> The data sheet doesn't explain anything either

Section 4.0 of the 16F690 manual is pretty clear, even if you're
starting from scratch. You should also look at the PICList I/O
and interrupt pages

http://www.piclist.com/techref/microchip/ios.htm

http://www.piclist.com/techref/microchip/ints.htm

and search the mail archives. The subject(s) have been covered many
many times

> There aren't many C examples for this

One you understand what is happening at the assembler level then you
can translate that to C

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