27095

Power-cycle the control completely (OFF for 30 seconds minimum) to force a full NCK/PLC synchronization cycle. Monitor the startup sequence in Diagnostics > System Information > Startup Log for any failed data comparison messages.

Ensure no NC program is running and all axes are in a safe position before power cycle.

Check MD 28000 (Safety Function Enabled) and MD 28010 (SPL Protection Active) in Parameters > Machine Data > Safety section. Verify both are set to TRUE (1). If MD 28000 = 0, SPL will not activate.

Validate PLC cycle time in PLC > Cycle Time under Diagnostics menu. Ensure cycle time is ≤12ms (typical safe default is 8ms). If PLC cycle time is too long, the NCK timeout for data validation will expire before synchronization completes.

Review the SPL firmware version against the NCK version in Diagnostics > Version Information. Request SPL firmware update from Siemens if versions are mismatched, as this causes synchronization checksum failures.

Access Diagnostics > Memory Check and run the Safety Memory Validation test. This performs CRC checks on all safety-critical parameter blocks. Document any failed memory regions reported.

In Siemens SINUMERIK PCU/CCU, access Maintenance > Safety Configuration Backup. Restore the last known-good backup or reload the factory default SPL safety configuration using the system recovery disk.

Restoring defaults will reset all custom safety parameters. Contact your machine builder before proceeding.

If no backup exists, access Service > Reset SPL and select 'Factory Reset for Safety Functions'. This clears corrupted safety memory and re-initializes SPL to default state. Requires service-level authentication.

Factory reset will disable all custom safety interlocks. Rebuild safety configuration afterward.

Re-verify SPL activation by power-cycling and observing Diagnostics > Safety Status. Confirm 'SPL Protection Active' displays TRUE and alarm 27095 does not recur within 5 startup cycles.

Verify SPL license status in Diagnostics > Licenses. Check for 'SINUMERIK Safety' or 'SPL Option' license. If status shows 'Expired' or 'Not Found', request license re-activation or hardware key replacement from Siemens.

In PLC editor (Siemens TIA Portal or STEP7), compile the safety program (Build > Compile Safety Code) and verify no errors in the safety function blocks (FB100+). Correct any syntax errors in Stop commands (MC_Stop, SafeStop2) and emergency stop logic.

Do not deploy untested PLC safety code to production; validate in simulation environment first.

Check that all PLC safety instance data blocks (DB100+) are properly initialized with valid values. In the PLC symbol table, verify that emergency stop status variables and safety flags have non-zero initialization.

Download the corrected PLC program and safety function blocks to the control. Power-cycle the 840D and confirm alarm 27095 clears during startup and 'SPL Protection Active' status is TRUE in Diagnostics.