mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
synced 2024-09-19 12:49:43 +02:00
f2e93d4949
added John Madden Football 93 in EEPROM database (fixes backup support) initiated ROM database for cartridges that uses SRAM (some ROM headers are definitively wrong !), need more...
120 lines
3.9 KiB
C
120 lines
3.9 KiB
C
/***************************************************************************************
|
|
* Genesis Plus
|
|
* Backup RAM support
|
|
*
|
|
* Copyright (C) 2007, 2008, 2009 Eke-Eke (GCN/Wii port)
|
|
*
|
|
* 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 "shared.h"
|
|
|
|
T_SRAM sram;
|
|
|
|
/****************************************************************************
|
|
* A quick guide to SRAM on the Genesis
|
|
*
|
|
* The SRAM definition is held at offset 0x1b0 of the ROM header.
|
|
*
|
|
* 1B0h: dc.b 'RA', %1x1yz000, %00100000
|
|
* 1B4h: dc.l RAM start address
|
|
* 1B8h: dc.l RAM end address
|
|
* x 1 for BACKUP and 0 If not BACKUP
|
|
* yz 10 if even address only
|
|
* 11 if odd address only
|
|
* 00 if both even and odd address
|
|
*
|
|
* Assuming max. 64k SRAM / Battery RAM throughout
|
|
****************************************************************************/
|
|
void sram_init()
|
|
{
|
|
memset (&sram, 0, sizeof (T_SRAM));
|
|
memset (&sram.sram[0], 0xFF, 0x10000);
|
|
sram.crc = crc32 (0, &sram.sram[0], 0x10000);
|
|
|
|
if ((READ_BYTE(cart.rom,0x1b0) == 0x52) && (READ_BYTE(cart.rom,0x1b1) == 0x41))
|
|
{
|
|
/* retrieve informations from headezr */
|
|
sram.detected = 1;
|
|
sram.start = READ_WORD_LONG(cart.rom, 0x1b4);
|
|
sram.end = READ_WORD_LONG(cart.rom, 0x1b8);
|
|
|
|
/* fixe some bad header informations */
|
|
if ((sram.start > sram.end) || ((sram.end - sram.start) >= 0x10000))
|
|
sram.end = sram.start + 0xffff;
|
|
sram.start &= 0xfffffffe;
|
|
sram.end |= 1;
|
|
sram.on = 1;
|
|
}
|
|
else
|
|
{
|
|
/* default SRAM region */
|
|
sram.start = 0x200000;
|
|
sram.end = 0x20ffff;
|
|
}
|
|
|
|
/* set SRAM ON by default when ROM is not mapped */
|
|
if (cart.romsize <= sram.start) sram.on = 1;
|
|
|
|
/* Some games with bad header or specific configuration */
|
|
if (strstr(rominfo.product,"T-113016") != NULL)
|
|
{
|
|
/* Pugsy (try accessing unmapped area for copy protection) */
|
|
sram.on = 0;
|
|
}
|
|
else if (strstr(rominfo.international,"SONIC THE HEDGEHOG 2") != NULL)
|
|
{
|
|
/* Sonic the Hedgehog 2 does not use SRAM */
|
|
/* this prevents SRAM activation when using Sonic & Knuckles LOCK-ON feature */
|
|
sram.on = 0;
|
|
}
|
|
else if (strstr(rominfo.product,"T-26013") != NULL)
|
|
{
|
|
/* Psy-O-Blade (bad header) */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x203fff;
|
|
}
|
|
else if (strstr(rominfo.product,"T-50086") != NULL)
|
|
{
|
|
/* PGA Tour Golf (no header) */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x203fff;
|
|
}
|
|
else if (strstr(rominfo.product,"ACLD007") != NULL)
|
|
{
|
|
/* Winter Challenge (no header) */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x200fff;
|
|
}
|
|
else if (strstr(rominfo.product,"T-50286") != NULL)
|
|
{
|
|
/* Buck Rogers - Countdown to Doomsday (no header) */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x203fff;
|
|
}
|
|
else if (((realchecksum == 0xaeaa) || (realchecksum == 0x8dba)) && (rominfo.checksum == 0x8104))
|
|
{
|
|
/* Xin Qigai Wangzi, aka Beggar Prince (no header, use uncommon area) */
|
|
sram.on = 1;
|
|
sram.start = 0x400000;
|
|
sram.end = 0x40ffff;
|
|
}
|
|
}
|