SINAMICS S120 F30885: DRIVE-CLIQ Cyclic Data Transfer Error Fix

1. Problem Overview

The SINAMICS S120 fault F30885 is raised by the Control Unit (CU320-2 PN) when the cyclic data transfer over a DRIVE-CLIQ link between the CU and a downstream component is interrupted, corrupted, or fails to maintain its expected isochronous cycle. In drive systems retrofitted with third-party absolute encoders (for example Heidenhain ECN 424S with EnDat 22), the fault is often reported on both Motor Modules simultaneously, which strongly suggests a configuration, encoder interface, or DRIVE-CLIQ topology problem rather than a hardware defect on a single axis.

The typical symptom pattern observed in the field is:

• Fault F30885 with the additional information "CU DRIVE-CLIQ cyclic data transfer error" appears on both drives shortly after commissioning.
• The motor rotates for a short period, stops briefly, then resumes rotation (the so-called "stutter" behaviour caused by cyclic telegrams being rejected).
• Encoder adjustment and commutation succeed during commissioning, but the fault reappears during cyclic operation.
• Rebuilding the project from scratch in SINAMICS STARTER / Startdrive does not clear the issue.

2. F30885 Fault Definition and Reactions

According to the SINAMICS S120/S150 List Manual, F30885 is a Control Unit fault. The relevant attributes are:

The fault value (r0949) and additional information field (r2124 / r3121 depending on firmware) identify which DRIVE-CLIQ node and which telegram word triggered the cycle violation. Always read both r0949 and r2124 before clearing the buffer.

3. Reference Hardware Configuration

The configuration in the field case driving this document is typical for a high-performance booksize drive line-up with two parallel axes. Catalog numbers and firmware versions are listed in the table below; always confirm that firmware versions on the CU, the Motor Modules, and the Sensor Modules are mutually compatible before commissioning.

4. Root Cause Analysis

When F30885 is reported on every drive connected to a CU320-2 PN after a torque-encoder replacement, the most likely root causes are listed below in order of probability observed in similar field cases.

1. DRIVE-CLIQ topology rule violation. The Heidenhain ECN 424S uses the EnDat 22 protocol, not native DRIVE-CLIQ. It cannot be plugged directly into a DRIVE-CLIQ port of the CU. An SMC20 (6SL3055-0AA00-5BA1) or SME20 Sensor Module is required to translate the encoder protocol to DRIVE-CLIQ.
2. Sensor Module configuration mismatch. The encoder interface (p0400) is set to an EnDat 2.1 / 2.2 value that does not match the ECN 424S interface version, or the resolution/singleturn bit count (p0421 / p0422) is not configured to match the ECN 424S singleturn resolution.
3. Cable screen bonding issue. Encoder cable shields are not bonded at the Sensor Module's shield clamp. DRIVE-CLIQ link quality is then disturbed by EMC, which in turn corrupts the cyclic telegram CRC and triggers F30885.
4. Firmware version mismatch. The CU320-2 PN runs V4.7.0 (4703538) while the Motor Modules run a slightly older V4.7.0 build (4703537). Mixed firmware within a topology can in some constellations create DRIVE-CLIQ cycle jitter that surfaces as cyclic data transfer faults.
5. Cycle time (p0115) or PROFIBUS/PROFINET isochronous setting too tight. Selecting a 62.5 µs current controller cycle without an adequate Sensor Module or with marginal cable lengths can produce sporadic cycle overruns. Check p0115[0..6] and p0922.
6. Defective DRIVE-CLIQ cable or connector. Verify each cable with a continuity test, paying particular attention to pins 3 and 6 (transmit/receive pairs) and the shield contact.

5. Diagnostic Procedure

Use the following ordered procedure to isolate the cause before changing any hardware. The steps assume STARTER or Startdrive with online access to the CU320-2 PN.

1. Connect to the drive online and read the diagnostic buffer of the CU. Filter for F30885 and capture the fault value, additional information, and time stamp.
2. In the topology view, compare the actual DRIVE-CLIQ topology to the configured topology. Address conflicts and "node missing" entries indicate wiring or address-switch problems.
3. Open Drive → Commissioning → Encoder and verify p0400, p0401, p0420, p0421, p0422, p0423 for the encoder in question. For ECN 424S the EnDat encoder type must read 9999 user-defined or the correct EnDat 22 ID and the resolution must match the encoder's nameplate (typically 24-bit singleturn for ECN 424S).
4. Use the Control Unit → Diagnostics → DRIVE-CLIQ diagnostics page to read r9926 and the per-node error counters r0143 / r0153 / r0163 / r0173. Repeated non-zero values confirm cyclic transfer errors rather than a one-off disturbance.
5. Force the drive to enter the cyclic test mode and let it run for several minutes while logging r7901 (DRIVE-CLIQ master diagnostics). Spikes in r7901 align with the moments the motor "stutters".
6. Inspect the encoder cable shield at both ends. The shield must make 360° contact with the backshell at the SMC20 side and at the encoder side. Floating shields are the most common EMC cause of F30885 retrofits.
7. Read the CBC10 diagnostics if CANopen masters are in use. A CANopen error storm can saturate the CU's task schedule and surface as a DRIVE-CLIQ cycle fault.
8. Capture a STARTER trace of the trace signals p1950[0..2] and the SM diagnostic r0471 over 5-10 s around the fault. The trace pinpoints the telegram word that fails.

6. Heidenhain ECN 424S Integration on SINAMICS S120

The ECN 424S is a singleturn absolute encoder with the EnDat 22 serial protocol. SINAMICS S120 does not support EnDat 22 directly on a DRIVE-CLIQ port; the encoder must terminate on a Sensor Module that supports EnDat 2.2 / 22, which then connects to the CU via DRIVE-CLIQ.

Encoder cable from ECN 424S to the SMC20 must use the Heidenhain-specified shielded twisted-pair cable and a 17-pin flange socket on the encoder side. The Heidenhain cable part numbers (for example 309 778-xx or 310 188-xx) are not interchangeable with DRIVE-CLIQ cables.

7. SMC20 Sensor Module: Wiring and Addressing

The SMC20 is the only sanctioned way to bring an EnDat 22 encoder into a SINAMICS S120 DRIVE-CLIQ topology. The module acts as a transparent EnDat 2.2 → DRIVE-CLIQ bridge.

1. Mount the SMC20 in a location where ambient temperature stays within 0 °C to +55 °C and the module is free of condensation.
2. Connect the EnDat cable to the 15-pin D-sub socket X520 of the SMC20. Pin assignment: pin 4 / 5 clock, pin 14 / 15 data, pin 12 +5 V supply, pin 2 / 6 / 8 / 13 / 10 ground/shield. The shield must be clamped in the backshell of the D-sub.
3. Connect a DRIVE-CLIQ cable from the SMC20 to the appropriate port of the CU320-2 PN. DRIVE-CLIQ port assignment rules:

• Port 0 of the CU is reserved for the basic operator panel / commissioning tools.
• Motor Modules and Sensor Modules can be cascaded; up to 14 nodes are allowed per DRIVE-CLIQ line on the CU320-2 PN.
• The total DRIVE-CLIQ cycle, including the longest cable, must remain within the configured p0115 cycle. The drive automatically inserts a propagation delay into the telegram scheduling, but a misconfigured p0115[0] (current-controller cycle) can still produce a fault.

4. Set the DRIVE-CLIQ address DIP switch on the SMC20 only if you are building a non-default topology. The default is automatic addressing, which is sufficient in nearly all cases.
5. Power cycle the CU320-2 PN after connecting the SMC20. The CU must re-detect the new DRIVE-CLIQ node and add it to the topology.

8. Encoder Parameter Configuration

Once the ECN 424S is wired to an SMC20, the SINAMICS drive object must be configured to recognize the encoder. The critical parameters are summarised below; values are valid for V4.7. Confirm the parameter numbers against the List Manual for your exact firmware.

9. Step-by-Step Resolution Procedure

Apply the following sequence to clear F30885 after an ECN 424S retrofit. Each step requires a positive verification before moving to the next.

1. Confirm the Sensor Module is present. In STARTER, open Drive → Configuration → DRIVE-CLIQ topology and verify that the SMC20 is detected at the expected port with the correct catalog number. A missing node means physical wiring, address-switch, or DRIVE-CLIQ cable problem.
2. Run automatic configuration. On the encoder page, click "Encoder data from nameplate". The drive reads the EnDat 2.2 electronic nameplate and proposes p0400/p0401/p0420/p0421/p0423 values. Accept the proposal and download.
3. Save and restart the CU. Use "Copy RAM to ROM" (p0971 = 1), then perform a warm restart (p0972 = 2 or the Startdrive Restart button). DRIVE-CLIQ nodes are re-enumerated.
4. Perform the encoder adjustment. With the motor uncoupled from the load and the drive in "No Speed Setpoint" state, run p1990 = 1 (determinate commutation with zero move) and verify p1992 returns zero. Then p1990 = 2 with a slow rotation, or p1990 = 4 for a standstill adjustment. Each step must end with r1992 = 0.
5. Verify the commutation sign. r0094 / r0451 / r0459 must agree with the configured direction in p1820. The brief stutter symptom is often the result of the commutation sign being ambiguous due to a missing absolute encoder adjustment.
6. Run the drive open-loop with a low speed setpoint for at least 10 minutes. Monitor r0021 and r0061. Watch for F30885 reappearing in the diagnostic buffer. If the fault reappears, capture r0949 and the trace.
7. Check the cycle consistency. p0115[0..6] must reflect the active topology. The current controller cycle (p0115[0]) and the speed controller cycle (p0115[1]) are usually 125 µs / 250 µs / 500 µs in booksize systems. Do not use a value that exceeds the encoder evaluation time of the SMC20.
8. Validate the firmware matrix. Use the SINAMICS S120 firmware compatibility matrix to verify the CU and Motor Module firmware are listed as a compatible pair. If not, upgrade the Motor Modules to the same branch as the CU using the CF card or Web server.
9. Re-run acceptance test. Issue a directed speed setpoint ramp, observe actual speed following and r0060 motor current, and confirm r0949 remains clear of F30885 for at least one hour of mixed operating states (jog, traverse, stop).

10. Verification Checklist

Before handing the machine back to production, confirm the following:

11. Related Faults to Investigate

Several other faults present similarly to F30885 after encoder retrofits. Treat them as a checklist if F30885 is the symptom but the root cause is shared with another fault.

12. Component Replacement Workflow Reference

When a complete encoder retrofit is performed on a SINAMICS S120 system, the standard Siemens workflow applies. Read Examples of replacing components for the official procedure; the steps in this document are compatible with that procedure. The key sequence is:

1. Save the project and back up the drive's parameters using STARTER or Startdrive.
2. Power down the line, replace the encoder hardware.
3. Power on, re-detect the DRIVE-CLIQ topology.
4. Re-load the saved project to restore the parameter set.
5. Update the encoder parameters (p0400, p0401, p0420, p0421, p0423) to match the new encoder's electronic nameplate.
6. Run the absolute encoder adjustment (p1990) and the commutation adjustment (p1991/p1992).
7. Accept the drive and complete the verification checklist above.

13. Preventive Recommendations

• Maintain DRIVE-CLIQ cabling with the original Siemens cordsets only (6FX2002-1DC00-xxxx, 6FX2002-1DC20-xxxx and similar). Mixing non-Siemens cables is the most common source of intermittent F30885.
• Tie the encoder and DRIVE-CLIQ cables to the cabinet frame with conductive clamps at minimum every 0.5 m. Do not run them in parallel to VFD motor output cables.
• When commissioning a new encoder, always perform a full p1990 sequence even if the previous setup worked; the new mechanical position of the encoder disk changes the absolute offset.
• Schedule firmware updates only after validating the matrix at SINAMICS S120 firmware compatibility. Mixed branches are a recurring cause of cycle-jitter faults.
• Keep a STARTER project file with the active p0437 (Sensor Module firmware) and p7820 (DRIVE-CLIQ baud rate) values; these help diagnose similar F30885 issues months later.

14. Frequently Asked Questions