On Tue, Jan 07, 2014 at 05:51:38PM -0700, David VanHorn wrote:
> I don't know what you mean by separate paths for wakeup and GPIO
> read.

Happy to explain.

The ARM core that I've most recently worked on shows a schematic for
the infrastructure in the chip that is electrically connected to a pin
on the package.

The schematic is needed because a pin has so many uses; not only GPIO,
but also selectable pullups, pulldowns, wakeup, interrupts, and
various alternate functions.

The schematic shows an input buffer for the GPIO read operation, which
is used when the CPU executes an instruction that reads from the GPIO
port.

Tied to the pin also is a pin change interrupt buffer.

By separate path, I mean that there exists some gates in a chip that
if they fail would render certain functions unavailable.

> I've worked with touchsense on the AVR, and we simply scan the keys at a
> low rate while sleeping.
> Over a year on the tiny battery so no complaints.
>=20
> ESD can definitely kill the I/O pins, especially if they didn't provide
> guarding copper.

While ESD can completely kill I/O pins, I'm speculating that a low
dose can also degrade certain functions first.

--=20
James Cameron
http://quozl.linux.org.au/
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.