PM5418 need prom dump

What's wrong with the one currently in it? Have you tried reading the data from it with a lowered VCC?

I can read it, but databit 6 is always '1' the pin is shorted to Vcc,

Ouch. Well, reading an EPROM at a lower VCC will sometimes allow you to get all the data off a flaky device, but in your case, it probably won't help. Did you actually measure the short right at the pin with a DMM, or just assume it was shorted to VCC from the data pattern?

It measures under 25 ohms, so no luck there, the prom is fried anyway, it gets warm and consumes too much power. It's a wonder I can read it at all, but without bit 6 it is no good.

If I had one, I'd be willing to read the binary for you. You could try these groups, lots of very helpful folks there:

If anyone on those lists have a PM5418, I'm sure they be willing to get you a copy. You could also try Fluke, the last time I dealt with them they were pretty helpful.

Good luck.

Thanks!

Does the supply current vary during read depending on the stored data? If so, you *MAY* be able to retrieve bit 6.

It is a little difficult to be certain when you don't know what it should be, but if you stick a sense resistor in the VCC supply (maybe with two diodes across it to prevent excessive drop while switching) and scope that and the read signal while reading the chip, you may find you can tell the difference when the lower MOSFET in the D6 output stage switches on to attempt to output logic 0.

If so, a PNP transistor, a few resistors and an inverter (possibly with a tristate output controlled by the read signal) may be enough to build a 'gimmick' jig to let your programmer read it.

won't

or

Have you had personal experience of this work-around ?

I can try that, interesting thought, thanks.

I have succesfully retrieved bit 6 with a pnp transistor, some resistors and a inverter directly at the output pin. Then came the weird part, I had to invert it a second time to get it right. So this problem is solved.

Thanks all who contributed!

Glad you got it to work. Obviously the internal damage was not just a simple short in the output stage and that you had the genius to try re-inverting bit 6. Its a neat dodge to be aware of for use as a last resort. After you have thoroughly tested the result, it would be nice if you could find somewhere reasonably stable to put the file online.

that

and

What sort of differential in the supply current ?

On Thu, 14 Jul 2011 16:36:59 +0100, IanM put finger to keyboard and composed:

That has to be one of the best hacks I've seen in a long time. Kudos and congratulations to both you and the OP.

BTW, I've "repaired" weak output signals in digital ICs by buffering them with a comparator, but I never would have dreamed of recovering a PROM in this way.

- Franc Zabkar