Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 122)

Publication 1756-UM528A-EN-P - April 2004
B-4 Integrating The HiProm GPS Module (1756HP-GPS) into a ControlLogix Sequence of Events Module System
Determining the Absolute
First Fault Across Multiple
Chassis For simplicity’s sake, Figure B.2 shows a system that determines the
absolute first fault of devices connected to a single Sequence of Events
module in a local chassis. However, the greatest benefit of using the
1756HP-GPS module comes when you need to determine the absolute
first fault among devices connected to multiple Sequence of Events
modules in remotely located chassis.
To determine absolute first fault among devices connected to multiple
Sequence of Events modules in remotely located chassis, you must
first synchronize the chassis; in other words, you must make sure all
the Sequence of Events modules are working from the same time
reference, the CSTs in their respective chassis.
You can synchronize CSTs among multiple ControlLogix chassis via
the ControlLogix SynchLink module. This method can only be used if
the chassis are located in close enough proximity to physically
connect the chassis via SynchLink fiber.
For more information on using SynchLink to synchronize multiple
ControlLogix chassis, see Appendix C.
The 1756HP-GPS modules in each system receive a common time
from the satellite that can be correlated to CST-format timestamps
produced in each system to report an absolute time reference for both
systems, effectively synchronizing the chassis.
The 1756HP-GPS module only allows conversion for 1 hour;
conversions to UCT should be done shortly after the event is received.