Cause : FBA B communication comes when cyclical communication between supply unit and fieldbus adapter module B or between PLC and fieldbus adapter module B is lost.

1. Check status of fieldbus communication. See user documentation of fieldbus interface.
2. Check settings of parameter group 150 FBA, 154 FBA B settings, 155 FBA B data in and 156 FBA B data out.
3. Check cable connections.
4. Check if communication master is able to communicate.