Siemens OP17 Serial Floppy Disk Station: FD20 Driver 6AV3982-1AF26-1AX2 (OFT) Technical Reference

The Siemens OP17 text-display HMI was paired, in many European production lines installed during the late 1990s, with a Sympat GmbH FD20 serial floppy disk station. The FD20 allowed operators and commissioning engineers to back up complete OP17 projects, archive and load recipe data sets, and clone configuration between OP17 units in the field. Because Sympat GmbH no longer exists, the device and its driver are treated as legacy hardware. The original driver order number was 6AV3982-1AF26-1AX2, designation OFT, version v4.xx for the FD20. This reference consolidates the hardware topology, the IF2 (DB-15) interface behavior, the ProTool integration sequence, LED diagnostics, recipe transfer model, and field-proven recovery paths when the original driver media is missing.

System Architecture and Hardware Topology

The OP17 + FD20 pairing is a point-to-point serial system; no hub, terminator, or multi-drop arrangement is supported by the OFT driver. The FD20 connects to the OP17's IF2 port only (not IF1, which is reserved for the engineering PC running ProTool). IF2 is a female DB-15 (DA-15) subminiature connector on the rear of the OP17 housing.

The FD20 chassis is a self-powered external enclosure containing:

• A standard 3.5" floppy drive mechanism (720 KB or 1.44 MB media)
• A Sympat-proprietary controller board implementing the OFT link layer
• A Siemens-specific RS-232 / serial interface on a DB-15 male connector
• A single front-panel status LED (red or green, depending on FD20 hardware revision)

Field installations show the original Sympat cable is a shielded DB-15 to DB-15 (1:1) cable, generally 1.5 m to 3 m in length. No handshaking lines other than those used by the OFT driver are required. Power is supplied to the FD20 through a separate 24 V DC inlet; the FD20 does not draw operating power from the OP17 IF2 port.

IF2 (DB-15) Interface on the OP17

The OP17 IF2 port was designed primarily to support Siemens "option field" devices such as:

• The Sympat FD20 serial floppy disk station
• External serial printers (Siemens option class)
• Certain barcode readers operating in transparent mode

The 6AV3982-1AF26-1AX2 OFT driver is a ProTool option driver, not a firmware update. OFT in Siemens order-number parlance designates the device driver media (a 3.5" floppy or CD shipped with the ProTool option pack) rather than a Siemens firmware version. The driver archive contains the .pdr (ProTool Driver) file that ProTool imports when configuring the OP17's serial port. The driver also includes a ProTool add-in and a small diagnostic test-pattern generator used during commissioning.

Driver Order Number Decoding

The string 6AV3982-1AF26-1AX2 decodes by Siemens convention as follows:

FD20 LED Behavior

The FD20 chassis has a single front-panel LED. Two distinct operating states are observable in field installations of the v4.xx driver:

These timings are useful as a "the system is alive" check before deeper diagnostics. The 10-second boot delay and 2-second read window are the most reliable indicators that the OFT driver and the FD20 controller are negotiating correctly.

ProTool Integration Sequence

ProTool is the engineering software used to configure the OP17 family. The 6AV3982-1AF26-1AX2 OFT driver is installed as follows:

1. Start ProTool / ProTool RT on the engineering PC (Windows-based, target PC must have a 3.5" floppy or compatible USB floppy drive to read the OFT media).
2. Open the target OP17 project (.pdb / .dbs).
3. Choose Options → Add Option and point the dialog at the 3.5" floppy containing the 6AV3982-1AF26-1AX2 OFT package.
4. ProTool copies the .pdr file into the project's Drivers subdirectory and adds a new entry under OP17 → Interfaces → IF2 → Protocol.
5. Set the protocol to OFT (Sympat FD20).
6. Configure the IF2 serial parameters to 9600 bit/s, 8 data bits, no parity, 1 stop bit (the OFT driver class is fixed to 8N1 at 9600 bit/s; this is the only combination supported by the v4.xx driver).
7. Compile and download the project to the OP17. The OP17 prompts for a restart after download.
8. After restart, connect the FD20 to the OP17's IF2 port and power the FD20 before applying OP17 power. The boot sequence is order-sensitive.

Wiring and Cable

The FD20 is supplied with a DB-15 (male) to DB-15 (male) cable. Field experience indicates a 1:1 shielded cable is required, with the shield bonded at the OP17 end only. Cable length should not exceed 3 m at 9600 bit/s. Cross-over or null-modem adapters are not required; the FD20 is a DTE-style device that expects a 1:1 cable into the OP17 IF2 port.

If the original cable is missing, the field-typical DB-15 pinout for the OFT driver class on the OP17 IF2 is:

Recipe Transfer Model

The OP17 stores recipes in internal battery-backed RAM. With the FD20 connected and the OFT driver loaded, the operator can:

• Read a recipe from the floppy to the OP17 (LED ~2 s)
• Write a recipe from the OP17 to the floppy (LED on, with brief flickers as sectors are written)
• Backup the entire OP17 project to the floppy
• Restore the project from the floppy

The recipe file format on the floppy is a sequential record layout. The OFT driver does not use a filesystem-aware layer; it writes raw records and trusts the OP17 to interpret the structure. Record size is determined by the OP17 recipe configuration (configured in ProTool under the recipe object's properties). A typical deployment uses a fixed-length record of either 64, 128, or 256 bytes per recipe entry, depending on the number and type of tags in the recipe.

Recovery When the Driver Is Missing

When the original 6AV3982-1AF26-1AX2 OFT floppy is lost, the following paths have been used in the field:

1. Industrial surplus / sealed media search — Siemens spare-parts resellers occasionally have sealed OFT media. Search by the exact order number. The order number is the most reliable key.
2. Siemens legacy support — Older Siemens support packages bundled the OFT driver into the ProTool "Option" CD set. Open a support ticket referencing the order number. Siemens Industry Online Support (search by 6AV3982-1AF26-1AX2) is the authoritative source for legacy part availability.
3. Engineering reconstruction — The .pdr file structure for ProTool option drivers is documented in the ProTool SDK. Power users have reconstructed a working .pdr by combining the .pdr skeleton from a similar ProTool option driver (for example, the printer driver) with the FD20 protocol tables. This is a last-resort option and is not endorsed by Siemens; the resulting driver may not pass the ProTool option integrity check on newer ProTool service packs.
4. Substitution — project transfer — Modern replacements for project transfer include:
   • USB floppy drive on a Windows PC running ProTool, transferring project files via ProTool's normal "Transfer → Floppy" dialog instead of the OFT driver
   • Direct serial port on the engineering PC running ProSave to upload the project to the OP17 via IF1
   • Ethernet-attached upload via an OP17 with the optional Ethernet module (only on specific OP17 hardware revisions)
5. Substitution — recipe handling — For recipe handling specifically, the substitution path is weaker; the OFT driver is the canonical recipe-floppy path on the OP17. Some sites have migrated recipes to a PC-based tool and used a serial printer or barcode reader to move recipe data, but this requires custom integration.

The substitution path is preferred when the OP17 firmware supports standard ProTool upload protocols and the OFT driver is only required for field recipe handling rather than for routine project maintenance.

Verification Procedure

After the OFT driver is installed and the FD20 is connected, verify operation with the following procedure:

1. Power up the FD20 first, then the OP17. The OP17 should display "FD20 ready" or an equivalent status-line message within 15 seconds.
2. Insert a 3.5" HD floppy (1.44 MB) into the FD20. The LED should illuminate for ~10 s, then extinguish.
3. Trigger a recipe read on the OP17 from the floppy. The LED should illuminate for ~2 s, then extinguish.
4. Read a recipe, modify a tag value on the OP17, and write the recipe back. The LED should flicker during the write.
5. Power-cycle the OP17 and verify the modified recipe persists in OP17 memory (the floppy was not the source of truth, the OP17 RAM was).
6. Trigger a full project backup to a separate floppy. Verify the backup completes and the OP17 reports success.

If all six steps pass, the OFT driver and FD20 are operating within specification.

Troubleshooting Matrix

Notes on Modern Equivalents

For new installations, the FD20 + OFT driver combination should be considered obsolete. Modern Siemens HMIs (Comfort Panels, Unified Panels) support:

• Project transfer via Ethernet / PROFINET
• Recipe handling via the SIMATIC WinCC recipe object (panel-side data medium)
• USB stick for project backup directly on the panel
• OPC UA for recipe exchange with higher-level systems

If the OP17 is being maintained rather than replaced, document the FD20 setup carefully: cable pinout, driver version (v4.xx), floppy format, and recipe record size. The FD20 chassis has no user-serviceable parts; failures of the floppy drive mechanism usually mean replacement of the entire FD20 unit. Third-party USB floppy drives on a Windows PC running ProTool can substitute for the FD20 for project transfer only; for recipe transfer on the OP17, the FD20 + OFT driver pairing remains the canonical path.