Strange ISP Behavior

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Greetings Freaks,

Have just encountered a very strange phenomenon whilst trying to program a board. Its a custom board with m664 @ 20MHz. 100s in the field all have been fine til this one.

I can read the signature, the fuse bits, lock bits. I can even verify the flash and eeprom contents but for some strange reason a write action has no affect. I can't write flash, eeprom or any fuse bits and a chip erase also has no affect.

The heartbeat LED simply pauses briefly with every action to enter programming mode.

I believe all connections are good as I can talk to it. I believe my ISP MKII is good as I've successfully programmed another board before and after this problem.

(edit)
I have just noticed the firmware also cannot write to its own eeprom when I try to change setting.
(/edit)

Anyone seen something remotely similar before? Know of any causes/solutions?

Thanks,
Steve

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Well, if you can read the signature correctly then the programmer interface is functioning, and the micro is running, (i.e. not a bad clock problem).

I'd take a quick look at the power supply to make sure it is operating correctly, and not oscillating or noisy.

I assume you have by-pass caps on the V+/Gnd, AVcc/Gnd pins.

I'd remove an cap on the Reset\ pin.

Then I'd think about how much your time is worth, as the common causes for programming failure will have been eliminated.

It may make more sense to put the board aside and move on.

Save the board, however, in case you start seeing more of the same problem show up.

Others may have more suggestions.

JC