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.

 

 

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Can you enable internal pull ups on those two pins?

If not define them as outputs and leave them disconnected.

 

 

 

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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.

The largest known prime number: 282589933-1

It's easy to stop breaking the 10th commandment! Break the 8th instead. 

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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.

The largest known prime number: 282589933-1

It's easy to stop breaking the 10th commandment! Break the 8th instead.