Resolving DP-NORM and Missing GSD Errors in Step 7 5.6

Overview: DP-NORM and Missing GSD Symptoms in Step 7 5.6

When a Profibus-DP slave appears with the identifier DP-NORM in the STEP 7 V5.6 hardware catalog and the Order Number column displays ??????????, the controller cannot positively identify the device on the bus. The slave remains electrically addressed but logically undefined to the DP master (for example, a CPU 315-2 DP / 6ES7 315-2AG10-0AB0 or CPU 417-4 / 6ES7 417-4XL05-0AB0). Two distinct symptoms are visible in HW Config:

The root cause is the same in both cases: the STEP 7 installation on the programming PC does not contain the GSD (Geräte-Stammdaten-Datei) description file for the third-party or older Siemens slave, so the slave is treated as a generic DP-NORM device rather than as a fully identified node.

Root Cause Analysis: Why DP Slaves Show DP-NORM

STEP 7 V5.6 stores third-party GSD files in a project-local directory and a global installation directory. When a hardware configuration is downloaded to the PLC and later uploaded, the configuration is rebuilt from the uploaded data plus the GSD files installed on the new PC. If those files are not present, STEP 7 substitutes a generic placeholder.

How a Profibus-DP Slave Becomes "Undefined"

1. The original project was created on PC-A. The GSD file for a third-party DP slave (for example, an ET 200S IM 151-1 6ES7 151-1AA04-0AB0 with a non-Siemens encoder, or a Phoenix Contact IBS RL 24 DO 8) was installed via Options > Install GSD File.
2. The hardware configuration was compiled and downloaded. The PLC retains only the slot and parameter assignment, not the GSD file itself.
3. The project was backed up to an archive (for example, a .zip of C:\Siemens\Projects\<projectname>) and transferred to PC-B. The GSDdata subfolder was either excluded from the archive, deleted, or located on a separate path.
4. On PC-B, STEP 7 opens the project but cannot resolve the slave identity. The Order Number field reverts to ??????????, and the slave name collapses to DP-NORM.

File Locations STEP 7 V5.6 Uses

If any of these paths are missing on the new programming PC, the symptom appears. The PLC itself is unaffected; only the offline view and any recompile/compare operation fails.

Prerequisites for Recovery

Before performing any recovery action, assemble the following items. Missing prerequisites will cause the recovery to fail or, worse, result in an inconsistent project that cannot be downloaded to the PLC.

1. STEP 7 V5.6 + SP2 (or later) installed with administrator rights on the recovery PC. Confirm the build via Help > About; version string should read at least V5.6 + SP2.
2. Full project archive, including the GSDdata folder. If you only have the program blocks (S7-Program), the hardware configuration cannot be reconstructed offline and must be re-detected online.
3. Access to the original programming PC (preferred) or the manufacturer's GSD files for every undefined slave. Common sources include the Siemens Product Support portal at support.industry.siemens.com and the third-party vendor's download area.
4. List of all DP slaves currently connected, captured either from the online hardware detection in STEP 7 or by walking the cabinet. Record each slave's Profibus address, manufacturer, order number (MLFB), and slot count.
5. Backup of the existing S7 program as a separate, immutable archive before any modification. Store the backup on removable media.
6. Online connection to the PLC via MPI/PROFIBUS or Ethernet (CP 343-1 / CP 443-1) for the verification step.

Step-by-Step: Locating and Installing Missing GSD Files

Path A — Recover GSD Files from the Original Project PC

1. On the original PC, open Windows Explorer and navigate to C:\Siemens\Projects\<projectname>\GSDdata.
2. Copy the entire GSDdata folder to a USB drive or network share. Include the gsd, bitmaps, and nsfiles subfolders.
3. On the recovery PC, open SIMATIC Manager and close the project (so STEP 7 releases all file handles).
4. Locate the local project directory (typically C:\Siemens\Automation\Projects\<projectname> or the path you chose during project creation).
5. Replace the existing GSDdata folder with the one from the original PC. If the folder does not exist, create it and copy the subfolders manually.
6. Open SIMATIC Manager and select Options > Install GSD File. Browse to the copied GSDdata\gsd folder. Check Include subdirectories and click Install. STEP 7 reads each *.gsd and *.gsd.xml, validates the checksum, and updates the hardware catalog.
7. Close and reopen HW Config. The previously DP-NORM slave should now appear with the proper order number and bitmap.

Path B — Download GSD Files from the Manufacturer

1. Identify the slave by walking the cabinet or by reading the diagnostic buffer (PLC > Diagnostic/Setting > Diagnostic Buffer). The buffer typically lists the affected DP address and the slot that failed configuration.
2. Look up the manufacturer and order number. For Siemens slaves, use the Siemens Product Support portal at support.industry.siemens.com, search for the MLFB, and download the matching GSD package from the "Support" tab. For non-Siemens devices (for example, Wago 750-303, Beckhoff BK3120, Phoenix Contact IL PB BK DP/V1), obtain the GSD from the vendor's download area.
3. Extract the archive. A typical GSD package contains SIExxxxx.GSD, *.bmp, and an .mdl or .ddb file. DP-V1 devices also include a *.gsd.xml (GSDML) file.
4. In SIMATIC Manager, select Options > Install GSD File > Browse. Navigate to the extracted folder. Choose Install.
5. Restart HW Config. The slave is now selectable from PROFIBUS DP > Additional Field Devices > <Manufacturer>.

Path C — Online Detection of Unknown Slaves

1. Open the project and launch HW Config.
2. Connect online to the PLC (PLC > Connect to Target System > Accessible Nodes or via the configured online interface).
3. Select PLC > Upload Station to PG. STEP 7 reads the actual hardware configuration from the PLC and rebuilds the offline view. Missing GSD files still produce DP-NORM entries, but the slot assignments are recovered.
4. Install the missing GSD files per Path B. After installation, right-click the DP-NORM slave and select Replace Object > .... STEP 7 matches the slot layout and proposes a replacement.

Step-by-Step: Adding New Modules to an Existing Project

When the recovery goal is to add new I/O modules (the original poster mentioned "343 bare modules" — interpreted as a count of additional modules to integrate, not a Siemens part number), follow this procedure after the existing configuration is stable.

1. Open HW Config on the master station.
2. Open the catalog (View > Catalog) and locate the new module under PROFIBUS DP > <Family> or SIMATIC 300 / SIMATIC 400 > <Rack> depending on whether the module is a distributed I/O station or a central rack module.
3. Drag the module onto the appropriate slot. For central rack modules, the slot must match the physical mounting position (slot 1 reserved for power supply, slot 2 for CPU, slots 4–11 for SM/FM/CP in S7-300). For ET 200S, drop the IM 151 first, then add the terminal modules by drag-and-drop.
4. Configure the Profibus address in the object properties. Each new DP slave must have a unique Profibus address in the range 1–126. Address 0 is reserved for masters, address 126 for commissioning devices.
5. Double-click each module to set parameters: input filter time, diagnostic enable, substitute value behavior, and so on. For analog modules, configure the measuring range (for example, 0–10 V, 4–20 mA, Pt100, TC type K).
6. Compile and save (Station > Save and Compile). STEP 7 reports address ranges in the bottom status bar, for example PIW 256..271 for an analog input module.
7. Download the new configuration to the PLC (PLC > Download). Confirm the prompt; the PLC performs an initialization that briefly drops existing DP slaves.
8. Update the symbol table or DB references to match the new addresses. Use LAD/STL/FBD > Options > Symbol Table or cross-references in the program editor.

Alternative Path: Removing Unidentified Slaves

If the missing GSD files cannot be recovered and the slaves are obsolete or no longer required, the alternative is to remove them. This is the second of the two choices available to the field engineer.

1. Open HW Config and identify each DP-NORM slave.
2. Right-click the slave and select Delete. Confirm the prompt.
3. Recompile the station. STEP 7 frees the address range and slot configuration previously occupied by the deleted slave.
4. Open the program blocks and search for any references to the deleted I/O. Use Options > Reference Data > Display and filter on the address range, or search in the editor with Ctrl+F for the symbolic name.
5. Replace each reference with either a safe default (for example, a constant in a DB) or a real input from a retained device. For outputs that no longer exist, wire them to a NULL placeholder or comment them out as // removed - DP-NORM slave deleted 2024-....
6. Download the program and the new hardware configuration to the PLC.
7. Monitor the diagnostic buffer (PLC > Diagnostic/Setting > Diagnostic Buffer) for any new peripheral access errors that point to lingering references. Correct them iteratively.

Hardware Configuration Download and Verification

Download Procedure

1. In HW Config, select Station > Consistency Check first to catch slot mismatches before the download.
2. Select PLC > Download. Choose Download to Target Device.
3. In the dialog, choose whether to download the entire station or only changes. For a recovery scenario after a missing GSD fix, a full download is recommended.
4. STEP 7 prompts to overwrite the existing program. Confirm with the operator on shift.
5. Wait for the download to complete. The CPU performs a restart (cold or warm, depending on the CPU's startup setting). The RUN LED should return to solid green within a few seconds for healthy slaves.

Verification Steps

1. Go online with the PLC (PLC > Connect to Target System).
2. Open HW Config and select Station > Open ONLINE. Compare the online view to the offline view. The status bar should display No differences.
3. For each previously DP-NORM slave, verify that the online view shows the correct order number, slot count, and module status (green check, not red X).
4. Force a value on one input and confirm it reaches the corresponding input word or input bit via Monitor/Modify > Monitor (VAT table) or online monitoring in the editor.
5. Check the diagnostic buffer for any residual entries. Healthy operation shows no new peripheral faults after the download.

Diagnostic Buffer and Online Diagnostics

The diagnostic buffer is the primary tool for confirming that all DP slaves are now correctly identified. Open PLC > Diagnostic/Setting > Diagnostic Buffer and look for the following event patterns.

If the buffer still reports peripheral addressing errors at the slots previously occupied by the DP-NORM slave, the program has not been updated to match the new configuration. Repeat the reference cleanup in the FC/FB code.

Best Practices for GSD File Management

1. Always archive the entire project folder, including GSDdata, Symbols, and S7_Progs. A simple "program only" backup cannot restore the hardware configuration.
2. Document the GSD source in the project documentation: manufacturer, version, release date, and SHA-256 checksum. GSD files change between firmware revisions; using the wrong version can cause parameterization errors.
3. Install GSD files for the project rather than for the system. Project-local GSDs travel with the archive and are reproducible across PCs.
4. Pin the STEP 7 service pack. The same GSD file can behave differently between SP levels; document the STEP 7 version in the project header.
5. Use a controlled library PC. Maintain a single repository of approved GSD files (for example, \\corp\controls\gsd\approved\) and copy only from there. Avoid ad-hoc downloads on production PCs.
6. Enable change tracking in HW Config (Station > Properties > Change Log) so future configuration diffs are documented.
7. Use DP-V1 diagnostic blocks (for example, FB 125 / SFB 52-54) for non-Siemens slaves that support them, rather than relying solely on the diagnostic buffer.
8. Verify Profibus topology before download. A hardware configuration download with a wrong address can briefly disrupt healthy slaves and trigger nuisance trips.

Troubleshooting Matrix

Field-Proven Caveats

• GSD version vs. firmware version. A GSD written for firmware V1.0 will often fail to parameterize a device running V2.0. Always match the major revision. When in doubt, use the GSD bundled with the device's setup CD or download the latest GSD that explicitly lists the firmware revision as supported.
• DP-V1 vs. DP-V0. GSDML (*.gsd.xml) files are used for DP-V1 and PROFINET-capable devices; classic *.gsd files are for DP-V0. STEP 7 V5.6 accepts both, but mixing them on the same slave produces unexpected slot configuration behavior.
• Maximum DP slaves per master. An S7-300 CPU with integrated DP interface supports up to 32 slaves on a single segment; an S7-400 CPU supports up to 125. Exceeding this limit produces a configuration error that is easy to misinterpret as a GSD issue. Check CPU Properties > DP > Operating Mode for the configured maximum.
• Address 126 reserved. The address 126 is the factory default for unconfigured slaves. Do not assign it in the offline configuration, or the master will not initialize the slave during startup.
• Watch for project duplication. STEP 7 supports Save As, which creates a separate project directory. After Save As, the GSD files installed "for this project only" are NOT copied to the new project. They must be reinstalled.
• Anti-virus interference. Some anti-virus products quarantine .gsd files on write because they are not commonly recognized. Add C:\Siemens and the project directory to the AV exclusion list.

Alternative Controller Notes

The same DP-NORM symptom can appear on TIA Portal (STEP 7 V15 or later) projects when a GSDML file is missing. The recovery procedure is functionally identical: install the GSDML via Options > Manage general station description files (GSD) and replace the placeholder. S7-1200 and S7-1500 systems use PROFINET instead of PROFIBUS by default, but PROFIBUS-capable variants (for example, CPU 1516-3 PN/DP with order number 6ES7 516-3AN02-0AB0) expose the same DP-NORM diagnostic when the GSD is absent.

For S7-200 (MicroWin) and S7-200 SMART systems, the term "DP-NORM" is not used; instead, an unknown slave appears in the configuration as a generic node. The recovery uses the MicroWin Tools > GSD File import and follows the same GSD data location conventions.

Commissioning Checklist After Recovery

1. Confirm all DP slaves report OK status in HW Config online view.
2. Verify every input and output via a VAT table or HMI forcing.
3. Trigger a CPU restart and observe that no DP slave drops out.
4. Capture the diagnostic buffer after restart and archive it in the project's Logs folder.
5. Update the As-Built documentation: device list, GSD versions, Profibus addresses, slot configurations.
6. Update the backup procedure to ensure future archives include GSDdata.

FAQ