Hello: Reading the specs for 12Cxx, looks like calibrated osc value can vary nearly +-500kHz. Has anyone used these parts (with internal osc) for serial comm, and if so, how? Bruce Cannon Style Management Systems 1228 Ceres ST Crockett CA 94525 (510) 787-6870 http://www.jps.net/bcannon Remember: electronics is changing your world...for good!