Switchover Conditions

The 1747-BSN module transfers control from the primary to the secondary

processor (switchover) if one of the following fault conditions occurs in the

primary system:

• power failure

• major fault in the processor

• 1747-BSN module fault

• primary processor mode change from Run to Program

Note: In order for switchover to occur, both primary and

secondary modules must be working without faults prior

to the event that triggers the switchover.

Configuration Errors

The module reports the following configuration errors by flashing the fault LED:

• two 1747-BSN modules are configured with the same address

• LSL addresses are not consecutive (addresses must be numbered 0, 1, 2,etc.)

• last LSL switch is not set in the last module in the link

• last LSL switch is set in a module that is not the last in the link, or

• primary and secondary modules do not have the same configuration settings

(secondary module shows the configuration error)