40 lines
973 B
C++
40 lines
973 B
C++
#include <cartridge/mbc/mbc1.h>
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#include <misc/exception.h>
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MBC1::MBC1(Cartridge& cart)
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: cart(cart),
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main_bankreg(0),
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external_ram(0x8000)
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{}
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u8 MBC1::read8(u16 addr)
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{
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if((addr & 0xC000) == 0x0000)
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return cart[addr];
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else if((addr & 0xC000) == 0x4000)
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{
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u8 bank = main_bankreg ? main_bankreg : 1;
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u8 numbanks = cart.size() >> 14;
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return cart[(bank % numbanks) << 14 | (addr - 0x4000)];
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}
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else if((addr & 0xE000) == 0xA000)
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{
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if(!ram_enabled) return 0xFF;
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return external_ram.read8(ram_bankreg << 13 | (addr - 0xA000));
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}
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else
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return 0xFF;
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}
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void MBC1::write8(u16 addr, u8 data)
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{
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if((addr & 0xE000) == 0x0000)
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ram_enabled = ((data & 0x0F) == 0x0A);
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else if((addr & 0xE000) == 0x2000)
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main_bankreg = data & 0x1F;
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else if((addr & 0xE000) == 0x4000)
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ram_bankreg = data & 0x03;
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else if((addr & 0xE000) == 0x6000)
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throw EmulatorException("MBC1: banking mode not supported");
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}
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