
Revision 6
HC900 Process & Safety Controller User and Installation Manual
169
21 April 2017
Figure 88
– Lead/Controller synchronization
Failover
Automatic Failover
Triggered on any of the following conditions of the Lead Controller:
Loss of communications with I/O Rack(s)
Processor exception conditions
Error conditions that occur in the following areas will not cause a failover:
Loss of communications to a Host on a network
Loss of communications to Modbus Slave devices
Loss of communications to Operator Interface
Loss of communications with a Peer controller
During the transition from the Lead to the Reserve, analog and digital output status is maintained at the
I/O racks.
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