Difference between ATMEGA644A & ATMEGA644P?

I wonder what is the difference between the ATMEGA644A and the ATMEGA644P version of the MCU that is used in all the MI designs?
All the MI BOMs state the P version. I noticed that at Farnell the A version is much cheaper than the P version
The only difference i could find (easily) is that the A also works on much lower voltages.
Would the A also work for the MI products?

Looking at the datasheet there is at least one register which is only available in the PA version. Not sure if P is the same as PA?

A is older, I dont recall what the differences are

I think i should have called them A and PA indeed. Only farnell seems to call it a P

If it works on much lower voltages, it will die sooner from higher voltages…

  • Atmega644: very old version, do not use! (doesn’t work with digital filter board because it has only one UART).
  • Atmega644PA: latest version with least energy consumption.
  • Atmega644P / Atmega644A: intermediary revisions, but I’m not sure which one came first…
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The P and PA versions are known to work. I buy whichever is cheaper - P at a time the PA was released and they were trying to get rid of the stock of those ; and now PA.

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Thanks!
And that’s why the A’s are so much cheaper at farnell… I’ve ordered one for use in the eurorack tester so i will find out of it works. Maybe i’ll also try it in a shruthi.