152 lines
3.1 KiB
C#
152 lines
3.1 KiB
C#
using BizHawk.Common;
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using BizHawk.Common.NumberExtensions;
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namespace BizHawk.Emulation.Cores.Atari.A7800Hawk
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{
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// Default Bank Switching Mapper used by most games
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public sealed class MapperSG : MapperBase
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{
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private byte _bank;
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private byte[] RAM = new byte[0x4000];
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public override byte ReadMemory(ushort addr)
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{
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if (addr >= 0x1000 && addr < 0x1800)
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{
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//could be hsbios RAM here
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if (Core._hsbios != null)
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{
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return Core._hsram[addr - 0x1000];
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}
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return 0xFF;
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}
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if (addr < 0x4000)
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{
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// could be either RAM mirror or ROM
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if (addr >= 0x3000 && Core._hsbios != null)
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{
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return Core._hsbios[addr - 0x3000];
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}
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return Core.RAM[0x800 + addr & 0x7FF];
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}
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// cartridge and other OPSYS
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if (addr >= (0x10000 - Core._bios.Length) && !Core.A7800_control_register.Bit(2))
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{
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return Core._bios[addr - (0x10000 - Core._bios.Length)];
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}
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if (addr >= 0xC000)
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{
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// bank 7 is fixed
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return Core._rom[Core._rom.Length - (0x10000 - addr)];
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}
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if (addr >= 0x8000)
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{
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// return whatever bank is there
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int tempAddr = addr - 0x8000;
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return Core._rom[tempAddr + _bank * 0x4000];
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}
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if (Core.cart_RAM == 0 && !Core.is_pokey)
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{
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// return bank 6
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int tempAddr = addr - 0x4000;
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if (!Core.small_flag)
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{
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return Core._rom[tempAddr + 6 * 0x4000];
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}
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if (Core.PAL_Kara)
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{
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return Core._rom[tempAddr + 2 * 0x4000];
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}
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// Should never get here, but in case we do just return FF
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return 0xFF;
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}
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if (Core.cart_RAM > 0)
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{
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// return RAM
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if (Core.cart_RAM == 8 && addr >= 0x6000)
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{
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return RAM[addr - 0x6000];
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}
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if (Core.cart_RAM == 16)
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{
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return RAM[addr - 0x4000];
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}
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// this would correspond to reading from 0x4000-0x5FFF with only 8k of RAM
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// Let's just return FF for now
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return 0xFF;
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}
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if (Core.is_pokey)
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{
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return Core.pokey.ReadReg(addr & 0xF);
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}
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return 0xFF;
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}
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public override void WriteMemory(ushort addr, byte value)
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{
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if (addr >= 0x1000 && addr < 0x1800)
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{
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//could be hsbios RAM here
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if (Core._hsbios != null)
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{
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Core._hsram[addr - 0x1000] = value;
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}
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}
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else if (addr < 0x4000)
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{
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// could be either RAM mirror or ROM
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if (addr >= 0x3000 && Core._hsbios != null)
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{
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}
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else
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{
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Core.RAM[0x800 + addr & 0x7FF] = value;
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}
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}
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else
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{
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// cartridge and other OPSYS
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if (addr>=0x8000)
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{
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_bank = (byte)(value & (Core.small_flag ? 0x3 : mask));
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}
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else if (Core.is_pokey)
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{
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Core.pokey.WriteReg(addr & 0xF, value);
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}
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else if (Core.cart_RAM > 0)
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{
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if (Core.cart_RAM==8 && addr >= 0x6000)
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{
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RAM[addr - 0x6000] = value;
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}
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else if (Core.cart_RAM==16)
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{
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RAM[addr - 0x4000] = value;
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}
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}
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}
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}
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public override void SyncState(Serializer ser)
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{
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ser.Sync("Bank", ref _bank);
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ser.Sync(nameof(RAM), ref RAM, false);
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}
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}
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}
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