SIWAREX FTA SIWATOOL: Commissioning, Backup, and MMC Card Reference

The SIWAREX FTA (Field Transmitter Amplifier) is a SIMATIC S7-300 distributed I/O module designed for the measurement of force, tension, and weight in non-automatic weighing machines. It is part of the SIWAREX weighing electronics portfolio and is identified by the order number 7MH4900-2AA01. The accompanying SIWATOOL commissioning software is the canonical field service tool used to set calibration data, scale parameters, and diagnostics on FTA modules without requiring a fully programmed SIMATIC CPU or TIA Portal project.

This reference consolidates the field-proven procedures for ordering, installing, and using SIWATOOL with the FTA, including the role of the optional MMC card, the difference between the legacy and current configuration packages, and the dual paths for parameter backup/restore (SIWATOOL GUI versus STEP 7 function calls).

1. SIWAREX FTA Module Identification and Scope

The SIWAREX FTA is a 1-channel weighing module that occupies one slot in a SIMATIC S7-300 rack and is addressed as a standard distributed I/O module on the backplane bus. It digitizes the load cell signal at high resolution and exposes scale data (gross, net, tare, status) to the CPU through the standard I/O process image and through function blocks in the SIWAREX FTA library.

2. SIWATOOL Licensing and Procurement

SIWATOOL is not freeware. It is shipped only as part of the SIWAREX FTA configuration package and is licensed per installation. End users who attempt to obtain a stand-alone copy must purchase the configuration package rather than downloading a runtime.

• Distribution channel: SIWAREX FTA configuration package, only.
• Re-distribution: Not permitted; SIWATOOL installs are tied to the configuration package license.
• Bundled with: RS-232 commissioning cable, CD or USB media with the SIWATOOL setup, and printed short manual.

For commercial procurement, refer to the Siemens Industry Mall SIWATOOL configurator. For product background, see the Siemens SIWAREX Weighing Software product page.

3. Configuration Package Selection: 7MH4900-2AK01 vs 7MH4900-2AK02

The SIWAREX FTA configuration package has undergone a part number transition. Field engineers should be aware of the legacy and current part numbers and the migration path when replacing a damaged or lost CD.

When ordering a replacement, specify 7MH4900-2AK02. The new package is fully compatible with the existing FTA hardware; the part-number change reflects updated media, manuals, and licensing rather than a firmware incompatibility.

4. MMC Card Purpose and Restrictions (7MH4900-2AY21)

The MMC card (Multi Media Card) for the SIWAREX FTA is a separate Siemens spare part:

• Order number: 7MH4900-2AY21
• Use case: Legal-for-trade alibi log only.
• Not used for: Backing up calibration or application parameters.

You do not need an MMC card to run the FTA. It is required only when the scale is used in a legally regulated environment (for example, when an inspector of the local weights-and-measures authority seals the FTA to certify commercial transactions). In that case, the MMC is mandatory because the FTA writes a tamper-evident, append-only protocol to it that records the date, time, and weight value of every legally relevant weighing.

4.1 When the MMC Is Not Required

• Process weighing (force, tension, level) where no commercial transaction is involved.
• Internal factory scales used for inventory or batching with no legal-for-trade certification.
• Test and engineering rigs.

4.2 When the MMC Is Required

• Scales sealed by a legal metrology inspector for commercial trade.
• Scales that must produce an alibi printout on demand.
• Scales subject to fiscal verification (Pharma, Food retail, Refined products, etc., per local law).

5. SIWATOOL Functional Scope

SIWATOOL exposes a Windows application that connects to the FTA through a dedicated RS-232 service cable. The tool is deliberately self-contained so that field service engineers can commission, calibrate, and diagnose a SIWAREX FTA without needing to know STEP 7, TIA Portal, or PCS 7.

Per the SIWATOOL service documentation in the SIMATIC manual collection, the canonical SIWATOOL workflow is:

1. Connect the SIWATOOL RS-232 cable between the PC and the FTA front service port.
2. Launch SIWATOOL; the tool auto-detects the connected FTA and reads the device version.
3. Use Receive all data to upload the current scale parameters into a backup file on the PC.
4. Edit parameters offline (calibration, limits, filter, units) and re-transmit them with Send all data.
5. Save the resulting file as the controlled backup record for the scale.

The same Receive/Send mechanism is used for full parameter backup and for cloning one FTA configuration to another identical unit of the same type and order number.

6. Parameter Backup and Restore via SIWATOOL

This is the primary backup/restore method for the FTA. It works on every FTA produced since 2004, with or without an MMC card.

6.1 Backup (Upload from FTA to PC)

1. Power on the S7-300 station; the FTA does not need to be in run mode but must be powered.
2. Connect the SIWATOOL service cable to the FTA's front service port and to the PC's RS-232 (or USB-RS232 adapter).
3. Start SIWATOOL and select the correct COM port and baud rate (default 9,600 bit/s on FTA).
4. Click Receive all data in the SIWATOOL menu.
5. When the transfer completes, File → Save As and store the .fwb (or version-specific) backup file with a meaningful name that includes the scale tag and date.

6.2 Restore (Download from PC to FTA)

1. Open SIWATOOL and connect to the FTA (same physical connection as above).
2. File → Open the previously saved backup file.
3. Click Send all data; SIWATOOL writes the entire parameter set to the FTA's non-volatile memory.
4. Cycle power on the FTA to ensure the new parameters are loaded at the next startup.
5. Re-read the parameters with Receive all data and compare to the source file to confirm bit-for-bit fidelity.

7. Parameter Backup and Restore via STEP 7 Commands

When the scale is integrated into a STEP 7 (or TIA Portal) automation project, parameter backup and restore can be triggered from the CPU program without a service PC. The FTA library exposes two function codes (FCs) for this purpose:

7.1 Typical Use Case

A PLC technician replaces a faulty FTA with a spare of the same order number. With the Scale-DB already populated from a previous backup, calling FC 699 from OB1 (or a startup OB) writes the saved parameters to the new module in seconds, avoiding a full SIWATOOL re-calibration on the plant floor.

7.2 Code Skeleton (STEP 7 STL-style pseudocode)

// In OB100 (startup) or OB1, on rising edge of trigger tag:
CALL  FC649   // Upload from FTA to Scale-DB
   iDB_No  := 100   // number of the Scale-DB
   RET_VAL := MW200 // return code (0 = OK)

// On restore command:
CALL  FC699   // Download from Scale-DB to FTA
   iDB_No  := 100
   RET_VAL := MW202 // return code (0 = OK)

Exact symbol names and the precise return-code definitions are documented in the SIWAREX FTA Function Block Library manual that ships with the configuration package; consult that PDF for the specific build you install.

8. SIWATOOL Communication Interface

SIWATOOL communicates with the FTA over an RS-232 point-to-point link through a Siemens service cable. The original configuration package shipped a 9-pin D-sub cable; modern PCs without a built-in COM port require a USB-to-RS-232 adapter rated for industrial use (FTDI-based adapters are recommended for repeatability).

Do not substitute a generic null-modem cable. The FTA service port is not a standard DCE and requires the Siemens-issued wiring for handshaking to be honored.

9. Migration Path: From SIWAREX FTA to WP Series

The SIWAREX FTA belongs to the S7-300 generation. Newer SIWAREX platforms in the ET 200SP and S7-1500 families — SIWAREX WP321, WP521, and WP522 — also use SIWATOOL for fast commissioning, but the tool's UI and the underlying function blocks are not interchangeable.

When replacing a fleet of FTAs, do not assume the WP-series tools will read FTA backup files. Treat them as separate platforms and re-do calibration when you swap generations.

10. Verification and Field Acceptance

After a SIWATOOL-driven backup, restore, or commissioning action, run the following verification sequence before releasing the scale to production:

1. Parameter-roundtrip check: Perform SIWATOOL Receive all data, compare against the source backup file using a diff or hash.
2. Zero and span check: With no load on the scale, command the FTA to zero through SIWATOOL or via the application. Apply a known test weight and verify the indicated value against the calibration.
3. Legal-for-trade sealing: If the scale is to be sealed, install the MMC (7MH4900-2AY21), let the FTA log at least one cycle, and confirm the alibi log reads back through the legal-for-trade tool chain.
4. CPU-side read consistency: From the STEP 7 / TIA project, read the Scale-DB and confirm it matches the SIWATOOL view (use FC 649 if necessary to re-sync).
5. Restart test: Power-cycle the S7-300 station and confirm the FTA retains calibration, zero, and span across the cold start.

11. Troubleshooting Matrix

12. Frequently Asked Questions