DataFlyer 500 schematic..

[Tony Duell]

> Is it possible to reverse engineer the PALs by hooking up a logic 

You normally need more than that, alas.

It is worth trying to read them out in the correct PAL programmer. Some 
manufacturers didn;'t blow the security fuse, so they can be read out. My 
experience somewhat echos the comments in one of the 'Art of Electronics' 
books -- namely that some manufacturers depends on 'security by solder' 
They didn't blow the security fuse, but they soldered the chip directly 
to the PCB. If you are prepared ot desolder it, you can have the PAL 
equations :-)

> analyzer?  Are PALs normally just combinational logic?  No timers, 
> counters, storage, and so on?  Just formulas for combining inputs and 
> producing outputs?

Some are, some aren't. The 10L8, etc is just combinatorial logic. The 
16L8 allows feedback terms -- that is the logic outputs are also 
connected back to the (programamble) AND gate array. This means you can 
make flip-flops, and thus sequential circuits. And of course the 'R' 
series (16R4, 16R8, etc) have built-in D-types _and feedback from the 
outputs of the D types to the AND array_ With those you can't just try 
all the imputs and see what the outputs do.

-tony