Hi, I now got a chance to come back to this problem of my pic. Apologies for the delay in updating you.
OK, I have programmed another 12C671 taking care of static discharges. Now the voltage part on GP3 is working fine. It is pulled high at 5V. But making it low does not initiate the required serout signal.
Is there something I am missing in the code to make proper use of GP3 as an input?
Thanks