Patent ID: 6535926
Filing Date: 2003-03-18
Classification: H04J,H04L

Abstract:
A method of synchronizing local clocks among industrial control devices communicating on a network, the synchronizable being to a time value of a master clock in a first industrial control device, the method comprising the steps of:(a) detecting at the first industrial control device a global reference pulse; (b) storing at the first industrial control device, a first time value of the master clock at the time of detection of the global reference pulse by the first industrial control device; (c) transmitting from the first industrial control device a time message on the network containing the stored first time value of the master clock; (d) detecting at a second industrial control device the global reference pulse; (e) storing at the second industrial control device, a second time value of a local clock in the second industrial control device at a time of detection of the global reference pulse at the second industrial control device; (f) receiving at the second industrial control device the time message and comparing the first time value to the second time value to produce an error value; and (g) correcting the local clock of the second industrial control device according to the error value.