ATmegas with split personalities

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While working on my debugWIRE hardware debugger, I came a across a very funny phenomenon. Some AtmegaX8 chips identify themselves correctly when the device signature is queried using the SPI protocol. After switching to debugWIRE, the MCUs queried using the corresponding debugWIRE command gave a different device signature. And this is not only one chip, but seems to be consistent over the different flash sizes:

ATmega48A -> ATmega48PA

ATmega88A -> ATmega88PA

ATmega168A -> ATmega168PA

ATmega328 -> ATmega328P


This is not a real problem, but I noticed that MPLAB X got confused. I wonder whether you have seen something like that as well. BTW: The chips without an A-suffix that I own do not show this behavior (except for the 328, of course).


Wish you a happy new year,