OP277 MP277 to TP1200/KP700 Migration: Why Original .hmi Project Files Are Mandatory

Siemens declared the OP277 and MP277 panel families obsolete with spare-part availability limited to 2021. Replacement paths now route almost exclusively through the Comfort line (KP700, TP1200, TP1500, TP1900, TP2200) configured in TIA Portal with WinCC Comfort/Advanced. The single most common field failure during this transition is the loss of the original WinCC flexible .hmi project. Engineers routinely have only a panel-side backup on USB stick or MMC/SD card and discover, often at the migration meeting, that this backup is not editable and cannot be opened in TIA Portal. This document consolidates the technical reasons for that restriction, the one engineering option that can salvage a project from a backup, and the official migration path Siemens supports for these two families.

1. Hardware and Software Generations at a Glance

Understanding why .hmi files are non-negotiable requires recognizing that OP277/MP277 and KP700/TP1200 belong to different engineering ecosystems.

2. The Three File Categories You Will Encounter

Engineers confuse three different artifacts that live in the OP277/MP277 ecosystem. Distinguishing them up front prevents a wasted commissioning visit.

2.1 Source project (.hmi)

The editable WinCC flexible 2008 project authored on the engineering station. It contains screens, tags, alarms, scripts, area pointers, schedules, and the device configuration. This is the only file TIA Portal's Migration command will accept. TIA Portal opens it via Project > Migrate project and produces a TIA Portal project that you can then re-target to a KP700 or TP1200.

2.2 Compiled runtime (.fwx)

Binary, version-locked, encrypted. Generated when the engineer performs Project > Compiler > Generate runtime and then Download to target device / Transfer > Panel. The panel boots from this file. It is not human-readable, not editable, and not convertible to an .hmi by any Siemens-supported tool. Decompilers exist in third-party space but are explicitly out of scope; reverse engineering will not produce a maintainable project.

2.3 Backup (.brf, .ar1, .pzd, MMC .img)

Produced by Service & Commissioning > Backup/Restore on the panel, by ProSave on the PC, or by WinCC flexible Project > Backup. The extension varies:

Only the last row can substitute for the original .hmi. Every other backup is a dead end for migration.

3. Why Backups Cannot Replace Original Projects

Three structural reasons force the requirement:

1. Compilation is one-way. The .fwx runtime is a frozen, optimized image. Variable names are replaced with numeric indices, alarm classes lose their textual identifiers, and script code is pre-parsed. TIA Portal's migration converter needs symbol tables, tag names, and the original area-pointer configuration to rebuild a TIA Portal project. None of these survive compilation.
2. Password hashing destroys round-trip data. A panel-side backup stores only the hashed user passwords, not the originals. The new TP1200 must reproduce the same user list with the same credentials. Without the source, you can re-author users from scratch, but you cannot recover previous credentials.
3. Vendor license terms. Siemens licensing treats the .hmi as the deliverable to the end customer. Backup images are recovery media for the deployed runtime, not engineering IP. The official WinCC flexible — Migration Guide (entry ID 109750174) accepts only .hmi source.

4. The "Enable Back Transfer" Lifeline

When the original .hmi is missing, the only engineering-controlled chance to recover an editable project is the Enable Back Transfer checkbox available in WinCC flexible during the original download step.

4.1 Where to find the option

In WinCC flexible 2008 SP5: Project > Transfer > Transfer Settings > Advanced (or directly in the Download to Target System dialog, second tab). The exact path depends on the SP level:

1. Open the project in WinCC flexible.
2. Select Project > Transfer > Transfer Settings.
3. Click Advanced on the right pane.
4. Tick Enable back transfer.
5. Select the destination: Memory card (MMC/SD) or External storage (USB).
6. Confirm with OK and proceed with the download.

4.2 What gets written back

If back transfer is enabled and the panel is connected to a memory card or USB stick at download time, WinCC flexible writes a copy of the editable .hmi to that media. On the OP277/MP277 the destination directory is \\Storage Card MMC\\HMI_PROJECT\\<projectname>.hmi or, on USB, \\USB Storage\\HMI_PROJECT\\<projectname>.hmi. Look for the HMI_PROJECT folder explicitly; the back transfer does not drop the file in the card root.

4.3 Field reality

Most OP277/MP277 installations on the field do not have back transfer enabled. The option adds a noticeable amount of time to each download (the panel re-stores the full editable project on the card) and historically required a separate memory card ordered as a spare because the active card was the one inside the panel at all times. Default installations therefore leave it unchecked. Treat any recovered .hmi on the MMC as a windfall, not a guarantee.

5. Reverse Engineering from MMC/USB Backups

If neither the source .hmi nor a back-transferred copy is available, the only remaining option is to recreate the project from I/O lists, wiring diagrams, and screen captures. The procedure below preserves as much of the original configuration as possible.

1. Inventory the PLC tags. Export the tag list from STEP 7 / TIA Portal on the controller side. Without this, the new TP1200 project cannot bind displays to live data.
2. Document the area pointers. OP277/MP277 projects use area pointers for date/time, PLC job mailbox, and project ID. Capture these from the HMI's diagnostic page (Main menu > Information > System) before powering down the panel for the last time.
3. Photograph every screen. Use a high-resolution camera with even lighting. Capture both the main screen and the pop-up/alarm views.
4. Restore the backup to a like-for-like OP277/MP277 via ProSave Restore if one is available on the shelf, then enable back transfer for the new project before downloading the replacement.
5. Rebuild the project in WinCC flexible 2008 SP5 to match the photos, then migrate through TIA Portal to the TP1200/KP700. This two-step path produces a clean migration result; going directly from "photos and tag list" to TIA Portal is possible but loses round-trip editability if a WinCC flexible engineer has to revisit the project.

6. Migration Path: WinCC flexible to TIA Portal

Once the editable .hmi is in hand, the official Siemens migration path applies. Follow the steps in the WinCC flexible — Migration Guide for the version of TIA Portal you are using; the procedure has been stable since V13 SP1.

6.1 Tool versions

6.2 Step-by-step migration

1. Open TIA Portal and select Open an existing project > Migrate project.
2. Browse to the .hmi file. TIA Portal reads the WinCC flexible project structure.
3. The migration log lists unsupported objects. For OP277/MP277, typical warnings are: legacy ActiveX controls, ProAgent, and SIMATIC HMI HTTP Protocol (replaced by the modern OPC UA server in TP1200).
4. Once the .hmi is migrated, change the HMI device to KP700 Comfort or TP1200 Comfort via Devices & networks > Device view > Change device.
5. Resolve compile errors. Common fixes:
   • Re-bind area pointers that no longer match the new panel's default offsets.
   • Re-author any Schedules that referenced OP277-only time zones.
   • Re-enter passwords; the migration log will list user accounts whose hashes could not be carried over.
6. Compile the project (right-click the HMI device > Compile > Software (rebuild all)).
7. Download to the new panel.

7. Commissioning the New Panel

The TP1200/KP700 hardware behaves differently from the OP277/MP277 in three areas. Budget extra time for these during commissioning.

7.1 Connection topology

OP277/MP277 use MPI/Profibus DP as the default PLC link. Comfort panels default to PROFINET. A migrated project retains the original MPI/Profibus configuration unless the engineer updates the connection. If the controller is a legacy S7-300/400 with Profibus, add a Profinet-to-Profibus gateway (e.g. IE/PB Link PN IO, 6GK1 411-5AB00) or migrate the controller first.

7.2 Boot time and transfer mode

Comfort panels take 30–45 seconds to boot to the loader, vs ~20 seconds for an OP277. The transfer-mode toggle (the small recessed button) is now labeled Service on the back of the panel. Update your commissioning checklist.

7.3 Storage media

Comfort panels use SD cards (not MMC) and support USB 3.0 sticks. Re-format any old MMC under the new panel; the FAT16 file system on legacy MMCs is not always readable on TP1200 hardware.

8. Verification Checklist Before Site Handover

Run the following checks after the migration is downloaded to the new panel and the controller is online.

Item 7 closes the loop. Enable back transfer in TIA Portal before every download to the new panel. The Comfort line stores the editable .apXX on the SD card by default when the option is set, giving you a recovery path for the next migration cycle.

9. Frequently Asked Questions