Reverse PAL / GAL Truth Tables

[Stephen]

A few of members are already familiar with truth tables and reversing PAL / GAL chips. If you're among the less familiar, these are chips with several inputs and several outputs. The output is dependent on the combination of input signals to individual pins — all of which can be customized. This customization is known as truth-tables. These chips were popular on early compact Apple computers because they could replace many chips into a single easy to prototype / customize chip.

I am not among those who are familiar but I hope more experienced members would share their input — I'm interested in making an Arduino-based platform to simplify the interface with chips. I see ReGAL has a tool to probe and generate truth tables but I don't really understand how the probing portion is connected to an Arduino.

What I'm describing would probably use shift registers to add a significant amount of IO ports. Pins could be labelled and configured arbitrarily in order to identify all permutable input / output combinations. The physical hardware would predominately be a PCB to house the required chips and a ZIF socket to conveniently interface with chips.

 

[Bolle]

This does already exist:

DuPAL - PAL Reversing Tools

Collection of tools I use to reverse engineer PAL devices. These tools are meant to satisfy my needs. I'm sharing them here in case someone finds them useful. - DuPAL - PAL Reversing Tools

github.com

Despite the "Dumper" in its name it does not dump anything. If you've just got a PAL and no idea where it was used and don't know what it did in a circuit you'll be having a hard time (that goes for all of the existing PAL "dumping" methods)
The tools contained in the github will assist you by doing a blackbox analysis on an unknown PAL. The result (if there is a result - asynchronous feedbacks and some nasty tricks that were possible with PALs will oftentimes let the analysis fail) will assist you with rewriting equations for that PAL.

The only "fast" way to dump PALs is to decap them and put them under a microscope. The "easier" but most of the time way more time consuming way is going to be careful observation of the behavior of a PAL and rewriting of equations to match it.