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figured out algorithm and replaced SnowBoard Championship lookup table with proper emulation of device [Samuel Neves & Peter Wilhelmsen]

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This commit is contained in:
David Haywood 2016-02-12 11:13:59 +00:00
parent d634cebf09
commit ae49c58f72
2 changed files with 67 additions and 17 deletions
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6
src/mame/drivers/gaelco2.cpp
View File

@ -1046,9 +1046,6 @@ ROM_START( snowboara )
ROM_LOAD( "sb44", 0x0000000, 0x0400000, CRC(1bbe88bc) SHA1(15bce9ada2b742ba4d537fa8efc0f29f661bff00) ) /* GFX only */
ROM_LOAD( "sb45", 0x0400000, 0x0400000, CRC(373983d9) SHA1(05e35a8b27cab469885f0ec2a5df200a366b50a1) ) /* Sound only */
ROM_LOAD( "sb46", 0x0800000, 0x0400000, CRC(22e7c648) SHA1(baddb9bc13accd83bea61533d7286cf61cd89279) ) /* GFX only */
DISK_REGION( "decrypt" )
DISK_IMAGE( "snowboar", 0, SHA1(fecf611bd9289d24a0b1cabaaf030e2cee322cfa) )
ROM_END
ROM_START( snowboar )
@ -1086,9 +1083,6 @@ ROM_START( snowboar )
ROM_LOAD( "sb.e2", 0x1100000, 0x0080000, CRC(f5948c6c) SHA1(91bba817ced194b02885ce84b7a8132ef5ca631a) ) /* GFX only */
ROM_LOAD( "sb.e3", 0x1180000, 0x0080000, CRC(4baa678f) SHA1(a7fbbd687e2d8d7e96207c8ace0799a3cc9c3272) ) /* GFX only */
ROM_FILL( 0x1200000, 0x0200000, 0x00 ) /* Empty */
DISK_REGION( "decrypt" )
DISK_IMAGE( "snowboar", 0, SHA1(fecf611bd9289d24a0b1cabaaf030e2cee322cfa) )
ROM_END

78
src/mame/machine/gaelco2.cpp
View File

@ -287,19 +287,75 @@ WRITE16_MEMBER(gaelco2_state::gaelco2_eeprom_data_w)
***************************************************************************/
static UINT32 rol(UINT32 x, unsigned int c)
{
return (x << c) | (x >> (32 - c));
}
static UINT16 get_lo(UINT32 x)
{
return ((x & 0x00000010) << 1) |
((x & 0x00000800) << 3) |
((x & 0x40000000) >> 27) |
((x & 0x00000005) << 6) |
((x & 0x00000008) << 8) |
rol(x & 0x00800040, 9) |
((x & 0x04000000) >> 16) |
((x & 0x00008000) >> 14) |
((x & 0x00002000) >> 11) |
((x & 0x00020000) >> 10) |
((x & 0x00100000) >> 8) |
((x & 0x00044000) >> 5) |
((x & 0x00000020) >> 1);
}
static UINT16 get_hi(UINT32 x)
{
return ((x & 0x00001400) >> 0) |
((x & 0x10000000) >> 26) |
((x & 0x02000000) >> 24) |
((x & 0x08000000) >> 21) |
((x & 0x00000002) << 12) |
((x & 0x01000000) >> 19) |
((x & 0x20000000) >> 18) |
((x & 0x80000000) >> 16) |
((x & 0x00200000) >> 13) |
((x & 0x00010000) >> 12) |
((x & 0x00080000) >> 10) |
((x & 0x00000200) >> 9) |
((x & 0x00400000) >> 8) |
((x & 0x00000080) >> 4) |
((x & 0x00000100) >> 1);
}
static UINT16 get_out(UINT16 x)
{
return ((x & 0xc840) << 0) |
((x & 0x0080) << 2) |
((x & 0x0004) << 3) |
((x & 0x0008) << 5) |
((x & 0x0010) << 8) |
((x & 0x0002) << 9) |
((x & 0x0001) << 13) |
((x & 0x0200) >> 9) |
((x & 0x1400) >> 8) |
((x & 0x0100) >> 7) |
((x & 0x2000) >> 6) |
((x & 0x0020) >> 2);
}
UINT16 mangle(UINT32 x)
{
UINT16 a = get_lo(x);
UINT16 b = get_hi(x);
return get_out(((a ^ 0x0010) - (b ^ 0x0024)) ^ 0x5496);
}
READ16_MEMBER(gaelco2_state::snowboar_protection_r)
{
chd_file * table = machine().rom_load().get_disk_handle(":decrypt");
UINT8 temp[1024];
table->read_hunk(snowboard_latch>>9, &temp[0]);
UINT16 data = (temp[(snowboard_latch & 0x1ff)*2]<<8) | temp[((snowboard_latch & 0x1ff)*2)+1];
// TODO: replace above lookup (8GB table) with emulation of device
logerror("%06x: protection read (input %08x output %04x)\n", space.device().safe_pc(), snowboard_latch, data);
return data;
UINT16 ret = mangle(snowboard_latch);
ret = ((ret & 0xff00) >> 8) | ((ret & 0x00ff) << 8);
return ret;
}