Posted By
SVS
on 2002-10-24
 |  The instructions of a 6502 uP family are about 150,
but a byte can have 256 different values. This is why if you *force* the micro to execute a non-standard code, it tries to do something...
Most of the times, it "partially" executes some works (since a legal instruction has many steps), some bits-patterns are able to start some steps.
Other times you simply obtain a processor crash. For example I found that all the codes with "2" as low nibble (02, 52, F2, etc.) crash the micro (except A2).
Greetz
P.S. - MegAssember recognized 4 non-standard instructions 
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