CF

Continuous operation during communication fault

Mitsubishi Electric · Mitsubishi FR-E800 Variable Frequency Drive

What does CF mean?

This warning appears when the inverter continues to operate despite an error detected in the communication line or communication option, specifically when Pr.502 is set to '6'. It indicates an ongoing communication problem that, while not immediately stopping the inverter, requires attention.

Common Causes

  • Intermittent breaks or high noise levels on the communication line (e.g., RS-485, Ethernet).
  • Loose or improperly terminated communication cable at either the inverter or the master device.
  • Incorrect communication protocol settings (e.g., baud rate, parity, data bits) between inverter and master.
  • Electrical interference affecting communication signals, especially if power and control cables are routed together.
  • Faulty communication port on the inverter or the master control device.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Inspect communication cable shielding and grounding, ensuring proper termination resistors are installed (e.g., 120 Ohm for RS-485).

  2. 2

    Verify communication parameters (e.g., Pr.117 Baud rate, Pr.118 Communication format) match the master device settings.

  3. 3

    Measure signal integrity on the communication line using an oscilloscope to detect noise or signal loss.

  4. 4

    Temporarily disconnect other devices from the communication bus to isolate the fault to a specific segment or device.

  5. 5

    Check the communication cable for continuity and shorts using a multimeter (e.g., between pins 1 and 2 of RJ45 for Ethernet).

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Verified technical data. Last updated: March 2026

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Source: Mitsubishi FR-E800 Variable Frequency Drive