Protecting I/O lines of microcontroller

[Rajinder]

Hi all
I am using a PIC which is connected via a 3 way connector. The connections are from PORTB of the PIC. PIC is powered from 3V.
I want to know what is the best way to protect the I/O lines of the PIC in case the user accidently applies too much voltage on the connector end.
Could i use a series resistor? Also what happens if on power up i select weak pull ups for the PIC?
Thanks in advance.

 

[(*steve*)]

A series resistor, reverse biased diodes to the supply rails, zener diode to ground, it a combination of more than one of these.

The existing protection for CMOS is akin to a combination of reverse biased diodes anda series resistor, but it isn't expected to (or capable of) handling a significant overvoltage from a low impedance source.

 

[Harald Kapp]

With pictures.