Resolving Sinamics S120 Fault 1900 Profibus Telegram Error 211

Resolving Sinamics S120 Fault 1900: Profibus Configuration Telegram Error 211

Problem Overview

When integrating a Siemens SINAMICS S120 drive with a Beckhoff Industrial PC through the EL6731 PROFIBUS master terminal, STARTER (or the SINAMICS commissioning software) can report:

• Fault number: 1900
• Fault text: PB/PN: Configuration telegram error
• Fault value: 211

The drive enters a fault state, the cyclic PROFIBUS communication does not start, and the Beckhoff master cannot exchange process data with the SINAMICS S120. The fault blocks all closed-loop operation, position control, and speed control through the master until the cause is corrected and the alarm buffer is acknowledged.

This error is a direct indication that the PROFIdrive telegram layout the master expects is not implementable by the drive. The most frequent root cause observed in the field is a GSD file version mismatch against the SINAMICS firmware, but secondary causes include telegram / p0922 mismatch, slot configuration drift, PROFIBUS address conflicts, and EL6731 process image issues in TwinCAT.

Root Cause Analysis

SINAMICS S120 firmware revisions are tightly coupled to the GSD (General Station Description) file used by the PROFIBUS master. The CU320-2DP firmware version, the S120 firmware version, and the GSD file must all be aligned. The drive's PROFIdrive interface builds its slot table from the active firmware build, and any master configuration that references a telegram or slot not present in that build is rejected with fault 1900 / 211.

Common root-cause scenarios encountered in commissioning:

1. GSD newer than firmware: The master project uses a GSD released for a newer SINAMICS firmware (for example V4.7) while the actual Control Unit runs an older firmware (V4.4). The drive cannot fulfil the configured telegrams and raises fault 1900 / 211.
2. Drive upgraded in the field: The SINAMICS firmware was updated (for example through STARTER's component assignment) but the master GSD and project were not refreshed. The drive now offers more telegrams than the master knows about, and any telegram mismatch returns the same fault.
3. Mixed drive objects: Multiple SINAMICS S120 drive objects of different firmware vintages are placed on the same PROFIBUS segment with the same GSD. A drive object loaded with a newer firmware will accept a telegram the older drive object rejects.
4. Slot / telegram drift: The drive's active telegram set by parameter p0922 is not the telegram inserted in the EL6731 slot. The drive expects telegram 5, the master sends telegram 1, and the drive raises the configuration telegram error.
5. GSD not re-imported after TwinCAT upgrade: After upgrading TwinCAT, the GSD repository may default to a bundled older or newer GSD. The change is silent and only shows up at the next configuration activation.

In all these cases, the drive's PROFIdrive interface issues fault 1900 with value 211, indicating that the configuration telegram is not assignable on the active drive build.

Affected Hardware and Firmware

Diagnostic Procedure

Before changing the project, capture the exact firmware version of the drive and the active alarm buffer.

1. Connect STARTER (matching the drive firmware vintage) to the CU320-2DP via PROFIBUS or service Ethernet. Use the version of STARTER that supports the drive firmware; an older STARTER will not display parameter ranges correctly.
2. Read firmware version through parameter r0018 (Control Unit firmware version) and r0979[0..24] (drive object firmware list). Note the SINAMICS firmware, the STARTER version, and any SCOUT / STARTER component versions.
3. Inspect the alarm buffer through parameters r0945[0..63] (fault codes) and r0946[0..63] (fault values). Fault 1900 with value 211 must be confirmed before applying the correction. Take a screenshot of the STARTER alarm window for the maintenance record.
4. Open TwinCAT System Manager and verify the GSD import date. Right-click the EL6731 node and navigate to PROFIBUS DP → GSD file to view the imported GSD metadata. The vendor, device family, and revision string should match the SINAMICS firmware.
5. Compare the master GSD revision string with the drive firmware. If they differ, the configuration telegram error 211 is the expected symptom.
6. Check parameter p0922: the value should match the telegram inserted in the EL6731 slot. A common confusion is that the drive defaults to telegram 1 while the master configures telegram 5 for DSC operation; the drive raises 1900 / 211 on the next parameter save cycle.
7. Check parameter p0918: the PROFIBUS slave address reported by the drive must match the slave address configured in TwinCAT. Address conflict or duplicate address can also surface as 1900 / 211 in some firmware versions.

For deeper investigation, capture the diagnostic counters of the EL6731: PROFIBUS DP State, DPV1 status, and the slave's Diag.Data buffer. These are exposed through the TwinCAT System Manager and provide timing information on parameterization and configuration phases. The DIAG LED of the EL6731 indicates the master / bus state: green continuous = RUN, green flashing = READY, red = bus error, red flashing = configuration error.

Solution: GSD Version Matching

The verified field fix is to install the GSD file that matches the drive firmware exactly. The original integration attempt used the V4.7 GSD against V4.4 firmware; replacing it with the V4.4 GSD cleared the fault.

1. Obtain the matching GSD from the Siemens Industry Online Support portal. The deliverable for CU320-2DP V4.4 is shipped as part of the SINAMICS S120 V4.4 install package or as a standalone GSD file inside the firmware install. The exact filename (for example SIEM_xxxx.GSD) depends on the Siemens release; verify against the package's release notes.
2. Close TwinCAT System Manager and any project that references the EL6731 to release the GSD file handle.
3. Open the GSD repository: from the Beckhoff control panel, navigate to TwinCAT → I/O → GSD Repository and import the new GSD. Delete the old V4.7 GSD entry if it persists to avoid accidental use by future projects.
4. Reopen the project, rescan the EL6731, and reassign the SINAMICS S120 slave to its slot using the new GSD revision. The slot table is rebuilt automatically when the slave is re-inserted.
5. Save the project and re-activate the configuration. Cycle the PROFIBUS communication if the drive does not respond within a few seconds.

After the change, the cyclic PROFIBUS handshake completes, the drive exits fault 1900, and the process data (PZD) channels are exchanged. This is the same result reported in the field when the V4.7 GSD was replaced by the V4.4 GSD on the EL6731.

EL6731 PROFIBUS Master Configuration

The EL6731 is a PROFIBUS DP master terminal inserted into a Beckhoff EtherCAT terminal strip. The terminal exposes one PROFIBUS channel (RS-485, isolated) and is configured in TwinCAT System Manager as an I/O device. When integrating a SINAMICS S120, the EL6731 acts as the PROFIdrive master, mapping the drive's PZD slots into EtherCAT process data.

The official Beckhoff documentation EL6731 PROFIdrive MC drive integration describes the integration of PROFIdrive MC drives (including SINAMICS S120) in Beckhoff TwinCAT NC/PTP. The reference covers the slot layout, axis configuration, and process image mapping for servo and vector telegrams.

Confirm the slot selected in TwinCAT matches the telegram activated in the SINAMICS S120 project. The telegram is selected at the drive object level through parameter p0922 or directly in STARTER under Configuration → Telegram configuration. Mismatches between p0922 and the slot selected in the master produce fault 1900 / 211 even when the GSD is correct.

TwinCAT Axis Disconnector Implementation

Even with the GSD aligned, TwinCAT may continue to push telegrams during master configuration, which can re-trigger fault 1900 if the drive is still processing the previous telegram. The documented best practice is to insert an AXIS DISCONNECTOR in the TwinCAT System Manager I/O tree after each axis telegram configuration node.

1. In the TwinCAT System Manager, expand the EL6731 node and the SINAMICS S120 slave node.
2. Right-click the axis telegram entry (for example, Telegram 1 or Telegram 5) and select Append PROFIdrive Axis Disconnector.
3. Configure the disconnector to enable only when the axis is being commissioned, disabling it once the drive is online and error-free.

Verification Steps

1. Activate the TwinCAT configuration. Confirm that the EL6731 enters OP (operator) state and that the SINAMICS S120 slave transitions from Wait Prm to Data Exchange on the PROFIBUS state machine.
2. Read the SINAMICS alarm buffer (r0945 / r0946) to confirm no fault 1900 / 211 is present. Clear the buffer and observe whether the fault re-appears within 30 seconds.
3. Use STARTER online mode to inspect the drive's cyclic PZD. Toggle a control word bit (for example bit 7 in STW1 for fault acknowledgement, bit 0 for ON/OFF1, bit 3 for enable / inhibit) and confirm the drive's status word follows.
4. From the Beckhoff PLC, force a setpoint via the EtherCAT process image. Verify the drive reports the corresponding actual value back through the PZD return channel (for example, NIST in NSOLL for telegram 1, or actual position in XIST_P for telegram 5).
5. Cycle power to the entire PROFIBUS segment and confirm the drive comes up without fault 1900. If the fault re-appears on cold start, the GSD import was not refreshed in the project that boots with the controller.
6. Monitor the drive's r2050 and r2060 PZD output / input words through STARTER to confirm the PZD channels are mapped correctly to the active telegram.

PROFIdrive Telegram Configuration Reference

SINAMICS S120 supports a defined set of PROFIdrive telegrams. The most common are:

Whatever telegram is selected on the drive through parameter p0922 must be the one inserted into the EL6731 slot configuration in TwinCAT. Mixed or default telegrams (often telegram 1) will not match a drive configured for telegram 5 and will resurface as fault 1900 / 211. For free telegrams 110 / 111, the drive's PZD mapping (p2051 / p2061) must match the slot's process image on the master side.

Diagnostic Parameter Reference

Before changing any project, dump the values of r0018, r0979, r0945, r0946, and p0922 to a STARTER trace for the change log.

PZD Word Layout and the PROFIdrive State Machine

The PZD (Prozessdaten / process data) words carry the real-time payload of the PROFIdrive link. For the SINAMICS S120, the active telegram defines the exact layout. Telegram 5 (servo, 6/10) for example carries STW1, STW2, NSOLL_B, MOMRED, G1_STW, G2_STW as outputs, and ZSW1, ZSW2, NIST_B, MELDW, G1_ZSW, G1_XIST1, G1_XIST2, G2_ZSW, G2_XIST1, G2_XIST2 as inputs. Mapping must be respected on both sides; if the master writes to a word that the drive does not decode, the drive ignores it silently but the cyclic handshake can still raise 1900 / 211 on slot mismatch.

The PROFIdrive state machine moves the drive through four primary states:

1. S1 – Switching on inhibited: the drive is powered but no enable signal is active. Used for safe commissioning.
2. S2 – Ready to switch on: the drive electronics are live, the controller is initialized, and OFF1 is held. The next command is ON / OFF1.
3. S3 – Switched on: the drive is in closed-loop control, no torque is generated because OFF2 / OFF3 are still active.
4. S4 – Operation enabled: full closed-loop control with torque-producing current. This is the only state in which the drive can move the motor.

Fault 1900 / 211 is raised during the transition from S1 to S2 because the parameterization phase (ChkPrm) fails when the master offers a configuration the drive cannot implement. Resolving the GSD / telegram mismatch is required before the state machine can advance.

Related Beckhoff Controller and NC Errors

When the PROFIdrive link is up, attention often shifts to NC / PLC issues in TwinCAT. The Beckhoff Information System documents several controller-related diagnostics that can appear after the SINAMICS S120 link is established:

• Error 4503 / 17667 – Controller operating mode not allowed: The controller operating mode in the TwinCAT axis is not within the allowed range. The Beckhoff Information System states: "The value for the controller operating mode is not allowed. Value range: [1]. Unit: 1. 4503. 17667. Parameter." See the Controller Errors – Beckhoff Information System page for the full set of controller diagnostics and remedies.
• Target position monitoring: If the position controller is weak or disabled (Kv = 0), the axis will not reach the target and TwinCAT will report target position monitoring errors. The Beckhoff Information System notes: "If the position controller is switched off (Kv=0) or weak, the target may not be reached. Target position monitoring: if target position monitoring is active..." See NC PLC errors – Beckhoff Information System for the full description.

These errors are not caused by fault 1900 / 211 but commonly surface once the PROFIBUS layer is restored, so they are useful diagnostics to keep in mind during commissioning.

PROFIBUS Electrical and Cabling Requirements

The physical layer between the EL6731 and the SINAMICS CU320-2DP must follow the PROFIBUS DP cable specification. Use a shielded, twisted-pair cable with characteristic impedance of 150 Ω and a loop resistance below 110 Ω/km. The shield must be bonded to the control cabinet backplate within 8 cm of each terminal entry, and the cable must be routed separately from VFD power cables to avoid capacitive coupling.

The EL6731 supports baud rates from 9.6 kbps to 12 Mbps; the SINAMICS CU320-2DP supports the same range. The baud rate is auto-detected, but it is good practice to lock the baud rate on the master to avoid the master downshifting after a transient. Termination power must be enabled on the EL6731 when the terminal sits at the segment end and disabled on intermediate EL6731 nodes. The CU320-2DP provides a PROFIBUS connector with built-in terminator; engage it only when the CU320-2DP is the segment end.

Maximum segment length depends on baud rate:

PROFIBUS DP cable Type A is the only cable approved for use at 12 Mbps and the only cable recommended for any of the higher baud rates. The values above are the cable-engineering limits from the PROFIBUS standard; refer to the IEC 61158 / IEC 61784 cable specification for the full requirements.

Field-Proven Commissioning Checklist

• Drive firmware matched to GSD: confirm r0018 equals the GSD release string in TwinCAT.
• Slot configuration: confirm slot in EL6731 maps to telegram activated by p0922.
• PROFIBUS address: confirm p0918 matches the slave address in the TwinCAT project.
• Baud rate: EL6731 supports up to 12 Mbps; SINAMICS CU320-2DP supports up to 12 Mbps. Use the same baud across the segment.
• Bus termination: terminator power on the EL6731 enabled only at the segment end. CU320-2DP terminator enabled only if the CU is at the segment end.
• Cable shielding: shield clamp bonded at the control cabinet backplate within 8 cm of the EL6731 terminal entry and the SINAMICS connector entry.
• AXIS DISCONNECTOR: inserted during commissioning, removed or disabled before normal operation.
• STARTER alarm buffer: cleared and monitored for at least 60 seconds after each configuration change.
• Free telegram 110 / 111: p2051 / p2061 word mapping matches the TwinCAT slot layout.
• PLC project activation: TwinCAT configuration activated and the controller restarted in Run mode after the change.

Alternative Integration Paths

If the PROFIBUS path continues to cause commissioning friction, consider the following alternatives that are supported by the same hardware family:

• PROFINET path with EL6732: the EL6732 is the PROFINET IO controller counterpart of the EL6731. The SINAMICS S120 can be migrated to a CU320-2PN (PROFINET-capable) Control Unit and integrated through the EL6732 with the same TwinCAT workflow. The GSD is replaced by a GSDML file; the alignment rule to firmware version still applies.
• EtherCAT path with AX5000: when the machine is already an EtherCAT machine, the SINAMICS S120 can be replaced by a Beckhoff AX5000 servo drive and integrated natively over EtherCAT. This removes the PROFIBUS layer entirely.
• TwinCAT 3 NC / PTP path: the SINAMICS S120 can be operated as a stepper-like axis in TwinCAT 3 NC / PTP through the EL6731 PROFIdrive MC profile, which is documented in the Beckhoff EL6731 PROFIdrive MC drive integration page.

Each of these paths has its own commissioning and versioning rules; the PROFIdrive concept of "telegram layout matched to firmware" remains the underlying constraint regardless of the physical layer.

Safety Considerations During Commissioning

When cycling the PROFIBUS bus, the drive's STW1 (control word 1) follows the PROFIdrive state machine. If the master is in OP state and the drive's enable is set, an unexpected start can occur. The standard practice is to apply ON / OFF1 = 0, inhibit operation, and acknowledge all faults before any GSD or slot change. After the change, re-arm the enable chain in the proper sequence (no fault → operation enable → pulse enable → setpoint enable).

When working near rotating machinery, follow the machine's lockout / tagout (LOTO) procedure. When the drive is integrated into a safety circuit (for example STO, SLS, or SS1), the safety functions must be tested after the PROFIdrive reconfiguration. A change to p0922 or to the slot mapping can affect the safety telegram if one is configured.

FAQ