Siemens .LDB File Format: SIMATIC NET PROFIBUS Configuration Recovery Reference

The Siemens .LDB file is a compiled binary network configuration artifact produced by SIMATIC NET configuration tools. It is generated when a PROFIBUS or PROFINET network is configured for a PC Station that hosts a Siemens Communication Processor (CP) such as the CP 5613 A2, CP 5614 A2, CP 5623, or CP 5711. Because the file is compiled rather than source-text, it cannot be opened in a text editor, hex editor in any meaningful sense, or a generic database viewer to recover the original network topology. This reference covers the file's purpose, the toolchain that creates it, the engineering procedure for recovery when source files are missing, and the diagnostic workflow that follows a backup-restore mismatch on an ET 200 distributed I/O installation.

1. .LDB File Purpose and Binary Structure

The .ldb file (sometimes written *.LDB, lowercase) is the compiled output of a SIMATIC NET project. It is the runtime-loadable representation of a network configuration that has been built from human-authored source files within the SIMATIC Manager or TIA Portal engineering environment.

The container holds station-level metadata, CP slot assignments, PROFIBUS DP master parameters, bus timing, slave addresses, and I/O module mappings. A partial hex dump will reveal a small readable header (typically ASCII strings beginning with LDB or vendor tokens) followed by dense binary token streams. No public decoder is available from Siemens, and reverse engineering is explicitly outside the scope of supported engineering practice.

2. SIMATIC NET PC Station Architecture

The .ldb is generated for a PC Station - a software-side control entity that runs on a Windows host and represents a SIMATIC NET runtime instance. A PC Station pairs a real CP card with virtual slots (Configuration Console) to expose a SIMATIC S7 / PROFIBUS interface to OPC, WinCC, S7-PCT, or user-mode FDL/SAPI applications.

2.1 Reference CP Card Specifications

2.2 PC Station Slot Model

The Configuration Console (part of SIMATIC NET PC software) shows the PC Station as a virtual rack:

1. Index 1 - Application slot (e.g., OPC server, S7-PCT, WinCC channel)
2. Index 2 - Application slot
3. Index 3 - Application slot
4. Index 4 - PROFIBUS CP module (CP 5613 / CP 5623, etc.)

The CP at index 4 is the bus master, and the .ldb encodes the master parameters, the connected ET 200 / DP slave list, and the diagnostic addresses used by the application slots above.

3. Why the .LDB File Cannot Be Read as Text

The compiled .ldb contains only tokenized network data, not the source configuration. Three engineering consequences follow:

• No reverse engineering. There is no public Siemens tool that decodes a .ldb back to a station subproject, GSD-driven slave list, or bus timing. Even a hex editor only shows proprietary token markers.
• No diff or audit. Two .ldb files cannot be meaningfully diffed because the compiler orders, hashes, and aligns structures at build time.
• No vendor edit. A binary edit is not supported; corruption requires a fresh compile from source.

This is by design: the source-of-truth configuration is the STEP 7 / TIA Portal project, not the .ldb. The .ldb is a deployment artifact, not a documentation artifact.

4. Authoring Tools and Generation Procedure

The .ldb is generated as a side-effect of the Compile (or Download) operation from one of three toolchains.

4.1 SIMATIC NCM Manager (Legacy, STEP 7 V5.x)

NCM Manager ships as a component of SIMATIC Manager. In a STEP 7 V5.x project, the PC Station is represented by an S7PCST subproject that contains the CP assignment, OPC server application slot, and bus parameters. NCM Manager opens from the SIMATIC Manager menu Options → NCM Manager → Configuration. After configuration is complete, the menu PC Station → Compile and Download (or Compile for offline) produces the .ldb in the station directory.

4.2 Com Profibus

Com Profibus is the pre-NCM standalone tool, used primarily with SIMATIC S5 controllers and early S7-300 installations. It can read GSD files, build a DP master / slave table, and export a .ldb for direct loading by the SIMATIC NET runtime. It is rarely used today but is still useful for .ldb generation on systems where the original NCM project has been lost and a GSD-based rebuild is the only path forward.

4.3 TIA Portal (STEP 7 V16+ with SIMATIC NET PC V16+)

In the TIA Portal flow the PC Station is a normal device object; the equivalent of the .ldb is the PC system data and the generated configuration file stored in the project archive. The TIA Portal ET 200SP configuration documentation shows the modern parameter model, and the SIMATIC NET PC software manual in TIA Portal describes the compile-to-runtime step. New deployments should not author PC station .ldb files by hand in NCM Manager - the TIA Portal path is the supported long-term workflow.

5. Step-by-Step: Compiling a Fresh .LDB from a Restored Project

The following procedure recovers an ET 200 inspection system when the PC station .ldb is missing or mismatched but a STEP 7 / TIA Portal project backup exists.

1. Verify the engineering station. Install a STEP 7 version matching the original (V5.5 SP4 is a common baseline) and the matching SIMATIC NET PC software. Open the project (*.s7p for STEP 7 V5.x, *.ap1x for TIA Portal).
2. Resolve GSD references. Confirm all DP slave GSD files referenced by the project are installed in the ...\Siemens\Automation\S7\Data\GSD directory (STEP 7 V5.x) or in the TIA Portal device catalog. Missing GSDs prevent compile.
3. Open the PC Station. Double-click the PC Station in the project tree to open NCM Manager / the TIA Portal PC device view. Verify that slot 1 is the OPC server (or S7-PCT application), and slot 4 is the CP card matching the physical hardware (CP 5613, CP 5623, etc.).
4. Reconcile the bus topology. Open the PROFIBUS subnet object. Cross-check master address, baud rate, bus timing, and the connected slave list against the physical ET 200 nodes. Mismatches here are the most common cause of the original symptom ("identical backup, different runtime behaviour").
5. Compile offline. In NCM Manager, PC Station → Compile produces an updated .ldb. In TIA Portal, Project tree → PC Station → Compile → Software (rebuild all) does the same.
6. Load to the PC Station. With SIMATIC NET PC software running and the Configuration Console showing the CP card in the correct index, use PC Station → Download (NCM) or Online → Download to device (TIA). The runtime copies the compiled .ldb to the configured deployment path (default: ...\Programs\Siemens\Automation\SIMATIC_Net\proj\<stationname>\ldb).
7. Restart the SIMATIC NET runtime. Use the SIMATIC NET Commissioning tool to stop and restart the PC Station service, then verify the OPC / S7 diagnostic tags show the expected inputs.

6. Step-by-Step: Recovery When No Project Backup Exists

If neither the .ldb nor the STEP 7 / TIA Portal project is available, the recovery path is a rediscovery from the physical plant.

1. Catalog the ET 200 nodes. Use a CP 5711 USB master and STEP 7 Accessible Nodes (or TIA Portal Online → Accessible nodes) to enumerate every DP slave on the segment. Note the PROFIBUS address of each ET 200 station.
2. Export GSDML / GSD for each slave. For each ET 200 type, identify the order number (e.g., 6ES7153-1AA03-0XB0 for IM 153-1) and import the matching GSD/GSDML from the Siemens Industry Online Support portal.
3. Rebuild the bus in NCM Manager / TIA Portal. Create a new PC Station, drop the CP card into index 4, and add each discovered slave in the order of the physical segment. The baud rate can be read from an online live view of the master parameters if the original is unknown; 1.5 Mbit/s and 12 Mbit/s are the most common on ET 200 segments.
4. Map I/O symbolically. Re-create the symbol table for the application slots (WinCC tags, OPC tags, S7-PCT project) that consume the process image.
5. Compile and load. Generate a fresh .ldb as in section 5.
6. Validate the application layer. Verify that the surface-inspection vendor application (Parsytec or equivalent) reads coherent sensor data. A signature that does not match a known-working configuration usually means an I/O slot ordering mismatch in the rebuilt project.

7. Common Failure Modes and Diagnostic Matrix

8. CP 5613 A2-Specific Notes

The CP 5613 A2 is a PCI card that requires the cp5613.sys / cp5613a2.sys kernel driver from the SIMATIC NET PC software installation. Key points for the recovery engineer:

• Driver version must be at least the matching SIMATIC NET PC software release; mixed versions (e.g., SIMATIC NET V8.x with CP 5613 driver V7.x) load but reject configuration downloads.
• The CP 5613 occupies only index 4 of the PC Station rack. Index assignments outside this are invalid.
• The card supports PROFIBUS DP master class 1 and class 2. Class 2 is required only if a PG/PC online connection is to be multiplexed onto the same card while the master is running.
• Maximum bus segment length is determined by baud rate: 1.5 Mbit/s → 200 m, 12 Mbit/s → 100 m, with repeaters extending this. Verify against the segment's physical plant.

9. Backup and Versioning Strategy

Because the .ldb is non-recoverable as source, the engineering project is the only durable artifact. Recommended practice:

1. Archive the whole STEP 7 / TIA Portal project, not just the .ldb deployment copy.
2. Include GSD files in a versioned ...\GSD\index.txt alongside the project.
3. Snapshot the HKEY_LOCAL_MACHINE\SOFTWARE\Siemens\SIMATIC_NET tree as part of the system image so a restored PC can be reconstructed to the same logical state.
4. Record the CP card order number, firmware revision, and SIMATIC NET PC software version with the project. This metadata is what makes the project portable to a spare PC.
5. Use a project version control system (or at minimum, dated zip archives) - the STEP 7 / TIA Portal project file format changes between major versions, so the toolchain must be re-installed to open a project years later.

10. Migration Considerations (NCM Manager → TIA Portal)

Long-running installations originally configured under STEP 7 V5.x and NCM Manager can be migrated to TIA Portal with the TIA Portal migration tool. The migration reads the S7PCST subproject and re-emits it as a TIA Portal PC device. The compiled .ldb is not the migration source - the STEP 7 project is. After migration, recompile to produce the modern deployment artifact.

For installations where the TIA Portal migration tool is not available, the recovery path in section 6 (rediscovery from the physical plant) is the supported fallback.

11. Disambiguating the .LDB Filename

The string ldb is reused by Microsoft Access as a record-locking sidecar file in shared database scenarios. The Microsoft 365 Apps documentation on Access lock files describes the .ldb (and the newer .laccdb) as transient lock-state markers. These files are created automatically by the Access runtime, hold no application data, and are deleted when the last user closes the database.

If a .ldb file is found in a Windows folder unrelated to a SIMATIC NET installation, it is almost certainly an Access lock file and can be ignored (or removed after confirming the .mdb is closed).

12. Summary

The Siemens .ldb file is a compiled runtime artifact for SIMATIC NET PC stations. It is generated from a STEP 7 / TIA Portal project, consumed by the SIMATIC NET runtime, and intentionally non-decompilable. Recovery from a missing or corrupt .ldb requires access to the original project (the supported path) or a physical rediscovery using Accessible Nodes (the fallback path). Engineers maintaining legacy systems should treat the engineering project, the GSD library, and the Windows registry state of the Configuration Console as a single coherent backup unit, because none of the three is recoverable from the .ldb alone.

Frequently Asked Questions