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royalcdc

Posted by iq_132 , 08 February 2007 · 373 views

I started looking at Royal Card (Slovakia, encrypted) on the funworld.c driver in mame. It has a preliminary status due to encryption.

Basically I started working by comparing it to the non-encrypted Royal Card (Austria, set 1).  

I was able to figure out how half of the bits affect the other bits:
Dec->Enc
00 -> 22
01 -> 23
02 -> 02
03 -> 03
04 -> 20
05 -> 21
06 -> 00
07 -> 01
08 -> 2a
09 -> 2b
0a -> 0a
0b -> 0b
0c -> 28
0d -> 29
0e -> 08
0f -> 09
this can be worked out, simply enough, as:
		if (~a & 0x02) b ^= 0x22; 
		if ( a & 0x04) b ^= 0x06;

I still need to figure out how the first four bits of the opcodes, but this is proving fairly difficult since the encrypted version will not match the non-encrypted version once it has been decrypted.




Good work!
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