Overview
The Siemens SIMATIC MP 277 is a 7" (or 10") Touch Panel from the 270 series, programmed with WinCC flexible 2008 (or WinCC flexible 2007/2005 for older firmware). When an integrator downloads the configuration to the panel, two fundamentally different outcomes are possible:
- Compiled runtime only – the panel receives a binary ".fwx" runtime file that can be executed but cannot be edited or uploaded as a project source.
- Compilable source (Backtransfer-enabled) – the panel stores the complete WinCC flexible project, including the original screens, tags, scripts, and connection data, and this source can be uploaded again using the Backtransfer function.
If the original programmer selected "Enable Backtransfer" when transferring the project to the MP 277 and the panel is fitted with an SD/MMC card of sufficient size, the project can be reconstructed from the HMI. This article documents the exact prerequisites, transfer channel options, memory card sizing, and the step-by-step Backtransfer workflow in WinCC flexible 2008.
Prerequisites
| Requirement | Specification |
|---|---|
| HMI | Siemens SIMATIC MP 277 (6" Touch, 8" Touch, 8" Key, 10" Touch variants) |
| HMI firmware | WinCC flexible Runtime ≥ V1.3 (Backtransfer supported from this build onward) |
| Programming software | WinCC flexible 2008 SP2 or SP5 (matching or newer than the runtime version on the panel) |
| Transfer channel | Ethernet (TCP/IP), USB, MPI/PROFIBUS, or serial – Backtransfer supports all channels used for download |
| Storage medium | SD card (1 GB / 2 GB) or MMC card inserted in the panel's card slot during the original download |
| Original project source flag | The original download must have been performed with "Enable Backtransfer" checked |
| Connected PLC | S7-200 (as in this case) via PPI/MPI/PROFINET or Ethernet; required for runtime verification but not strictly required for Backtransfer itself |
Understanding ProSave vs. Backtransfer
Engineers frequently confuse the two recovery paths available in ProSave and WinCC flexible. They are not interchangeable.
| Function | Tool | Output | Editable? |
|---|---|---|---|
| ProSave Backup / Restore | ProSave (standalone) or WinCC flexible → Project → Transfer → Backup | Compressed ".psb" / \*.tgz" archive of the runtime image and operating system | No – the file is a binary runtime snapshot, no project source, no screens, no scripts |
| WinCC flexible Backtransfer | WinCC flexible → Project → Transfer → Backtransfer | Recreates a compilable WinCC flexible project (".hmi" project file) with screens, tags, alarms, scripts, and connections | Yes – fully editable in WinCC flexible 2008, can be recompiled and re-downloaded |
ProSave is suitable for cloning or disaster recovery of the runtime, but it cannot yield the source ".hmi" project. Only the Backtransfer path can recover a project that can be re-edited and re-compiled.
Memory Card Requirements for the MP 277
The MP 277 has one SD/MMC card slot on the rear of the device. The card is used for:
- Operating system updates and image backup
- Recipe data, logs, and user administration
- Storage of the Backtransfer source project
| Card Type | Capacity | Approved by Siemens | Notes |
|---|---|---|---|
| SD (up to 2 GB) | 512 MB – 2 GB | Yes (Siemens 6AV6 671-1CB00-0AX2 for 2 GB) | Recommended for MP 277 Backtransfer |
| MMC | 128 MB – 1 GB | Yes (legacy) | Older card type, still supported |
| SDHC (>2 GB) | 4 GB and up | Not supported on MP 277 | Do not insert SDHC cards; the panel will not recognize them |
Rule of thumb for sizing: the Backtransfer source occupies roughly 1.5× to 3× the size of the compiled ".fwx" runtime, depending on the number of bitmaps, scripts, and language files. A 1 GB SD card is sufficient for the vast majority of MP 277 projects; 512 MB is generally adequate for projects below ~2,000 tags and ~500 KB of graphics.
Verifying the Panel's State Before Backtransfer
Before launching the recovery procedure, confirm that the panel actually holds a Backtransfer-capable source. If the original integrator did not tick the "Enable Backtransfer" box, no recovery is possible from this hardware.
- Power on the MP 277 and wait for the loader / Control Panel to appear.
- Open the Control Panel on the panel (double-tap the "Control Panel" icon or use the Start menu).
- Navigate to OP Properties (or "Device") and then the Storage tab.
- Inspect the inserted card: if a folder named
\Backup\<ProjectName>or a file*.fwxis listed together with a*.logand anactive*directory, Backtransfer source is likely present. - Confirm the card's free space is greater than the project size; if the original download ran out of card memory, only a partial Backtransfer image may have been written.
Start=>Transfer in the project. Otherwise, the only way to break into the loader is to change the start.ini on the card with a PC.Step-by-Step Backtransfer Procedure
The following procedure recovers a WinCC flexible project from an MP 277 that was originally downloaded with the "Enable Backtransfer" option enabled.
Step 1 – Install the Correct WinCC flexible Version
Install WinCC flexible 2008 on the engineering PC. The version installed must be the same major release or newer than the one that originally compiled the project. Mixing a newer WinCC flexible build (e.g., 2008 SP5) with a much older runtime (e.g., compiled under 2005) is acceptable for opening the project, but the panel image version must match the runtime you intend to install. Verify your installed build via Help → About WinCC flexible.
Step 2 – Establish Communication Between PC and MP 277
Connect the engineering PC to the MP 277 using the same channel that was used for the original download.
-
Ethernet: Use a crossover cable or a switch. The MP 277 default IP is
192.168.0.1(mask255.255.255.0). Set the PC to a matching subnet, e.g.,192.168.0.10. - USB: The MP 277 uses a USB-to-serial bridge. Install the Siemens USB driver from the WinCC flexible installation media.
- MPI/PROFIBUS: Use a Siemens PC adapter (e.g., 6ES7 972-0CB20-0XA0) and the panel's MPI/DP port.
Step 3 – Configure the Transfer Settings in WinCC flexible
- Open WinCC flexible 2008 on the PC. Do not open an existing project – start with a blank workspace so that Backtransfer can create a new project for you.
- Select Project → Transfer → Backtransfer…
- In the dialog Backtransfer, choose the connection mode that matches your cable (Ethernet / USB / MPI / Serial).
- Enter the panel's IP address (Ethernet) or MPI/PROFIBUS address. The default values are:
Channel Default address Ethernet 192.168.0.1 (port 102 for S7ONLINE) MPI 1 (baud 187.5 kbps) USB USB\COM port assigned by driver - Click Transfer. WinCC flexible establishes communication, reads the source image from the SD/MMC card inside the MP 277, and prompts for a directory on the PC.
- Specify a new empty folder such as
C:\Projects\MP277_Recovered\. WinCC flexible creates a fresh ".hmi" project in this folder and imports all screens, tags, scripts, alarms, and connection data. - Click Finish. The new project opens automatically in WinCC flexible.
Step 4 – Verify the Recovered Project
Before adding the new functionality, validate the recovered project:
- Open the project tree and confirm that the screen count, tag count, and alarm count match the expected inventory.
- Check the HMI tags under Project → HMI Tags; missing tags indicate a partial Backtransfer or an interrupted write to the SD card.
- Confirm the connection to the S7-200: open Project → Connections and verify that the PPI/MPI/Ethernet parameters match the actual PLC configuration. The S7-200 station address defaults to
2, baud9.6 kbpsfor PPI, or187.5 kbpsfor MPI. - Compile the project (Project → Compiler → All). A clean compile verifies the integrity of the recovered source.
Step 5 – Add the New Functionality and Re-Download
- Open the recovered project in WinCC flexible and add the missing function block, screen, or tag required by the user.
- Save the project as a new revision (e.g.,
MP277_Plant42_Rev02.hmi) and store a copy in a versioned archive path such as\\fileserver\Siemens\MP277\. - When transferring the updated project back to the MP 277, leave "Enable Backtransfer" ticked and ensure the SD card remains inserted. This guarantees that the next person in your situation can perform a recovery without any help.
Transfer Channel Notes and Pitfalls
| Channel | Throughput (typical) | Backtransfer reliability | Common pitfall |
|---|---|---|---|
| Ethernet TCP/IP | 10/100 Mbit | Best – fastest, supports large projects | Subnet mismatch; firewall on PC blocking ports 102/5001 |
| USB | ~12 Mbit | Good for projects < 4 MB | USB driver must be installed before cable is plugged in |
| MPI / PROFIBUS | 1.5 – 12 Mbit | Adequate | Address conflict with S7-200 (default 2) |
| Serial (RS-422/485 on rear) | 115 kbit | Slowest | Null-modem adapter required |
Error Codes and Recovery Messages
| Message in WinCC flexible | Likely Cause | Remediation |
|---|---|---|
| "Backtransfer not possible – no project on storage medium" | Card not inserted, or original download was performed without "Enable Backtransfer" | Insert card; check with integrator; without the flag, recovery is not possible |
| "Connection to HMI device failed (timeout)" | Wrong IP/address or subnet mismatch | Verify IP with Control Panel → OP Properties → Network |
| "Transfer cancelled – incompatible firmware version" | WinCC flexible on PC is older than the runtime on the panel | Upgrade WinCC flexible or install matching Service Pack |
| "Insufficient memory on storage card" | Card too small for the project (usually < 128 MB with large bitmap libraries) | Use a 1 GB or 2 GB SD card |
| "Project file on storage medium is corrupt" | Card was removed during a write, or card has bad blocks | Replace card; re-download project with Backtransfer enabled |
Best Practices for Future Proofing
- Always enable Backtransfer. The runtime size increase is negligible compared with the cost of a lost project.
- Use a name-labelled SD card in every MP 277 (e.g., "MP277_Plant42"). The card slot is hidden behind a small cover and is easy to confuse with adjacent panels.
-
Maintain a master archive. Store every WinCC flexible project under version control –
\\fileserver\Siemens\MP277\<PlantTag>\Rev##\– with the matching*.fwxruntime, the*.psbProSave backup, and a dated PDF of the project documentation. - Tag the configuration computer. Each panel should have a small label on the rear showing: project name, revision, WinCC flexible version, panel IP, and PLC address. This is invaluable during commissioning and troubleshooting.
- Schedule periodic ProSave backups as a defense-in-depth measure. ProSave cannot recover the source, but it can restore the runtime quickly while you rebuild the source from Backtransfer.
What If Backtransfer Is Not Possible?
If the panel does not hold a Backtransfer-capable source, three remaining options exist:
- Ask the original integrator for the project archive. Most engineers retain copies for the warranty period. Demand the ".hmi" file, not just a screenshot of the runtime.
- Reverse-engineer the runtime. Reverse-engineering a compiled ".fwx" runtime back to a compilable ".hmi" source is technically possible with third-party tools but is not officially supported by Siemens. For S7-200 systems, focus on identifying all tags and screens visually, then rebuild the project from scratch.
- Replace the panel and PLC. For legacy S7-200 + MP 277 installations that cannot be recovered, an upgrade path to a S7-1200 with a SIMATIC Comfort Panel (TP700 Comfort, 6AV2 124-1GC01-0AX0) programmed in TIA Portal V17 or later is the modern Siemens-supported solution. Plan for the migration cost during budgeting.
Related Siemens Documentation
The following official Siemens resources are the authoritative references for the MP 277, WinCC flexible 2008, ProSave, and the Backtransfer function. Use them as the primary source of truth for any further procedure or error code not covered in this article.
- WinCC flexible 2008 – Backtransfer of projects from operator panels
- SIMATIC MP 277 – Operating Instructions (6AV6 643-0CD01-1AX1)
- ProSave – Service Tool for SIMATIC Panels
- FAQ: How do you back-transfer the projects of an operator panel and what should you watch out for?
Can I upload a project from any Siemens HMI, not only the MP 277?
Yes, the Backtransfer function is supported across the WinCC flexible 2008 panel family (OP 73, OP 77, TP 177, OP 177, TP/OP 270, MP 270, MP 277, MP 377) and also on WinCC (TIA Portal) Comfort Panels and Unified Comfort Panels provided that "Enable Backtransfer" was checked at download time and the panel has sufficient storage.
Do I really need an SD card for Backtransfer on the MP 277?
Yes. The MP 277's internal flash stores only the compiled runtime; the source project used by Backtransfer lives on the SD/MMC card. Without a card inserted at the time of the original download, the panel never wrote a Backtransfer-capable image and recovery by Backtransfer is impossible.
What is the difference between ProSave Backup and WinCC flexible Backtransfer?
ProSave Backup produces a binary "*.psb" snapshot of the runtime that can only be restored to the same or a compatible panel – it contains no editable source. WinCC flexible Backtransfer reconstructs a compilable "*.hmi" project with all screens, tags, scripts, alarms, and connections, which can then be edited and re-compiled in WinCC flexible 2008.
What size SD card do I need for a typical MP 277 project?
A 1 GB SD card is sufficient for the vast majority of MP 277 projects. 512 MB is adequate below roughly 2,000 tags and 500 KB of graphics. SDHC cards (4 GB and up) are not supported on the MP 277 and must not be inserted.
Which WinCC flexible version should I install for Backtransfer?
Install WinCC flexible 2008 SP5 (or at minimum SP2) and ensure the build is the same major release or newer than the runtime that was originally downloaded to the MP 277. Mixing newer and older Service Packs is generally tolerated, but reverting to a much older WinCC flexible build (e.g., 2005) for a project that was compiled in 2008 will fail with an "incompatible firmware version" message.