Electronics > Projects, Designs, and Technical Stuff

ST M2716-1F1 21V FAST UVEPROM Behaviour

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NivagSwerdna:
I'm trying to use two 2716 UVEPROMs in an old arcade game and getting very strange behaviour...

[attachimg=1]

On the board pin 21 is wired to a 1k Pullup to 5V but when the ROM is fully inserted it doesn't seem to operate correctly... no data returned.  If I pull the pin low then it seems to operate (although some bits go missing) but if I leave it floating it seems to work.

[attachimg=2]

The ROMs were fully erased and then programmed in my TL8266 with VPP set to 21V

There is something spooky going on.

Thanks in advance

fourtytwo42:
I wonder if it has not programmed properly, the spec seems to say it should be 25V on vpp, not 21V.

retiredfeline:
I don't think the TL866 can program 25V EPROMs. Someone once reported that it didn't even reach 21V for 21V EPROMs. You could use a 2816 instead.

CaptDon:
I know it seems stupid, but maybe they are 'too fast' for the rest of the data/address bus. It makes no sense that 'floating' gives the best results. You could try a stiffer pull-up like 330 ohms and bypass it with a .1uf disk ceramic cap. Also, was the mother board strapped for an Intel 2716 or something else? There were different pinout versions and I think there was the strapping option for (2316?) ROM's. I have noted that many of the old gamers are having troubles similar to yours with mis-matched access times on 2016/6116 rams for instance.

NivagSwerdna:
I UV erased them and dug out my Data I/O 29B from the loft and programmed them as 2716 (Fam 19 Pin23) which I assume blasted them with the 25V from the 2716 spec...

... and they work with all Pins attached.

So I guess the theories above are correct... they were incompletely programmed by the TL866A and the 21V on the chip is probably a bit optimistic.

At least I can put these to good use rather binning them as 'fake', 'counterfeit' etc. even if there labelling is a bit bogus.

Thanks all.

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