SINAMICS S120 CU320-2 PN Firmware 4.4 Compatibility

Problem Overview

After upgrading the SINAMICS S120 control unit CU320-2 PN (6SL3040-1MA01-0AA0) to firmware V4.4, the control unit refuses to load an offline project that was originally commissioned on a CU320-2 running firmware V2.4. The downstream hardware in the affected cabinets includes the Double Motor Module 6SL3120-2TE13-0AA0 and the Smart Line Module 6SL3130-6AE21-0AA0. STARTER / Startdrive aborts the download during topology validation with a Drive-CLiQ (DQ) component mismatch, and the control unit surfaces F0135x faults on power-up.

The technical root cause is that the 6SL3040-1MA01-0AA0 variant is supported only from firmware V4.4.x onward. The boot loader on this article number checks the firmware signature against an expected range; a V2.x card image is rejected at boot, before parameter download begins. Even when the card image is accepted, the V4.4 topology objects expect component identifiers and parameter layouts that did not exist on V2.4-era DQ components.

Affected Hardware Components and Article Numbers

Use the table below to identify the components involved in the fault and their role in the SINAMICS S120 topology. Always cross-reference the MLFB on the rating plate before ordering firmware cards or replacement parts.

Root Cause: Firmware Architecture Shift

SINAMICS S120 firmware V4.x restructured the parameter set, the Drive-CLiQ topology descriptors, and the Safety Integrated channel map relative to the V2.x baseline. The parameter p0009 (Device commissioning parameter filter) carries a different scope, the topology objects compiled at offline time include new component identifiers, and the Safety Integrated telegram layout was extended. The CU320-2 PN 6SL3040-1MA01-0AA0 was introduced with the V4.x generation; its file system and CF card layout are physically incompatible with V2.4 images.

Boot signature check

At power-up, the control unit reads the firmware signature from the inserted CF card and validates it against the range expected by the hardware variant. The 6SL3040-1MA01-0AA0 expects a V4.4.x or higher image. A V2.x card produces a non-matching signature and the boot process halts without loading parameters. There is no field procedure to override this check; the only remedies are (a) use a V4.4.x image, or (b) replace the control unit hardware with a variant that supports V2.x.

Topology migration is not equivalent to firmware downgrade

Even when the V2.4 image loaded successfully, the V4.4 Drive-CLiQ topology objects expect component identifiers and parameter layouts that did not exist on V2.4-era components. The fault appears during the first commissioning download, not during parameter editing. STARTER / Startdrive reports component firmware mismatches at the DQ ports, and the affected drives remain in commissioning lock.

Firmware Compatibility Matrix

Use this matrix to determine whether a hardware swap or a firmware swap is the cheapest path forward. For each component, note the lowest supported firmware version, the recommended firmware version, and the compatibility with a V2.4 topology compiled offline.

Solution Paths

Three engineering paths resolve the compatibility fault. Select the path that matches your cabinet count, budget, and forward-looking I/O architecture.

Path A: Migrate Drive-CLiQ topology to V4.4 components

This path keeps the CU320-2 PN hardware and the V4.4 firmware generation. Replace the affected Motor Modules and Line Module with V4.4-compatible equivalents, and update all SMC and TM modules on the same DQ ring to match. This is the correct path when V4.4 components were the long-term target anyway.

1. Inventory all DQ-attached components and record each MLFB from the rating plate.
2. Cross-reference each MLFB against the SINAMICS S120 V4.4 compatibility list in the firmware release notes.
3. Order replacement modules with the appropriate CF card image for V4.4.
4. Update the offline STARTER / Startdrive project to reference the new MLFBs.
5. Run the topology comparison and load the project to the control unit.
6. Verify drive object assignment: 1 Line Module plus up to 6 Servo drives (or the equivalent Vector configuration).
7. Execute the Safety Integrated acceptance test if Basic Safety is configured.

Path B: Revert to legacy CU320 with FW V2.6.2

This is the most cost-effective alternative when only the CU320-2 PN was ordered in error and the existing V2.4 components are to be retained. The legacy CU320 (6SL3040-0MA00-0AA1) supports EPOS, retains the same maximum drive count as the CU320-2, and accepts the original V2.4 topology objects. PROFINET is added via the CBE20 communication board.

Legacy CU320 Configuration Limits

• Servo control: 1 Line Module + 6 Drives maximum.
• Vector control: Reduced drive count; consult the SINAMICS S120 function manual for the exact limit on the chosen drive type.
• EPOS (Basic Positioner): Supported.
• PROFINET: Available with CBE20 inserted into the option slot.
• PROFIBUS: Integrated on the legacy CU320.

Commissioning steps (legacy path)

1. Order CU320 (6SL3040-0MA00-0AA1) and CBE20 (6SL3055-0AA00-2EB0).
2. Insert a CF card with SINAMICS S120 FW V2.6.2 image.
3. Connect the CBE20 to the option slot and wire PROFINET to the PLC.
4. Load the existing V2.4 offline project; verify Drive objects 1-6 map correctly.
5. Configure the PLC (e.g., SIMATIC S7-300 / CPU 315-2 PN/DP) PROFINET interface to the new control unit.
6. Assign the PROFINET device name and IP via the Topology Editor or the PRONETA tool.
7. Run the drive acceptance test and verify Safety Integrated if enabled.

Path C: SIMATIC Drive Controller with SINAMICS Integrated

For greenfield installations, the SIMATIC Drive Controller embeds SINAMICS Integrated that exposes the same Safety Integrated Basic Functions as the standalone CU320-2. This consolidates PLC and drive control into a single device and removes the separate control unit from the PROFINET line.

Drive-CLiQ Topology and Component Rules

Drive-CLiQ is the internal bus between the control unit, line modules, motor modules, and sensor modules in a SINAMICS S120 cabinet. Rules enforced by the topology check include:

• Single firmware generation: All DQ-attached components must run firmware from the same generation. Mixing V2.x and V4.x components on a single DQ ring is not supported.
• No loops: The DQ topology is a tree; closed rings produce topology faults at commissioning.
• Port mapping: The control unit DQ ports (X100-X105) are populated in a defined order; the port nearest the Line Module is typically the first Motor Module port.
• Cable length: Standard DQ cables support up to 70 m. Longer runs require fiber-optic DQ cabling with DQI converters.
• Maximum stations: The CU320-2 / CU320 supports up to 16 DQ stations per ring, limited by the firmware generation and drive type.

When migrating from V2.4 to V4.4, treat every DQ station as a candidate for firmware update. The CU firmware alone does not bring the cabinet onto V4.4 - every Motor Module, Line Module, SMC, and TM must be brought to the same generation.

Drive Object Configuration and PROFINET Integration

Drive object (DO) layout

The SINAMICS S120 control unit organises drive objects in a fixed numeric map. The standard layout is:

• DO 1: Control Unit (CU320 / CU320-2)
• DO 2: Line Module (Smart Line Module / Active Line Module / Basic Line Module)
• DO 3, 4, 5, 6, 7, 8: Drives (up to 6 on Servo configuration)
• DO 9+: Optional terminal modules, SMC, or additional DO slots defined by the project

PROFINET integration on CU320-2 PN

The CU320-2 PN has PROFINET integrated on the control unit itself. Two PROFINET ports (X150 P1, X150 P2) are available. The control unit acts as a PROFINET IO Device with a configurable device name and IP. Telegrams from the IO Controller map to the drive objects via the slot configuration in the GSDML file.

PROFINET integration on legacy CU320 with CBE20

The legacy CU320 does not include PROFINET. Insert the CBE20 board into the option slot to add PROFINET connectivity. The CBE20 provides two PROFINET ports and uses its own firmware image that must match the control unit firmware generation.

EPOS and PROFIdrive Telegram Mapping

EPOS (Basic Positioner) is supported on the legacy CU320 running V2.6.2 and on the CU320-2 PN running V4.4.x. Telegram 111 is the standard EPOS telegram; it carries position setpoint, position actual value, status word, and control word across the PROFINET boundary. When migrating from PROFIBUS to PROFINET, the cyclic data mapping must be reconfigured; the slot assignment is recreated from the GSDML file rather than copied directly from the PROFIBUS configuration.

Firmware Update Procedure (V2.x to V4.4.x)

Per the official Siemens update instructions, the supported update path on the CU320-2 PN is V4.3.x to V4.4 (and higher). Direct upgrade from V2.x to V4.4 in a single step is not supported because the boot loader signature check on the 6SL3040-1MA01-0AA0 expects a V4.x intermediate image. Use STARTER / Startdrive with a PC connected to the CU320-2 PN service interface (X127) or via the plant network.

Update sequence

1. Back up the parameter set using STARTER / Startdrive (Project > Save to memory card).
2. Verify the current firmware version on the control unit via parameter r0018 or r0976.
3. Insert a CF card containing the V4.4.x firmware image; the control unit auto-detects on power-up.
4. Wait for the LED sequence: RDY green steady, COM green steady. Do not interrupt power.
5. Reload the project and verify the topology comparison report.
6. Update downstream component CF cards to match the control unit generation.
7. Run the Safety Integrated acceptance test if Basic Safety is configured.

LED Diagnostics and Fault Code Reference

Control unit LED indicators

Common fault codes

Verification and Commissioning Checklist

1. Article number check: Confirm the CU320-2 PN label reads 6SL3040-1MA01-0AA0 before any firmware operations.
2. Firmware version: Parameter r0018 (or r0976) returns the installed FW; cross-check against the SINAMICS S120 compatibility list.
3. Topology diagnostics: The Drive-CLiQ diagnostics page in STARTER shows green port status for every DQ port.
4. Drive object count: DO 1 = Control Unit, DO 2 = Line Module, DO 3+ = drives. Maximum 6 drives on Servo configuration.
5. Safety Integrated: If Basic Safety is configured, verify Safety functions pass the acceptance test.
6. PROFINET connectivity: Ping the control unit from the PLC engineering station; verify the device name and IP are set.
7. EPOS homing: Perform reference run for each EPOS-configured axis.
8. Brake check: Run the brake control test if the drive is configured with a holding brake.
9. Encoder check: Verify the encoder actual value matches the mechanical position after homing.

Field Troubleshooting Matrix

Field-Engineered Recommendations

When the cabinet contains more than five affected components (Motor Modules, Line Modules, SMCs, TMs), the cost analysis typically favours Path B (legacy CU320 with V2.6.2) because new modules plus a V4.4 commissioning cycle exceed the price of one CU320 plus CBE20. Reserve Path A for greenfield installations where V4.4 components can be ordered from the start.

Always confirm the control unit MLFB before ordering firmware cards. The boot loader signature check is enforced at the hardware level and cannot be bypassed via parameter changes. The official Siemens firmware update instructions for the CU310-2 / CU320-2 document the supported image-to-hardware matrix.

For new installations where Safety Integrated is required and a compact footprint is preferred, evaluate the SIMATIC Drive Controller with SINAMICS Integrated as a single-device alternative that exposes the same Safety Integrated Basic Functions as the standalone CU320-2.