A7C1 warning in ABB DCS880 drive indicates FBA A communication error. This means Cyclical communication between PLC and fieldbus adapter module A or between drive and fieldbus adapter module A is lost.

1. Check the status of the fieldbus communication.
2. Check the settings of groups 50 Fieldbus adapter (FBA), 51 FBA A settings, 52 FBA A data in and 53 FBA A data out.
3. Check the cable connections. The fieldbus termination.
4. Check the fieldbus adapter.
5. Check that the master is able to communicate.