82S123 PROM adapter (read only) for GQ-4X

DarrenF

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So I accept that my inexpensive EPROM programmer isn't going to program bi-polar PROMs. But I want to be able to *READ* them, so I'm only ordering ones that are actually bad.

Attached is a photo of the adapter I built installed on the reader. Wiring is straightforward; I pulled up pinout for the 82S123 & a regular 2716. The 8 data lines were connected respectively, and the 5 address lines that the 82S123 has were connected to A0-A4 of the 2716. The rest of the address line were left unconnected (the GQ-4X doesn't care about unconnected address lines). And of course Vcc and Vss (GND) were connected.

I put in a PROM (in this case, one from Taito Grand Champion) and just read it as a 2716. Of course I end up with the same data (the 32 bytes in the PROM) over and over (64 times, to be exact). No big deal, as there are only 32 bytes, I can just compare them manually to the correct contents of the PROM (from MAME). Screenshot of read attached also.

I intend to also build one for the other most common PROM I see, 82S129 (256x4).
 

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Nice work. Have you contacted them to see if they will add it to their database? They seemed responsive to requests at one point in the past.
 
That would be a nice adapter for alot of guys to have if someone wanted to build them. Proms are expensive so it would be a big plus to be able to read them to verify.
For most people its hard to justify buying a data I/O just for occasional use. I tell you, I hate dragging mine out just to read a couple proms. I have a prom adapter for my PP3 but its more of a pain to use than hooking up the data IO so it just collects dust.
 
Have you contacted them to see if they will add it to their database?

If I thought there was a chance in hell of that happening, I probably woudn't have built it. They've been promising a Linux version of the software for years, and haven't delivered. This little unit could do a LOT more if the software were opened up, or at least some sort of XML method to allow users to add new devices. TTL & RAM comes to mind immediately.

That would be a nice adapter for alot of guys to have if someone wanted to build them. Proms are expensive so it would be a big plus to be able to read them to verify. For most people its hard to justify buying a data I/O just for occasional use. I tell you, I hate dragging mine out just to read a couple proms. I have a prom adapter for my PP3 but its more of a pain to use than hooking up the data IO so it just collects dust.

Yeah, it should be dead-easy to layout for someone skilled with that sort of thing. I've installed Eagle, but haven't had time to learn to use it. Probably a 30 minute job for someone with experience. I even have some ideas for it:

-it could probably be laid out such that the 0.3" socket fits between the 0.6" headers on the bottom, to keep the PCB very small.

-on the other hand, it might be cool to design it such that the top socket could optionally be a ZIF.

-the 82S123 & 82S129 could be combined into a single PCB with two top-side sockets.

-For the (4 data bit) 82S129, it might be useful to have a jumper to select how the upper data bits read (high or low). From the few I've looked at, MAME leaves them low, but I'm not sure if that's universal.

I also haven't looked closely at the pinouts of some other PROMs to see if there's opprotunity to add some jumpers and cover some more bases with a single adapter.
 
Kinda like this:

prom-adapters.jpg
 
Damn Matt. Yes, exactly like that :) I'm tired of slaving over pinouts, and fiddling with delicate wire... How much you want for a full set of bare PCBs?
 
Sorry to be a big tease... I don't have any more of these. They're good for filling up the extra space on a PCB layout, so perhaps more will be made.
 
Alright then. Time to learn some Eagle...
 

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Well, I went through all of the Eagle tutorial I could stand, then just drew up a schematic, and fumbled through the PCB layout. Not sure why I was trying to make it a single-sinded PCB... Anyhow, I re-did it double sided, and then checked it out in gerbv, and uploaded to BatchPCB. So I should have a board in a month or two... If everything goes together and works fine (not likely... my first PCB), I'll share the gerber files for anyone who wants to have one built (and try doing the same for some other common PROMs).
 

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Another thing to consider when designing these is that the same board could be used in reverse. That is, you could use them on a PCB to replace a PROM with a 2K JEDEC device. A 2716 EPROM is too slow, but there are more modern devices (like the Simtek NVRAMs) that are plenty fast enough.
 
Didn't really think about doing that. Perhaps as the availability of bipolar PROMs continues to dwindle, and the prices rise, it'll make more sense. But for now, the cost of a programmed PROM has got to be less than a PCB replacement...

I guess the main considerations for making the PCB able to be used either way would be minding Vpp and the select/enable lines?

I searched Jameco, Mouser, etc, and didn't find any "Simtek" NVRAMs. Is there a particular part number I should be searching for?

I'm starting to wish I'd spent my time learning the gEDA tools rather than Eagle... oh well, only 2"x3" PCBs for me for now.
 
Yeah, not really economical at the moment. One advantage is that it's easy to program NVRAMs (while finding a programmer for bipolar PROMs that doesn't cost $1000 or weigh as much as a boat anchor can be a challenge). Also, your 2K chip can hold multiple PROM programmings. Make them DIP selectable and you've got a handy tool for your test bench.

The 2K Simteks aren't made anymore. You could use an 8K Simtek, but then you'd have to change your pinout. Maybe the Ramtron chips would work? I haven't checked the specs on those.

Edit: Yes, the Ramtron chips are fast enough (70ns).
 
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I don't find any 24-pin Ramtron products (nor anything in DIP available...) The FM1808 is the closest I see, but it's a 28-pin 32k x 8 device. The only 2Kx8 Ramtron I find is serial. But I may be looking in the wrong places for the wrong things...
 
Maybe Ramtron never made a 2K parallel device.... There is an 8K you can get in DIP, the FM1608. But then you might as well go with the Simtek instead (e.g. STK12C68). BTW, I believe both Simtek and Ramtron are owned by Cypress now.
 
Meh... I have a couple thousand 82S129 and several thousand 82S126 here... New old stock Signetics.

I have several hundred 82S123 equivalents from different manufacturers... 82S23, now those have been hard to find.

:)
 
BTW, I believe both Simtek and Ramtron are owned by Cypress now.

Ahh, that helps. I still can't find any small DIP parallel Ramtrons, but I'll keep looking. I only go to ebay as a LAAAAST resort.

Meh... I have a couple thousand 82S129 and several thousand 82S126 here... New old stock Signetics.

Good to know. That's part of the reason why my orig post was focused on a way for me to READ the damn things. They're pretty resilient from what I've seen... don't fail too often. But when something isn't working right, and I can't put my finger on it, I always start wondering if a bad PROM might be the problem. So if I can read them, I can either rule it out as a problem, or order a new one programmed from channelmani(a)c. I like to be self-sufficient, but I think for now being dependant on others to program PROMs is for me.

But if I see a Data I/O 29B at a yard sale for $10, I'll will grab it...

In the mean time, according to BatchPCB, somewhere in China someone is making my crappy little PCB...
 
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My First PCB

I got my order from BatchPCB yesterday... pic attached. Looking forward to learning more about Eagle, and maybe the EDA tools.
 

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