248.cpp

PocketNester的c++源代码,很好的学习例子,仅供大家学习

/////////////////////////////////////////////////////////////////////
// Mapper 248
void NES_mapper248::Reset()
{
  // clear registers FIRST!!!
  for(int i = 0; i < 8; i++) regs[i] = 0x00;

  // set CPU bank pointers
  prg0 = 0;
  prg1 = 1;
  MMC3_set_CPU_banks();

  // set VROM banks
  chr01 = 0;
  chr23 = 2;
  chr4  = 4;
  chr5  = 5;
  chr6  = 6;
  chr7  = 7;
  MMC3_set_PPU_banks();

  irq_enabled = 0;
  irq_counter = 0;
  irq_latch = 0;
}

void NES_mapper248::MemoryWriteSaveRAM(uint32 addr, uint8 data)
{
  set_CPU_banks(2*data,2*data+1,num_8k_ROM_banks-2,num_8k_ROM_banks-1);
}

void NES_mapper248::MemoryWrite(uint32 addr, uint8 data)
{
  switch(addr & 0xE001)
  {
    case 0x8000:
      {
        regs[0] = data;
        MMC3_set_PPU_banks();
        MMC3_set_CPU_banks();
      }
      break;

    case 0x8001:
      {
        uint32 bank_num;

        regs[1] = data;
        bank_num = regs[1];

        switch(regs[0] & 0x07)
        {
          case 0x00:
            {
              //if(num_1k_VROM_banks)
              {
                bank_num &= 0xfe;
                chr01 = bank_num;
                MMC3_set_PPU_banks();
              }
            }
            break;

          case 0x01:
            {
              //if(num_1k_VROM_banks)
              {
                bank_num &= 0xfe;
                chr23 = bank_num;
                MMC3_set_PPU_banks();
              }
            }
            break;

          case 0x02:
            {
              //if(num_1k_VROM_banks)
              {
                chr4 = bank_num;
                MMC3_set_PPU_banks();
              }
            }
            break;

          case 0x03:
            {
              //if(num_1k_VROM_banks)
              {
                chr5 = bank_num;
                MMC3_set_PPU_banks();
              }
            }
            break;

          case 0x04:
            {
              //if(num_1k_VROM_banks)
              {
                chr6 = bank_num;
                MMC3_set_PPU_banks();
              }
            }
            break;

          case 0x05:
            {
              //if(num_1k_VROM_banks)
              {
                chr7 = bank_num;
                MMC3_set_PPU_banks();
              }
            }
            break;

          case 0x06:
            {
              prg0 = bank_num;
              MMC3_set_CPU_banks();
            }
            break;

          case 0x07:
            {
              prg1 = bank_num;
              MMC3_set_CPU_banks();
            }
            break;
        }
      }
      break;

    case 0xA000:
      {
        regs[2] = data;

        if(parent_NES->ROM->get_mirroring() != NES_PPU::MIRROR_FOUR_SCREEN)
        {
          if(data & 0x01)
          {
            set_mirroring(NES_PPU::MIRROR_HORIZ);
          }
          else
          {
            set_mirroring(NES_PPU::MIRROR_VERT);
          }
        }
      }
      break;

    case 0xA001:
      {
        if(data & 0x80)
        {
          // enable save RAM $6000-$7FFF
        }
        else
        {
          // disable save RAM $6000-$7FFF
        }
      }
      break;

    case 0xC000:
      {
        irq_counter = irq_latch = 0xbe;
        irq_enabled = 0;
      }
      break;

    case 0xC001:
      {
        irq_counter = irq_latch = 0xbe;
        irq_enabled = 1;
      }
      break;

    case 0xE000:
      {
        irq_enabled = 0;
      }
      break;

    case 0xE001:
      {
        irq_enabled = 1;
      }
      break;
  }
}

void NES_mapper248::HSync(uint32 scanline)
{
  if(irq_enabled)
  {
    if((scanline >= 0) && (scanline <= 239))
    {
      if(parent_NES->ppu->spr_enabled() || parent_NES->ppu->bg_enabled())
      {
        if(!(irq_counter--))
        {
          irq_counter = irq_latch;
          parent_NES->cpu->DoIRQ();
        }
      }
    }
  }
}

void NES_mapper248::MMC3_set_CPU_banks()
{
  if(prg_swap())
  {
    set_CPU_banks(num_8k_ROM_banks-2,prg1,prg0,num_8k_ROM_banks-1);
  }
  else
  {
    set_CPU_banks(prg0,prg1,num_8k_ROM_banks-2,num_8k_ROM_banks-1);
  }
}

void NES_mapper248::MMC3_set_PPU_banks()
{
  if(chr_swap())
  {
    set_PPU_banks(chr4,chr5,chr6,chr7,chr01,chr01+1,chr23,chr23+1);
  }
  else
  {
    set_PPU_banks(chr01,chr01+1,chr23,chr23+1,chr4,chr5,chr6,chr7);
  }
}

#define MAP248_ROM(ptr)  (((ptr)-parent_NES->ROM->get_ROM_banks())  >> 13)
#define MAP248_VROM(ptr) (((ptr)-parent_NES->ROM->get_VROM_banks()) >> 10)

void NES_mapper248::SNSS_fixup() // HACK HACK HACK HACK
{
  NES_6502::Context context;
  parent_NES->cpu->GetContext(&context);

  prg0 = MAP248_ROM(context.mem_page[prg_swap() ? 6 : 4]);
  prg1 = MAP248_ROM(context.mem_page[5]);

  if(chr_swap())
  {
    chr01 = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[4]);
    chr23 = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[6]);
    chr4  = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[0]);
    chr5  = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[1]);
    chr6  = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[2]);
    chr7  = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[3]);
  }
  else
  {
    chr01 = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[0]);
    chr23 = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[2]);
    chr4  = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[4]);
    chr5  = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[5]);
    chr6  = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[6]);
    chr7  = MAP248_VROM(parent_NES->ppu->PPU_VRAM_banks[7]);
  }
}
/////////////////////////////////////////////////////////////////////