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