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Issue cloning some EPROMs. Is it my programmer?

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Rat_Patrol:
Sorry if this is the wrong area. But anyway...

I am trying to clone some EPROMs, and I'm wondering if its my programmer causing my grief..

I have some TMS27PC256 EPROMs, trying to clone them out. I am working to put them on some ATMEL AT27C256R chips, new from DigiKey.

Programmer is an MCUMALL GQ-4X, and an older version, not the new one. I'm also using the programmer adapter they recommended, with the jumper set to 5v.

That last part interested me, as Vcc needs to jump to 6.5, and Vpp to 13 for programming. I have NOT put it on the scope yet to check the voltages, but I may play with that yet to see what I get.

So I pull the data off the old chip (I have multiple examples, they all seem to read the same), switch over the device on the UI to the ATMEL, blank check, burn chip, verify, and everything seems fine. I install the chip onto the PCB, nothing. I put the old chips back in, works fine.

I'm wondering if my budget programmer just isn't going to cut it. Supposedly it can handle these chips, but maybe not. Sure, it seems to read them fine, but maybe it can't program? Thinking of shelling out the money for a Dataman programmer, but I'm not sure if that will fix my issue.

The programmer works just fine for cloning other chips, such as the X28C64.

Any thoughts are appreciated.

amyk:
Check the specs of the EPROM you're replacing with that of the original. The circuitry may be designed for a specific speed and even a newer faster one may not work.

I would also do a quick "spot check" of a few bytes' worth of content of random addresses using a breadboard, some current-limiting resistors, and LEDs; as you suspect, perhaps the programmer isn't writing the data into them.

greenpossum:
I wonder if there are other differences between the TMS and the AT chip which shouldn't matter but do, like the drive capability of the outputs, or the state of some of the other pins like /OE, or the timing charts. Maybe peruse the respective datasheets?

eblc1388:
Read your source Eprom content, save it to a .bin file. Then read your newly programmed chip and save its content to another bin file. Now compare the two files for content difference and you will know the answer one way or the other.

Rat_Patrol:
Coming back to this project this morning...

These chips are in a PLCC package, so naturally when I took the chips off, I soldered on sockets.

After the new chips failing, and the old chips working, I took the old chips out of the sockets, put them right back in, and now they don't work either.

I've taken them out and put them back a dozen times, thinking a connection issue, and nothing.

 :wtf:

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