[vcf-midatlantic] Bag-o-chips sorting, storing, testing

[Bob Applegate]

Do any of these testers perform tests at real speed or are they just a bunch of I/O ports that software writes to, then reads back the values to make sure they are correct?  That would week out most bad chips, but I’ve had quite a few chips that passed those tests only to fail in a real circuit because they were no longer switching at full speed.  ESD damage?  Who knows.

I ended up building some of my own testers where the chips under test are in a live circuit and their outputs are latched and compared to expected results.

As far as RAM tests go, a common failure scenario is where they can pass memory tests but then not work in the real circuit because of timing.  I like to have memory tests that run out of ROM and not use the RAM except as a test target, then use a RAM based tool so that the code running the test is also in the same RAM.  Access to memory under test is really slow for any test running in ROM… lots of code execution in ROM, write a byte, lots of ROM code, write a byte, etc.  By running the memory test in RAM then it is constant access to the device being tested.  Some chips fail the latter case.

Just my two cents.

Bob

> On Apr 21, 2021, at 9:23 AM, Jonathan Sturges via vcf-midatlantic <vcf-midatlantic at lists.vcfed.org> wrote:
> 
> 
> From: Jonathan Sturges <jonathansturges at yahoo.com>
> Subject: Re: [vcf-midatlantic] Bag-o-chips sorting, storing, testing
> Date: April 21, 2021 at 9:23:44 AM EDT
> To: "vcf-midatlantic at lists.vcfed.org" <vcf-midatlantic at lists.vcfed.org>
> 
> 
>> My TL866 can test the 74XX and 40XX logic chips to see if they are good.
> 
> I've got a TL866 as well and will bring mine.  Do you use their Windows software or something else?  I use minipro in Linux for PROMs and flash, but minipro doesn't have chip-testing capabilities.  Alex J. & I also have another tester, who's name I forget, which can test TTLs however.
> 
> Alex & I also have Neoloch Inquisitors, which can test many common SRAM and DRAMs, as well as PIAs and RIOTs.
> 
> With multiple testers, hopefully we can knock out the testing easily.
> 
> -Jonathan
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>