When the enabler detects the following conditions, the following actions are taken:

Communication failure to the current slave Series 90

The enabler generates an alarm and continues to communicate with the current master Series 90 PLC.

The enabler then retries communications to the slave Series 90 PLC at the configured retry rate.

Communication failure to the current master Series 90

The enabler generates an alarm then performs a failover to the slave Series 90 PLC after ensuring the "mode" of the slave is changed to master. The slave Series 90 PLC is now the new master.

The enabler then retries communications to the new slave Series 90 PLC at the configured retry rate.

Failover or failback is detected

The enabler generates an alarm and begins communicating to the current, active master Series 90.

The enabler retries communications to the failed PLC at the configured retry rate.

Mode bits indicate no current master

The enabler generates an alarm and no further communication takes place to either PLC in the redundant pair.

The enabler continues to monitor the mode bits at the configured heartbeat timer interval.

You can override this default behavior with the GMR_NO_MASTER global parameter.

Mode bits indicate multiple masters

The enabler generates an alarm, marks the configured secondary Series 90 as "down", and communicates only with the configured primary Series 90.

The enabler continues to monitor the mode bits at the configured heartbeat timer interval.

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