By default, when the Series 90 TCP/IP Redundant Communications enabler loses its connection to the master PLC of a redundant pair and the slave PLC fails to set its Master bit, the enabler declares a $DEVICE_DOWN alarm for the redundant device and marks all its points as "Unavailable" until one of the PLCs declares itself the master.

You can use a global parameter to change this behavior so that when the master PLC of a redundant pair fails, the enabler automatically starts collecting data from the slave PLC, without waiting for it to set its Master bit.

To enable this option, add the following to the global parameter file: