SIMOTION C240 MMC License Assignment Error: Hardware Fix

Problem Summary

A SIMOTION C240 controller (MLFB 6AU1240-1AA00-0AA0, hardware release D per the type plate marking A5E00346777 VERSION D) returns the message "license cannot be assigned and or has been assigned already" when the engineer attempts either of the following actions in SIMOTION SCOUT:

1. Pressing the Accept button after SCOUT has discovered the C240 on Ethernet (the Accept control remains grayed out / inactive).
2. Registering the runtime license key from the CoA (Certificate of License) paper against the controller's MMC serial number on the Siemens web license portal.

Concurrent symptoms include a steady-blinking SF (System Fault) LED on the C240 after the MMC has been inserted and the controller booted. The BF (Bus Fault) LED behavior, RUN/STOP states, and the 7-segment display code provide additional diagnostic data that must be captured before the controller is reset.

Affected Hardware Identification

Before applying any firmware work, capture and verify the type plate data on every C240 in scope. The hardware release letter is the single most important value for compatibility.

The hardware release letter (A, B, C, ... G, H, ...) is printed after "VERSION" on the type plate. It is not the same as the firmware version, the Scout version, or the MMC card's software version. Mixing these three version axes is the most common cause of "the controller should work but it doesn't" incidents on the SIMOTION C platform.

Root Cause: Hardware/Firmware Version Mismatch

SIMOTION controllers enforce a one-way compatibility rule between the controller hardware release and the SIMOTION runtime firmware loaded onto the MMC. From SIMOTION runtime V4.5 onward, the C240 platform requires a controller with hardware release G or higher. Controllers with hardware releases A through F cannot boot a V4.5 or V5.x runtime; the bootloader rejects the firmware image, the SF LED starts to blink, and the license key on the MMC is reported as "already assigned" because the runtime that owns the license never came up to validate it.

The reported controller has hardware release D. The MMC ships with V5.4 SP3 firmware. The combination is therefore incompatible at the bootloader level, and no amount of project re-creation, license re-registration, or Scout reinstallation will resolve it. The fix is to match the runtime firmware to the hardware release, not to upgrade the hardware.

SIMOTION C240 Hardware/Firmware Compatibility Matrix

The matrix below summarizes the compatibility boundaries relevant to C240 hardware releases A through H. The authoritative list is the SIMOTION Compatibility List at the Siemens support page cited below.

Source: SIMOTION Compatibility List (Entry ID 18857317), page 9 of 45 (controller/hardware compatibility table) and page 39 of 45 (MMC compatibility table).

Required Firmware Selection

For a C240 with hardware release D, the supported SIMOTION runtime is the V4.4 line. The recommended hot-fix level is V4.4 HF11, which carries all released defect corrections for the V4.4 line and is the version Siemens continued to validate against late-life C240 hardware. The runtime files are distributed as a single .zip archive containing the MMC image (SIMOTION_C240.bin or equivalent) plus the SCOUT add-on.

Download the V4.4 HF11 image from the official Siemens support entry:

• SIMOTION SCOUT V4.4 HF11 firmware download (Entry ID 31263919)

MMC Card Verification Before Re-flashing

Before writing a new firmware image to the MMC, confirm the card itself is healthy. The MMC carries the runtime, the technology packages, the user program, and the runtime license. A failing MMC will produce symptoms that look like a firmware mismatch.

Step-by-Step Recovery Procedure

The procedure restores the C240 to a bootable state with the firmware the hardware can actually run. Total time on a single controller is typically 20 to 35 minutes, dominated by the MMC write operation and the firmware download.

Step 1 - Capture project archive (if controller still partially responsive)

1. Power the C240 and insert the MMC with V5.4 SP3 firmware.
2. Connect the engineering PC to the C240's RJ45 (X127) port.
3. In SCOUT, open Project > Accessible nodes. The C240 should appear with its IP address and the system fault banner.
4. If the controller is still online enough to read the project, perform Project > Save project archive before any further action.

Step 2 - Power down and remove the MMC

1. Switch off the 24 V supply to the C240. Wait at least 10 s for the internal capacitors to discharge.
2. Press the MMC ejector to release the card. Do not use tools.

Step 3 - Write V4.4 HF11 to the MMC

1. Insert the MMC in the PC's SD/MMC card reader.
2. Back up any user files (USER/, project archives, recipes) to a separate folder on the PC. The next step will erase the card.
3. Unzip the V4.4 HF11 firmware archive downloaded from Entry ID 31263919.
4. Run the included write tool (SIMOTION_MMC_Writer.exe or the Scout-integrated Write MMC image action). Select the correct drive letter for the MMC and the V4.4 HF11 image.
5. Wait for the write to complete and verify the tool's success message. Do not interrupt the write.

Step 4 - Restore the license key

1. Open the MMC partition in Windows Explorer. The new image contains a KEYS.TXT with placeholder lines.
2. Edit KEYS.TXT (use Notepad in administrator mode if Windows protects the file) and replace the placeholder with the license key from the CoA paper. Save.
3. Eject the MMC safely through the operating system.

Step 5 - Re-insert and power up

1. Insert the MMC into the C240 with the controller powered off.
2. Apply 24 V. Observe the LED sequence.
3. The expected sequence: SF LED on briefly, then a 5 to 15 s period where the bootloader decompresses the runtime, then a slow regular blink from the SF LED for ~30 s during the initial project load, then SF off, RUN green.

Step 6 - Recreate the SCOUT project

1. In SCOUT V5.4, create a new project. Select controller type SIMOTION C240.
2. Set the Ethernet address of the new project to match the C240's X127 address range. The C240 default is 169.254.11.22; the engineering PC must be on the same subnet (commonly 169.254.x.y / 16 or a static IP such as 192.168.0.1 / 24 with the C240 set to 192.168.0.2).
3. Use Project > Download to target with the option Download project to target with reset (PO without reset is acceptable once the project matches the target configuration).
4. Wait for the download to complete. SCOUT will report Target state: RUN.

Ethernet Addressing Constraints

SCOUT will refuse the "Accept" action when the controller's configured IP and the engineering PC's IP are not on the same subnet or when a firewall blocks UDP broadcast on the SIMOTION discovery ports. The two most common discovery failure modes and their fixes:

Verification

After completing Step 6, confirm the controller is fully operational:

1. LED state: SF off, BF off, RUN solid green. The 7-segment display shows 8 (boot OK) momentarily then - or a node number.
2. Scout diagnostics: Target system > Diagnostics > Version overview shows runtime V4.4.0.x (HF11 build number).
3. License status: Target system > Licenses shows the CoA license key as valid and assigned to the C240 with the correct MMC serial number.
4. Project round-trip: Project > Save project archive and Project > Read from target both complete without errors.
5. Runtime test: Set a test output, toggle from SCOUT, observe the C240's digital output hardware indicator LED.

Troubleshooting Matrix

Field-Proven Cautions

• Never power-cycle the C240 during the initial 30-second MMC boot sequence. Removing power mid-decompress can corrupt the MMC and produce a secondary failure mode that masks the original "already assigned" message.
• Do not attempt to flash firmware V4.5 or V5.x onto a hardware-release D C240, even "just to test." The bootloader will reject the image, but the failed flash can leave the MMC in a state that requires re-imaging on a PC.
• Always back up the user project, recipes, and the USER/ directory from the MMC before re-imaging. Re-imaging overwrites everything except the bootloader partition.
• License keys are MMC-bound, not controller-bound. Moving an MMC to a different C240 transfers the license to that controller's serial number; the web portal must be updated to match.
• SCOUT cross-mode: SCOUT V5.4 can manage V4.4 targets, but the reverse is not true - SCOUT V4.4 cannot load a V5.x project. Plan engineering PC installations accordingly.
• Hardware release G is the boundary for V4.5+ runtime support. If the application requires V5.x features (for example, new technology packages), the C240 hardware must be replaced - the controller cannot be firmware-upgraded past its hardware release boundary.

Related Documentation

• SIMOTION Compatibility List (Entry ID 18857317)
• SIMOTION SCOUT V4.4 HF11 firmware (Entry ID 31263919)