It's a bit tougher when they're
registered and can maintain (relatively)
complex state, though. Many (most?) PALs are registered.
I still think it is easier to look at the circuit, understanding how it
works and recreating the equations...
I prefer to use all possible sources of information. So yes, in this case
I might well try to work out the logic equations from the scheamtic and
what functions are required. I would then test an existing PAL (if I had
one) to see if that behaved in a way consistent with what I'd 'guessed'.
(ha ha ha, I have a logic analyser, I can do
anything up to 400MHz, la
la la, I'm the greatest hacker of the world, la la la) :oD
Good for you...
-tony