Serial Link Failure

What does SLF mean?

This fault signifies an issue with the serial communication link to the drive controller, such as an incorrect connection or a break in communication. This prevents the drive from receiving commands or sending status information via the serial interface.

• Incorrect wiring (e.g., swapped A/B lines, missing common) on the serial communication bus (e.g., RS-485).
• Broken or damaged communication cable (e.g., cut wire, crushed cable).
• Missing or incorrect termination resistors (e.g., 120Ω for RS-485) at the ends of the communication bus.
• Communication parameters (e.g., baud rate, parity, data bits, station ID - P4-01 to P4-04) mismatched between drive and master.
• Excessive electrical noise on the communication bus due to unshielded cables or improper grounding.

Click steps to track your progress.

1. 1

   1. Verify serial cable connections at the drive (e.g., DA+, DB-, SG terminals) match the master device and are secure.

2. 2

   2. Check resistance across A and B terminals at both ends of the RS-485 bus (power off); it should be ~60Ω if two 120Ω termination resistors are present.

3. 3

   3. Confirm all communication parameters (e.g., P4-01 Baud rate, P4-02 Parity, P4-03 Data format, P4-04 Drive ID) match between the drive and the master controller.

4. 4

   4. Inspect the communication cable for physical damage, continuity, and proper shielding connected at one end to chassis ground.

5. 5

   5. Use a communication analyzer or oscilloscope to monitor signal integrity on the serial lines if possible.