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modified SRAM/ROM mapper default behavior (not 100% correct but at least this prevents Sonic Megamix from crashing because of wrong coding while remaining compatible with games actually using the mapper)

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This commit is contained in:
ekeeke31 2011-04-28 18:54:39 +00:00
parent a834e63ce4
commit b6bc325353
1 changed files with 12 additions and 26 deletions
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38
source/cart_hw/md_cart.c
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@ -787,50 +787,36 @@ static void mapper_sega_w(uint32 data)
if (data & 1)
{
/* Only if SRAM is detected */
if (sram.on)
{
/* $200000-$3fffff is mapped to SRAM */
for (i=0x20; i<0x40; i++)
{
m68k_memory_map[i].base = sram.sram;
}
/* Backup RAM mapped to $200000-$20ffff (normally mirrored up to $3fffff but this breaks Sonic Megamix and no game need it) */
m68k_memory_map[0x20].base = sram.sram;
m68k_memory_map[0x20].write8 = NULL;
m68k_memory_map[0x20].write16 = NULL;
zbank_memory_map[0x20].write = NULL;
/* Backup RAM write protection */
if (data & 2)
{
/* SRAM write disabled */
for (i=0x20; i<0x40; i++)
{
m68k_memory_map[i].write8 = m68k_unused_8_w;
m68k_memory_map[i].write16 = m68k_unused_16_w;
zbank_memory_map[i].write = zbank_unused_w;
}
}
else
{
/* SRAM write enabled */
for (i=0x20; i<0x40; i++)
{
m68k_memory_map[i].write8 = NULL;
m68k_memory_map[i].write16 = NULL;
zbank_memory_map[i].write = NULL;
}
m68k_memory_map[0x20].write8 = m68k_unused_8_w;
m68k_memory_map[0x20].write16 = m68k_unused_16_w;
zbank_memory_map[0x20].write = zbank_unused_w;
}
}
/* S&K lock-on chip */
if ((cart.special & HW_LOCK_ON) && (config.lock_on == TYPE_SK))
{
/* $300000-$3fffff is mapped to S2K upmem chip */
/* S2K upmem chip mapped to $300000-$3fffff (256K mirrored) */
for (i=0x30; i<0x40; i++)
{
m68k_memory_map[i].base = (cart.rom + 0x800000) + ((i & 3)<<16);
m68k_memory_map[i].base = (cart.rom + 0x800000) + ((i & 3) << 16);
}
}
}
else
{
/* $200000-$3fffff is mapped to ROM */
/* cartridge ROM mapped to $200000-$3fffff */
for (i=0x20; i<0x40; i++)
{
m68k_memory_map[i].base = cart.rom + ((i<<16) & cart.mask);