Retrieving code from an old PAL

I just checked and the TopMAX programmer from eetools can read a PLS101, and shows no Secure option. It will also vector test this device. Other device programmers will be similar.

Thus you can probably get the fuse info, directly, and simply program new devices. JDR still show stock ;)

If you need to move to a new device, you could work from this fuse into, with an old PLS101 data sheet, and your circuit diagrams. The vector test feature allows you to confirm, as far as your test coverage goes :)

Candidate replacement devices ( assumes you want to keep ~package, and 5V ) can be found at

-jg

No non-ouput registers (no registers at all in that device) means no hidden state. So you can just read it out as eight 64k x 1 roms. And "compress" the data. First by eliminating any inputs that don't effect a given output. Then by identifying all local areas where changing one or several inputs does not change the output. Write a product term for each such group anding the state of the inputs that do mattter, then or all such product terms together to create that output. It's a fun undegrad exercise for 4-input devices, circling the product terms on a little grid of two bits by two bits counted in grey code - but for 16 inputs and 8 outputs you want software...

Of course the tools exist as the Jim mentioned. But you could also do it in a long afternoon with a pc printer port, an 8255 for I/O expansion, and the programming language of your choice.