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Siemens SINUMERIK Controller
Parameter · Intermediate · 30-120 minutes
Siemens 4275 - Machine data and both assign the same NCK output byte no. several times
Alarm 4275 fires when two different NC functions are configured in machine data to control the same NCK output byte, creating a resource conflict. This occurs during machine data initialization when the SINUMERIK 840D system detects duplicate output assignments that would cause undefined control behavior.
4275
Siemens 4275 - Machine data and both assign the same NCK output byte no. several times
Machine data and both assign the same NCK output byte no. several times
The specified machine data assign two NC functions to the same digital/analog output Control reaction: NC not ready. Channel not ready. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm.
Root Cause Summary
Alarm 4275 fires when two different NC functions are configured in machine data to control the same NCK output byte, creating a resource conflict. This occurs during machine data initialization when the SINUMERIK 840D system detects duplicate output assignments that would cause undefined control behavior.
Safety
- Only qualified personnel should diagnose and clear control alarms; follow the machine builder's safety procedures and lockout/tagout where hardware work is required.
Causes and Fixes
- 1
Access Diagnostics > Machine Data menu. Locate the two MD parameters listed in alarm message (%1 and %2). Document their current byte assignments by viewing MD-Number and MD-Byte-Offset values.
- 2
Cross-reference the NCK output byte number (%3) against your system's I/O mapping documentation. Verify which two NC functions (e.g., spindle.enable, coolant.mist) both reference this byte.
Do not modify MD values while cycle is active; use offline mode only.
- 3
Reassign one conflicting function to an available, unused NCK output byte. Update the corresponding MD parameter's byte offset value and validate the new byte is not in use by other MDs via machine data list view.
- 4
Save machine data changes (Ctrl+S in Diagnostics), perform warm restart of NCK, and verify alarm clears during startup. Run a test program to confirm both functions operate independently.
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