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ST M2716-1F1 21V FAST UVEPROM Behaviour

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


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.


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

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

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.

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.

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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