Hello,

I have a battery powered design using 16C84. I need to be able to read a
keypad, this requires 3 inputs. The design will spend a lot of time asleep.
Long battery life isn't critical, but I would like to extend it as much as
possible.

These inputs must be pulled up to 5v. I could use the weak pull-ups, but the
other pins on port B are inputs, and I would rather not pull them up. Also,
I think that it will be more economical (in terms of power consumption) to
just pull those 3 pins.

However, there is no reference of the input current required to pull-up a
input pin in the PICs specification. It mentions that the port B pull-up
current is typically 250uA, so if I divide by 8 pins I get 31.25uA. So
should I pull up each port with 160K (5/31.25uA)? Or is the 250uA per pin,
not for the port? Maybe is it completely wrong to use this value?

Any advice gratefully received,

Regards,

Stuart.