Troubleshooting and Solutions for Input Data Refresh Issues in EtherCAT Bus Network Devices

When configuring communication for Solidot’s EtherCAT branch devices using TwinCAT software, the following issue occurred during the setup of the XB6S-EC2002 coupler with servo drives: all devices were in normal OP (Operation) state, but input data was not refreshing. The coupler’s input signals failed to upload to the PLC, while output signals remained functional. Below are the troubleshooting steps and solutions:

1. Check Device Wiring

Conduct a thorough inspection of the terminal connections. If the channel-side indicator lights are on, the physical signal input path is intact. If all signals in the Input data area remain "0" with no channel status changes, proceed to the next step.

2. Verify Coupler Operational State

If the coupler is in SafeOP or other abnormal states, it may allow output control but block input data reading. Use TwinCAT’s state machine to toggle the coupler’s communication state and observe its communication indicators. If the coupler responds normally to state changes and indicators show proper status, rule out coupler failure and proceed.

3. Test Coupler Hardware Integrity

After confirming wiring and communication are normal, isolate the coupler from the EtherCAT topology and test it independently in a controlled environment. If input data uploads correctly during testing, the coupler is functionally intact, eliminating hardware issues. Proceed to the next step.

4. Isolate Faulty Slave Devices

Given that all input signals fail to refresh while outputs remain functional, the issue likely resides in the EtherCAT bus input chain. Test input data reading from connected slave devices (e.g., servo drives). If input data remains unrefreshed across the entire system, confirm the problem lies at the bus input data flow level.

With the coupler confirmed functional, use segment isolation to test other slave devices. Disconnect all slaves except the XB6S-EC2002 coupler and observe bus communication. Eventually, disconnecting a specific slave restores input data refresh. Further inspection reveals that this slave caused the input signal interruption.

5. Solution Summary

In EtherCAT networks, abnormal slaves (e.g., topology misconfiguration or device errors) can disrupt bus data transmission, blocking input refresh. Even if slaves are in OP state, faults in other slaves may destabilize the network. Errors like ERRINIT in any slave can interfere with PDO data upload, affecting system stability. Therefore, strengthen slave status monitoring and fault isolation to ensure network reliability.

This concludes the troubleshooting and solutions for input data refresh issues in EtherCAT bus networks. Thank you for your attention!