Resolving PLCSIM CPUcommon Firmware Version Error in TIA Portal

Problem Statement

The S7-PLCSIM runtime inside TIA Portal reports "CPUcommon has incompatible firmware version" (sometimes surfaced as "module CPUcommon has version of firmware no valid" or "error downloading to module CPUcommon") when the engineer attempts to download the hardware configuration to a software PLC. The download dialog halts before the configuration is committed, the project remains associated with the physical CPU in the project tree rather than the virtual S7-PLCSIM instance, and online blocks cannot be monitored or forced.

This fault appears in two common configurations:

• TIA Portal V13 SP1 (with optional Update 9) paired with S7-PLCSIM V13 SP1, simulating CPU 1511 firmware 1.7 or earlier.
• TIA Portal V15.1 Update 1 or later paired with PLCSIM Advanced V2.0, simulating CPU 1517 firmware 2.6.

The error is not a project corruption issue, license issue, or PG/PC interface misconfiguration. It is a binary compatibility mismatch between the firmware generation declared in the device configuration and the firmware image bundled inside the PLCSIM component installed on the engineering station.

Affected Software and Hardware Versions

Root Cause Analysis

PLCSIM does not emulate firmware dynamically. When it is installed, it loads a static image set that includes a CPUcommon device driver matching the firmware generation active at the time the PLCSIM installation media was built. The CPUcommon device is the host-side proxy that maps the configured S7-1500 (or S7-1200) CPU type into the simulation runtime.

When the project hardware configuration is downloaded, the TIA Portal download service queries the installed PLCSIM for its supported firmware generation. The check uses the firmware version encoded in the device description (GSD-equivalent STEP 7 internal metadata) of the configured CPU and compares it against the firmware generation PLCSIM advertises. If the configured CPU firmware is newer than what PLCSIM can host, the service returns the CPUcommon has incompatible firmware version diagnostic and refuses the download. The check is hard-fail by design: PLCSIM cannot run a firmware revision it does not contain, because the runtime expects specific system data block layouts, OB interface signatures, and instruction-set opcodes tied to each firmware generation.

Three structural reasons drive this in practice:

1. HSP drift. Hardware Support Packages installed in TIA Portal expose the latest CPU firmware catalog. If TIA Portal is updated before PLCSIM, the configuration editor lists CPUs (or firmware revisions) that PLCSIM does not yet recognize.
2. Major firmware jumps. Siemens occasionally re-baselines the CPUcommon device descriptor across firmware major versions (for example, V1.x to V2.x of CPU 1517). PLCSIM must be rebuilt to match each new major generation.
3. PLCSIM vs. PLCSIM Advanced divergence. PLCSIM Advanced is a separate installer and a separate runtime (now positioned as the long-term replacement for the legacy S7-PLCSIM in-process component). Compatibility tables do not cross between the two.

Diagnostic Procedure

1. Open the TIA Portal project and select the PLC device in the project tree.
2. Open Online → Accessible nodes and confirm that PLCSIM is reachable on the PG/PC interface configured for PLCSIM. If no node appears, the issue is not firmware compatibility but interface routing.
3. Right-click the PLC and choose Properties → General → Catalog Information. Record the exact CPU order number (for example, 6ES7511-1AK02-0AB0) and the configured firmware version (for example, V2.6.0).
4. Compare the configured firmware against the firmware list exposed by PLCSIM. In legacy S7-PLCSIM, click Start → Siemens Automation → S7-PLCSIM and inspect the version printed in the splash screen and the About dialog. In PLCSIM Advanced, start the PLCSIM Advanced Manager and read the build version.
5. Cross-reference both firmware values against the Siemens compatibility matrix. If the PLCSIM build predates the CPU firmware, the CPUcommon mismatch is confirmed.
6. Verify the exact error string by re-attempting the download with Online → Download to device. Capture the dialog text. The two relevant strings are "CPUcommon has incompatible firmware version" (PLCSIM Advanced lineage) and "module CPUcommon has version of firmware no valid" (legacy S7-PLCSIM V13 SP1 lineage).

Resolution Path A: TIA Portal V13 SP1 with Legacy S7-PLCSIM

This path applies when the project uses TIA Portal V13 SP1 and the engineer has selected an S7-1500 CPU whose firmware generation is newer than the PLCSIM V13 SP1 base image.

Step-by-step

1. Close TIA Portal and any running PLCSIM instance.
2. Download the cumulative update package for S7-PLCSIM V13 SP1 from the Siemens Support entry 109477180 - Updates for S7-PLCSIM V13 SP1. The package is delivered as a self-extracting HSP/Setup bundle.
3. Run the installer with administrator privileges. Confirm the installation path matches the TIA Portal V13 SP1 installation directory (default C:\Program Files\Siemens\Automation\Portal V13\).
4. After installation, restart Windows to release any locked PLCSIM services.
5. Reopen the project in TIA Portal. In the device configuration, open the CPU properties and confirm that the firmware version dropdown now offers the value you need, or that the previously configured firmware is now accepted.
6. Start PLCSIM and attempt the download again.

Resolution Path B: TIA Portal V15.1 with PLCSIM Advanced

This path applies when the project uses TIA Portal V15.1 (or later) and the CPU firmware is V2.x. Legacy S7-PLCSIM V15 cannot host V2.x firmware; PLCSIM Advanced is required.

Step-by-step

1. Close TIA Portal and the PLCSIM Advanced Manager.
2. Download PLCSIM Advanced V2.0 SP1 from the Siemens Support entry 109758848 - PLCSIM Advanced V2.0 SP1.
3. Run the installer. PLCSIM Advanced V2.0 SP1 supersedes the V2.0 baseline and adds firmware V2.6 CPUcommon support for CPU 1517 (and the V2.6 family of CPU 1511/1513/1515/1516 where applicable).
4. After installation, open the PLCSIM Advanced Manager and verify that the version banner reports V2.0 SP1 (build ≥ the SP1 release).
5. Start a new PLCSIM Advanced instance, select the CPU type matching your configuration (for example, CPU 1517-3 PN/DP), and note the IP address assigned to the virtual PLC.
6. Return to TIA Portal. In the project tree, right-click the PLC and choose Properties → PROFINET interface → Ethernet addresses. Set the PLC IP address to match the PLCSIM Advanced instance, or use the Find PROFINET devices browse function.
7. Select the PLCSIM TCP/IP interface as the PG/PC access point and execute Download to device.

Resolution Flow Diagram

Firmware-to-PLCSIM Compatibility Reference

Verification Procedure

1. Open the project in TIA Portal after applying the PLCSIM update.
2. Start the PLCSIM instance (either legacy S7-PLCSIM from the Start menu or PLCSIM Advanced Manager).
3. Right-click the PLC device in the project tree and select Download to device → All.
4. Confirm that the download completes without the CPUcommon error and that the progress dialog reaches 100%.
5. Click Go online. Verify that the online view shows the configured firmware version in the diagnostic buffer and that the operating mode indicator reports RUN (or STOP if the user program is intentionally stopped).
6. Open a monitoring view on a known tag (for example, "DB_Sim".Tag_Heartbeat) and confirm the value updates. If monitoring returns "not available online", the CPUcommon handshake succeeded but program blocks failed to load; check the download log for block-level errors separately.
7. Force a tag value from the watch table and observe the response in PLCSIM to confirm bidirectional online communication.

Edge Cases and Field Caveats

• Multiple TIA Portal versions co-installed. If TIA Portal V13 SP1 and V15.1 are co-installed, each maintains its own PLCSIM integration. Updating one does not update the other. Verify the update inside each TIA Portal installation directory.
• PLCSIM Advanced license not activated. PLCSIM Advanced requires a valid license (trial or purchased). A missing license produces a different error ("no valid license"), but engineers sometimes mistake it for a firmware mismatch because the runtime refuses to start. Confirm the license state in the PLCSIM Advanced Manager before chasing firmware updates.
• HSP-only CPU types. Some CPUs are added to TIA Portal exclusively through Hardware Support Packages. If the project CPU order number appears in the hardware catalog but the configured firmware is newer than what the installed HSP supports, PLCSIM will also reject the configuration. Re-install or refresh the HSP.
• Windows real-time clock skew. PLCSIM Advanced timestamps its CPUcommon handshake against the host clock. Severe clock drift (more than a few minutes) can produce spurious handshake failures on some builds. Synchronize the host time before declaring a true firmware mismatch.
• Antivirus interference. Some endpoint protection products quarantine PLCSIM helper services. After updating PLCSIM, whitelist the Siemens\PLCSIM Advanced and S7-PLCSIM directories to avoid DLL loading failures that mimic firmware errors.
• Download to PLCSIM via S7 routing. If the project is configured for routed download through a non-existent intermediate CPU, the download service can present the CPUcommon error even though the actual fault is the route. Confirm that the PG/PC interface points directly to the PLCSIM virtual adapter.

Preventive Maintenance Checklist

1. Track the TIA Portal version, PLCSIM/PLCSIM Advanced version, and CPU firmware version as a single triplet in the project documentation. Drift between any two members triggers this fault class.
2. When commissioning a new firmware revision on a production fleet, upgrade the engineering station's PLCSIM first and validate the download before touching hardware.
3. Subscribe to the Siemens Product Information (PI) feed for the PLCSIM component used. The cumulative update for legacy S7-PLCSIM and the SP/HF updates for PLCSIM Advanced are not auto-installed.
4. Maintain a clean engineering image with TIA Portal, PLCSIM, and PLCSIM Advanced at the same released-month revision. Avoid mixing a recent PLCSIM Advanced with an old TIA Portal or vice versa.
5. For virtual commissioning teams, document the exact PLCSIM build string (for example, PLCSIM Advanced V2.0 SP1 HF3) in the simulation environment definition. This eliminates the common confusion between V2.0 and V2.0 SP1.

Related Diagnostic Strings

FAQ