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Date:	Thu, 17 Nov 2011 20:45:24 -0500
From:	Vanessa Ezekowitz <vanessaezekowitz AT gmail DOT com>
To:	geda-user AT delorie DOT com
Subject:	[geda-user] Modern GAL/PAL design with gEDA?
Message-ID:	<20111117204524.10e586f5@rainbird>
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Reply-To:	geda-user AT delorie DOT com

When it comes to making circuit boards out of chips and discrete components, I'm reasonably well educated, and gschem -> pcb is a no-brainer for me these days.  Similarly, I'm no stranger to programming, though I prefer to direct my efforts at vintage computing. Still, I think I've gotten pretty good at both concepts.  :-)

However, my latest project requires something I've never even begun to touch before:  Programmable logic devices.

So, here's what I want to do:

I've drawn a small circuit in gschem consisting of four flip-flops and a handful of gates.  It isn't complete yet, but what I have seems to work exactly the way I want, and there's enough here to build a physical circuit to test the design's core function.  Each symbol has a refdes, none have been assigned footprints or slots (since neither seems like it would make sense in this case).

Now I need to translate that schematic into something (a JEDEC file?) that I can burn into a 22V10 GAL.  I realize this is an older type of chip, but they are easy to purchase from Digikey and the like, and my current project only calls for enough logic to fill one of these - a CPLD or FPGA is just plain overkill.

The top-level circuit that will USE the burned GAL has not, itself, been drawn yet.  But, for these first tests, I only need my oscilloscope, a power supply, and a few  momentary switches.

This project does not call for specific types of gates, speeds, etc. - all that matters here is that each gate act at least somewhat close to how they're supposed to act - one NAND is as good as another in this circuit.

So, what do I do next?  Aside from acquiring the necessary hardware, what steps do I take to get from this schematic to a functioning GAL chip that I can plug into my final board design once I get to that point?

I've searched the web for several hours now and have come to this conclusion:  The web hasn't been updated since sometime last century - everything I'm finding is cryptic, out of date, requires datafiles that can only be obtained from large corporations, is based on stuff that doesn't work anymore, and is written by people who don't know how to explain these things to a n00b like me.

But this doesn't make sense - I see people designing things left and right using programmable logic of one sort or another, some of which are of such complexity that it would be next to impossible to do using just lists of logic equations.

Whatever the case, I don't want to have to resort to using closed-source or proprietary software or operating systems to do any more of this than is absolutely necessary.

-- 
"There are some things in life worth obsessing over.  Most
things aren't, and when you learn that, life improves."
http://digitalaudioconcepts.com
Vanessa Ezekowitz <vanessaezekowitz AT gmail DOT com>

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