20 Jun
2016
20 Jun
'16
8:53 p.m.
Most of the FPGA companies provide (free) tools that allow you to write in
verilog/VHDL and then simulate and observe the outputs (you can even ?drill
down? and see internal signals as well.
It?s fairly easy to write a little bit of code (there are lots of examples on the
web) and try it out on the simulator.
If you get an FPGA eval board (I have a number of Digilent Xilinx boards)
you can take your sample code and download it to the eval board and run it.
TTFN - Guy
On Jun 20, 2016, at 1:47 PM, Swift Griggs
<swiftgriggs at gmail.com> wrote:
On Mon, 20 Jun 2016, Ian Finder wrote:
Some PALs, PLAs, and GALs will yield the fuse map
if you try and read them
with a programmer. This makes your job really easy. Take the fuse map and
compare to the original data sheet. Cool beans.
That sounds like magic. I'm reading about what "fuse map" is, now.
That's
a new term for me.
Some have the security bits set- in this case you
would use a home-made
test setup to stimulate enough test conditions to build a truth table
that would allow you to infer the underlying logic.
Hmm, so there is something akin to "copy protection" even at the chip
level. Ugh. I'm not surprised.
If the part is registered, then things get
tricker. For that, I might
take substantial in-system dumps with a logic analyzer (My favorite
beginner LA is the Agilent 16700, which comes with DOOM preinstalled, so
you know it's good stuff)
Oh, cool. I was just browsing for one a few days ago. I was looking at the
ones from Saleae and Tektronix. I'll have to check that out. If they were
cool enough to pre-install Doom, I think we have a winner. :-)
ROMS are easy- once you read a bit about how HDLs
work, you will be able
to build one. Many languages offer functions to help with these (see
readmemh and readmemb in verilog)
I actually did burn some ROM code in college. I remember it being fairly
easy. However, I would look like a stunned fish if someone asked me to
reverse engineer one.
Things get more complicated quickly- this is a
deep topic and not
something that can be covered quickly. I suggest you start with the two
books I linked, and if you like them, there are a lot more around. Any
edition should be suitable- get or find whatever is cheapest.
Oh good lord, I'm so out of my depth already. However, it's still
interesting and I'm still trying (I'm stubborn that way). I've got to get
the simplest basics down before I dive in all the way with a "real" book.
I'm going to try to stick with my digital logic self-refresh first, but
this Verilog business is awfully cool. I will be sorely tempted to come
back to this same point, I'm sure.
We have not touched yet on practical things, like
how to interface
modern 1.8v FPGA I/O lines with 5V TTL logic- that is a topic for
another day.
Hmm, I never even knew of that problem, but after doing a bunch of analog,
I get the impression that would create a lot of hassles, especially if you
were just trying to duplicate some already laid-out logic, but it was all
at 5V...
-Swift