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Old 09-05-2005, 02:49 PM
Grant Stockly Grant Stockly is offline
Join Date: Jan 2005
Posts: 447
Default Microscope examination of a PLD

Article: 77917
Subject: Microscope examination of a PLD
From: "logjam" <>
Date: 22 Jan 2005 02:13:56 -0800
Links: << >> << T >> << A >>
I'm probably going to attempt a distructive test on a PLD to determine
its function. I'm wondering if anyone has tried this, and with what

I found this:

"An important architectural feature that is found on virtually all PLDs
is not shown on logic diagrams. This feature is the security fuse.
Normally, the fuse pattern programmed into a PLD can, like a PROM, be
read and displayed or copied by programming hardware. Devices with a
security fuse, however, provide the ability to disable this read
function. This allows the design to be somewhat secure from attempts to
copy or reverse engineer it.

In reality, it's relatively easy to shave the top off of a bipolar PLD
and examine the programmed fuses with a microscope. For bipolar PLDs,
then, would be copiers are merely inconvenienced. Erasable CMOS PLDs
are considerably more secure, since it's very difficult, if not
impossible, to determine their function from examination."


Anyone here ever "shave" a chip for examination? I have access to a
video microscope at the university. I also have a DV camcorder with DV
in, so I could take the pictures, post them, and then beg for more

Any suggestions? I would be shaving the top off of some 16R8/4 chips.
Would heating them to around 250-300F for a while help? Shaving the
tops down while hot?

I eventually want to rewrite all of the equations for speed, but
getting a 100% copy of the OEM work was the goal.

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