Learning CPLD and testing GALs

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PhilC
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Learning CPLD and testing GALs

Post by PhilC » Thu May 21, 2020 9:29 pm

Evening All.

So I've got WinCPLD loaded up on my Windoze laptop and am going to learn CPLD programming.

But since there are so many fake or faulty GAL chips out there im going to write a small program that tests the Gal inputs and outputs.

I could use simple switches and Leds but that wouldn't be as much fun, so my idea is to use an Arduino to toggle the inputs and check the outputs are as expected.

What is it that you guys find fails with the fake Gals? Is it just they are simply dead or something else?
If it ain't broke, test it to Destruction.

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Re: Learning CPLD and testing GALs

Post by exxos » Thu May 21, 2020 9:50 pm

They mostly fail erase, or programming, or don't program at all, but almost certainly they are not the speed printed on them!
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Re: Learning CPLD and testing GALs

Post by PhilC » Thu May 21, 2020 10:07 pm

exxos wrote:
Thu May 21, 2020 9:50 pm
They mostly fail erase, or programming, or don't program at all, but almost certainly they are not the speed printed on them!
Ok, so erase, prigram, test operation for the first test.

I'll have to have a think about how to test the speed.
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Re: Learning CPLD and testing GALs

Post by exxos » Thu May 21, 2020 10:17 pm

PhilC wrote:
Thu May 21, 2020 10:07 pm
I'll have to have a think about how to test the speed.
I think how I did it was just test a inverter, and look on the scope of the before and after to check the speed.
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Re: Learning CPLD and testing GALs

Post by JezC » Thu May 21, 2020 10:27 pm

I know that the counterfeit/fake marking is a growing problem with many components but are there any legitimate distributors who can still sell these?
I saw that Farnell has a limited number of some GAL/PAL devices (e.g. 20R8 IIRC) but not of the ones I've been after (22V10 for example).

Following on from comments on one of TF's threads, I'm not suggesting that we post anything publicly on here but some indication of sellers (and likely success rates) would be useful.

Maybe the information could be managed less publicly (e.g. by PM or similar) compared to just posting on the forum?

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Re: Learning CPLD and testing GALs

Post by exxos » Thu May 21, 2020 10:43 pm

AFAIK nobody sells them anymore.. Don't go with the Atmel ones, geeze... https://www.ecstaticlyrics.com/electronics/ATF22V10C/

I am however going to try and put some tested used ones in my store at some point soon...
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Re: Learning CPLD and testing GALs

Post by JezC » Thu May 21, 2020 10:53 pm

I think my first (and so far only) requirement for them is to give the HD support to the two H4 boards...

:threadjacked:
Minor deviation from the topic...so feel free to move somewhere more appropriate if you deem fit!...

I know the H4 can swap drive A/B via jumpers (and so on demand via a switch) but is there any way to make it override the drive select setting on the floppy itself?
I have some HD floppy drives from various PCs etc. and would like to use them with the H4 boards...but not all of them have an accessible drive select jumper (or at least not one I can find).

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Re: Learning CPLD and testing GALs

Post by exxos » Thu May 21, 2020 10:55 pm

@JezC you can force 1.44MB all the time if thats what you mean ?
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Re: Learning CPLD and testing GALs

Post by JezC » Thu May 21, 2020 10:59 pm

exxos wrote:
Thu May 21, 2020 10:55 pm
@JezC you can force 1.44MB all the time if thats what you mean ?
@exxos No, but good to know anyway.
From what I've seen/read, most 3.5" floppy drives for a PC have the DS1 jumper set but the ST needs it set for DS0 instead so I was wondering if we could 'correct' the DS jumper setting on the H4/floppy cable somehow, rather than having to mod the floppy itself.

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Re: Learning CPLD and testing GALs

Post by exxos » Thu May 21, 2020 11:01 pm

JezC wrote:
Thu May 21, 2020 10:59 pm
@exxos No, but good to know anyway.
From what I've seen/read, most 3.5" floppy drives for a PC have the DS1 jumper set but the ST needs it set for DS0 instead so I was wondering if we could 'correct' the DS jumper setting on the H4/floppy cable somehow, rather than having to mod the floppy itself.
I cannot remember if it was tested, but any drive should work on the H4 without needing to change the jumper...
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