AVR accidentally erased?

I received a product of ours from a customer, which was defective. After investigation it turned out that the AVR( an AT90C8515) in the product was erased. When I tried to read the signature of the micro, 0x00,0x01,0x02 was returned, which is normal for a locked device. However, after erasing the AVR, it returned a signatue of 0xff,0xff,0xff. I could however reprogram and lock the AVR after which the device operated fine.

This device has been sitting on a boat and the customer said they had overvoltage on the 12V grid, resulting in more defective equipment on board. I'd rather think that this is the result of a lighting strike nearby, but the behaviour of the AVR seems strange to me. Any opinions out here? It seems that the signature is also factory programmed and the entire chip got erased, instead of the program memory only.

Meindert

Reply to
Meindert Sprang
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Is the reset pin clamped, so that it can't exceed Vcc? I've seen cases where a short transient exceeding the 12V needed to enter parallel programming mode caused complete or partly erasing of AVRs. I've never worked with the AT90C8515, though. You may also look into Atmel's app note "AVR040: EMC Design Considerations" which explains more details about this and similiar problems.

Klaus

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Reply to
Klaus Bahner

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Considerations"

Yes, the reset is clamped. I followed that app note very closely with regards to the reset input.

Meindert

Reply to
Meindert Sprang

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