SINAMICS G120C PN Firmware Upgrade V4.7.3 to V4.7.6 via SD Card

Problem Overview: Mixed Firmware Versions on a Multi-Drive Project

A common engineering bottleneck on SINAMICS G120C PN installations is firmware drift between identical hardware units. The Control Unit (CU) firmware level must match across every drive that is added to a single TIA Portal project or PROFIdrive topology; otherwise the engineering tool refuses to commission the device or downloads parameters with a type-mismatch fault. In the case described here, an integrator had four SINAMICS G120C PN drives running firmware V4.7.3 and a fifth unit running V4.7.6 (the SP6 HF5 release line). The goal was to harmonise the fleet to a single firmware version so that all five drives could be added to one Startdrive project and operated against the same PLC.

Two upgrade attempts failed before the correct path was identified:

1. Upgrade V4.7.3 → V4.7.6 via TIA Portal (Startdrive V14 SP1 Update 7): The download was rejected with an error popup originating in the drive's parameter layer. No clear root-cause text was presented inside Startdrive.
2. Downgrade V4.7.6 → V4.7.3 via TIA Portal: The download proceeded past the firmware-version compatibility warning ("compatible, but not identical") but aborted at parameter p2968[0] with the PROFIdrive diagnostic "Parameter type mismatch". No fallback option was offered in the dialog.

Both paths point to the same underlying constraint: SINAMICS G120C firmware updates are not a TIA Portal or Starter task. They are a Control Unit firmware-loader task that requires a memory card (SD or MMC) inserted directly into the drive. The remainder of this article documents the working procedure, the parameter-level root cause, and the verification steps that confirm a clean upgrade.

Affected Products, Firmware and Article Numbers

Why TIA Portal / Starter Cannot Perform the G120C Firmware Update

SINAMICS firmware updates on the G120 / G120C / G120D product family are split into two distinct operations, and the boundary is not always obvious to first-time users:

The Startdrive "Go online → Load to device" function updates the parameter image on the CU, not the firmware image stored in the CU's flash. When the target firmware version on the CU differs from the version compiled into the Startdrive device description, the loader detects an internal data-structure mismatch and aborts before writing any data. The error returned by Startdrive is generic because the underlying rejection originates inside the CU's parameter manager, not inside TIA Portal.

The "downgrade" attempt (V4.7.6 → V4.7.3) reaches further into the parameter layer before failing. Parameter p2968[0] (Quadrature-axis flux model configuration) was added or redefined between V4.7.3 and V4.7.6; the parameter type stored on the drive differs from the type that the offline project expects. The PROFIdrive telegram carries an attribute that flags the type difference, and the download is rejected with "Parameter type mismatch". This is correct behaviour: a parameter download that targets a different firmware version can corrupt non-volatile parameter sets because the data-type layout has changed. Siemens intentionally blocks this path.

Root Cause Analysis – Parameter p2968 and the Firmware Loader Boundary

Parameter p2968 is part of the induction-motor flux-model feature (open-loop / sensorless control). Its data type and index layout were touched in the V4.7 SP6 service pack. The exact symptom depends on which direction the user tries to move:

Both messages are warnings that the engineering tool layer cannot honour. The correct remediation is to perform the firmware update first (via SD card or Web server) and only then re-run the parameter download.

Identifying the SD Card Slot on the G120C

The location of the SD card slot depends on the frame size (FS) of the G120C power module:

The BOP-2 operator panel does not contain an SD slot. The SD slot lives on the Control Unit itself. The earlier confusion in the field report stems from the BOP-2 interface – users sometimes assume the operator panel accepts the card. It does not.

Use only Siemens-approved SD cards (article number 6SL3054-4AG00-2AA0 for the 512 MB card, or the empty-card article 6ES7794-0AA00-0AA0). Third-party SD cards work if they meet the FAT32 requirement and the SD 1.1 / 2.0 specification, but Siemens warranty conditions apply to the card combination only when the OEM part is used.

Preparing the SD Card for the V4.7.6 Image

1. From Siemens Support entry 109482659, download the SINAMICS V4.7 SP6 HF5 firmware ZIP. The ZIP contains a folder named after the target Control Unit (e.g., CU240E-2_PN_V4.7.6) with the following files:
   • FW_CU240E2PN_V4.7.6.bin – Control Unit firmware image
   • FW_CU240E2PN_V4.7.6.txt – Release notes / changelog
   • For G120C: additional FW_G120C_*.bin for the power-module side (if updating the PM as well)
2. Format the SD card to FAT32 with default allocation-unit size. exFAT is not supported by the CU firmware loader.
3. Copy the .bin file(s) into the root directory of the SD card. Do not place them in sub-folders; the loader scans only the root.
4. Optionally rename the file to FW_CU.bin if multiple firmware files for different CUs are present. The CU searches for files prefixed with FW_ and selects the matching one by hardware ID.

Step-by-Step: Upgrading G120C PN from V4.7.3 to V4.7.6 via SD Card

1. De-energise the drive. Lock-out / tag-out the line contactor. Wait five minutes for the DC-link capacitors to discharge below the safe-touch threshold (status LEDs on the CU indicate < 50 V DC).
2. Insert the prepared SD card into the slot identified in the table above. The card must click into the spring-loaded socket; orientation is with the contacts facing down and the bevel toward the front of the drive.
3. Re-apply control voltage only (24 V on the CU terminals, line power still OFF). The CU boots and detects the firmware file on the SD card.
4. Observe the LED sequence. The RDY (green) and BF (red) LEDs blink in a 2 Hz pattern to indicate a firmware update is pending. The display (if an IOP-2 or BOP-2 is connected) shows "FW update ready" or equivalent.
5. Trigger the update by pressing the OK key on the connected operator panel for at least 3 seconds, or by setting parameter p7826 = 1 from the Starter / Startdrive online interface. For G120C with only a BOP-2 connected, the parameter route requires a temporary commissioning-cable connection to a PC running Starter.
6. Wait for completion. The flash process takes 2 – 4 minutes depending on the CU type and the size of the firmware image. Do not remove the SD card during the flash; corruption of the CU firmware is unrecoverable without a service replacement.
7. Cycle the control voltage (24 V OFF, then ON) once the RDY LED returns to solid green. The CU boots into the new firmware.
8. Apply line power and verify that the drive reaches the RDY state. The display reads "FW V4.7.6".
9. Restore the parameter set by uploading the backup taken in the pre-condition step. Where parameter types have changed (e.g., p2968), accept the tool's "Reset to factory default" prompt before loading the backed-up set.

Alternative Upgrade Paths

Web-Server Method (Quick Reference)

1. Open a browser and connect to the CU IP address (default 169.254.11.22 if unconfigured).
2. Log in as administrator (default user "admin", password printed on the CU front panel under a flap).
3. Navigate to Functions → Firmware update.
4. Upload the .bin file. The CU restarts after a successful flash.
5. This method does not require an SD card but does require a network path with sufficient bandwidth and the firmware-loader feature to be enabled in parameter p7826.

Verification Procedure After Upgrade

1. Read the firmware version from parameter r0018 (Control Unit firmware version). It must show "4.7.6" as the active version. The boot-block version is reported in r0197.
2. Confirm the firmware checksum by reading parameter r0260; this is the SINAMICS-internal CRC of the active firmware image.
3. Check parameter p2968[0] by writing a non-zero value (e.g., 1 = improved transient response) and reading it back. If the round-trip succeeds without a type-mismatch error, the parameter manager has been rebuilt correctly.
4. Perform a guided test run using parameter p0010 = 1 (commissioning mode) and the Starter "Commissioning wizard". Verify that the motor identification and the speed-controller auto-tuning complete without fault.
5. Re-add the drive to the TIA Portal project. After the firmware version matches the project version, the "Add new device" wizard accepts the drive without further prompt.

Troubleshooting Matrix

Field-Proven Caveats and Best Practices

• Always upgrade before commissioning. Field reports show that attempting to commission a drive with mixed firmware versions leads to intermittent PROFIsafe errors and inconsistent diagnostic buffers.
• Document the firmware source. Siemens ships two firmware channels: "Release" (production) and "Update" (latest fixes). SP6 HF5 is the latest HF on the V4.7 branch; for new installations prefer "Release", for resolving field issues use "Update".
• Keep a fleet spreadsheet. When managing more than three G120C units, record CU serial number, hardware version, firmware version, and last parameter backup date. The CSV file is also accepted by the SINAMICS "Drive Control Chart" batch upload tool.
• Safety-related parameters. After any firmware change on a Safety-Integrated drive, re-validate the STO, SS1 and SLS functions. The acceptance test must be repeated and the test protocol signed – this is a CE requirement for machine builders.
• Hot-plug of the SD card is not supported. Insert and remove the card only with the drive de-energised (24 V control voltage OFF).
• Card capacity sweet spot. A 4 GB SD card is more than sufficient and reduces the risk of the CU misreading the partition table. Avoid 32 GB+ cards.

Edge Cases Specific to the G120C PN Variant

• PROFINET device name reset. V4.7.6 normalises the device-name storage area; some units have been observed to revert to the factory-assigned name after the upgrade. Plan for a PROFINET topology re-assignment step.
• Safety-Integrated PN G120C (CU240E-2 PN-F variant): the firmware loader checks parameter p9601 (SI enable). If the drive was delivered with Safety-Integrated enabled and the password is unknown, the firmware update still proceeds, but Safety commissioning must be repeated.
• Identical FW versions across a fleet. For machines shipped to multiple end customers, Siemens recommends locking the firmware version via the parameter p7825 (firmware update lock) once the final version is in production.

Glossary

FAQ