Rockwell Automation Technologies Incorporated

Steven T Seidlitz

Taryl Jon Jasper

Michael A Bush

Joseph P Izzo

Arun K Guru

Kevin E Colloton

Yanbin Zhang

Xiaobo Peng

Sikai Zhang

James Grosskreuz

David P Sullivan

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.

Diagnostic system and method for network synchronized time in safety applications

A circuit may include one or more first ports that may receive one or more input signals from a first device, such that the one or more first ports may couple to a control system. The control system may generate one or more output signals based on the one or more input signals. The circuit may also include one or more second ports that may couple to a second device, such that the one or more second ports may couple to the one or more first ports via a direct connection. The control system may also couple the one or more output signals to the one or more second ports.

Systems and methods for gating local control signals

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Eagle, WI, United States of America

Steven T Seidlitz