Troubleshooting SIMOCODE PRO V 'Return Feedback Off' Fault in a Direct Online (SMC_DIR) Starter

The SIMOCODE pro V is a modular motor management system from Siemens (SIRIUS family) that combines motor protection, control, and diagnostics over PROFIBUS DP or PROFINET. One of the most common field failures when commissioning a direct online starter in PCS 7 — or a stand-alone S7-1200/S7-1500 environment — is the "Return Feedback Off" alarm. The motor accepts the start pulse, accelerates, then trips after a short delay even though the contactor is closed and the current path is intact. This article explains the root cause, the correct SIMOCODE ES parameterization, and the verification steps required to resolve the fault across all 80 devices in a typical PCS 7 fleet.

1. Problem Description

Engineer symptom log on the affected cabinet:

• Topology: ~80x SIMOCODE pro V basic units, PCS 7 V9.x, PROFIBUS DP ring to ET 200M / DMF-Local operator panels.
• Starter type: SMC_DIR (direct online, non-reversing).
• Sequence: Operator issues Start → contactor closes → motor begins to rotate → 200–500 ms later SIMOCODE raises the Return Feedback Off (RFC) alarm → PCS 7 shows red fault banner → motor coasts to stop.
• Test: Activating the Jog bit (JOG_ON = 1) starts the motor and keeps it running without the alarm. The control word without the jog only produces a single rising edge.
• Wiring verification: Confirmed by a Siemens France field engineer — the main power path, PE, and current measurement inputs (IL1/IL2/IL3) are correct.

This exact pattern is a signature of a command-signal level/duration mismatch between the PLC control word and the SIMOCODE "command source." SIMOCODE is a stateful controller; it expects a continuous (maintained) level, not an edge, on the ON command unless the configuration explicitly maps to a different operating mode.

2. Root Cause Analysis

SIMOCODE pro V distinguishes between two physical/control levels for motor start commands:

The behavior the engineer observed — "Jog starts the motor, but the PLC command only produces a rise edge and trips" — means the SIMOCODE was parameterized for a pulsed / jog control input, while PCS 7 (or the S7-1200/1500 driver block) is delivering a maintained (level) control word. The PCS 7 block sets ON = 1 on each cyclic update. If SIMOCODE interprets the same bit as a jog, it sees the rising edge, latches internally, but then evaluates feedback against an expected behavior the wiring cannot satisfy, producing the Return Feedback Off event after the configurable feedback-off delay (default 2 s).

2.1 Secondary Causes That Can Produce the Same Symptom

1. Test Position Feedback (TPF) is enabled in SIMOCODE ES → Device configuration → Inputs/Outputs → "Test position feedback." When the DMF-Local operator panel is plugged in or the test bit is asserted, SIMOCODE expects the contactor to be open and trips the running motor.
2. Feedback Off Delay is set too short for the contactor closure time (typical Q-line contactor closure 30–80 ms, with 100–250 ms contactor-side debounce).
3. Wrong feedback source assigned in SIMOCODE ES — the input that is wired to the contactor's Auxiliary Normally Open is mapped to a different bit (e.g., a status bit that only follows the ON command).
4. DMF-Local / DM-F Local operator panel in "Local/Remote" mode with the Local-Hand key switch in a position that asserts a permissive the PLC does not provide.

3. Solution: Configure SIMOCODE ES for a Standard Direct Online Starter (SMC_DIR)

Use the official SIMOCODE pro System Manual (PDF) and the SIMOCODE pro V PN / FDI Programming and Operating Manual (PDF) as the authoritative reference. The block diagram below summarizes the parameter set required for a PCS 7-driven SMC_DIR with maintained commands and a contactor-feedback (R) wired to a digital input on the digital module (DM).

3.1 Step-by-Step SIMOCODE ES Configuration

1. Open the device in SIMOCODE ES 2007 / TIA Portal (V15+). For PROFINET variants, the device is added under Devices & Networks and parametrized in the device view. For PROFIBUS DP, use the SIMOCODE ES stand-alone tool with a USB-to-PROFIBUS or Ethernet routing path.
2. Select the starter function block. In the device tree, navigate to Parameter → Function blocks → Motor control → Starter and choose SMC_DIR (Direct Online Starter, non-reversing). Do not select SMC_REV unless the reversing contactor is wired and the feedback interlock is present.
3. Assign the command source — CRITICAL FIX. Under Parameters → Command sources:
   • Control station 1 = PLC (cyclic) for PCS 7 / S7-1500 drivers.
   • Control station 2 = Field device (DOL / jog pushbutton) if the DMF-Local is wired for hand-operation.
   • Set the command type to "Maintained command (level)". In SIMOCODE ES this is the default; verify it is not set to "Jog (pulse)" or "Jog mode with reversal".
4. Map the ON / OFF bits to the cyclic PROFIBUS/PROFINET control word. Default for PCS 7 driver block SIMOCODE pro V (V6.0):

   Bit (Control Word)	Meaning	Value for ON
   Bit 0	ON / OFF (motor ON)	1
   Bit 1	OFF2 (coast to stop, optional)	0
   Bit 2	OFF3 (quick stop, optional)	0
   Bit 3	Enable / Reset	1
   Bit 4	Local/Remote	0 = Remote (PLC)
   Bit 5	Jog	0 (use jog input instead if needed)

5. Map the return feedback (R) input. Navigate to Parameters → Inputs → Digital inputs. For the contactor auxiliary NO, assign the chosen DM input (e.g., DI0 on the digital module) to "Return feedback closed (R)". The status of this input must follow the contactor state, not the current-transformer threshold.
6. Disable Test Position Feedback unless the drawer is used. In Parameters → Function blocks → Inputs, uncheck Test position feedback (TPF). Withdrawable motor starters that require test-mode handling should use the dedicated "TPF" function block, not the standard SMC_DIR.
7. Set the Feedback Off Delay. Default 2.0 s in SIMOCODE ES. For Q-line contactors, set to 3.0–5.0 s to ride through contactor closure and any one-cycle PLC scan jitter when the controller is on the same PROFIBUS cycle as the SIMOCODE.
8. Enable Motor Current Monitoring. Threshold I > 0.10 × I_e; undercurrent threshold I < 0.05 × I_e for the trip after start (catches belt breakage / coupling shear).
9. Compile and download. Right-click the device in the project tree → Download to device. Always run a "Download to target device — Stop and restart of the SIMOCODE" so the new command-source mapping takes effect on the next power-up.

3.2 PCS 7 Driver Block Wiring

The PCS 7 Advanced Process Library (APL) block MOT_SPED or MOT_SLOW drives the SIMOCODE pro V via the channel block CH_MOT and the driver block SIMO_3UF7. Confirm in CFC:

1. SIMO_3UF7.QBAD = 0 (good quality).
2. SIMO_3UF7.AUX_PRIM wired to the contactor feedback (R) — not to the current bit.
3. SIMO_3UF7.SP_RPM / SP_SPEED not used for SMC_DIR; leave the speed-related inputs at default.
4. The faceplate does not need to be set to "Jog" mode. If the operator selected "Jog" by mistake, the local/remote permissive will conflict with the cyclic PLC word and the RFC will recur.

4. S7-1200 / S7-1500 Parameterization via TIA Portal

For a stand-alone S7-1500 connected to SIMOCODE pro V PN over PROFINET, you do not need the special USB-to-PROFIBUS cable. The PROFINET device can be parametrized through the PLC's PROFINET interface as long as SIMOCODE is assigned to the IO controller and the GSDML file (Siemens-DE.0811) is installed. TIA Portal then loads the parameter record into SIMOCODE on every restart of the IO device. The official path is documented in the SIMOCODE pro V PN FDI Programming and Operating Manual, section "Parameter assignment via PROFINET."

5. Verification

1. Read the diagnostic buffer from the SIMOCODE device via web server (SIMOCODE pro V PN only) or SIMOCODE ES → Online → Diagnostics → Event log. Look for event code 0x102A (Return Feedback Off).
2. Check the cyclic status word in PCS 7: bit 0 (Running) and the feedback bit from SIMO_3UF7.AUX_PRIM. Both must be 1 within 1.0 s of the start command.
3. Toggle ON/OFF 20 times in succession from the faceplate. If the motor starts cleanly every time, the original RFC is fixed.
4. Pull the DMF-Local panel off while the motor is running. If the motor stops and an RFC appears, TPF is incorrectly enabled. Re-check step 3.1.6.
5. Duplicate the working configuration across the 80 devices. In SIMOCODE ES, right-click the device → Copy, then paste the parameter record into each downstream instance. Always re-flash the firmware record to keep revisions consistent — the supported record versions for PCS 7 V9.0 SPx are listed in the Siemens SIMOCODE product page under "Software & firmware."

6. Quick Configuration Checklist

7. Related Fault Codes

8. Common Pitfalls Across a 80-Device Fleet

• Per-device copy in SIMOCODE ES is faster than HM-to-device export for a uniform SMC_DIR fleet, but always re-read the parameter view from the device (right-click → Upload from device) before signing off, to catch devices that rejected a partial download.
• PROFIBUS DP diagnostic addresses must be unique per PCS 7 AS. A duplicated address causes a single device to go offline and can be misread as a contactor fault.
• Firmware mismatch between basic unit and digital module (e.g., 3UF7011-xA-x-x.xx vs. 3UF7011-xB-x-x.xx) can lock the device in TPF mode. The cross-compatibility matrix is in the system manual linked above.
• CT orientation: for the SIMOCODE pro V current measuring module, the L1/L2/L3 feed must enter the labeled side (P1) and exit P2. Reversed CTs read zero current → undercurrent trip after the start ramp.

9. Frequently Asked Questions