Probably I'm not the first person to ask this but would like to hear it again. Yes what I ask is not what the datasheet recommends.
I use ATmega644PA in 44 QFN and I leave AVcc pin not connected to anything. I dont need ADC functionality.
So my question is what happens?
- Port A can still work as 'open drain'
- Any voltage on Port A cannot be clamped to Vcc through internal diodes
Is that all? It should not affect any other functionality of the chip, shouldn't it?