Microscope examination of a PLD

I never tried it, however it might be possible to determine the location of the fuse by a focused UV laser that is scanned over an identical part. Scan the laser and read out until the fuse is gone.

Rene

--
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I hope you have more than one :)

If that is the goal, why not simply reverse engineer the logic ?

16R8/4 devices are not complex, and if you also have the product circuit diagram [or application circuits of the devices], you can greatly reduce the vector-search complexity.

All you need is pencil, paper, text editor, and a PLD programmer that can run test vectors (most can).

-jg

Two friends and I read a bipolar PROM optically. It was interesting to view it under the microscope. I'd heard that there was a long-term problem with regrowth of the fuses, but we were actually able to see it.

Also, Peter Monta optically extracted the contents of three 2560-bit PMOS masked ROM chips circa 1973, in order to run the code on my simulator:

How would you suggest I split my chips? I plucked 5 off of an AST motherboard and put two in the toaster oven for an hour at 300. Who knows why I did that. ;) Even if I can learn the logic, it would still be fun to see if I can see it. :) This stupid project has forced me to learn a ton of stuff in the past few days. Thats what I love, learning new useless things. ;)

Can you suggest an innexpensive PAL programmer that can run a test vector?

I shaved an IC down with my dremel tool, ripped all the legs off, then chipped away at the remaining material, decided to shave a little more off, and finally hit the silicon, with the dremel, and further chipped on it until the IC broke in half. I didn't have a good light source, but at 400x I thought I could see some traces.

Is there a substance that will break down the IC potting material but not the electronics? I noticed that the back of the silicon was coated with metal. Next I might try comming in from the back, carving around the back plane, and lifting the guy out. Forget that x-ray stuff. My in-head math was off by a few decimal places. ;)

Tradationally people use fuming nitric acid to remove the encapsulation.I wouldnt recomment it though without some serious protection as fuming nitric acid is highly toxic and will strip flesh to the bone in seconds.

Try searching Google - fuming nitric acid is commonly used I believe. Be careful with it though...

I know I have access to 20% nitric acid, possibly stronger if I sweet talk the metallurgy lab guy. We use it for etching polished metals to look at the microstructure.

So I will try this on monday:

-Shave PLD about 1/8"

-place flat on a hot plate, around 130*C

-Drip nitric acid on it until the silicon is visible

I'll be doing this in a lab with full negative pressure fume hood and a face shield. Not a range top stove and exhaust vent. ;)

If that doesn't work I guess there are companies who do it for $50. There are also manufactures of these decapping machines. I might try sweet talking them into helping out a poor student. ;)

Here is a link I found on decapping the little buggers:

If all else fails, I'm getting a 100MHz 18 channel 128k+ sample logic analyzer...so... ;)

Grant

...

Well, even if you get a visual reading of the bits, I would still want to verify it by frobbing pins. However, rather than a logic analyzer, why not simply hook it fully up to an FPGA? There are plenty < $500 boards out there that would be up for the job. That would give you all the functionality of the LA with the additional ability to incrementally build up and verify the reengineered model, all within the same framework.

Just an idea, Tommy

Here are the results of decapping my IC...