mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
synced 2024-12-30 21:21:49 +01:00
232 lines
7.7 KiB
C
232 lines
7.7 KiB
C
/***************************************************************************************
|
|
* Genesis Plus
|
|
* Backup RAM support
|
|
*
|
|
* Copyright (C) 2007-2016 Eke-Eke (Genesis Plus GX)
|
|
*
|
|
* Redistribution and use of this code or any derivative works are permitted
|
|
* provided that the following conditions are met:
|
|
*
|
|
* - Redistributions may not be sold, nor may they be used in a commercial
|
|
* product or activity.
|
|
*
|
|
* - Redistributions that are modified from the original source must include the
|
|
* complete source code, including the source code for all components used by a
|
|
* binary built from the modified sources. However, as a special exception, the
|
|
* source code distributed need not include anything that is normally distributed
|
|
* (in either source or binary form) with the major components (compiler, kernel,
|
|
* and so on) of the operating system on which the executable runs, unless that
|
|
* component itself accompanies the executable.
|
|
*
|
|
* - Redistributions must reproduce the above copyright notice, this list of
|
|
* conditions and the following disclaimer in the documentation and/or other
|
|
* materials provided with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
|
|
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
|
|
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*
|
|
****************************************************************************************/
|
|
|
|
#include "shared.h"
|
|
|
|
T_SRAM sram;
|
|
|
|
/****************************************************************************
|
|
* A quick guide to external RAM on the Genesis
|
|
*
|
|
* The external RAM definition is held at offset 0x1b0 of the ROM header.
|
|
*
|
|
* 1B0h: dc.b 'RA', %1x1yz000, %abc00000
|
|
* 1B4h: dc.l RAM start address
|
|
* 1B8h: dc.l RAM end address
|
|
* x 1 for BACKUP (not volatile), 0 for volatile RAM
|
|
* yz 10 if even address only
|
|
* 11 if odd address only
|
|
* 00 if both even and odd address
|
|
* 01 others (serial EEPROM, RAM with 4-bit data bus, etc)
|
|
* abc 001 if SRAM
|
|
* 010 if EEPROM (serial or parallel)
|
|
* other values unused
|
|
*
|
|
* Assuming max. 64k backup RAM throughout
|
|
****************************************************************************/
|
|
void sram_init()
|
|
{
|
|
memset(&sram, 0, sizeof (T_SRAM));
|
|
|
|
/* backup RAM data is stored above cartridge ROM area, at $800000-$80FFFF (max. 64K) */
|
|
if (cart.romsize > 0x800000) return;
|
|
sram.sram = cart.rom + 0x800000;
|
|
|
|
/* initialize Backup RAM */
|
|
if (strstr(rominfo.international,"Sonic 1 Remastered"))
|
|
{
|
|
/* Sonic 1 Remastered hack crashes if backup RAM is not initialized to zero */
|
|
memset(sram.sram, 0x00, 0x10000);
|
|
}
|
|
else
|
|
{
|
|
/* by default, assume backup RAM is initialized to 0xFF (Micro Machines 2, Dino Dini Soccer) */
|
|
memset(sram.sram, 0xFF, 0x10000);
|
|
}
|
|
|
|
sram.crc = crc32(0, sram.sram, 0x10000);
|
|
|
|
/* retrieve informations from header */
|
|
if ((READ_BYTE(cart.rom,0x1b0) == 0x52) && (READ_BYTE(cart.rom,0x1b1) == 0x41))
|
|
{
|
|
/* backup RAM detected */
|
|
sram.detected = 1;
|
|
|
|
/* enable backup RAM */
|
|
sram.on = 1;
|
|
|
|
/* retrieve backup RAM start & end addresses */
|
|
sram.start = READ_WORD_LONG(cart.rom, 0x1b4);
|
|
sram.end = READ_WORD_LONG(cart.rom, 0x1b8);
|
|
|
|
/* autodetect games with wrong header infos */
|
|
if (strstr(rominfo.product,"T-26013") != NULL)
|
|
{
|
|
/* Psy-O-Blade (wrong header) */
|
|
sram.start = 0x200001;
|
|
sram.end = 0x203fff;
|
|
}
|
|
|
|
/* fixe games indicating internal RAM as volatile external RAM (Feng Kuang Tao Hua Yuan) */
|
|
else if (sram.start == 0xff0000)
|
|
{
|
|
/* backup RAM should be disabled */
|
|
sram.on = 0;
|
|
}
|
|
|
|
/* fixe other bad header informations */
|
|
else if ((sram.start > sram.end) || ((sram.end - sram.start) >= 0x10000))
|
|
{
|
|
sram.end = sram.start + 0xffff;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* autodetect games with missing header infos */
|
|
if (strstr(rominfo.product,"T-50086") != NULL)
|
|
{
|
|
/* PGA Tour Golf */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x203fff;
|
|
}
|
|
else if (strstr(rominfo.product,"ACLD007") != NULL)
|
|
{
|
|
/* Winter Challenge */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x200fff;
|
|
}
|
|
else if (strstr(rominfo.product,"T-50286") != NULL)
|
|
{
|
|
/* Buck Rogers - Countdown to Doomsday */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x203fff;
|
|
}
|
|
else if (((rominfo.realchecksum == 0xaeaa) || (rominfo.realchecksum == 0x8dba)) &&
|
|
(rominfo.checksum == 0x8104))
|
|
{
|
|
/* Xin Qigai Wangzi (use uncommon area) */
|
|
sram.on = 1;
|
|
sram.start = 0x400001;
|
|
sram.end = 0x40ffff;
|
|
}
|
|
else if ((strstr(rominfo.ROMType,"SF") != NULL) && (strstr(rominfo.product,"001") != NULL))
|
|
{
|
|
/* SF-001 */
|
|
sram.on = 1;
|
|
if (rominfo.checksum == 0x3e08)
|
|
{
|
|
/* last revision (use bankswitching) */
|
|
sram.start = 0x3c0001;
|
|
sram.end = 0x3cffff;
|
|
}
|
|
else
|
|
{
|
|
/* older revisions (use uncommon area) */
|
|
sram.start = 0x400001;
|
|
sram.end = 0x40ffff;
|
|
}
|
|
}
|
|
else if ((strstr(rominfo.ROMType,"SF") != NULL) && (strstr(rominfo.product,"004") != NULL))
|
|
{
|
|
/* SF-004 (use bankswitching) */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x203fff;
|
|
}
|
|
else if (strstr(rominfo.international,"SONIC & KNUCKLES") != NULL)
|
|
{
|
|
/* Sonic 3 & Knuckles combined ROM */
|
|
if (cart.romsize == 0x400000)
|
|
{
|
|
/* Sonic & Knuckle does not have backup RAM but can access FRAM from Sonic 3 cartridge */
|
|
sram.on = 1;
|
|
sram.start = 0x200001;
|
|
sram.end = 0x203fff;
|
|
}
|
|
}
|
|
|
|
/* auto-detect games which need disabled backup RAM */
|
|
else if (strstr(rominfo.product,"T-113016") != NULL)
|
|
{
|
|
/* Pugsy (does not have backup RAM but tries writing outside ROM area as copy protection) */
|
|
sram.on = 0;
|
|
}
|
|
else if (strstr(rominfo.international,"SONIC THE HEDGEHOG 2") != NULL)
|
|
{
|
|
/* Sonic the Hedgehog 2 (does not have backup RAM) */
|
|
/* this prevents backup RAM from being mapped in place of mirrored ROM when using S&K LOCK-ON feature */
|
|
sram.on = 0;
|
|
}
|
|
|
|
/* by default, enable backup RAM for ROM smaller than 2MB */
|
|
else if (cart.romsize <= 0x200000)
|
|
{
|
|
/* 64KB static RAM mapped to $200000-$20ffff */
|
|
sram.start = 0x200000;
|
|
sram.end = 0x20ffff;
|
|
sram.on = 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
unsigned int sram_read_byte(unsigned int address)
|
|
{
|
|
return sram.sram[address & 0xffff];
|
|
}
|
|
|
|
unsigned int sram_read_word(unsigned int address)
|
|
{
|
|
address &= 0xfffe;
|
|
return (sram.sram[address + 1] | (sram.sram[address] << 8));
|
|
}
|
|
|
|
void sram_write_byte(unsigned int address, unsigned int data)
|
|
{
|
|
sram.sram[address & 0xffff] = data;
|
|
}
|
|
|
|
void sram_write_word(unsigned int address, unsigned int data)
|
|
{
|
|
address &= 0xfffe;
|
|
sram.sram[address] = data >> 8;
|
|
sram.sram[address + 1] = data & 0xff;
|
|
}
|