Code 28010: NCU link: the NCU %1 has not received a message
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical NCU link: the NCU %1 has not received a message alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Parameters: %1 = NCU number Definitions: Error message of the NCU link module. During operation of the NCU link, a message from the local NCU to the NCU specified in the alarm parameter has failed. A hardware error may have occurred (e.g. sporadic disturbances on the communication line). Reaction: NC not ready. Channel not ready. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm. Remedy: The message does not fail until several attempts have been made to repeat the communication. The number of repetitions can be increased with MD12550 $MN_LINK_RETRY_CTR. Diagnostics Manual (DAsl), 03/2009 Program Continuation: Switch control OFF - ON.
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 28010 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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