18f252-i/sp

[Armadus]

Thanks for the reply. I am using a 9600 baud rate, and the clock is set as "HS" with a 20 mHz resonator. The code has worked for a couple of years, but sometimes it will not work with some PIC chips. The code for this project is very long, and I am working on getting the representative code posted.

[HenrikOlsson]

Aha, 20mHz - there's your proplem...just kidding - you mean 20MHz ;-)

Did you use the same PCB, same resonator and everthing else and ONLY swapped the PIC when 4 out of 10 didn't work? Or was it actually 4 out of 10 boards that didn't work?
Datasheet for the specific resonator you're using? Short of that, measure the actual bit-time generated to verify at which frequency the PIC is ACTUALLY running.

/Henrik.