WinCC Flexible 2008: Configuring Data Log Paths for MP277

Problem: "Invalid Path for Log" in WinCC Flexible 2008 Data Log Editor

When configuring a tag or message log in the WinCC Flexible 2008 SP2/SP3 engineering software, the Data Logs dialog rejects user-defined local Windows paths such as C:\WinCCTrend\Logs with the message "Invalid path for log". The path field then defaults to a panel-specific template such as \Storage Card MMC\Logs, which is not useful on a development workstation that has no physical HMI attached.

This is the most common data-logging configuration fault reported on Multi Panel projects (MP 177, MP 277, MP 377) when engineers attempt to commission tag logging against the WinCC Flexible Runtime simulator instead of the physical panel.

Root Cause: Device-Type Specific Storage Targets

WinCC Flexible 2008 binds every Data Log to a storage medium declared in the project, not to a Windows filesystem path. The set of valid media targets is derived from the selected HMI device type:

When the project is bound to a panel that has no internal flash log area (the MP 277 is one of these), the only valid log targets are removable media or an explicit network share. The Windows drive letter C:\ resolves to the panel's internal C: drive, which is reserved for the firmware image and the running project — it is not writable for user data logs. This is why the dialog flags the path as invalid and reverts to the MMC template.

Affected Versions and Products

• Engineering software: WinCC Flexible 2008 (all Service Packs), WinCC Flexible 2008 SP2, WinCC Flexible 2008 SP3, WinCC Flexible 2008 SP4 (HF6 / HF7). Behavior is identical across SPs.
• Runtime targets verified: SIMATIC MP 277 10" Touch (6AV6 643-0CD01-1AX1), MP 277 10" Key (6AV6 643-0CB01-1AX1), MP 277 8" Touch/Key, MP 377 12"/15"/19" Touch.
• Runtime image: Windows CE 5.0 / CE 6.0 on the panel; Windows XP SP3 / Windows 7 (32-bit) on the engineering PC for the simulator.

Solution 1: Test Data Logs in the WinCC Flexible Runtime Simulator

If the goal is to verify tag and alarm archiving on the engineering PC (no panel hardware available), the device type in the project must be changed from the MP 277 to the WinCC Flexible Runtime target. This unblocks local Windows paths.

1. In the WinCC Flexible project tree, right-click the HMI device and select Change Device Type.
2. In the device selector, navigate to PC systems > WinCC Flexible Runtime and pick the resolution that matches your development monitor (e.g., WinCC Flexible Runtime 1024 x 768).
3. Confirm the device swap. WinCC Flexible will re-validate all references; some MP 277-specific objects (PROFINET IO diagnostics, Sm@rtAccess view) will be lost.
4. Open Historical Data > Data Logs. Create a new log, for example TrendLog_01.
5. In the Storage location dropdown choose File (not Database). For RDB logs a Microsoft SQL Server instance is required; for a quick functional check, file-based CSV logs are sufficient.
6. Enter the path as a standard Windows path: C:\WinCCTrend\Logs\. The dialog will now accept it because the target runtime is Windows, not Windows CE.
7. Compile the project with Project > Compiler > All (with consistency check) and start the runtime with Start Runtime (F5) or Start > Start Runtime from the menu.
8. Insert a Trend View control bound to the log, force a tag value change, and verify that a new *.csv / *.rdb file appears in C:\WinCCTrend\Logs\.

Solution 2: Configure Data Logs on a Physical MP 277

For the deployed panel, configure a removable storage target. The MP 277 has one MMC/SD slot and one USB-A port; either can host the log files.

1. Insert a Siemens-approved MMC or SD card (FAT16/FAT32, 32 MB – 2 GB for MMC, up to 32 GB for SDHC on later firmware) into the slot, or plug in a USB stick.
2. In WinCC Flexible 2008, with the MP 277 device selected, open Historical Data > Data Logs.
3. Create a new log. The Path field will offer pre-defined entries:
   • \Storage Card MMC\Logs\ (default for the on-board slot)
   • \USB\Logs\ (only present on panels with USB host support, e.g. MP 277 8"/10")
   • \Network\Logs\ (when a network share is declared under Device Settings > Network)
4. Do not invent new root directories; the runtime only mounts these three virtual roots regardless of physical partitioning. Append a project-specific subfolder, e.g. \Storage Card MMC\Logs\Line01\.
5. Under Storage Parameters, set:
   • Storage method: Circular log (recommended for continuous trend data) or Segmented log with a 24-hour segment cycle for shift reports.
   • Maximum number of segments: 30 (default), increase to 365 only for long-term archiving with sufficient card capacity.
6. Assign the log to one or more tags under Properties > Tag Selection. The acquisition cycle should match the Trend View update rate (default 1 s).
7. Compile and transfer the project to the panel via Ethernet (S7RT or PN/IE), MPI/PROFIBUS, or USB. After the first transfer, format the storage card on the panel: Control Panel > System > Storage Manager > select card > Format (FAT, allocation unit 4 KB).

Solution 3: Network Path as a Universal Target

When a removable card is undesirable — for example, the panel is in a sealed enclosure — a UNC network share is the only valid non-removable target the dialog will accept.

1. On the Windows file server, create a share: \\PLCSRV\HMI_Logs\MP277_Line01\. Grant the panel's Windows CE user Everyone : Change.
2. In the WinCC Flexible project, open Device Settings > Network > Network Drives and map the share. Authentication: enter a service-account user/password. The runtime will reconnect on each panel reboot.
3. Set the Data Log path to \Network\MP277_Line01\. The leading backslash is mandatory; it is the CE mount root, not a UNC root.
4. Verify reachability with a Ping or by reading/writing a recipe on the same share before commissioning the trend.

Verification Checklist

Path Format Reference

Why the Dialog Auto-Accepts "\Storage Card MMC\Logs"

WinCC Flexible scans the currently selected device type's HMI device description file (the *.hmi or device database entry) for declared storage locations. When the device is an MP 277, the description enumerates \Storage Card MMC\ and \USB\ as legal mount roots; when it is a PC runtime, it enumerates the Windows drive letters. The validation routine in flexlogedit.dll simply rejects any path whose root does not appear in that enumeration — which is why your C:\WinCCTrend\Logs entry is overwritten and why the MMC template is restored as a hint.

Common Follow-On Errors and Fixes

Recommendations by Use Case

Related Configuration Touchpoints

• Control Panel settings on the MP 277: Control Panel > Transfer — set channel, enable automatic transfer for commissioning.
• ProSave: Use Siemens ProSave to back up the panel image and the storage card contents; ProSave is the only tool that reads the internal flash structure correctly.
• Runtime version on the panel: The MP 277 ships with WinCC Flexible Runtime. The compiled project transfers as a *.fwc file; mismatched versions produce a "Different runtime version" transfer error rather than the path error described here.
• Licensing: Logging is a base feature of WinCC Flexible 2008; no additional license key is required for tag or alarm logs. Audit Trail / GMP logs do require the WinCC Flexible / Audit option.

References to Official Documentation

• Siemens Support: How are tags and messages archived in WinCC flexible? (PDF, entry ID 26190515)