10K is typically used for pullups, there's no point in putting one on your
supply pins (if that was what you were asking.)  I use the internal weak
pullups for pins not connected to anything (floating).  Regarding your
question, if its necessary to use pullups on something you are connecting
to, that depends on the type of output on the PIC pin (open collector,
tristate) and the type of gate at the device the pin is connected to
(active-high, active-low, etc.)

Regards,
Bob

On 3/24/06, mrgizmo <mrgizmo@vianet.ca> wrote:
>
>
> I have 2 projects one using a 16F628 and another using a 12F675 both
> running
> on 5V. Is there an exact value to use as a pull up resistor, or is it even
> nessasary?
>
>
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