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Siemens SINUMERIK Controller
Servo/Axis · Intermediate · 30-120 minutes
Siemens 840D 6540 - Too many directories in the NC memory
Alarm 6540 occurs when the NCK file system directory count exceeds the maximum limit defined by MD20110 (MaxDirectories). This is a file system constraint on the SINUMERIK 840D controller that prevents creation of new part programs, workpiece directories, or user-defined folder structures. The alarm typically fires during program creation, upload operations, or file system reorganization when directory allocation reaches saturation.
6540
Siemens 840D 6540 - Too many directories in the NC memory
Too many directories in the NC memory
Siemens SINUMERIK alarm 6540: Too many directories in the NC memory. This alarm indicates a fault or error condition on the SINUMERIK 840D control. Refer to the Siemens SINUMERIK alarm documentation for the complete description and remedy.
Root Cause Summary
Alarm 6540 occurs when the NCK file system directory count exceeds the maximum limit defined by MD20110 (MaxDirectories). This is a file system constraint on the SINUMERIK 840D controller that prevents creation of new part programs, workpiece directories, or user-defined folder structures. The alarm typically fires during program creation, upload operations, or file system reorganization when directory allocation reaches saturation.
Safety
- Refer to Siemens documentation
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Access the NCK file system via HMI menu: Diagnostics > Files > NC Memory. Count existing directories and compare against MD20110 value using menu path: Machine > Parameters > Machine Data > Search MD20110.
Do not modify MD20110 without consulting Siemens; increasing this parameter may destabilize memory allocation.
- 2
Identify and delete obsolete part program directories using HMI file manager. Consolidate related programs into single parent directories rather than maintaining multiple single-program folders.
Backup all programs before deletion; use SINUMERIK file backup utility (FXUP) to preserve program data.
- 3
Verify directory count has decreased below the MD20110 threshold by re-checking Diagnostics > Files > NC Memory. Attempt to create a new directory to confirm alarm no longer fires.
- 4
If alarm persists, perform NCK file system defragmentation via Service menu: System > Maintenance > File System > Optimize (if available on your firmware version).
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