IO Pin state during under voltage conditions

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Assume I am driving Atmega328P from battery and I have set one of the port pins to HIGH. Now battery drains and voltage goes below safe operating conditions and processor goes to protection mode. Under this situation, what will be the output pin state? Will it become 0V or remain at same level? Which part of the datasheet explains this?

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joneewheelock wrote:
processor goes to protection mode.

Never seen this mode before, but assuming you have the BOD setup, then the processor goes into reset mode.

 

From the DS: 11.1 Restting the AVR

The I/O ports of the AVR are immediately reset to their initial state when a reset source goes active. This does
not require any clock source to be running.

Initial state is Input, so high impedance mode!

 

edit: added DS ref

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

Last Edited: Fri. Nov 30, 2018 - 03:07 PM
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The further implication of that is that if you need them held in a "fixed state" even when the CPU has reset (or in the short time between it resetting and your code driving them as outputs to a fixed state) then you can use external pull-ups/pull-downs to present the 1/0 state syou want until the CPU is ready to take over again. Make them weak so that if the pin is later set the "other way" then it won't involve a large current bun fight !

 

(and yes that pun was unintentional but I rather like it!! cheeky)

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Yes I meant Brown Out Protection mode. Thank you for the clarification.

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Cliff, whilst i understood what you mean by a ‘bun fight’, i did wonder if our North American friends would. I also wondered the source of the expression. Seems there is some debate.
https://english.stackexchange.com/questions/351211/what-is-the-origin-of-bunfight-and-how-has-the-term-evolved

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"Bun fight" is a new one for me. My first reading of Cliff's "current bun fight" evoked images of a fight with or over current buns. Then a step back allowed me to realize that the reference was probably to GPIO pin (electron) current rather than (ribes "current" or Little Corinth Grape "current"), hence the "bun fight" was probably a metaphor (and not a bad one). 

 

Kartman's reference to and about "bun fight" was interesting but marginally enlightening. To me, the words suggest a food fight (e.g. with food rather than about food), perhaps at a large dining table with the "school boys" launching buns every which way. But, in any case, it is hardly a common term in the long-ago former colonies, that tie having been severed around 1776 or so, not withstanding attempts to restore the colonial status in 1812.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!