Resolving F1910 PROFIBUS Timeout on SINAMICS G120 CU240E-2-DP

Resolving F1910 PROFIBUS Timeout on SINAMICS G120 CU240E-2-DP

The SINAMICS G120 modular drive system with a CU240E-2-DP Control Unit communicating over PROFIBUS to a SIMATIC S7-317F-2PN/DP fail-safe PLC can enter fault state F1910 (PROFIBUS communication failure) immediately after a start command. The fault is typically transient: communication drops for one or two DP cycles, the drive latches off, then the bus recovers. This article documents the three root causes confirmed on this hardware combination and the field-proven remediation steps drawn from official Siemens documentation.

1. Problem Statement

The reported symptoms on a SINAMICS G120 (PM240 + CU240E-2-DP, FW >= V4.4) connected to an S7-317F-2PN/DP via PROFIBUS DP are:

• STARTER (or TIA Portal with Startdrive) successfully downloads the drive configuration.
• Six PZD words (4 PKW + 6 PZD or pure 6 PZD) are configured and acknowledged by both PLC HW Config and STARTER.
• On issuing 047E (control word 1) to PQW, the drive trips with F1910 - PROFIBUS communication failure.
• Bus communication recovers automatically within one to two DP cycles, but the drive remains in fault state and must be acknowledged.
• Replacing the G120 with a different drive on the same PROFIBUS segment reproduces the identical F1910, isolating the problem to the master class 1 (PLC) or class 2 (PG/PC) configuration rather than the drive hardware.

The fault is not a cable, terminator, or baud-rate issue: the bus is otherwise healthy. The F1910 latches on a logical timeout, not a physical link failure.

2. Affected Hardware and Firmware

Reference: SINAMICS G120 CU240B-2/CU240E-2 List Manual.

3. Root Cause Analysis

F1910 on a SINAMICS PROFIBUS slave is generated by the firmware monitor p2047 (PROFIBUS monitoring time). When no new process data is received within p2047 × 2 DP cycles, the drive raises F1910. On a CU240E-2-DP, p2047 defaults to 10 ms (firmware >= V4.4 SP3) and is internally scaled to the configured DP cycle. Three configuration mistakes produce this symptom on otherwise healthy hardware:

3.1 PPO / Telegram Mismatch Between HW Config and STARTER

The S7 HW Config slot for the G120 is set to one PPO type (e.g. PPO 1: 4 PKW + 4 PZD), while STARTER configures the drive for a different telegram (e.g. PPO 4: 0 PKW + 6 PZD, or standard telegram 1: 2 PZD). The slave accepts the first Set_Prm from the class 1 master, but when STARTER (acting as a class 2 master) reads/writes with its own telegrams, the slave's process-data image is reset and the next class 1 telegram is rejected as a checksum mismatch. The PLC interprets the missing ACK as a timeout, raising F1910.

3.2 "PG/PC is the only master on the bus" Option Active

In the PG/PC interface assignment of STARTER (or Startdrive), the option "PG/PC is the only master on the bus" is enabled by default. When checked, the PG acts as PROFIBUS class 1 master, which forces the slave into a single-master mode and breaks token passing with the S7-317F acting as the second class 1 master. The slave momentarily drops process data, the S7 raises the F1910 fault, and the bus recovers only after the PG releases the token. This symptom also appears on SINAMICS G130 in the same network configuration.

3.3 Motor Not Connected at First Start

On a PM240 Power Module, the first run attempt with the motor terminals open (U2/V2/W2 unconnected) drives the output stage into a heavy IGBT overcurrent at the moment the inverter tries to ramp. The CU240E-2-DP interprets the resulting DC-link disturbance as a comms-cycle stall and generates F1910 in parallel with a current-related fault (F0001 or F3001). The PROFIBUS error is therefore a secondary indication of a primary motor-wiring problem.

4. Solution Procedure

4.1 Align the PPO Type in Both Engineering Tools

1. Open the S7 project in STEP 7 (or TIA Portal) and load the G120 station.
2. In HW Config, right-click the G120 slot and open Object Properties → PROFIBUS interface → Telegram configuration.
3. Note the selected PPO type or standard telegram. Write it down.
4. Open STARTER and connect to the drive (use the same CP, e.g. CP5512 / CP5711, or route through the PLC).
5. In STARTER, navigate to Drive → Communication → PROFIBUS and set the identical PPO type. For 6 PZD only, select PPO 4 (0 PKW + 6 PZD) or standard telegram 1 for control/status word + speed setpoint/actual.
6. Download the project to the drive and save RAM-to-ROM (copy RAM to ROM via p0977 = 1).
7. Repeat for any second drive on the same bus - the same PPO type must be used on every G120 / G130 in the segment when shared with a single class 1 master.

Standard telegram mapping for the CU240E-2-DP (per List Manual, section "Telegram types"):

4.2 Uncheck "PG/PC is the only master on the bus"

1. In STARTER, open Options → Set PG/PC interface.
2. Select the CP that is connected to PROFIBUS (for example S7ONLINE (STEP7) → CP5711.PROFIBUS.1).
3. Click Properties and on the PROFIBUS tab, uncheck the box "PG/PC is the only master on the bus".
4. Confirm with OK and re-connect to the drive.

The same setting is found in Startdrive (TIA Portal) under Online → Online access → ... → PROFIBUS interface properties. With this checkbox cleared, the PG operates strictly as a class 2 master and the S7-317F retains class 1 token-holding rights without contention.

4.3 Verify Motor Wiring Before the First Start

1. Open the PM240 terminal cover and confirm the motor cables are landed on U2 / V2 / W2 and that the shield is clamped to the PE bar.
2. Measure the insulation resistance phase-to-phase and phase-to-PE with a 500 V megohmmeter; readings > 1 MΩ are mandatory for a healthy PM240 output stage.
3. Confirm the motor star/delta configuration matches the drive's p0304 / p0305 / p0307 / p0308 / p0310 rating plate parameters.
4. Perform a motor identification run (p1900 = 2) with the motor decoupled from the load, or with the load mechanically locked.

5. Telegram and PZD Configuration Details

For the user's six-PZD case, two options are valid:

• Option A - PPO 4 (0 PKW + 6 PZD): Used when parameter access is performed via STARTER (acyclic) and the cyclic channel is dedicated to control/status plus setpoint/actual speed plus process data (e.g. torque, current). Word assignment:
  • Receive (PLC → Drive): PQW 0=STW1, 2=NSOLL_B, 4=free, 6=free, 8=free, 10=free.
  • Send (Drive → PLC): PIW 0=ZSW1, 2=NIST_B, 4=IAIST_GLATT, 6=MIST_GLATT, 8=PIST_GLATT, 10=free.
• Option B - Standard Telegram 1 + free extension (BICO): Use telegram 1 (STW1 / ZSW1 + NSOLL_B / NIST_B) and interconnect the remaining four PZDs through BICO (r2050 / p2051).

The control word 0x047E (binary 0000 0100 0111 1110) is the standard SINAMICS "OFF2 + OFF3 + Enable + Pulse enable" precondition; bit-by-bit:

To start the drive, set bit 0 to 1 (ON command). The 0x047E value is correct for the pre-conditions; the PLC must raise bit 0 to 1 in the next cycle to issue the run command.

6. Diagnostic Parameters and Verification

After applying the three fixes, perform the following verification sequence before re-energizing the load.

If F1910 still latches, repeat step 4.2 (clear "only master" checkbox) and confirm that STARTER is not also configured as a class 1 master in another active project. Only one class 1 master is allowed per PROFIBUS segment during cyclic data exchange.

7. Parameter Reference for PROFIBUS on CU240E-2-DP

Reference: SINAMICS G120 CU240B-2/CU240E-2 List Manual (PDF).

8. Common Pitfalls

• GSD file version mismatch: The GSD imported in HW Config must match the CU240E-2-DP firmware. Mismatched GSD versions silently downgrade telegram support and force the slave to fall back to a default PPO, generating F1910 at the first cyclic I/O update.
• Two class 1 masters on the same segment: The S7-317F is class 1. STARTER (with "only master" enabled) is also class 1. This double-master situation causes token loss and the slave drops the I/O exchange.
• Fail-safe CPU in RUN with F-CPU password locked: Modifications to the F-CPU's PROFIBUS configuration require the F-CPU to be in STOP. If the PLC ignores the STOP command because of a safety program signature mismatch, the new telegram cannot be downloaded.
• Motor identification with load connected: Running p1900 = 2 with the load attached causes the motor to rotate briefly; for vertical loads, set p1900 = 1 or decouple the load.
• Excessive p2047 setting: Setting p2047 too high delays the F1910 detection, masking genuine comms errors. Keep it ≤ 50 ms unless the DP cycle is > 25 ms.

9. Related Issues on the G120 / G130 Family

The same "PG/PC is the only master on the bus" symptom has been confirmed on SINAMICS G130 (CU320-2 DP) connected to the same S7-300/400 PROFIBUS class 1 master. The remediation is identical: uncheck the PG/PC class 1 master option in STARTER or Startdrive. The G130 additionally requires p2030 = 2 (PROFIBUS) and a valid GSD file SIEM8130.GSD or higher, depending on firmware.

For Safety Integrated applications on the G120 (SINAMICS Safety Integrated, see SINAMICS G120 Safety Integrated Function Manual (PDF)), the F-CPU in PROFIsafe mode uses PROFIBUS DP with PROFIsafe on top of PPO type 1 or standard telegram 30. PROFIsafe slot verification is enforced by the F-CPU, and an F1910 in that context can immediately drop the safety function, requiring a new PROFIsafe sign-off.

10. Verification Checklist

Use this checklist before returning the machine to production:

1. PPO type in HW Config and STARTER is identical (e.g. PPO 4).
2. "PG/PC is the only master on the bus" checkbox is cleared in the active PG/PC interface.
3. Motor leads U2/V2/W2 are connected, shields bonded, insulation tested.
4. Motor rating plate parameters (p0301..p0311) are entered exactly as printed.
5. Motor identification completed (p1900 = 2).
6. STARTER project saved to the drive (RAM-to-ROM) and to the PG hard drive.
7. S7 project compiled and downloaded to the CPU.
8. PLC issues 0x047E then 0x047F; ZSW1 bit 2 = 1; r0947[0] = 0 (no fault).
9. Safety program signature unchanged, F-CPU in RUN without diagnostic interruption.

11. Frequently Asked Questions