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21.c

/* FCE Ultra - NES/Famicom Emulator
 *
 * Copyright notice for this file:
 *  Copyright (C) 2002 Xodnizel
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "mapinc.h"

#define K4buf mapbyte2
#define K4IRQ mapbyte1[1]
#define K4sel mapbyte1[0]

static int acount=0;

DECLFW(Mapper21_write)
{
      A|=((A>>5)&0xF);

      if((A&0xF000)==0xA000)
        ROM_BANK8(0xA000,V);
      else if((A&0xF000)==0x8000)
      {
         if(K4sel&2)
          ROM_BANK8(0xC000,V);
         else
          ROM_BANK8(0x8000,V);
      }
      else if(A>=0xb000 && A<=0xefff)
      {
        A&=0xF006;
          {
           int x=((A>>2)&1)|((A-0xB000)>>11);

           K4buf[x]&=(0xF0)>>((A&2)<<1);
           K4buf[x]|=(V&0xF)<<((A&2)<<1);
           VROM_BANK1(x<<10,K4buf[x]);
          }
 
      }
      else switch(A&0xF006)
        {
       case 0x9000:
                 switch(V&0x3)
                   {
                  case 0:MIRROR_SET(0);break;
                    case 1:MIRROR_SET(1);break;
                    case 2:onemir(0);break;
                    case 3:onemir(1);break;
                 }
                   break;
       case 0x9006:
       case 0x9004:
       case 0x9002:if((K4sel&2)!=(V&2))
                 {
                        uint8 swa;
                    swa=PRGBankList[0];
                  ROM_BANK8(0x8000,PRGBankList[2]);
                    ROM_BANK8(0xc000,swa);
                 }
                   K4sel=V;
                 break;
       case 0xf000:IRQLatch&=0xF0;IRQLatch|=V&0xF;break;
         case 0xf002:IRQLatch&=0x0F;IRQLatch|=V<<4;break;
       case 0xf004:IRQCount=IRQLatch;acount=0;
                   IRQa=V&2;K4IRQ=V&1;
                 X6502_IRQEnd(FCEU_IQEXT);
                 break;
       case 0xf006:IRQa=K4IRQ;X6502_IRQEnd(FCEU_IQEXT);break;
 }
}
static void FP_FASTAPASS(1) KonamiIRQHook(int a)
{
  #define LCYCS ((227*2)+1)
  //#define LCYCS 341
  if(IRQa)
  {
//    acount+=a*3;
    acount+=a*4;
    if(acount>=LCYCS)
    {
     doagainbub:acount-=LCYCS;IRQCount++;
     if(IRQCount&0x100) {X6502_IRQBegin(FCEU_IQEXT);IRQCount=IRQLatch;}
     if(acount>=LCYCS) goto doagainbub;
    }
 }
}

void Mapper21_init(void)
{
        SetWriteHandler(0x8000,0xffff,Mapper21_write);
        MapIRQHook=KonamiIRQHook;
}

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