PR0 and PR1

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In a battery system where you don't want to leave inputs floating, what do you do with PR0 and PR1 if you're not using a crystal? I've just always ignored them, but I wonder if that's wise. I have an xMega192D3 on this board.

 

It appears you can use them as interrupt pins if you're not using a crystal.

 

 

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

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Can you enable internal pull ups on those two pins?

If not define them as outputs and leave them disconnected.

 

 

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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Oh. It appears that you can use PORTR as an IO port of 2 pins. So I'll just treat PORTR as an IO port unless I'm using a crystal.

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

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For the lowest possible power consumption it is best to drive them low. Set them as outputs.

 

Atmel's app note recommends you enable the pull up / pull down configuration on unused pins, but I prefer to drive pins... I seem to recall I did some experiments and found it was slightly lower power, by some very small margin.

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I just never realized they were a real port.

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut.