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Tutorial on Programmable Logic Devices?

Can anyone point me in the direction of some tutorials on PEEL's.

I just picked up a couple of Z80 processor boards on EBay. I was going to try and i/o / memory map the board by tracing the IC's until I ran into a few of these suckers. Looks like they are being used for decoders. I've got to try and figure out how they are programmed so I can make sense/use of my controller board. I downloaded a .PDF for PEEL18CV8P, but I'm still confused. Is there any easy way to figure out how they are programmed?

Thanks, Dave

Reply to
Dave Nubury
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They are generally programmed with a hardware description language (HDL) like VHDL, ABEL, CUPL, ... Looking at the fuse map would allow you to trace out the functions but, like having disassembled program code into bare assembler instructions, you'll still have some work to do to understand it. You'll need a gizmo like

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to read it.

Note that if they've burned the security bit, you will not be able to read the fuse map. All you can do is look at the goze-ins and goze-outs and take it from there.

If you assume that the designers didn't intentionally obfuscate things, then you can probably work out the intended behavior by what it connects to.

--
Rich Webb   Norfolk, VA
Reply to
Rich Webb

------------------ If all they are is address decoders, then they are static logic, with no dynamic/sequential logic contributions, in other words, a simple gate array with no feedback loops. That means you can map them by simulating inputs to their inputs and watching their outputs.

But if they are not, then lots of luck! I have the specs on programming 18V8 Peel devices, but again, if the security is set, you have only external testing to arrive at their gate circuit equivalent. You could go through random addresses and write a program to look for any outputs that have differing results with the same inputs, and that would fine any sequential logic statements.

-Steve

--
-Steve Walz  rstevew@armory.com   ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000\'s of Files and Dirs!!  With Schematics Galore!!
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Reply to
R. Steve Walz

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