Serial Link Failure

What does -SLF mean?

This fault occurs when communication is lost between the drive controller and its connected serial devices, such as a remote keypad display or a MODBUS master controller. This prevents external control, monitoring, or parameter adjustment of the drive, interrupting automated processes. The cause could be physical disconnection, incorrect settings, or device malfunction.

• Broken, loose, or improperly terminated communication cable (e.g., RS-485 A/B wires, Ethernet cable) between the drive and master device.
• Incorrect communication parameters (e.g., baud rate P6-01, parity P6-02, drive address P6-03) configured in the drive or the master controller.
• Excessive electrical noise or electromagnetic interference (EMI) disrupting the communication signal integrity.
• Faulty communication module or port on either the drive or the master device (e.g., PLC, HMI).
• Device address conflict on the communication bus, where multiple devices respond to the same address.

Click steps to track your progress.

1. 1

   Verify physical communication cable integrity (e.g., check for cuts, bends) and ensure all connectors are securely seated.

2. 2

   Confirm all communication parameters (e.g., P6-01 baud rate, P6-02 parity, P6-03 drive address) match the master device settings precisely.

3. 3

   Check for proper termination resistors (e.g., 120 Ohm for RS-485) at both physical ends of the communication bus.

4. 4

   Measure communication signal levels (e.g., using an oscilloscope for RS-485) to detect noise or signal degradation.

5. 5

   Temporarily disconnect other devices from the communication bus to isolate potential address conflicts or faulty devices.