27050

Check physical CAN connectors (X521/X522 on typical 840D control) and drive-side connectors for corrosion, loose pins, or bent contacts. Verify 120-ohm termination resistors are present at both CAN bus ends.

Power off control and drive before inspecting connectors to avoid short circuits.

In NCK Diagnostics menu (HMI > Diagnose > Drives > CAN Status), confirm CAN bus voltage is 4.75–5.25V and bus load is <80%. Monitor for CAN error frames or arbitration loss.

Verify SI communication parameters: check MD 30200 (SI telegram cycle time, typically 10 ms) and MD 32800+ axis-specific SI enable flags match the configured drive model. Confirm no SD/MD overrides disable SI on the affected axis.

If CAN appears healthy, perform a CAN cable swap or route the cable away from high-voltage motor leads (minimum 15 cm separation) to rule out EMI. Reboot the control and monitor for recurrence.

Access the drive parameter menu (via HMI Drives menu or ServiceTool), navigate to SI/Safety section, and compare the drive SI firmware version (typically shown as SI Module Ver. X.XX) against the NCK version (Diagnose > Version > SI Protocol). Both must match within minor revision levels.

In the drive's safety parameter set, verify that mandatory SI functions are enabled and checksummed correctly. Use Siemens DriveMonitor or the control's Data tab to read drive OD 6040.7 (Safety Control Word) and 6041.15 (Safety Status Word) to confirm the drive acknowledges SI mode active.

If firmware mismatch is confirmed, update the drive SI module firmware using the control's Maintenance > Drive Firmware menu or ServiceTool. Ensure the control and all axes are powered down during the update and allow 5+ minutes for EEPROM write completion.

Do not interrupt drive power during firmware update; this can corrupt SI EEPROM and require factory reset.

After firmware update, perform a full system boot cycle (power off for 30 seconds, power on, allow 60 seconds for SI handshake), then manually jog each affected axis to verify 27050 does not recur.

In NCK Diagnostics > Performance > Real-Time Monitor, check the SI task cycle time and max execution time. If max execution time regularly exceeds 80% of the configured SI cycle (e.g., 8 ms out of 10 ms), the system is overloaded. Note any task overruns or deadline misses logged in the event buffer.

Review PLC source code for blocking function calls or indefinite loops in the main cycle. Optimize high-frequency I/O operations and move complex calculations to background tasks. Use SIOS profiling tool or HMI cycle time display to identify bottlenecks.