182 ControlEdge HC900 Process & Safety Controller User and Installation Manual Revision 10
May 2019
Lead/Reserve controller synchronization
Lead Controller automatically synchronizes the Reserve with the configuration database
During download of a configuration from a Host to the Lead
During process operation to bring a Reserve Controller from the Unavailable state to the On-
Line state
Lead Controller automatically synchronizes the Reserve with run-time data during each
function block execution cycle
Both the Lead and Reserve Controllers execute the function blocks in the control strategy, but
only the Lead Controller writes the physical outputs to the I/O Racks. See Figure 100.
The Lead and Reserve controllers exchange system status to determine conditions for failover.
Figure 100 – Lead/Controller synchronization