bUS

Option Communication Error

Yaskawa · V1000

What does bUS mean?

An error has occurred in the communication with an installed option card, such as a fieldbus communication card. This can stem from the drive not receiving a signal from the controller, incorrect or damaged communication cable wiring (short-circuited or disconnected), or significant electrical interference. An improperly installed or physically damaged option card can also trigger this fault, preventing the drive from responding to external commands.

Common Causes

  • Option card (e.g., fieldbus card) is improperly seated or loose in the drive's expansion slot.
  • Mismatched fieldbus communication parameters (e.g., A1-01 address, A1-02 baud rate) between card and network.
  • Damaged fieldbus communication cable, connectors, or improper termination.
  • Failure of the master controller to establish communication with the option card.
  • Faulty or incompatible option card hardware.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Power down the drive, then remove and reinsert the option card firmly into its expansion slot.

  2. 2

    Verify all option card communication parameters (e.g., A1-01 for Address, A1-02 for Baud Rate) match the fieldbus network settings.

  3. 3

    Inspect the fieldbus communication cable for physical damage, proper shielding, and correct termination at both ends.

  4. 4

    Use a fieldbus network analyzer to diagnose communication activity and identify polling failures.

  5. 5

    Test the drive with a known good, compatible option card (if available) to rule out hardware failure.

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Verified technical data. Last updated: March 2026

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