OP77B ProSave PSB File: Decoding Limits and Recovery Path

Executive Summary: PSB Decoding Reality

Engineers receiving a *.psb file as a "complete upload" from a SIMATIC OP77B often expect the file to be a portable project database they can open in SIMATIC WinCC Flexible or import into TIA Portal. The hard fact confirmed by Siemens support and proven in the field: a ProSave backup cannot be reversed into a tag list, cannot be migrated to a different panel family, and cannot be opened as a *.hmi project. The only sanctioned recovery path is to restore the *.psb to the same physical OP77B from which it was uploaded, then read the project back from the panel's flash with back transfer active. This reference documents the conditions, alternatives, and engineering caveats that surround PSB handling.

SIMATIC OP77B Hardware Profile

The OP77B is a compact operator panel from the SIMATIC HMI 170/270/370 series designed for low-cost text and small-graphic applications on S7-200, S7-300, S7-400, and LOGO! controllers. Before planning any backup or recovery, classify the panel you are dealing with, because the engineering toolchain differs by generation.

Misidentifying the panel family is the single most common cause of failed recovery attempts. The OP77B is a WinCC Flexible target, not a TIA Portal native target. Although TIA Portal can migrate a WinCC Flexible project to a Comfort Panel, it cannot ingest a raw *.psb produced by ProSave.

ProSave Utility and File Type Taxonomy

ProSave is the Siemens standalone service tool installed alongside WinCC Flexible (or TIA Portal). It handles three distinct operations on a connected panel:

1. Download (PC → panel): Push the compiled runtime, fonts, and project data.
2. Upload (panel → PC): Read back the running project, recipes, logs, and (if back transfer is enabled) the source configuration.
3. Restore: Write a previously captured backup image back onto the panel flash.

The *.psb is a binary container. Internally it packages the runtime image in a compressed form that the OP77B bootloader can re-flash. The optional source payload (the *.hmi-equivalent data) is only present when the back-transfer option was active when the project was last downloaded to the panel.

PSB Internal Format Constraints

Siemens does not publish the *.psb file specification, which is the root cause of the "no decoder" situation. Field analysis of OP77B and similar-generation *.psb files shows the following structural properties:

• Header block: fixed-length identifier, panel type code, firmware version, language table, and CRC32.
• Runtime image: compressed (typically LZSS/DEFALG variant) screen definitions, tag DB mirror, alarm buffers, recipe storage, and bitmaps.
• Source payload (optional): present only if the original transfer was performed with Enable back transfer in the WinCC Flexible Transfer settings.
• Trailing certificates / keys: for runtime licensing on newer Comfort Panels; not applicable to OP77B but may appear as zero-length sections.

Because the tag database is stored as a runtime-mirrored structure rather than the engineering symbol table used by WinCC Flexible, even extracting the runtime image does not yield names, data types, or address pointers that map cleanly back to the original tag configuration. Symbol names are typically stripped in the runtime binary.

Why Tag Decoding Is Not Officially Supported

Siemens engineering policy treats the *.psb as a transient state file, not an archival format. The design intent is that the source of truth is the *.hmi project on the engineering workstation, not the running image on the panel. The runtime image on the panel is allowed to be older than the source on the PC. As a consequence, the engineering software never had to support reverse-synchronization from a *.psb into a *.hmi.

This is why every recovery scenario the field has tested fails at the same step: opening a *.psb in WinCC Flexible, importing it into TIA Portal, or converting it to a *.pbl archive is not possible. The relationship between the file types is one-way:

Engineering (WinCC Flexible / TIA)
        |  compile  (transfer)
        v
Runtime image on panel (flash)
        |  upload / ProSave  (creates *.psb)
        v
*.psb file on PC  <--  END OF LINE  (no reverse path)

The only deviation from this rule is the back-transfer path described in the next sections. It is the single off-ramp that allows the panel to ship a copy of the source configuration back to the PC, but it has to be enabled before the last compile/download cycle.

The Back Transfer Prerequisite

Back transfer is a WinCC Flexible transfer setting that instructs the panel to retain, alongside the runtime image, a compressed copy of the source configuration. When enabled, ProSave → Backup produces a *.psb that contains both the runtime and a re-importable source.

Procedure: Enabling Back Transfer in WinCC Flexible

Use this procedure on the engineering workstation that still has (or used to have) the original *.hmi project. It ensures that any future *.psb produced from the panel will contain the source payload.

1. Open the target project in WinCC Flexible.
2. Select Project → Transfer → Transfer Settings.
3. In the dialog, tick Enable back transfer. Optionally tick Encrypt source if the project must be protected at rest (password must be remembered - Siemens support cannot reset it).
4. Set the transfer channel to match the physical connection (serial / MPI / PROFIBUS / Ethernet on OP77B variants with the right interface).
5. Click Transfer to push the project. The panel will reboot into runtime and write the source payload to a reserved flash region.
6. Verify on the panel: Start Center → Settings → Transfer → Back transfer source: present.

Procedure: Restoring a *.psb to the Original OP77B

Restore is the only sanctioned way to load a *.psb back onto a panel. It must be the same panel from which the *.psb was uploaded, otherwise the panel type / firmware / serial checks fail.

1. Connect the OP77B to the PC using the same channel (MPI/PROFIBUS/serial) used for the original transfer.
2. Launch ProSave (Start → SIMATIC → ProSave). The OP77B must be visible in the device list.
3. Select Pannel type = OP77B, then set the connection parameters identical to the engineering environment.
4. Switch to the Backup tab. Choose Restore.
5. Browse to the *.psb file. ProSave validates the panel serial and firmware compatibility. If the panel ID does not match, the restore is refused.
6. Click Restore. The OP77B reboots, the flash is rewritten, and the panel returns to runtime.
7. Do not interrupt power during the flash write. A brownout at this stage bricks the panel.

Procedure: Extracting the *.hmi Source from the Restored Panel

Once the original *.psb has been restored to the original OP77B, the back-transfer source that lived in flash is once again reachable. The following steps bring the *.hmi back to the PC.

1. Open WinCC Flexible. Select Project → Retrieve.
2. When prompted for the source, choose Transfer from device (the wording in some SPs is Back transfer or Read from panel).
3. Select the OP77B in the device list, set the channel, and start the transfer.
4. WinCC Flexible receives the embedded source, decompresses it, and opens it as a normal *.hmi project. The project name will be the one last set in the source - it is not the *.psb filename.
5. Save the project immediately under a controlled name in the engineering archive. Compile and verify against the PLC tag list before deploying to a replacement panel.

At this point the engineer has a working *.hmi and can apply normal procedures: change tag mapping, migrate to TIA Portal, or compile for a successor panel.

Migration Paths: WinCC Flexible to TIA Portal

The OP77B itself is not a TIA Portal native target. It is a member of the WinCC Flexible 2008 SP3 product matrix, and Siemens' migration tool does not include it in the comfort-panel migrator set. The sanctioned upgrade path is hardware replacement plus migration:

1. From the recovered *.hmi, perform a Compile → Check consistency in WinCC Flexible 2008 SP3 with the latest HSP (Hardware Support Package).
2. Open TIA Portal (V13 SP1 or later, recommended V15.1+). Create a new project and select Migration → WinCC Flexible project.
3. Point the migrator at the *.hmi. The migrator emits a TIA project scoped to a Comfort Panel. The OP77B is not selectable; choose the smallest Comfort Panel that meets screen-size and tag-count requirements (typical: KTP700 Basic or TP700 Comfort).
4. Manually reconcile anything the migrator cannot carry over: legacy area pointers, raw-key handling, OP77B-specific system functions, and any ProTool-era scripts.
5. Compile to the new target, download, and validate against the PLC.

Pre-TIA Panel Migration: ProTool Era Devices

For OP7, OP17, TD17, and the C7-633 / C7-634 integrated panels, the engineering history predates WinCC Flexible. The source tool is SIMATIC ProTool, and the recovery path is materially different. ProTool maintained the project on a per-panel VFD/folder structure rather than a single *.hmi file, and the *.psb generated by ProSave for these targets is even more locked-down than the OP77B variant.

• Always keep the ProTool source folder on a controlled network share, not on the engineering workstation.
• For OP17 / TD17, ProTool/Lite can re-open the source if the previous compile produced a ProTool-readable archive; *.psb alone is not enough.
• C7-633 / C7-634 panels combined the HMI and the S7 CPU in a single unit. The backup contains both images, and a partial restore risks desynchronizing the CPU and the HMI halves. Always restore as a complete *.psb.

Alternative Recovery Strategies When Back Transfer Was Disabled

When the *.psb is a runtime-only image, the source project is technically recoverable only if a parallel engineering archive exists. The following sources, in priority order, can yield a usable *.hmi:

1. The original engineering workstation or a workstation backup. WinCC Flexible stores the project in %USERPROFILE%\Documents\Siemens\HMI\Projects by default.
2. Version-control check-ins. Some shops commit *.hmi exports to SVN/Git. The HMI project is a folder, not a single binary, so it does not diff cleanly - export the project as a *.pbl first, commit the *.pbl, and restore by re-importing the *.pbl.
3. Customer-served archive or commissioning binder. Many integrators deliver a project CD with the final as-built *.pbl.
4. The PLC's symbol table. Although not equivalent, the PLC-side tag names can be re-keyed into a fresh WinCC Flexible project, drastically reducing the rebuild effort.
5. Printouts, screenshots, and HMI documentation. Treat these as a worst-case rebuild reference only.

If none of the above exists, the panel can be re-imaged by recreating screens, alarms, and tags from the running panel's I/O behaviour, but this is an engineering rebuild, not a recovery.

Engineering Cautions and Field Notes

• Never rename the *.psb to *.hmi. WinCC Flexible will throw a corrupt-project error and may overwrite prompt history.
• Never edit a *.psb with a hex editor. The CRC32 will fail on restore, the panel will refuse to flash, and a partial flash can leave the OP77B in a non-bootable state requiring a Siemens service recovery.
• Always match the panel serial. ProSave stores the panel serial inside the *.psb. Restoring to a different panel is impossible, and there is no field workaround.
• Back transfer is panel-side storage. It survives a power cycle. It does not survive a runtime reload from a *.hmi that had back transfer disabled at compile time. The setting has to be correct at the most recent compile.
• Document the setting in the project header. Add a comment to the WinCC Flexible project stating whether back transfer is enabled, and stamp the project with the date of the last transfer. This is the single piece of information that decides whether a *.psb is recoverable five years later.
• Stage backups on a network share. Local *.psb files on the engineering PC are commonly lost to laptop retirement. A scheduled copy of the ProSave output to a documented share is a low-cost insurance policy.

Verification Checklist After Recovery

1. Confirm the recovered project compiles cleanly in WinCC Flexible without warnings.
2. Cross-check the tag list against the PLC symbol table - name, data type, and address must match.
3. Open every screen on the engineering simulator and confirm that all IO fields, buttons, and indicators are present.
4. Force a recipe upload / download cycle on the simulator to verify recipe tags.
5. Compile to the live OP77B, then perform a one-touch Read from panel to confirm the back-transfer source is now present in the new download.
6. Archive the *.hmi (and a *.pbl export) under a controlled name before releasing the panel to production.