Resolving MP277 PDATA.FWX Load Failure on Runtime Startup

1. Problem Overview

The SIMATIC MP277 10" Touch (6AV6 643-0CD01-1AX1, MLFB variants 6AV6 643-0CB01-1AX1 / 6AV6 643-0CD01-1AX1) is a Windows CE 5.0-based Multi Panel from the SIMATIC HMI portfolio. After a panel reboot — or after restoring an image file created with ProSave — the operator panel may refuse to start the WinCC Flexible runtime and instead display an error dialog reading:

flash/simatic/PDATA.FWX could not be loaded

The dialog originates from the HmiEs.exe loader process and is generated before the runtime project is mapped into memory. The same message can also be triggered by a successful ProSave backup that the user later attempts to redeploy, by a partial OS update that does not complete, or by a factory reset that does not recreate the \flash\simatic\ working directory properly.

The fault is not a hardware failure of the touch panel itself, the flash memory, or the touch controller. It is a project-data integrity fault in the internal flash file system of the HMI device. The panel boots its CE image normally; only the WinCC Flexible runtime subsystem fails to load the project data file PDATA.FWX.

2. Affected Hardware and Software

3. The PDATA.FWX File: What It Is and Why It Matters

During a WinCC Flexible project transfer, the engineering tool compresses the entire runtime project (screens, tags, alarms, recipes, scripts, language databases) into a single binary blob named PDATA.FWX and writes it to \flash\simatic\ on the panel. The runtime loader at boot time must map this file into memory and decompress it. If the file is missing, truncated, CRC-mismatched, or its directory entry is damaged, the loader prints the message and aborts.

On a healthy panel the \flash\simatic\ directory also contains supporting files such as HMIRES.DLL, PROSAVE.INI, and any recipe/log databases referenced by the project. The most common cause of the could not be loaded fault is that the file PDATA.FWX no longer exists at that path, or exists but is shorter than the loader's expected length.

4. Root Cause Analysis

The fault has five distinct triggers that all converge on the same observable error. Diagnosing which one applies is the first step of the recovery.

1. Interrupted transfer write — power loss, USB unplug, or Ethernet link drop while PDATA.FWX is being written. The CRC fails, but Windows CE has already deleted the previous good copy.
2. Memory card absent — the MP277 uses an internal SD/MMC card slot that, for some firmware revisions, holds a cached copy of the project that the loader falls back to. With the card removed (slot empty or card unreadable), the loader reports the file as missing on the internal NAND flash.
3. OS update overwrote project data — an OS update performed through ProSave clears \flash\simatic\ but does not re-transfer the project. The panel boots into CE cleanly, then cannot find a runtime project.
4. Factory reset wiped the directory — a factory reset through the panel's Service Programs menu restores the operating system image but does not re-install WinCC Flexible project data.
5. Image file was created against a different panel variant — the user restored an *.img archive that was originally taken from a different MP277 (different display size, key vs. touch, different MLFB) whose internal partition layout does not match.

5. Pre-Recovery Diagnostic Flowchart

Run through the following checks before attempting a restore. Each step costs only a panel reboot and avoids the risk of an unneeded OS image rewrite.

5.1 Direct file system check (no PC required)

1. Power the panel.
2. When the error dialog appears, tap Cancel (do not tap OK / Transfer).
3. From the loader menu select OP → Control Panel. If the loader hides the menu, hold the bottom-right corner during boot to enter Service Programs directly.
4. Open Storage Manager. Three storage regions should be listed: Internal Flash, Storage Card (if a card is inserted), and the network share if mounted.
5. Navigate to \flash\simatic\. If the folder is empty, or if PDATA.FWX is present but its size is reported as 0 KB, the file system is corrupt — proceed to recovery.

5.2 Reading the error log

The CE image writes a text log to \flash\system\HmiLoader.log. Open it in Notepad on the panel. The most useful lines look like:

[HmiLoader] Project data file not found: \flash\simatic\PDATA.FWX
[HmiLoader] CRC mismatch: expected 0xA17B43E1, got 0x00000000
[HmiLoader] Loader abort, error code 0x8004

The first line confirms the file is genuinely missing. The second confirms a corruption. The third is the Win32-equivalent error code the runtime returns to the loader before it bails. Capture the log before performing a recovery — it is the only unambiguous evidence of root cause.

6. Recovery Procedure A — External Storage Card Plus Clean Re-transfer

This is the recommended first path. It is non-destructive to the panel's OS image and only takes a working SD/MMC card plus a WinCC Flexible project source.

6.1 Prerequisites

• WinCC Flexible 2008 SP3 installed on a Windows XP / 7 / 10 engineering station (run as administrator; SP2 is the minimum supported for the MP277).
• Original project file *.hmi or *.fwx from the engineering backup.
• SD/MMC card formatted as FAT32, ≤ 4 GB recommended (the MP277 does not support SDHC > 4 GB reliably; SDXC is not supported at all).
• Ethernet crossover cable or direct connection via switch, with both PC and panel in the same subnet (e.g. PC = 192.168.0.1, panel = 192.168.0.10).

6.2 Step-by-step

1. Open WinCC Flexible on the engineering station.
2. From Project → Transfer → Transfer Settings, configure the transfer channel: Ethernet, mode PN/IE, panel IP 192.168.0.10 / 255.255.255.0.
3. Click Transfer. WinCC Flexible opens the transfer wizard.
4. On the MP277, enter Service Programs by holding the lower-right corner of the screen during power-up.
5. From the menu select Transfer → Ethernet and confirm. The panel will start its transfer server on TCP port 1024 (CE/PN/IE transfer protocol).
6. On the PC, click Transfer in WinCC Flexible. The transfer takes between 30 s (small project) and 8 min (60 MB project over 100 Mbit Ethernet).
7. When complete, the panel reboots automatically. The runtime should start with no error.

7. Recovery Procedure B — OS Update Followed by Project Re-transfer

Use this path if the panel's CE image is itself suspect (random freezes, touch calibration drifting, slow startup) or if you suspect the OS image is from a different panel variant.

7.1 Required files

• ProSave V9.0 or higher (bundled with WinCC Flexible 2008 SP3, also available standalone from Siemens support).
• Matching Operating System Update image for the exact MP277 variant. The image filename pattern is MP277_*.img for the Touch variants and MP277_Key_*.img for the Key variant. The image must be downloaded from the Siemens Industry Online Support portal at support.industry.siemens.com; do not use a generic 277 image.

7.2 OS update via ProSave

1. Launch ProSave. Choose Panel type = MP277 Touch 10".
2. Set Connection = Ethernet, target IP = panel IP, MAC of the panel (printed on its label).
3. Click OS Update, browse to the *.img file, then click Execute.
4. Wait for the dialog OS update complete. The panel reboots automatically. Do not interrupt power.
5. Once the panel is back, the desktop appears with no project loaded. Now perform a project transfer using the steps of Section 6.2 from step 4 onward.

7.3 Factory reset (only as a last resort)

The MP277's Service Programs → Reset to Factory Settings menu formats the entire internal flash. It is appropriate only if the OS image is corrupt and ProSave cannot connect. The procedure is destructive: any project data on the panel is lost and must be re-transferred.

1. Hold lower-right corner during power-up.
2. Select Service Programs → Reset to Factory Settings.
3. Confirm twice. The process takes approximately 2 minutes.
4. Re-apply the OS image (Section 7.2) — a factory reset does not leave a working OS on the device.
5. Re-transfer the project (Section 6.2).

8. Recovery Procedure C — Restore from a ProSave Image File

An *.img archive created by ProSave contains the OS image plus the project data at the time of backup. Restoring it should bring the panel back to its original state. If it does not, the image itself is the source of the problem.

8.1 Standard restore

1. In ProSave, choose Restore (not OS Update).
2. Select the *.img file. ProSave prompts to confirm the panel variant; verify that the target panel matches.
3. Execute. The panel reboots and applies the image.

8.2 Why a restore can still leave the panel in the fault state

9. Extracting the WinCC Flexible Project from a ProSave Image

When the original *.hmi project source is missing but a *.img image backup exists, the project can be recovered from the image file. The image file is essentially a raw NAND dump; the embedded PDATA.FWX can be located with a hex search and extracted.

1. Copy the *.img to the engineering PC.
2. Open the file in a hex editor such as HxD.
3. Search for the ASCII signature FWX in the file. The WinCC Flexible blob is preceded by an 8-byte header containing the byte sequence 46 57 58 01 00 00 00 followed by a 32-bit little-endian length field.
4. Note the offset of the length field. Read it: it is the project size in bytes (e.g. 0x004B12A4 = 4 920 996 bytes).
5. Select length bytes from the next offset and export the block to recovered.FWX.
6. Open WinCC Flexible, choose Project → Retrieve, point to recovered.FWX. The project is decompressed and re-assembled into a normal *.hmi workspace.

10. Memory Card Caveats for the MP277

The MP277's SD/MMC slot accepts cards up to 4 GB. The card is treated as a fallback storage location for the project. A field-proven rule is:

If the project was originally deployed to a panel that had a card installed, always keep a card of the same make, model, and capacity installed in the panel. A missing card causes the loader to look at the internal flash and report the PDATA.FWX error, even though the file is intact on the card.

11. Verification

After any recovery, perform the following four checks before declaring the panel healthy.

1. Boot check: Power-cycle the panel three times consecutively. Each time the runtime should reach its start screen within 25 s of the CE splash screen.
2. File check: Open Control Panel → Storage Manager → \flash\simatic\. Verify PDATA.FWX is present and that its size matches the size in the WinCC Flexible build log.
3. Log check: Open \flash\system\HmiLoader.log. The most recent lines should read [HmiLoader] Project data file loaded with no CRC mismatch or not found messages.
4. Tag check: On the start screen, force a tag update (toggle a digital input that the project reads) and confirm the value reflects in the display within one screen update cycle (typically 250 ms).

12. Preventive Measures

• UPS the panel. Brief power loss during a transfer is the dominant cause of PDATA.FWX corruption. A 24 V UPS on the panel supply line is a low-cost insurance.
• Keep a verified image. After every project change, regenerate the ProSave backup. Test the backup once a year by restoring it to a spare panel.
• Standardize the card. Pin a single SD card make/model for the entire fleet. Mixing cards across panels is a frequent root cause of intermittent PDATA.FWX faults after a card swap.
• Disable fast shutdown. In the WinCC Flexible project settings, set Shutdown behavior = Project-controlled with a 5-second delay before actual CE shutdown. This lets the loader flush PDATA.FWX writes.
• Lock the loader. In WinCC Flexible, enable Disable operating system update from CE desktop to prevent operators from triggering an OS update that overwrites the project.

13. Related Error Conditions

14. Quick Reference Command Sequence

For engineers familiar with the toolchain, the full recovery is summarized as follows.

# 1. Connect to the panel from ProSave
Prosave.exe /panel MP277_Touch_10 /conn Ethernet /ip 192.168.0.10 /mac 00-0E-8C-XX-XX-XX

# 2. Apply the OS image (skip if OS is healthy)
Prosave.exe /action OSUpdate /file "C:\images\MP277_10Touch_V12_05_00_00.img"

# 3. Reboot the panel
Prosave.exe /action Reboot

# 4. Push the project
Prosave.exe /action Restore /file "D:\backups\Line3_HMI.psb"

# 5. Verify HmiLoader.log on the panel via Storage Manager
#    Expect: "[HmiLoader] Project data file loaded"