u32 x = 0; x < 54; x++) { cart.cam_reg[x] = 0; }
cart.cam_buffer.clear();
cart.cam_lock = false;
cart.sonar_byte = 0;
cart.frame_data.clear();
cart.pulse_count = 0;
cart.frame_count = 0;
cart.depth = 0;
for(u32 x = 0; x < 16; x++) { cart.tama_reg[x] = 0; }
for(u32 x = 0; x < 256; x++) { cart.tama_ram[x] = 0; }
cart.tama_cmd = 0;
cart.tama_out = 0;
if(cart.flash_stat != 0x40)
{
for(u32 x = 0; x < 128; x++) { cart.gb_mem_map[x] = 0xFF; }
}
ir_signal = 0;
ir_send = false;
ir_trigger = false;
ir_counter = 0;
div_reset = false;
//Resize various banks
read_only_bank.resize(0x200);
for(int x = 0; x < 0x200; x++) { read_only_bank[x].resize(0x4000, 0); }
random_access_bank.resize(0x10);
for(int x = 0; x < 0x10; x++) { random_access_bank[x].resize(0x2000, 0); }
working_ram_bank.resize(0x8);
for(int x = 0; x < 0x8; x++) { working_ram_bank[x].resize(0x1000, 0); }
video_ram.resize(0x2);
for(int x = 0; x < 0x2; x++) { video_ram[x].resize(0x2000, 0); }
flash.resize(0x80);
for(int x = 0; x < 0x80; x++) { flash[x].resize(0x2000, 0x00); }
g_pad = NULL;
sub_screen_buffer.clear();
sub_screen_update = 0;
sub_screen_lock = false;
//Advanced debugging
#ifdef GBE_DEBUG
debug_write = false;
debug_read = true;
debug_addr = 0;
#endif
//Load Pocket Sonar data now
if(cart.sonar) { mbc1s_load_sonar_data(config::external_image_file); }
std::cout<<"MMU::Initialized\n";
}
/****** Read MMU data from save state ******/
bool DMG_MMU::mmu_read(u32 offset, std::string filename)
{
std::ifstream file(filename.c_str(), std::ios::binary);
if(!file.is_open()) { return false; }
//Go to offset
file.seekg(offset);
//Serialize DMG/GBC RAM from save state
u8* ex_ram = &memory_map[0x8000];
file.read((char*)ex_ram, 0x8000);
for(int x = 0; x < 0x2; x++)
{
ex_ram = &video_ram[x][0];
file.read((char*)ex_ram, 0x2000);
}
for(int x = 0; x < 0x8; x++)
{
ex_ram = &working_ram_bank[x][0];
file.read((char*)ex_ram, 0x1000);
}
for(int x = 0; x < 0x10; x++)
{
ex_ram = &random_access_bank[x][0];
file.read((char*)ex_ram, 0x2000);
}
//Serialize misc MMU data from save state
file.read((char*)&rom_bank, sizeof(rom_bank));
file.read((char*)&ram_bank, sizeof(ram_bank));
file.read((char*)&wram_bank, sizeof(wram_bank));
file.read((char*)&vram_bank, sizeof(vram_bank));
file.read((char*)&bank_bits, sizeof(bank_bits));
file.read((char*)&bank_mode, sizeof(bank_mode));
file.read((char*)&ram_banking_enabled, sizeof(ram_banking_enabled));
file.read((char*)&in_bios, sizeof(in_bios));
file.read((char*)&bios_type, sizeof(bios_type));
file.read((char*)&bios_size, sizeof(bios_size));
file.read((char*)&cart, sizeof(cart));
file.read((char*)&previous_value, sizeof(previous_value));
//Sanitize MMU data from save state
if((bios_size != 0x100) && (bios_size != 0x900)) { bios_size = 0x100; }
rom_bank &= 0x1FF;
ram_bank &= 0xF;
wram_bank &= 0x3;
vram_bank &= 0x1;
bank_mode &= 0x1;
bank_bits &= 0xF;
file.close();
return true;
}
/****** Write MMU data to save state ******/
bool DMG_MMU::mmu_write(std::string filename)
{
std::ofstream file(filename.c_str(), std::ios::binary | std::ios::app);
if(!file.is_open()) { return false; }
//Serialize DMG/GBC RAM to save state
file.write(reinterpret_cast<char*> (&memory_map[0x8000]), 0x8000);
for(int x = 0; x < 0x2; x++) { file.write(reinterpret_cast<char*> (&video_ram[x][0]), 0x2000); }
for(int x = 0; x < 0x8; x++) { file.write(reinterpret_cast<char*> (&working_ram_bank[x][0]), 0x1000); }
for(int x = 0; x < 0x10; x++) { file.write(reinterpret_cast<char*> (&random_access_bank[x][0]), 0x2000); }
//Serialize misc MMU data to save state
file.write((char*)&rom_bank, sizeof(rom_bank));
file.write((char*)&ram_bank, sizeof(ram_bank));
file.write((char*)&wram_bank, sizeof(wram_bank));
file.write((char*)&vram_bank, sizeof(vram_bank));
file.write((char*)&bank_bits, sizeof(bank_bits));
file.write((char*)&bank_mode, sizeof(bank_mode));
file.write((char*)&ram_banking_enabled, sizeof(ram_banking_enabled));
file.write((char*)&in_bios, sizeof(in_bios));
file.write((char*)&bios_type, sizeof(bios_type));
file.write((char*)&bios_size, sizeof(bios_size));
file.write((char*)&cart, sizeof(cart));
file.write((char*)&previous_value, sizeof(previous_value));
file.close();
return true;
}
/****** Gets the size of MMU data for serialization ******/
u32 DMG_MMU::size()
{
u32 mmu_size = 0;
mmu_size += 0x34000;
mmu_size += sizeof(rom_bank);
mmu_size += sizeof(ram_bank);
mmu_size += sizeof(wram_bank);
mmu_size += sizeof(vram_bank);
mmu_size += sizeof(bank_bits);
mmu_size += sizeof(bank_mode);
mmu_size += sizeof(ram_banking_enabled);
mmu_size += sizeof(in_bios);
mmu_size += sizeof(bios_type);
mmu_size += sizeof(bios_size);
mmu_size += sizeof(cart);
mmu_size += sizeof(previous_value);
return mmu_size;
}
/****** Read byte from memory ******/
u8 DMG_MMU::read_u8(u16 address)
{
//Advanced debugging
#ifdef GBE_DEBUG
debug_read = true;
debug_addr = address;
#endif
//Read from BIOS
if(in_bios)
{
//GBC BIOS reads from 0x00 to 0xFF and 0x200 to 0x900
//0x100 - 0x1FF is reserved for the Nintendo logo + checksum + first lines of game code
//For the latter, just read from the cartridge ROM
if((bios_size == 0x900) && (address > 0x100) && (address < 0x200)) { return memory_map[address]; }
else if(address == 0x100)
{
in_bios = false;
std::cout<<"MMU::Exiting BIOS \n";
//For DMG on GBC games, we switch back to DMG Mode (we just take the colors the BIOS gives us)
if((bios_size == 0x900) && (memory_map[ROM_COLOR] != 0x80) && (memory_map[ROM_COLOR] != 0xC0)) { config::gb_type = 1; }
}
else if(address < bios_size) { return bios[address]; }
}
//Read using ROM Banking
if((cart.multicart) && (address <= 0x3FFF)) { return mbc_read(address); }
//Read using ROM Banking
if((address >= 0x4000) && (address <= 0x7FFF) && (cart.mbc_type != ROM_ONLY)) { return mbc_read(address); }
//Read using RAM Banking
if((address >= 0xA000) && (address <= 0xBFFF) && (cart.ram) && (cart.mbc_type != ROM_ONLY)) { return mbc_read(address); }
//MBC7 always has RAM enabled for reading
else if((address >= 0xA000) && (address <= 0xBFFF) && (cart.mbc_type == MBC7)) { return mbc7_read(address); }
//Read from VRAM, GBC uses banking
if((address >= 0x8000) && (address <= 0x9FFF))
{
//GBC read from VRAM Bank 1
if((vram_bank == 1) && (config::gb_type == 2)) { return video_ram[1][address - 0x8000]; }
//GBC read from VRAM Bank 0 - DMG read normally, also from Bank 0, though it doesn't use banking technically
else { return video_ram[0][address - 0x8000]; }
}
//In GBC mode, read from Working RAM using Banking
if((address >= 0xC000) && (address <= 0xDFFF) && (config::gb_type == 2))
{
//Read from Bank 0 always when address is within 0xC000 - 0xCFFF
if((address >= 0xC000) && (address <= 0xCFFF)) { return working_ram_bank[0][address - 0xC000]; }
//Read from selected Bank when address is within 0xD000 - 0xDFFF
else if((address >= 0xD000) && (address <= 0xDFFF)) { return working_ram_bank[wram_bank][address - 0xD000]; }
}
//Read background color palette data
if(address == REG_BCPD)
{
u8 hi_lo = (memory_map[REG_BCPS] & 0x1);
u8 color = (memory_map[REG_BCPS] >> 1) & 0x3;
u8 palette = (memory_map[REG_BCPS] >> 3) & 0x7;
//Read lower-nibble of color
if(hi_lo == 0)
{
return (lcd_stat->bg_colors_raw[color][palette] & 0xFF);
}
//Read upper-nibble of color
else
{
return (lcd_stat->bg_colors_raw[color][palette] >> 8);
}
}
//Read sprite color palette data
if(address == REG_OCPD)
{
u8 hi_lo = (memory_map[REG_OCPS] & 0x1);
u8 color = (memory_map[REG_OCPS] >> 1) & 0x3;
u8 palette = (memory_map[REG_OCPS] >> 3) & 0x7;
//Read lower-nibble of color
if(hi_lo == 0)
{
return (lcd_stat->obj_colors_raw[color][palette] & 0xFF);
}
//Read upper-nibble of color
else
{
return (lcd_stat->obj_colors_raw[color][palette] >> 8);
}
}
//Read from RP
else if(address == REG_RP)
{
//GBC only
if(config::gb_type < 2) { return 0x0; }
//Initiate manual IR transmission (Full Changer, Pokemon Pikachu 2, Pocket Sakura, TV Remote)
if(!ir_signal && (ir_trigger == 1))
{
ir_trigger++;
sio_stat->shift_counter = 0;
sio_stat->shift_clock = 0;
sio_stat->shifts_left = 1;
}
//If Bits 6 and 7 are not set, treat Bit 1 as HIGH
if((memory_map[address] & 0xC0) == 0) { return memory_map[address] | 0x2; }
//Otherwise, read RP normally
else { return memory_map[address]; }
}
//Read from P1
else if(address == 0xFF00) { return g_pad->read(); }
//Read normally
return memory_map[address];
}
/****** Read signed byte from memory ******/
s8 DMG_MMU::read_s8(u16 address)
{
u8 temp = read_u8(address);
s8 s_temp = (s8)temp;
return s_temp;
}
/****** Read word from memory ******/
u16 DMG_MMU::read_u16(u16 address)
{
return (read_u8(address+1) << 8) | read_u8(address);
}
/****** Write Byte To Memory ******/
void DMG_MMU::write_u8(u16 address, u8 value)
{
//Advanced debugging
#ifdef GBE_DEBUG
debug_write = true;
debug_addr = address;
#endif
if(cart.mbc_type != ROM_ONLY)
{
mbc_write(address, value);
if((address >= 0xA000) && (address <= 0xBFFF)) { return; }
}
//Write to VRAM, GBC uses banking
if((address >= 0x8000) && (address <= 0x9FFF))
{
//GBC write to VRAM Bank 1
if((vram_bank == 1) && (config::gb_type == 2))
{
previous_value = video_ram[1][address - 0x8000];
video_ram[1][address - 0x8000] = value;
}
//GBC write to VRAM Bank 0 - DMG read normally, also from Bank 0, though it doesn't use banking technically
else
{
previous_value = video_ram[0][address - 0x8000];
video_ram[0][address - 0x8000] = value;
}
}
//DIV - Reset register to zero
else if(address == REG_DIV)
{
memory_map[address] = 0;
div_reset = true;
}
//NR11 - Duty Cycle
else if(address == NR11)
{
memory_map[address] = value;
apu_stat->channel[0].duty_cycle = (value >> 6) & 0x3;
switch(apu_stat->channel[0].duty_cycle)
{
case 0x0:
apu_stat->channel[0].duty_cycle_start = 0;
apu_stat->channel[0].duty_cycle_end = 1;
break;
case 0x1:
apu_stat->channel[0].duty_cycle_start = 0;
apu_stat->channel[0].duty_cycle_end = 2;
break;
case 0x2:
apu_stat->channel[0].duty_cycle_start = 0;
apu_stat->channel[0].duty_cycle_end = 4;
break;
case 0x3:
apu_stat->channel[0].duty_cycle_start = 0;
apu_stat->channel[0].duty_cycle_end = 6;
break;
}
}
//NR12 - Envelope, Volume
else if(address == NR12)
{
memory_map[address] = value;
u8 current_step = apu_stat->channel[0].envelope_step;
u8 next_step = (value & 0x07) ? 1 : 0;
u8 next_volume = (value >> 4);
u8 next_direction = (value & 0x08) ? 1 : 0;
//Envelope timer is not reset unless sound is initializes
//Envelope timer does start if it is turned off at first, but turned on after sound initializes
if((current_step == 0) && (next_step != 0))
{
apu_stat->channel[0].volume = (value >> 4);
apu_stat->channel[0].envelope_direction = (value & 0x08) ? 1 : 0;
apu_stat->channel[0].envelope_step = (value & 0x07);
apu_stat->channel[0].envelope_counter = 0;
}
//Turn off sound channel if envelope volume is 0 and mode is subtraction
if((next_direction == 0) && (next_volume == 0))
{
apu_stat->channel[0].playing = false;
memory_map[NR52] &= ~0x1;
}
//Zombie Mode Behavior - If envolope mode is changed while sound is playing, set volume to 16 (0x10)
if((apu_stat->channel[0].playing) && (next_direction != apu_stat->channel[0].envelope_direction))
{
apu_stat->channel[0].volume = 0x10;
}
}
//NR13 - Frequency LO
else if(address == NR13)
{
memory_map[address] = value;
//If sweep is active, do not update frequency
//This emulates the sweep's shadow registers
if(!apu_stat->channel[0].sweep_on)
{
apu_stat->channel[0].raw_frequency = ((memory_map[NR14] << 8) | memory_map[NR13]) & 0x7FF;
apu_stat->channel[0].output_frequency = (131072.0 / (2048 - apu_stat->channel[0].raw_frequency));
}
}
//NR14 - Frequency HI, Initial
else if(address == NR14)
{
memory_map[address] = value;
//If sweep is active, do not update frequency
//This emulates the sweep's shadow registers
//However, always update frequency when initializing sound
if((!apu_stat->channel[0].sweep_on) || (value & 0x80))
{
apu_stat->channel[0].raw_frequency = ((memory_map[NR14] << 8) | memory_map[NR13]) & 0x7FF;
apu_stat->channel[0].output_frequency = (131072.0 / (2048 - apu_stat->channel[0].raw_frequency));
}
//Check initial flag to start playing sound, check length flag
if(value & 0x80) { apu_stat->channel[0].playing = true; }
apu_stat->channel[0].length_flag = (value & 0x40) ? true : false;
//Initialize sound
//Updates various sound parameters
if(value & 0x80)
{
//Duty cycle
switch((memory_map[NR11] >> 6))
{
case 0x0:
apu_stat->channel[0].duty_cycle_start = 1;
apu_stat->channel[0].duty_cycle_end = 2;
break;
case 0x1:
apu_stat->channel[0].duty_cycle_start = 0;
apu_stat->channel[0].duty_cycle_end = 2;
break;
case 0x2:
apu_stat->channel[0].duty_cycle_start = 0;
apu_stat->channel[0].duty_cycle_end = 4;
break;
case 0x3:
apu_stat->channel[0].duty_cycle_start = 2;
apu_stat->channel[0].duty_cycle_end = 8;
break;
}
//Duration
if(!apu_stat->channel[0].length_flag) { apu_stat->channel[0].duration = 5000; }
else
{
apu_stat->channel[0].duration = (memory_map[NR11] & 0x3F);
apu_stat->channel[0].duration = ((64 - apu_stat->channel[0].duration) / 256.0) * 1000.0;
}
//Volume & Envelope
apu_stat->channel[0].volume = (memory_map[NR12] >> 4);
apu_stat->channel[0].envelope_direction = (memory_map[NR12] & 0x08) ? 1 : 0;
apu_stat->channel[0].envelope_step = (memory_map[NR12] & 0x07);
//Turn off sound channel if envelope volume is 0 and mode is subtraction
if((apu_stat->channel[0].envelope_direction == 0) && (apu_stat->channel[0].volume == 0))
{
apu_stat->channel[0].playing = false;
memory_map[NR52] &= ~0x1;
}
//Sweep
apu_stat->channel[0].sweep_direction = (memory_map[NR10] & 0x08) ? 1 : 0;
apu_stat->channel[0].sweep_time = ((memory_map[NR10] >> 4) & 0x7);
apu_stat->channel[0].sweep_shift = (memory_map[NR10] & 0x7);
if((apu_stat->channel[0].sweep_shift != 0) || (apu_stat->channel[0].sweep_time != 0)) { apu_stat->channel[0].sweep_on = true; }
else { apu_stat->channel[0].sweep_on = false; }
//Internal APU time-keeping
apu_stat->channel[0].frequency_distance = 0;
apu_stat->channel[0].sample_length = (apu_stat->channel[0].duration * apu_stat->sample_rate)/1000;
apu_stat->channel[0].envelope_counter = 0;
apu_stat->channel[0].sweep_counter = 0;
}
//Set NR52 flag
if(apu_stat->channel[0].playing) { memory_map[NR52] |= 0x1; }
}
//NR21 - Duration, Duty Cycle
else if(address == NR21)
{
memory_map[address] = value;
apu_stat->channel[1].duty_cycle = (value >> 6) & 0x3;
switch(apu_stat->channel[1].duty_cycle)
{
case 0x0:
apu_stat->channel[1].duty_cycle_start = 0;
apu_stat->channel[1].duty_cycle_end = 1;
break;
case 0x1:
apu_stat->channel[1].duty_cycle_start = 0;
apu_stat->channel[1].duty_cycle_end = 2;
break;
case 0x2:
apu_stat->channel[1].duty_cycle_start = 0;
apu_stat->channel[1].duty_cycle_end = 4;
break;
case 0x3:
apu_stat->channel[1].duty_cycle_start = 0;
apu_stat->channel[1].duty_cycle_end = 6;
break;
}
}
//NR22 - Envelope, Volume
else if(address == NR22)
{
memory_map[address] = value;
u8 current_step = apu_stat->channel[1].envelope_step;
u8 next_step = (value & 0x07) ? 1 : 0;
u8 next_volume = (value >> 4);
u8 next_direction = (value & 0x08) ? 1 : 0;
//Envelope timer is not reset unless sound initializes
//Envelope timer does start if it is turned off at first, but turned on after sound initializes
if((current_step == 0) && (next_step != 0))
{
apu_stat->channel[1].volume = (value >> 4);
apu_stat->channel[1].envelope_direction = (value & 0x08) ? 1 : 0;
apu_stat->channel[1].envelope_step = (value & 0x07);
apu_stat->channel[1].envelope_counter = 0;
}
//Turn off sound channel if envelope volume is 0 and mode is subtraction
if((next_direction == 0) && (next_volume == 0))
{
apu_stat->channel[1].playing = false;
memory_map[NR52] &= ~0x2;
}
//Zombie Mode Behavior - If envolope mode is changed while sound is playing, set volume to 16 (0x10)
if((apu_stat->channel[1].playing) && (next_direction != apu_stat->channel[1].envelope_direction))
{
apu_stat->channel[1].volume = 0x10;
}
}
//NR23 - Frequency LO
else if(address == NR23)
{
memory_map[address] = value;
apu_stat->channel[1].raw_frequency = ((memory_map[NR24] << 8) | memory_map[NR23]) & 0x7FF;
apu_stat->channel[1].output_frequency = (131072.0 / (2048 - apu_stat->channel[1].raw_frequency));
}
//NR24 - Frequency HI, Initial
else if(address == NR24)
{
memory_map[address] = value;
//Frequency
apu_stat->channel[1].raw_frequency = ((memory_map[NR24] << 8) | memory_map[NR23]) & 0x7FF;
apu_stat->channel[1].output_frequency = (131072.0 / (2048 - apu_stat->channel[1].raw_frequency));
//Check initial flag to start playing sound, check length flag
if(value & 0x80) { apu_stat->channel[1].playing = true; }
apu_stat->channel[1].length_flag = (value & 0x40) ? true : false;
//Initialize sound
//Updates various sound parameters
if(value & 0x80)
{
//Duty cycle
switch((memory_map[NR21] >> 6))
{
case 0x0:
apu_stat->channel[1].duty_cycle_start = 1;
apu_stat->channel[1].duty_cycle_end = 2;
break;
case 0x1:
apu_stat->channel[1].duty_cycle_start = 0;
apu_stat->channel[1].duty_cycle_end = 2;
break;
case 0x2:
apu_stat->channel[1].duty_cycle_start = 0;
apu_stat->channel[1].duty_cycle_end = 4;
break;
case 0x3:
apu_stat->channel[1].duty_cycle_start = 2;
apu_stat->channel[1].duty_cycle_end = 8;
break;
}
//Duration
if(!apu_stat->channel[1].length_flag) { apu_stat->channel[1].duration = 5000; }
else
{
apu_stat->channel[1].duration = (memory_map[NR21] & 0x3F);
apu_stat->channel[1].duration = ((64 - apu_stat->channel[1].duration) / 256.0) * 1000.0;
}
//Volume & Envelope
apu_stat->channel[1].volume = (memory_map[NR22] >> 4);
apu_stat->channel[1].envelope_direction = (memory_map[NR22] & 0x08) ? 1 : 0;
apu_stat->channel[1].envelope_step = (memory_map[NR22] & 0x07);
//Turn off sound channel if envelope volume is 0 and mode is subtraction
if((apu_stat->channel[1].envelope_direction == 0) && (apu_stat->channel[1].volume == 0))
{
apu_stat->channel[1].playing = false;
memory_map[NR52] &= ~0x2;
}
//Internal APU time-keeping
apu_stat->channel[1].frequency_distance = 0;
apu_stat->channel[1].sample_length = (apu_stat->channel[1].duration * apu_stat->sample_rate)/1000;
apu_stat->channel[1].envelope_counter = 0;
apu_stat->channel[1].sweep_counter = 0;
}
//Set NR52 flag
if(apu_stat->channel[1].playing) { memory_map[NR52] |= 0x2; }
}
//NR30 - Sound3 Enable/Disable
else if(address == NR30)
{
memory_map[address] = value;
if((value & 0x80) == 0)
{
apu_stat->channel[2].playing = false;
memory_map[NR52] &= ~0x4;
}
}
//NR31 - Duration
else if(address == NR31)
{
memory_map[address] = value;
//Duration
if(!apu_stat->channel[2].length_flag) { apu_stat->channel[2].duration = 5000; }
else
{
apu_stat->channel[2].duration = memory_map[NR31];
apu_stat->channel[2].duration = ((256 - apu_stat->channel[2].duration) / 256.0) * 1000.0;
}
apu_stat->channel[2].sample_length = (apu_stat->channel[2].duration * apu_stat->sample_rate)/1000;
}
//NR32 - Volume
else if(address == NR32)
{
memory_map[address] = value;
switch((value >> 5) & 0x3)
{
//0%
case 0x0: apu_stat->channel[2].volume = 4; break;
//100%
case 0x1: apu_stat->channel[2].volume = 0; break;
//50%
case 0x2: apu_stat->channel[2].volume = 1; break;
//25%
case 0x3: apu_stat->channel[2].volume = 2; break;
}
}
//NR33 - Frequency LO
else if(address == NR33)
{
memory_map[address] = value;
apu_stat->channel[2].raw_frequency = ((memory_map[NR34] << 8) | memory_map[NR33]) & 0x7FF;
apu_stat->channel[2].output_frequency = (131072.0 / (2048 - apu_stat->channel[2].raw_frequency));
apu_stat->channel[2].output_frequency /= 2.0;
}
//NR34 - Frequency HI, Initial
else if(address == NR34)
{
memory_map[address] = value;
//Check initial flag to start playing sound, check length flag
if(value & 0x80) { apu_stat->channel[2].playing = true; }
apu_stat->channel[2].length_flag = (value & 0x40) ? true : false;
//Frequency
apu_stat->channel[2].raw_frequency = ((memory_map[NR34] << 8) | memory_map[NR33]) & 0x7FF;
apu_stat->channel[2].output_frequency = (131072.0 / (2048 - apu_stat->channel[2].raw_frequency));
apu_stat->channel[2].output_frequency /= 2.0;
if(value & 0x80)
{
//Duration
if(!apu_stat->channel[2].length_flag) { apu_stat->channel[2].duration = 5000; }
else
{
apu_stat->channel[2].duration = memory_map[NR31];
apu_stat->channel[2].duration = ((256 - apu_stat->channel[2].duration) / 256.0) * 1000.0;
}
//Internal APU time-keeping
apu_stat->channel[2].frequency_distance = 0;
apu_stat->channel[2].sample_length = (apu_stat->channel[2].duration * apu_stat->sample_rate)/1000;
}
//Set NR52 flag
if(apu_stat->channel[2].playing) { memory_map[NR52] |= 0x4; }
}
//NR42 - Envelope, Volume
else if(address == NR42)
{
memory_map[address] = value;
u8 current_step = apu_stat->channel[3].envelope_step;
u8 next_step = (value & 0x07) ? 1 : 0;
u8 next_volume = (value >> 4);
u8 next_direction = (value & 0x08) ? 1 : 0;
//Envelope timer is not reset unless sound initializes
//Envelope timer does start if it is turned off at first, but turned on after sound initializes
if((current_step == 0) && (next_step != 0))
{
apu_stat->channel[3].volume = (value >> 4);
apu_stat->channel[3].envelope_direction = (value & 0x08) ? 1 : 0;
apu_stat->channel[3].envelope_step = (value & 0x07);
apu_stat->channel[3].envelope_counter = 0;
}
//Turn off sound channel if envelope volume is 0 and mode is subtraction
if((next_direction == 0) && (next_volume == 0))
{
apu_stat->channel[3].playing = false;
memory_map[NR52] &= ~0x8;
}
//Zombie Mode Behavior - If envolope mode is changed while sound is playing, set volume to 16 (0x10)
if((apu_stat->channel[3].playing) && (next_direction != apu_stat->channel[3].envelope_direction))
{
apu_stat->channel[3].volume = 0x10;
}
}
//NR43 - Polynomial Counter
else if(address == NR43)
{
memory_map[address] = value;
//Dividing ratio
switch(value & 0x7)
{
case 0x0: apu_stat->noise_dividing_ratio = 0.5; break;
case 0x1: apu_stat->noise_dividing_ratio = 1.0; break;
case 0x2: apu_stat->noise_dividing_ratio = 2.0; break;
case 0x3: apu_stat->noise_dividing_ratio = 3.0; break;
case 0x4: apu_stat->noise_dividing_ratio = 4.0; break;
case 0x5: apu_stat->noise_dividing_ratio = 5.0; break;
case 0x6: apu_stat->noise_dividing_ratio = 6.0; break;
case 0x7: apu_stat->noise_dividing_ratio = 7.0; break;
}
//Prescalar
apu_stat->noise_prescalar = 2 << (value >> 4);
//LSFR Stages
if(value & 0x8) { apu_stat->noise_stages = 7; }
else { apu_stat->noise_stages = 15; }
apu_stat->channel[3].output_frequency = (524288/apu_stat->noise_dividing_ratio)/apu_stat->noise_prescalar;
}
//NR44 - Initial
else if(address == NR44)
{
memory_map[address] = value;
//Check initial flag to start playing sound, check length flag
if(value & 0x80) { apu_stat->channel[3].playing = true; }
apu_stat->channel[3].length_flag = (value & 0x40) ? true : false;
if(value & 0x80)
{
//Duration
if(!apu_stat->channel[3].length_flag) { apu_stat->channel[3].duration = 5000; }
else
{
apu_stat->channel[3].duration = (memory_map[NR41] & 0x3F);
apu_stat->channel[3].duration = ((64 - apu_stat->channel[3].duration) / 256.0) * 1000.0;
}
apu_stat->channel[3].sample_length = (apu_stat->channel[3].duration * apu_stat->sample_rate)/1000;
//Volume & Envelope
apu_stat->channel[3].volume = (memory_map[NR42] >> 4);
apu_stat->channel[3].envelope_direction = (memory_map[NR42] & 0x08) ? 1 : 0;
apu_stat->channel[3].envelope_step = (memory_map[NR42] & 0x07);
//Turn off sound channel if envelope volume is 0 and mode is subtraction
if((apu_stat->channel[3].envelope_direction == 0) && (apu_stat->channel[3].volume == 0))
{
apu_stat->channel[3].playing = false;
memory_map[NR52] &= ~0x8;
}
//Internal APU time-keeping
apu_stat->channel[3].frequency_distance = 0;
apu_stat->channel[3].envelope_counter = 0;
apu_stat->noise_7_stage_lsfr = 0x40;
apu_stat->noise_15_stage_lsfr = 0x4000;
}
//Set NR52 flag
if(apu_stat->channel[3].playing) { memory_map[NR52] |= 0x8; }
}
//NR50 S01-S02 volume
else if(address == NR50)
{
memory_map[address] = value;
apu_stat->channel_left_volume = (value & 0x7) / 7.0;
apu_stat->channel_right_volume = ((value >> 4) & 0x7) / 7.0;
}
//NR51 SO1-SO2 Sound Channel Output
//Note, in mono-sound mode, these effectively control per-channel sound output
else if(address == NR51)
{
memory_map[address] = value;
apu_stat->channel[0].so1_output = (value & 0x1) ? true : false;
apu_stat->channel[1].so1_output = (value & 0x2) ? true : false;
apu_stat->channel[2].so1_output = (value & 0x4) ? true : false;
apu_stat->channel[3].so1_output = (value & 0x8) ? true : false;
apu_stat->channel[0].so2_output = (value & 0x10) ? true : false;
apu_stat->channel[1].so2_output = (value & 0x20) ? true : false;
apu_stat->channel[2].so2_output = (value & 0x40) ? true : false;
apu_stat->channel[3].so2_output = (value & 0x80) ? true : false;
}
//NR52 Sound On/Off
else if(address == NR52)
{
//Sound on
if(value & 0x80)
{
memory_map[address] |= 0x80;
apu_stat->sound_on = true;
}
//Sound off
else
{