公开(公告)号：US20230318728A1

公开(公告)日：2023-10-05

申请号：US17709341

申请日：2022-03-30

Applicant: Rockwell Automation Technologies, Inc.

Inventor： Yanbin Zhang ,  Xiaobo Peng ,  Sikai Zhang ,  Steven T. Seidlitz ,  Arun K. Guru

IPC: H04J3/06

CPC classification number: H04J3/0661 ,  H04J3/062

Abstract: To improve integrity of time synchronization, a node in a safety rated system verifies that its clock remains synchronized to another clock. Two adjacent, time-synchronized nodes transmit diagnostic messages to each other at an agreed upon interval and generate timestamps when the diagnostic message is received from the other node. The nodes then transmit their respective timestamp back to the sending node. Clock drift is detected by comparing a difference between the two timestamps at which the messages were received against a threshold. To avoid accidental detection of clock drift, a difference in transmission delays between the two nodes is stored in a FIFO buffer. Each node monitors the average of the data in the FIFO buffer. If the average deviates from the target value by too great a value, then the node determines the values of the clocks have skewed beyond an acceptable range and generates a fault condition.