Rockwell Automation 1756-RMxx ControlLogix Enhanced Redundancy System User Manual - Manual (Page 82)

82 Rockwell Automation Publication 1756-UM535D-EN-P - November 2012
Chapter 4 Configure the EtherNet/IP Network
• If the primary controller is the Grandmaster, the enhanced redundancy
system automatically manages the CIP Sync clock attributes so that the
controller in the primary chassis is always set to be the Grandmaster
instead of the secondary controller. This clock management ensures a
change to a new Grandmaster when the redundancy system switches over.
• When a switchover occurs, these events take place:
– The Grandmaster status transfers from the original primary controller
to the new primary controller. This transfer can take longer to
complete than if Grandmaster status was transferred between devices
in a nonredundant system.
– After the switchover is complete, system synchronization can take
longer in an enhanced redundancy system, revision 19.052 or later, that
uses CIP technology than one that does not.
• If you attempt to use the Redundant System Update (RSU) feature to
update an enhanced redundancy system, revision 16.081 or earlier, that
uses Coordinated System Time (CST), the enhanced redundancy system,
revision 19.052 or later, does not permit a locked switchover and the
update fails to complete.
To work around this restriction, first disable CST Mastership in the
original redundancy system and then use RSU to update to enhanced
redundancy system, revision 19.052 or later.