Siwarex FTA Firmware Update Failure Recovery and Standalone Mode Configuration

The Siemens SIWAREX FTA (Flexible Technology, Automation) is a weighing electronics function module (FM) designed primarily for the SIMATIC S7-300 and ET 200M platforms. It is officially documented that the FTA can also be operated in a standalone mode without a SIMATIC CPU, which makes it usable in legacy scales, retrofit installations, and OEM machines that do not require the full TIA Portal / STEP 7 stack. When the firmware on the FTA is updated incorrectly, the module can enter a state where it no longer processes any commands from the backplane or from the service interface, leaving the system with a hard weight-measurement fault. This guide combines the official Siemens recovery workflow with the standalone-mode commissioning procedure so that the module can be brought back to a known-good state and then configured for CPU-less operation.

1. Siwarex FTA Module Identification

Before applying any recovery or standalone procedure, confirm the exact article number (MLFB) and the currently loaded firmware. The FTA module is identified as:

2. Symptoms of a Failed Firmware Update

A failed or interrupted firmware update on the SIWAREX FTA typically manifests as one or more of the following conditions:

• The SF LED (red) is lit solid, indicating a module fault.
• The BF LED (red) may be lit if the backplane or fieldbus handshake cannot complete.
• The ON LED (green) does not transition to steady-on or blinks at an abnormal rate.
• No command (e.g., zero, tare, calibration) is executed even though SIWATOOL FTA reports the connection as established.
• STEP 7 / TIA Portal reports "Module does not respond" or "Firmware update failed" in the diagnostic buffer.
• Service port (RS-232) returns no recognizable Siwarex protocol response.

If the original update was performed via SIMATIC and is now in an inconsistent state, do not assume that the module is bricked. Siemens FM modules almost always retain a recovery path through a clean repeat of the firmware update procedure.

3. Root Cause Analysis

The most common root causes for a Siwarex FTA that stops responding after a firmware change are:

1. Power interruption during flash write. The flash region was partially overwritten, leaving the bootloader intact but the application image incomplete.
2. Incompatible firmware image. A firmware package intended for SIWAREX U, MS, or a different FTA variant was loaded. The bootloader rejects it but may leave the module in a non-executing state until a valid image is reapplied.
3. Wrong firmware channel. The update was sent to the wrong interface (e.g., the SIMATIC backplane channel instead of the SIWATOOL service channel) and the flash partition was corrupted mid-write.
4. STEP 7 / TIA Portal version mismatch. The tool version does not match the firmware container format, causing the upload to abort without rolling back.

The first three causes are recoverable by repeating a clean firmware update through the documented Siemens path. The fourth typically requires aligning the engineering tool to a version compatible with the firmware file shipped by Siemens.

4. Pre-Recovery Verification

Before you attempt the recovery update, perform these checks in order:

1. Confirm the firmware file. Only use the firmware executable published on the Siemens Industry Online Support. Do not source firmware from third-party mirrors.
2. Check the engineering tool version. If you originally used STEP 7 V5.x, ensure the same or newer SP level is used for the recovery. If you used TIA Portal, ensure the firmware container matches the TIA version on the PC.
3. Confirm the service cable. For SIWATOOL-based recovery, use the dedicated serial cable (Siemens RS-232 service cable) wired to the front 9-pin Sub-D of the FTA. Pinout is documented in the manual referenced above.
4. Verify power stability. The 24 V supply to the S7-300 rail / ET 200M station must be stable for the duration of the update. A UPS or stabilized bench supply is recommended during recovery.
5. Document the current state. Capture the LED states and the diagnostic buffer entries from STEP 7 (if the CPU is still online) before powering down.

5. Firmware Recovery Procedure (STEP 7 / TIA Portal Path)

For a SIMATIC-attached FTA, perform the recovery as follows:

1. Open STEP 7 V5.x or TIA Portal with the project that contains the FTA in HW Config / device view.
2. Right-click the FTA slot and select "Target system > Firmware update" (STEP 7 V5.x) or use the equivalent "Firmware update" entry in the TIA Portal device inspection window.
3. Browse to the valid FTA firmware file (.exe or .upd, depending on tool) downloaded from the Siemens support portal.
4. Confirm the article number and target firmware version. Mismatches are blocked by the tool.
5. Trigger the update. The progress dialog shows the active flash erase and write phases. Do not interrupt the process.
6. Wait for the module to complete the automatic restart. The ON LED must return to steady green and SF must clear.
7. Re-load the SIWATOOL FTA parameter set if the engineering tool warns that parameters were reset.

If the first attempt fails again, repeat with the same firmware file before escalating. A consistent failure on multiple passes typically indicates a corrupted firmware container or a hardware fault on the FTA itself.

6. Firmware Recovery Procedure (SIWATOOL FTA Path)

If the backplane path is not available (for example, the CPU is removed or the station has no S7 master), the SIWATOOL FTA service tool can drive the update directly over the RS-232 service port:

1. Connect the FTA front Sub-D (RS-232) to the PC using the Siemens service cable. Default service port parameters: 9600 baud, 8 data bits, no parity, 1 stop bit. Confirm the exact values in the manual.
2. Launch SIWATOOL FTA and open the connection. The tool negotiates with the bootloader if the main image is invalid.
3. Use the firmware update menu in SIWATOOL and point it to the official firmware image.
4. Confirm and start the update. Maintain power throughout.
5. After the update completes, power-cycle the FTA and re-establish the SIWATOOL session.

7. Siwarex FTA Standalone Mode Overview

Per the Siemens Knowledge Base article 10183487, the Siwarex FTA provides a dedicated standalone mode. In standalone mode, the FTA functions as an independent weighing transmitter. It no longer requires a SIMATIC CPU or STEP 7/TIA project to perform weighing, and it exposes its measurement data, status, and commands through the standard FTA interfaces (RS-232 service, RS-485, and the analog/digital I/O channels).

This makes the FTA usable in:

• Standalone platform scales with a remote display.
• Retrofit installations on existing machines with a non-Siemens controller.
• OEM skids that only require weight + status via Modbus RTU or serial ASCII.
• Test benches where a SIMATIC CPU would be excessive.

8. Hardware Configuration for Standalone Operation

To run the FTA in standalone mode, the module must be mechanically installed and powered even though no S7 CPU is present. The supported configurations are:

The load cells connect to the FTA front connector as in any standard FTA wiring scheme. Refer to the FTA manual, chapter 4 (Installation and Wiring), for the exact pinout and the four-wire / six-wire load cell wiring convention.

9. Parameter Assignment in Standalone Mode

Parameters for the standalone application are loaded into the FTA through SIWATOOL FTA over the RS-232 service port. The typical parameter set covers:

• DR (scale code): calibration mode (e.g., calculated, calibration weight, default).
• Adjustment values: zero, span, and the corresponding decimal places and unit (kg, g, t, lb).
• Filter: low-pass filter and stability window for the weight signal.
• Limits: empty, min, max, and over-range thresholds.
• I/O configuration: assignment of the digital inputs/outputs and the analog output behavior.
• Communication: serial interface mode (Siwarex protocol, Modbus RTU, ASCII) and baud rate.

Once written, the FTA retains the parameter set in non-volatile memory. SIWATOOL FTA can save the parameter set to a backup file (.fta) so that it can be reloaded after any firmware update that resets parameters.

10. Communication Interfaces in Standalone Mode

The FTA supports multiple serial modes in standalone operation. Confirm the active mode against the manual because the exact list is firmware-revision dependent:

11. Verification and Commissioning

After the firmware has been restored and the standalone parameter set has been loaded, verify the module using this sequence:

1. Power-cycle the FTA and confirm the ON LED is steady green with SF and BF off.
2. Connect SIWATOOL FTA and read out the live weight. Apply a known test weight and confirm the displayed value matches within the calibrated tolerance.
3. Trigger a zero command from SIWATOOL and verify the zero is taken and stored.
4. Trigger a tare command with an empty scale and verify the net value reads 0.
5. Apply the configured calibration weight and confirm the span adjustment is accepted.
6. If a Modbus RTU master is connected, read holding register 0 (process weight) and verify cyclic updates.
7. If a remote display is connected, confirm that the weight value is broadcast without frame errors.

12. Troubleshooting Matrix

13. Escalation Path

If the recovery steps above do not bring the FTA back to service, the next step is to open a Siemens Industry Online Support request and provide:

• The full MLFB (including the -Z options if present).
• The firmware version you attempted to install and the version you attempted to recover to.
• The engineering tool version (STEP 7 SP / TIA Portal version).
• A photo of the LED state on power-up.
• The diagnostic buffer entries from the SIMATIC CPU if available.

With these details, Siemens support can determine whether the module is recoverable or needs to be returned through the standard RMA process.