Failover; File Download/Upload Functions - Honeywell 900U02-0100 User And Installation Manual

9.5.

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.
Manual Failover

Via Key Switch on the Redundancy Switch Module in the Redundant Controller Rack. For
manual failover with keyed switch, turn key to Failover and hold it there until both Reserve
lights are on, then release the key.

Via Software Command from HC Designer & HC Utilities PC Software

Via Software Command from Modbus / TCP & Serial Modbus RTU Hosts

Via Software Command from 900 Control Station.

Via input to RSTAT Function Block to initiate failover (User can configure logical conditions
such as loss of communication handshake between Host and Controller to initiate failover).
Failover Performance
Failure condition detection and failover from Lead to Reserve CPU executed in 4 analog control cycles or
less.
Redundancy Diagnostic Monitoring

From HC Designer and HC Utilities PC Software
Redundant System Status - current status of Lead/Reserve Controller CPU's


On-Line Monitoring, Controller Diagnostics, Communications Loop-Back tests
Redundant Link Status – status of communications between Lead and Reserve controllers.


Lead CPU status

Reserve CPU status

Scanner status
9.6.

File Download/Upload Functions

See page 171.
Revision 10 ControlEdge HC900 Process & Safety Controller User and Installation Manual
May 2019
183