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I have a JED file from a GAL 16V8 as an example. Is there a tool to decode this into a schematic of gates and registers?

Coders: Is this a hard "interface" program to write to have ispLever or some other CAD create an schematic output from a jed file as input?


Disappointed "are you stealing code?" is an automatic goto for anyone wanting a decompiler. I have been writing in OPAL for quite a while, while they were still shipping the demo-disc bundle kit I got from them in the mail in '93. Limited availability, and I got one. Thank you National Semiconductor.

But schematic tools were not at my finger tips then, and tools shareware or licenced have advanced in the market since 1993.

My computers have died many times since then, and sometimes only my project remains without the files. I don't lock my chips unless they are going into the wild. So I can read them anytime I want. Copy them anytime I want.

Having spent far-to-long yesterday reverse-engineering a JEDEC file I created looking for and hand-correcting errors, it would be nice if I could load it into a translator and see if my edits look like what I think they should be.

30 years was quite a while ago, and I haven't GAL'd in years. I get rusty in what I knew then. It was all clearer 30 years ago. Where are my notes???

It would be nice to read my old chips, and see what I was thinking back then, or take a few out of the pile and see what they were supposed to represent.

If I have to hand-draw and decipher the maps, I don't have that kind of time anymore. Yet at one time to me this chip had purpose. Like reading an old flash drive from a box of them you have. At one time this was important, having a look is not a crime.

Automatically accusing everyone of code theft needs to end.

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    \$\begingroup\$ What program writes a "JED" file? Why can't you look at the file in that? \$\endgroup\$
    – Solar Mike
    Jan 27, 2023 at 19:12
  • \$\begingroup\$ Because he (OP) probably doesn't have the source code. \$\endgroup\$
    – SteveSh
    Jan 27, 2023 at 19:15
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    \$\begingroup\$ Have you extracted the JED file from a GAL? Do you have permission to do that? Do you need permission to do that? \$\endgroup\$
    – Andy aka
    Jan 27, 2023 at 19:16
  • \$\begingroup\$ Look for a Jedec decompiler. You will probably not get a schematic but a number of logic equations as the output. \$\endgroup\$
    – StarCat
    Jan 27, 2023 at 19:20
  • \$\begingroup\$ @Andyaka people who don't want JED files being extracted from their GALs protect them. In many countries, decompiling code without the author's permission is perfectly legal for 'educational' purposes. \$\endgroup\$ Jan 27, 2023 at 21:02

2 Answers 2

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GAL JED files are generally not generated from a schematic, but from a set of logic equations. There are two programs I know of that can 'decompile' JED files back into equations:-

  1. JED2EQN, included in National Semiconductor's OPALjr PAL/GAL programming suite, which runs in DOS.

  2. GALer, a GAL programmer for Amiga computers. If you don't have an Amiga you can emulate it on a PC or Mac. Alternatively you could compile the necessary source code (which is written in C) for your preferred platform.

Once you have the equations, converting them to a schematic diagram is relatively easy.

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  • \$\begingroup\$ I would think converting the equations to Verilog or VHDL would be more useful. Each SOP would basically map onto a single assign. \$\endgroup\$ Jan 27, 2023 at 22:48
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    \$\begingroup\$ Another option: github.com/psurply/ReGAL \$\endgroup\$ Jan 27, 2023 at 23:03
  • \$\begingroup\$ @hacktastical for my own projects I used WinCUPL and simply wrote in the equations I wanted. I found this easier than using VHDL or Verilog, which I just can't get my head around. Didn't draw schematic equivalents either - no point when its all inside the IC. \$\endgroup\$ Jan 28, 2023 at 12:21
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Way back when when I was programming PALs and PLAs, we used tool like PALASM that took boolean equations and turned them in a JED file. The JED file then was sent to a programmer that was used to program the logic device.

I do not recall if those tools had the capability to reverse engineer (which is what it sounds like you're looking to do) a programmable logic device or not.

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    \$\begingroup\$ If I recall correctly there was a tool called jed2eqn that could do that. \$\endgroup\$
    – StarCat
    Jan 27, 2023 at 19:22
  • \$\begingroup\$ OpalJr. includes jed2eqn. Thanks StarCat. \$\endgroup\$ Jan 27, 2023 at 20:46

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