What causes a CNF or field bus communication interrupt fault on the ATV630 and ATV930 process drives?

Issue:
Why I got a CNF or field bus communication interrupt fault on the ATV630 and ATV930 process drives?

Product Line:
Altivar ATV630 and ATV930

Environment:
All

Cause:
Communication network fault.

Resolution:

CnF

[Fieldbus Com Interrupt]

Fieldbus communication interrupt Principle This fault appears when the Modbus communication between the option card and the master (PLC) is interrupted. Probable causes • Communication fault between the option card and the master (protocol interrupted). Remedies • Check the environment (electromagnetic compatibility). • Check the wiring. • Choose menu "Diagnostics" for more information about the fault.

When a drive is being controlled over a network, there must be frequent communication between the controller and the drive to ensure safe operation.
The timeout for modbus communication is set by parameter tto [Modbus Timeout] which is found in the Communication menu under the Modbus Fieldbus sub menu.
If you are using a different communication network be sure to review the instructions for that network for details on Timeout.

To resolve, verify the controller is performing a Read or Write request within the timeout period.
Review wiring for proper connections, terminating resistors, shielding as detailed in the instructions for the network being used.
Verify proper grounding of the VFD and cable routing of control, communication and power to reduce electrical noise.

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