Comments on: GALS for Electronics Hobby

By: John

John — Sun, 27 Apr 2008 13:12:39 +0000

David and Steve,

Thanks much for your great replies!! I suspected that such (day-time clock pulse work-difficulty) may be the case yet wanted to make sure…

Thanks too for your great tutorials and projects, which help all of us new-users who are just getting started…!!

John

By: mad93

mad93 — Mon, 14 Apr 2008 09:08:09 +0000

In the university we simulated a CAM memory with a RAM and implemented the states machine (sorry, literal translation from my language, i don’t know how it’s called in english) with six GALs.

It worked fine, but the consume was insane, 1 A, and after three months the GALs were ‘erased’.

I found them useful and easy to play, but not useful for any ‘serious’ implementation, since it’s consume it’s crazy (comparted to a uc) and it’s fragility.

We used 16v8 and 22v10, and I think they are quite expensive for what the are able to do.

By: Steve Chamberlin

Steve Chamberlin — Sun, 13 Apr 2008 00:53:49 +0000

I agree a GAL isn’t a good solution for the proposed “time of day” circuit. A microcontroller or stand-alone RTC seems more appropriate. Likewise, I don’t think you could use a GAL to replace the synthesizer chip that Alan mentioned. They are really quite basic, with at most 10 bits of internal state (one flip-flop per output).

Where I think GALs make the most sense is as “glue” between two or more other chips, where some set of existing signals must be converted/muxed/stored/shifted/reversed/whatever to produce a new set of output signals. This might sound very limiting, but it still allows for some quite interesting applications, as I tried to show with the examples I gave earlier.

By: dfowler

dfowler — Tue, 08 Apr 2008 00:12:59 +0000

John,

Thank you for the compliments. This article was written by Steve Chamberlin so he deserves the praise.

A GAL could be configured to do as you sugest. It would take more then just the GAL however. You would need a time base and somththing to press the button. All the logic to implment a state machine that waited for the correct amount of time and signaled the button press could be implemented in one or more GALs.

In your example a small uC might be a better solution.

By: John

John — Mon, 07 Apr 2008 11:36:18 +0000

David,

1. Very well written summary. Thanks!!! New users need all the help they can get – and that was spot-on!! (myself included)

2. Do you think a GAL could be used to Provide a signal (to push a button) at a set of user-specified times-of-day over a weeks duration. Typically it will (or can) be “on the hour” if-that-helps, making 168 possibilities (24*7=168). Time-specs and changes to them can be re/programed to the GAL each time, or preferable would be to include an interface of some sort to specify the times and changes to them.
…Any insights able to be provided on how to do this or what else may be needed, or to better approaches, would be much-appreciated!…

John

By: Alan in D.C.

Alan in D.C. — Fri, 04 Apr 2008 21:29:32 +0000

I was told a GAL would be the ideal replacement for the old Top-Octave Synthesizer chips of the early ’80s. You would input a high-frequency signal on the order of about 2 MHz or so, and the chip would divide this down to a single, fairly accurate, C-to-C chromatic musical octave.

I like the idea, but I’ve got a mental block when it comes to programming the divisors. Has anyone done this, and just how simple is it?

By: Jonathan

Jonathan — Fri, 04 Apr 2008 18:32:11 +0000

My first really big digital project used two GAL16V8s. I made a home-made programmer and used a really terrible program by atmel to make the jed file

This way required no experience or money, and is an ideal introduction to PLDs. I am very surprised the store I went to actually had the chips, wow

The down side is GAL16V8s use over 70 mA each!!!

Now I just use Altera CPLDs, they are way better

By: Steve Chamberlin

Steve Chamberlin — Fri, 04 Apr 2008 14:30:26 +0000

Olivier, I am using Opal Jr. http://www.brouhaha.com/~eric/retrocomputing/mmi/palasm/opaljr21.zip

By: Olivier

Olivier — Fri, 04 Apr 2008 11:21:05 +0000

Hi,
Which software do you use to compile from abel or schematic to obtain jedec file ?
and to download jedec file into chip ?

ispGAL is an old chip, and i didn’t find this ref in the chip configuration tool of lattice software.

thank.

By: Viadd

Viadd — Fri, 04 Apr 2008 01:45:45 +0000

Digikey shows 7 different types of CPLDs in DIP format (28-40 pin). These are all from Atmel.