124 lines
2.6 KiB
C++
124 lines
2.6 KiB
C++
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// Nes_Emu 0.7.0. http://www.slack.net/~ant/
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#include "Nes_Mapper.h"
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#include <string.h>
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/* Copyright (C) 2004-2006 Shay Green. This module is free software; you
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can redistribute it and/or modify it under the terms of the GNU Lesser
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General Public License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version. This
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module is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
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more details. You should have received a copy of the GNU Lesser General
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Public License along with this module; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#include "blargg_source.h"
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class Mapper_Mmc1 : public Nes_Mapper, mmc1_state_t {
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public:
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Mapper_Mmc1()
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{
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mmc1_state_t* state = this;
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register_state( state, sizeof *state );
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}
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virtual void reset_state()
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{
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regs [0] = 0x0f;
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regs [1] = 0x00;
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regs [2] = 0x01;
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regs [3] = 0x00;
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}
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void register_changed( int );
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virtual void apply_mapping()
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{
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enable_sram(); // early MMC1 always had SRAM enabled
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register_changed( 0 );
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}
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virtual void write( nes_time_t, nes_addr_t addr, int data )
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{
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if ( !(data & 0x80) )
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{
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buf |= (data & 1) << bit;
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bit++;
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if ( bit >= 5 )
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{
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int reg = addr >> 13 & 3;
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regs [reg] = buf & 0x1f;
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bit = 0;
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buf = 0;
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register_changed( reg );
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}
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}
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else
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{
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bit = 0;
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buf = 0;
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regs [0] |= 0x0c;
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register_changed( 0 );
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}
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}
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};
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void Mapper_Mmc1::register_changed( int reg )
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{
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// Mirroring
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if ( reg == 0 )
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{
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int mode = regs [0] & 3;
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if ( mode < 2 )
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mirror_single( mode & 1 );
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else if ( mode == 2 )
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mirror_vert();
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else
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mirror_horiz();
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}
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// CHR
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if ( reg < 3 && cart().chr_size() > 0 )
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{
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if ( regs [0] & 0x10 )
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{
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set_chr_bank( 0x0000, bank_4k, regs [1] );
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set_chr_bank( 0x1000, bank_4k, regs [2] );
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}
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else
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{
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set_chr_bank( 0, bank_8k, regs [1] >> 1 );
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}
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}
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// PRG
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int bank = (regs [1] & 0x10) | (regs [3] & 0x0f);
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if ( !(regs [0] & 0x08) )
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{
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set_prg_bank( 0x8000, bank_32k, bank >> 1 );
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}
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else if ( regs [0] & 0x04 )
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{
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set_prg_bank( 0x8000, bank_16k, bank );
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set_prg_bank( 0xC000, bank_16k, bank | 0x0f );
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}
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else
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{
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set_prg_bank( 0x8000, bank_16k, bank & ~0x0f );
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set_prg_bank( 0xC000, bank_16k, bank );
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}
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}
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Nes_Mapper* Nes_Mapper::make_mmc1()
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{
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return BLARGG_NEW Mapper_Mmc1;
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}
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