Code 4270: Machine data %1 assigns not activated NCK input/output byte %2
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical Machine data %1 assigns not activated NCK input/output byte %2 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 = String: MD identifier %2 = Index Definitions: The specified machine data assigns a digital input/output byte or an analog input/output signal the processing of which has not been activated to an NC function. Reaction: NC not ready. Channel not ready. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm. Remedy: Please inform the authorized personnel/service department. Correct machine data. Activate required inputs/outputs via MDs: MD10350 $MN_FASTIO_DIG_NUM_INPUTS MD10360 $MN_FASTIO_DIG_NUM_OUTPUTS MD10300 $MN_FASTIO_ANA_NUM_INPUTS MD10310 $MN_FASTIO_ANA_NUM_OUTPUTS Activation of fast inputs/outputs does not require the corresponding hardware configuration to be available at the control. All functions using fast inputs/outputs can also be made use of by the PLC specification/modification defined in the VDI interfac e, if the response time requirements are reduced accordingly. Activated inputs/outputs increase the computation time requirement of the interpolation cycle because the PLC manipulation signals are handl ed cyclically. Note: Deactivate any inputs/outputs not in use. 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 4270 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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