4250

Access PLC project in STEP 7 and verify FastPlcCom communication blocks are instantiated. Check that FB 'FastPlcCom' or equivalent communication function blocks are present in the PLC program and properly declared in the interface.

Do not modify PLC code without backing up the original project first.

Verify OB40 (Cyclic Interrupt) is configured and assigned to a 5ms or 10ms cycle time. OB40 must execute synchronously with NCK cycle. Navigate to PLC Hardware Configuration > Interrupt Handling > OB40 and confirm cycle time aligns with NCK cycle (typically found in MD1900 - NCK cycle time).

Recompile and download the PLC project to the controller. Verify that compilation shows no errors in the FastPlcCom interface. Power cycle the machine controller after download.

Ensure machine is in safe state before power cycle; coordinate with production.

Check PLC startup diagnostics via SIMATIC Automation Tool or TIA Portal online view. Confirm that FastPlcCom handshake completes during PLC startup (search system messages for 'FastPlcCom' acknowledgment).

Access Siemens SINUMERIK HMI (Operate > Diagnostics > System Information) and document current NCK software version, PLC firmware version, and SINUMERIK OS version. Compare against machine documentation or contact Siemens for compatibility matrix.

Check Machine Data parameter related to PLC communication: Navigate to HMI > Diagnostics > Parameters > Machine Data and search for 'FastPlc' or 'PLC' communication flags (commonly in MD range 3000-3500 for communication settings). Verify that MD entries requesting FastPlcCom are not conflicting with PLC capabilities.

Do not modify MD parameters without understanding their function; refer to SINUMERIK parameter documentation.

Verify that PLC project was compiled against compatible SINUMERIK/Simatic libraries. In STEP 7/TIA Portal, check project properties for target firmware version match. Recompile with matching SINUMERIK communication library versions if mismatch is found.

If version mismatch confirmed, contact Siemens Field Service to arrange firmware alignment. Typically requires coordinated update of NCK and PLC software to compatible release levels.

Firmware updates must follow Siemens change management procedures; do not attempt ad-hoc updates.

Monitor PLC startup sequence using Simatic Automation Tool or TIA Portal online diagnostics. Enable extended logging and observe PLC CPU LED states (green=ready, blinking=running, red=error). Document any error indicators or aborted OB blocks during startup.

Do not interrupt PLC startup sequence during troubleshooting; allow complete boot cycle to completion.

Check PLC CPU memory utilization and runtime behavior: Access PLC Diagnostics > CPU > Memory and verify available memory is >20% free. Review PLC cycle time in OB1 and OB40; if cycle time is excessive (>100ms for OB40), reduce program complexity or optimize code.