8023

Access the NCK/PLC memory configuration via HMI menu: Maintenance > System Information > Memory or use SINUMERIK service menu to view current PLC user memory allocation vs. configured option limit.

Do not proceed without noting the exact memory values displayed.

Check the OEM machine data parameter controlling PLC memory licensing (typically MD 18004 or equivalent in your control version). Cross-reference the current setting against the SINUMERIK 840D technical data sheet for available memory options (e.g., 32 KB, 64 KB, 128 KB, 256 KB).

Review the actual PLC program size by accessing Diagnostics > PLC > Memory Usage in the control. Compare reported user memory consumption to the MD parameter setting; the alarm fires when actual usage exceeds the configured option.

Memory usage may include symbol table and temporary storage; request the PLC programmer provide exact segment sizes.

Update the memory option MD parameter to a higher tier (e.g., from 128 KB to 256 KB option) and perform a cold restart (Ctrl+Alt+Del or warm reset via diagnostics). Verify alarm 8023 clears on startup.

Changing memory options may require license key update or OEM authorization; contact Siemens if licensed memory cannot be increased.

Obtain the current PLC project from the machine builder or backup source. Open in STEP 7 or TIA Portal and check project properties > Compile > Code/Data Size to determine actual memory footprint required.

Ensure you are viewing the compiled size, not the source code size.

Cross-reference the compiled PLC memory requirement against the current memory option setting in the control's Machine Data (typically viewed via Parameter Editor in Diagnostics menu). If actual size exceeds option, the alarm is correctly identifying the over-allocation.

Coordinate with OEM technical support or machine builder to issue updated Machine Data with a larger memory option parameter value corresponding to a higher licensed tier (e.g., 64 KB to 128 KB).

Some OEM licenses lock memory options; verify licensing allows the requested increase before updating MD parameters.

Apply the updated MD parameter set, save, and restart the control. Verify the PLC program downloads successfully and alarm 8023 does not recur during startup diagnostics.

Access Diagnostics > Parameters in the control HMI. Navigate to the Memory Configuration section and document all MD parameters in the 18000–18030 range. Check for any values marked as invalid, uninitialized (zero), or flagged with a warning symbol.

Do not modify parameters until root cause is confirmed.

Compare the documented MD parameter values against the OEM machine data backup file (.mcp or .mdf format). Load the backup file into SINUMERIK Parameter Editor and verify expected memory option values match the running system.

If backup is also suspect, obtain reference data from OEM technical documentation or contact Siemens field service.

If mismatch detected, perform a parameter restore using the validated backup (Maintenance > Backup/Restore > Restore Parameters), or manually update the Memory Configuration MD parameters to factory OEM settings via Parameter Editor.

Ensure backup source is trusted and documented before restoring; an incorrect backup will perpetuate the issue.