I recall a while ago somebody (Scott?) posted a routine for very accurate measurement of pulses. I need to measure a 500-2500 instruction cycle pulse at 4 or better cycle resolution on a standard PORTB pin (not int-on-change) in a '711. I also need to catch and report invalid (short or long) pulses. Anybody have that posting? Thanks. Andy ================================================================== Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA ==================================================================