Siemens LOGO! Program Recovery: FBD Upload Without Software

Overview

Recovering a control program from a deployed Siemens LOGO! controller without the original project file forces a specific set of decisions: obtain the correct PC cable, install the correct generation of LOGO! Soft Comfort, accept the on-device FBD-only editing limit, and recognize that password protection or a red (program-disabled) memory card will defeat every recovery path. This reference covers the practical workflow for the LOGO! 24, 8DI(4AI)/4DO, 200-block module with ordering code 6ED1052-1CC00-0BA6 (LOGO! 12/24RCE generation) and clarifies what an engineer can and cannot do without the original engineering software and cable.

Hardware Identification: LOGO! 6ED1052-1CC00-0BA6

Before any recovery attempt, verify the exact module on the machine. The string 6ED1052-1CC00-0BA6 decodes as follows in the Siemens MLFB scheme:

The 0BA6 suffix is the critical discriminator. It tells the engineer which generation of cable and software to procure:

For 6ED1052-1CC00-0BA6, the correct cable is the LOGO! USB PC cable, order number 6ED1057-1AA01-0BA0. The older RS-232 cable 6ED1057-1AA00-0BA0 will not be recognized by a 0BA6 module and may damage the RS-232 port on legacy PCs.

Program Storage and Memory Architecture

Internally, a LOGO! 0BA6 stores exactly one program in non-volatile EEPROM. There is no source-vs-runtime distinction as found in a S7-1200/1500. The program is held as a compiled, proprietary block graph that is functionally equivalent to a Function Block Diagram (FBD) representation. The compiled graph is not a structured text source file, not a ladder list, and not a SCL/ST archive — it is the result of FBD/UDT compilation by LOGO! Soft Comfort.

Consequences for recovery:

• On-device edit always presents the program as FBD, regardless of the editor mode used in Soft Comfort. The text display cannot show a true IEC 61131-3 ladder diagram.
• A round-trip upload → save → edit in Soft Comfort returns the program in FBD. If the original was written in Ladder Diagram (LD), Soft Comfort will convert it to FBD on upload; the LD aesthetic is lost.
• The uploaded file is a .lsc (LOGO! Soft Comfort) or .lscz project, not a generic FBD file. It will not open in TIA Portal, STEP 7, or Codesys.

On-Device Programming Limits (FBD Only)

Without any PC connection, the LOGO! 0BA6 supports the following on-device operations using the cursor keys and the OK/ESC buttons:

To reach the program-editing menu from the integrated display, hold ESC, then press OK to enter the main menu, navigate to Program → Edit Program, and step through blocks with the up/down keys. Block inputs and outputs are navigated with left/right. New blocks are inserted with the OK key on a free node.

Password Protection — What It Really Does

The 0BA6 supports a 4-character alphanumeric program password. With a password set:

• Any on-device attempt to Edit Program or to change parameters will prompt for the password. Three failed attempts lock the device for 60 minutes.
• Soft Comfort Upload → PC operations require the same password.
• Removing the password on-device is not possible without erasing the user program. The Program → Clear Program action first asks for the password; if the password is forgotten, the only supported recovery is to Clear All, which wipes the program and resets the password.
• A hard reset does not bypass the password — it simply clears the user program area, after which a new password (or none) is applied on the next save.

Memory Card Behavior

Siemens LOGO! memory cards (order code family 6ED1056-…) come in two colors and three sizes. Color is the field-visible indicator of the card's mode:

For 6ED1052-1CC00-0BA6 (0BA6), the gray 6ED1056-1BA00-0BA0 (32 KB) or 6ED1056-1CA00-0BA0 (64 KB) cards hold the program backup. To copy the program from the controller to the card:

1. Power the LOGO! and enter the main menu.
2. Navigate to Card → LOGO! → Card and select Copy.
3. Confirm. The controller writes its active program to the card, including the password hash.

The card can then be read by any LOGO! Soft Comfort installation that supports the 0BA6 generation (V7.0 or later). The card is inserted into the PC card reader via a LOGO! card reader, or — on 0BA8 and later — directly via the SD slot of the controller when connected over Ethernet.

A red card blocks this path entirely. The controller will not expose the user program, and Soft Comfort will see the device as program-suppressed. Remove the red card and insert a gray card; the LOGO! will then offer the standard Copy to card menu.

Cable Options for Upload to PC

The 0BA6 has no Ethernet port. The only PC-side upload path is the LOGO! USB PC cable, 6ED1057-1AA01-0BA0. The cable terminates in a 4-pin keyed connector on the LOGO! end (the integrated serial interface on the right side of the module) and a USB-A on the PC end. Driver support is built into Windows 10 and 11; on older Windows versions a virtual COM port driver from the Soft Comfort install media is required.

For a 0BA6 controller, the USB cable is non-negotiable. Procure it before any other recovery step. A typical lead time is one to two business days from a Siemens distributor; some industrial supply houses stock the cable as LOGO! USB programming cable.

Software Selection: LOGO! Soft Comfort

LOGO! Soft Comfort is the only engineering tool that can read a 0BA6 program in source form. Versions are cumulative — newer versions can read older projects, but older versions cannot read newer ones:

For the task in the source question, a Soft Comfort V7.x or later is preferred over V6.1. V6.1 predates the 0BA6 feature set in some areas (analog scaling block, edge-triggered counters), and the upload operation may produce a project that round-trips incorrectly. The current generation is described on the Siemens LOGO! software product page, which lists the all-in-one download of program and web project introduced in V9.

Step-by-Step: Upload Program from a 0BA6

1. Verify the controller part number on the front label matches 6ED1052-1CC00-0BA6 and confirm the 0BA6 platform suffix.
2. Obtain the LOGO! USB PC cable (6ED1057-1AA01-0BA0). Do not substitute a generic USB-serial adapter; the cable contains a SiLabs CP210x-class bridge and a logic-level shifter that maps the LOGO!'s 5 V serial to USB levels.
3. Install LOGO! Soft Comfort V7.0 or later. V8.4 is the most conservative choice for a 0BA6-targeted project in 2024–2025 environments. Accept the default virtual COM port driver.
4. Power the LOGO!. Do not interrupt the field wiring — leave inputs live. The program in the controller is non-volatile and will survive power-down, but the controller must be in Run or Stop mode (not Program-suppress) for the upload to be offered.
5. Connect the cable: USB end to the engineering PC, keyed end to the LOGO! serial port. Windows will enumerate the device and assign a COM port (typically COM3–COM7 on first connection).
6. Start LOGO! Soft Comfort. From the menu bar, select Tools → Transfer → Upload from LOGO!… (or the keyboard equivalent, F11 in V8.x). The PC will prompt for a destination folder; the project will be saved as <filename>.lsc (uncompressed) or <filename>.lscz (zipped archive).
7. If the controller has a password set, Soft Comfort will request it. Enter the four-character password. After three incorrect attempts, the LOGO! enters a 60-minute lockout; restart Soft Comfort to clear the PC-side retry counter only after the lockout has expired.
8. On success, Soft Comfort opens the uploaded project. The FBD diagram appears in the work area. If the original was authored in Ladder, the FBD view will show the same logic but reorganized as a flat block graph — this is normal, not corruption.
9. Save the project to a known location. Add a revision note in the comment field. Move a copy to the engineering documentation library.

Verification: Confirm the Upload Is Complete

After upload, perform these checks before trusting the recovered project:

1. Compare the block count reported by the LOGO! on-device menu (Program → Memory Usage or Info) to the block count displayed in Soft Comfort Tools → Info. A mismatch indicates a partial upload or a password-induced truncation.
2. Compare the controller's reported program name and password status (if visible) to the Soft Comfort project header.
3. Run the on-device simulation in Soft Comfort: Tools → Simulation (or F8). The simulator must show the same I/O behavior as the running controller under steady-state conditions. Walk through every input change documented in the machine's sequence-of-operations.
4. Generate a cross-reference: in Soft Comfort, Tools → Cross Reference lists every block, its inputs, and the connectors that use it. Confirm the count matches the machine's electrical drawing.
5. If a .lscz archive is required for archival, re-save as a zipped project. The archive contains the source FBD plus the compiled program image and the password hash.

Field Editing Without a Cable — Realistic Use Cases

Some changes can be made on-device without recovering the full program. These are the legitimate field edits and should be the first question asked of any maintenance call:

When the original commissioning engineer disabled parameter protection, the field technician can make most tuning changes from the display without ever needing a PC. This is the design intent of the on-device edit mode and is the reason LOGO! is popular for small machines.

Troubleshooting Matrix

Cross-Generation Compatibility Notes

If the controller in the field is not a 0BA6 but a 0BA7 or 0BA8 (visually identical, same MLFB family but a different suffix), the recovery path changes in two ways:

• 0BA8 Standard modules expose a 10/100 Mbit Ethernet port. The USB cable still works, but a standard CAT5 patch cable plus Soft Comfort V8.1+ is the simpler field path. The Ethernet connection does not require a crossover; the LOGO! supports auto-MDI/MDIX.
• 0BA7 modules add the SD card slot used by the gray memory card. Programs can be copied to a gray SD card on a 0BA7/0BA8 and read into Soft Comfort V8.x without ever opening the controller's wiring compartment — a useful option when the machine is in a wash-down area and the cover cannot be removed.

For 0BA6, the SD card slot does not exist. Only the proprietary LOGO! memory card works, and only via the side slot.

Safety and Documentation Practice

Whenever a LOGO! program is uploaded from a running machine, capture three pieces of evidence at the same time:

1. The Soft Comfort project file (.lsc or .lscz).
2. A screenshot of the on-device Memory Usage / Info screen showing block count, program name, and program version.
3. The electrical drawing of the machine, marked with the I/O addresses used by the program. The 0BA6 supports I1…I8, AI1…AI4, Q1…Q4, AQ1…AQ2 (where present), and the network markers M1…M27 / shift registers S1…S8. The drawing is the only source of truth for the wiring of those addresses, since the uploaded program carries the logic but not the wire list.

Store all three in the same folder, named with the controller's serial number, the date, and the operator's initials. A lost password or a cleared program is then recoverable from the documentation set, not from the controller itself.

FAQ