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SNES (MESS-specific): Preliminary open bus emulation for allowing Shien's Revenge / Shien the Blade Chaser to boot

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This commit is contained in:
Angelo Salese 2009-08-03 21:48:28 +00:00
parent 23612784b3
commit 3a4ef6d6c9
2 changed files with 22 additions and 2 deletions
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4
src/mame/audio/snes.c
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@ -1241,6 +1241,8 @@ READ8_HANDLER( spc_io_r )
{
switch( offset ) /* Offset is from 0x00f0 */
{
case 0x1:
return 0; //Super Kick Boxing reads port 1 and wants it to be zero.
case 0x2: /* Register address */
return spc_ram[0xf2];
case 0x3: /* Register data */
@ -1265,7 +1267,7 @@ READ8_HANDLER( spc_io_r )
}
}
return 0; //Super Kick Boxing reads port 1 and wants it to be zero.
return 0xff;
}
WRITE8_HANDLER( spc_io_w )

20
src/mame/machine/snes.c
View File

@ -280,6 +280,21 @@ static TIMER_CALLBACK( snes_hblank_tick )
*************************************/
static READ8_HANDLER( snes_open_bus_r )
{
static UINT8 recurse = 0;
UINT16 result;
/* prevent recursion */
if (recurse)
return 0xff;
recurse = 1;
result = memory_read_byte_8le(space, cpu_get_pc(space->cpu)+2); //TODO: must be the LAST opcode that's fetched on the bus
recurse = 0;
return result;
}
/*
* DR - Double read : address is read twice to return a 16bit value.
* low - This is the low byte of a 16 or 24 bit value
@ -299,7 +314,7 @@ READ8_HANDLER( snes_r_io )
/* offset is from 0x000000 */
switch( offset )
{
/* hacks for SimCity 2000 to boot - I presume openbus emulation will fix */
/* hacks for SimCity 2000 (J) to boot - I presume openbus emulation will fix */
case 0x221a:
case 0x231c:
case 0x241e:
@ -312,6 +327,9 @@ READ8_HANDLER( snes_r_io )
case 0x2016:
return 2;
/* Shien The Blade Chaser / Shien's Revenge reads here instead */
case NMITIMEN:
return snes_open_bus_r(space,0);
case OAMADDL:
case OAMADDH:
case VMADDL: