Google found this:
   https://www.sparkfun.com/tutorials/218

Didn't have much luck finding a definitive answer on microchip.com.

chuckc



-----Original Message-----
>From: Allen Mulvey <allen@amulvey.com>
>Sent: Apr 3, 2013 12:46 PM
>To: PIC List <PICList@mit.edu>
>Subject: [PIC] Pull Up Resistors
>
>Sorry, this is my first post. I forgot to tag the subject
>line.
>
>=20
>
>Is there a way to compute the optimum value of pull up (or
>
>pull down) resistors on PIC digital inputs?
>
>=20
>
>Most example circuits I have seen seem to use 10k. My
>
>EasyPIC7 board uses 4k7. I have been experimenting and 20k
>
>resistors produce unreliable results. I don't see anything
>
>in the data sheet to help with this.=20
>
>=20
>
>I am using a pic16f877a. The leakage current is one
>
>micro-amp. Sampling the port must draw considerably more. My
>
>current project is not battery operated but, if it were, I
>
>would like to use the largest resistors possible.
>
>=20
>
>Thanks,
>
>=20
>
>Allen
>
>=20
>
>--=20
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