When a PIC input is configured as an analog input, then the digital input
buffer is disconnected from the pin and held at ground. This will result in
the digital input reading zero, no matter what voltage is on the pin, and it
also avoids the issue of excessive (more than data sheet) current draw
caused by 'shoot through' in the digital input buffer.

OTOH, if you configure a pin to be both an AD input and a digital output,
then the AD will convert the digital output voltage. This could be a useful
way of checking for shorts or other problems on the pin.

Bob Ammerman
RAm Systems

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