connecting a 4X4 keypad

[fadibasic]

Melanie,
What about pic16f877? and what do you guys mean by Pull Ups?

[mister_e]

Whatever the PIC you're using, you can use almost every I/O on it. The software must be done to work with your own assignment. Not much.

PIC16F877A have internal pull-up which can be enable by software... but they're on PORTB ONLY. No problem if you don't need any feature available on PORTB. Just hook your keypad on PORTB, use

OPTION_REG.7=0 ' Enable internal pull-up on PORTB

and away you go.

Explanation of pull-up.
http://www.seattlerobotics.org/encod...97/basics.html

[Melanie]

By the kind of question you've asked, it looks like you're not too experienced with PICs. Yes, 16F877 is fine, if you checked you'd discover it has a PORTB and if you look at the Datasheet (which you can freely download from the Microchip website - and is a MUST!!!) you will discover that PORTB on that PIC also has pull-up's. All a pull-up is, is a Resistor internal to the PIC, which you can program the PIC to switch-in if you need it. That Resistor connects between the relevant PIC pin and Vdd (+ve supply rail) pulling that pin up to +ve (hence the name). Just saves you having to provide one externally.