Recovering Programs from Siemens LOGO! 24RCL Protected Cards

Problem Overview: Lost Siemens LOGO! 24RCL Program After Controller Failure

The reported incident involves four Siemens LOGO! 24RCL logic modules installed aboard a vessel, each controlling a lifeboat launch and recovery hydraulic system. After a surge event, two of the four 24RCL base units failed together with their associated program cards. Replacement 24RCL modules were installed and new red program cards were obtained, but the new cards arrived blank. The surviving program cards from the two un-failed controllers still run in the new base units, confirming the program itself is intact, but the menus show "Program Protect" the moment the user attempts to enter Program Edit and no password prompt appears. The crew has no copy of the original LOGO!Soft Comfort project file on a PC.

This is a textbook case of knowhow-protected program recovery on the LOGO! platform. The program physically exists on the card, but Siemens' Copy & Knowhow protection prevents the user from extracting it back to a PC or writing it to a blank card without the original LSC source. The remainder of this article walks through the engineering reasons, the realistic options to recover control of the hydraulic systems, and the prevention strategy that should follow.

Hardware Identification: 24RCL Base Module and Red Program Card

The official SIMATIC LOGO! Manual on Siemens Industry Online Support documents the program module behaviour in the chapter on the LOGO! program module. The sections relevant to this fault are "Inserting the program module", "Copy protection", and "Know-how protection". These three sections together describe exactly what the crew is observing: the card carries a know-how flag that prevents the program from being uploaded into LSC.

Root Cause: Why the Program Cannot Be Read Back

When a program is written from LOGO!Soft Comfort to a red program module, LSC can optionally set two independent protection flags on the card:

1. Copy protection — the card becomes tied to a specific base unit serial number. The program can still be executed on any compatible LOGO!, but the card cannot be copied to another card and the program cannot be written to multiple units.
2. Know-how protection — the program on the card is encrypted. The LOGO! executes the program normally, but no editing or upload is possible from the front panel, and the project cannot be reverse-engineered into an LSC source file.

The message "Program Protect" that appears on the 24RCL keypad when the operator selects OK from Program Edit is the front-panel indication of know-how protection. Because the protection was set on the card and not in the base unit, swapping the base does not clear it. Only the original LSC source file, which holds the password, can unlock the program.

Why the Original LSC Project Is the Only Clean Recovery Path

Reverse engineering a know-how-protected LOGO! program is not supported by Siemens and is technically blocked because the executable on the card is stored as tokenised bytecode, not as a human-readable circuit diagram. Without the LSC source, three legitimate engineering paths remain:

1. Recover the LSC project file from the shipyard, system integrator, or end-customer archive.
2. Recreate the program from the hydraulic schematic, the I/O list, and an operational sequence description.
3. Request a replacement project from Siemens against the original project order, where one exists.

Each path is treated in detail below. The choice depends on the documentation available, the urgency of returning the lifeboat system to service, and the cost of onboard engineering time versus replacement.

Option 1: Recover the Original LSC Project File

Before assuming the program must be rebuilt, check the following sources in priority order:

1. Shipyard archive. New-build vessels typically carry an automation documentation package that includes the LSC project, the I/O list, and the functional description. The program is usually stored under the shipyard's project number with a name such as LBA_LAUNCH_RECOVERY_1.lsc or similar.
2. System integrator archive. If the LOGO! was retrofitted, the integrator will hold the source file in their version-control system and can supply it on request.
3. Siemens project order. If Siemens built the program as a paid engineering service, the project can be requested via regional Siemens support. The ship will need the original order number or the MLFB of the affected LOGO! units.
4. Class society files. For lifeboat launching systems on classed vessels, the IACS-classed vessel usually files the control logic as part of the safety case. The classification society does not store the LSC source itself, but the documentation set will reference the integrator or yard that does.

If any of these sources yield an LSC file, the recovery is straightforward: open the project in LOGO!Soft Comfort, connect a programming cable to a test 24RCL on the bench, write the program to a new red card, and the new card becomes the master. The know-how password must be entered at the write step; if the source file still carries the original password, this is automatic.

Option 2: Recreate the Program from Schematic and Sequence

If no source file is recoverable, the only engineering path is to rebuild the FBD/ladder logic from the existing documentation. The minimum inputs are:

For a typical lifeboat launch and recovery system, the rebuilt program will consist of:

• Mode-select gating (manual launch / manual recovery / auto launch / auto recovery / emergency release)
• Permissive logic (davit hook engaged, gripes released, hydro pack running, hydraulic pressure OK)
• Sequencer for the wire winch and the release mechanism, with timed steps and end-of-travel feedback
• Alarm handling: hydraulic low pressure, overspeed, slack wire, limit-switch disagreement
• Manual override block, often gated by a key-switch input on a dedicated LOGO! input

This option requires the most engineering effort but also gives the shipowner full long-term control of the source files. Once rebuilt, the program must be archived on a network share and a printed copy filed with the safety case so that the next failure does not repeat the problem.

Option 3: Procure LOGO!Soft Comfort and the Programming Cable

Whether the program is recovered or rebuilt, a licensed copy of LOGO!Soft Comfort and the appropriate PC cable are required. The complete toolchain is:

Siemens publishes a demo edition of LSC at no charge through its Industry Online Support pages. The demo allows full circuit editing, online monitoring against a connected LOGO!, and simulation, but it cannot write to or read from a real base unit. The demo is therefore useful for training and for offline editing of the rebuilt FBD, but a paid license is required before any program can be transferred to the ship.

Step-by-Step: Rebuilding and Loading the Program

The following procedure assumes the program must be rebuilt because the LSC source is not available. It is intentionally written so that a marine automation engineer with no LOGO! experience can execute it on board.

1. Document the I/O list. With the lifeboat system in a safe state, open the cabinet and read every terminal on the LOGO!. Label each I1, I2, … In input and each Q1, Q2, … Qn output with the wire number from the schematic. Photograph the wiring and store the photos in the project folder.
2. Capture the operational sequence. Sit with the chief engineer and walk through manual launch, manual recovery, automatic launch, and the emergency release. Note every interlock, every alarm, and every timer value. If timers are adjustable in the field, capture the present values from the LOGO! display as a baseline.
3. Install LOGO!Soft Comfort on the engineering laptop. Use the licensed edition. Connect the programming cable to a free USB port on the laptop and confirm the cable enumerates before proceeding.
4. Build the FBD. Create a new project. Lay out inputs on the left, outputs on the right, and the function blocks in between. Use the LOGO! on-screen simulation to verify the sequence before connecting to hardware.
5. Transfer to a bench test 24RCL. Before going near the ship, write the program to a spare 24RCL on the bench, insert the new red card, and confirm the program runs. Verify every input by shorting the input terminal to 24 V and observing the LOGO! display and the output relay. Verify every output by listening for the relay click and measuring the contact.
6. Install on the ship. Once the bench test passes, power down the lifeboat hydraulic cabinet, swap the card from the bench test to the shipboard 24RCL, and power back up.
7. Functional test under no-load conditions. Verify each operating mode from the ship's control station. Confirm every alarm and every interlock. Have the chief engineer counter-sign the test sheet.
8. Load test on-load. Lower and recover a soft-weight or test load under supervision, then sign the system back into service.

Programming Cable Selection by Base Unit Generation

Two cable generations exist in the LOGO! fleet. The original 24RCL base units in the 0BA4 and 0BA5 hardware generations communicate only over RS-232 at 19 200 baud through a 4-pin mini-DIN connector on the left side of the module. Later generations added a USB port on the same mini-DIN footprint. Confirm the generation from the rating plate before ordering a cable, because a USB cable will not work on a serial-only base and vice versa.

If the shipboard 24RCL is a serial-only unit and the engineering laptop has no DB-9, plan for a USB-to-serial adapter based on an FTDI chip. Avoid unbranded adapters with Prolific chipsets, which are unreliable on modern Windows builds.

Verification and Commissioning of the Recovered System

After the program is loaded into the shipboard 24RCL and the new red card is inserted, the following checks must be completed before the lifeboat system is returned to operational status. Each step must be recorded on a commissioning sheet signed by the chief engineer and the class surveyor where applicable.

1. Power-on checks. Confirm the LOGO! powers up in RUN, not in STOP or PROGRAM mode. Confirm the green RDY LED is steady and the red ERROR LED is off.
2. Display checks. Cycle through the I/O status screen and confirm every digital input reads the correct state when the corresponding field device is actuated. Confirm every relay output clicks and that the corresponding contact closes on the output terminals.
3. Mode switch checks. From the ship's control station, exercise every mode-select switch and confirm the LOGO! enables only the correct outputs for that mode.
4. Alarm checks. Force each alarm condition in turn (e.g. simulated low hydraulic pressure) and confirm the LOGO! latches the alarm and disables the relevant outputs.
5. No-load functional test. Run the launch sequence with the hydraulic dump valve open and the wire winch uncoupled, confirming every step and every interlock.
6. On-load functional test. Run the launch sequence with a soft-weight on the hook. Confirm smooth acceleration, correct speed transitions, and correct stop.
7. Recovery functional test. Recover the soft-weight. Confirm correct gripes-engage sequence and correct stowing on the davit.
8. Blackout and restart. Remove power from the LOGO! for at least 30 seconds and re-apply. Confirm the program auto-restarts from the card and that no operator action is required to return to RUN.

Prevention: Program Backup and Knowhow Protection Strategy

The failure mode described in this article is fully preventable. The following controls should be applied to every LOGO!-based safety-relevant system on board, whether the controller drives a lifeboat davit, a fire pump, or a hatch.

1. Maintain a master LSC file. Every project must have one and only one master .lsc file held on the company's engineering network share, with version history. The master must be under change control.
2. Avoid knowhow protection on safety-relevant systems. Knowhow protection makes recovery harder after a failure and provides no real benefit on a vessel where the source must be available to class. If copy protection is required, use it without knowhow protection so that an authorised engineer with the cable and the software can still read the program back.
3. Store one redundant blank red card on board. If the active card fails, a blank card plus the master LSC file allows the program to be re-loaded in under an hour, without waiting for a Siemens delivery.
4. Label every card. Mark each card with the controller ID, the program version, and the date of issue. Discard obsolete cards rather than leaving them in a drawer where they can be confused with the current master.
5. Hold a printed schematic of the program in the same cabinet as the LOGO!. A printed FBD or ladder printout, even a simplified one, is the fastest recovery tool when the PC toolchain is unavailable.
6. Schedule an annual program audit. Once a year, verify that the program running on the LOGO! matches the master LSC file by uploading into LSC (this is possible only if the card is not knowhow-protected) and comparing the network of blocks block-for-block.

Troubleshooting Matrix

Frequently Asked Questions