Modifying STEP 7 V5.0 Projects in V5.5 SP4 for Legacy CPU

Overview: Why a 2006 STEP 7 Project Cannot Be Resolved with a Simple Installer

Plant-floor engineers routinely inherit STEP 7 V5.0 and WinCC V6.0 archives from systems commissioned around 2003-2007. The natural first reaction is to ask for the original installer media; the realistic answer is that the legacy Siemens installers (STEP 7 V5.0 through V5.3, WinCC V6.0 and V6.2) have been pulled from public download servers and are only available through a paid support request to your local Siemens representative. This article documents the engineering path that does work: editing the legacy project in the last V5.x release, SIMATIC STEP 7 V5.5 SP4, and pushing only the modified compiled blocks to the plant CPU. The technique is reliable because the S7 machine code stored inside the CPU is independent of the STEP 7 version that produced it.

STEP 7 V5.x Release Timeline and Project-File Compatibility

The critical rule: STEP 7 V5.x is a one-way compatibility ladder. A newer release can open an older project, but it cannot save the project back to the older release format. If you have an archive produced on STEP 7 V5.0 in 2006, the only legal file-format destinations are STEP 7 V5.5 SP4 or a TIA Portal migration target.

Why the Compiled Block Transfer Still Works Across Versions

The block container inside an S7-300 or S7-400 CPU does not store the STEP 7 editor version. It stores the compiled MC7 code plus interface description (IN/OUT/STAT/TEMP) compiled from STL, LAD, or FBD by the S7 compiler. That MC7 instruction set has been frozen since the introduction of the S7-400 and was extended in a backward-compatible way for S7-300. Any V5.x release — including V5.5 SP4 — produces MC7 code that the original CPU (even a 1996-era S7-300) executes correctly.

The download protocol (MPI / PROFIBUS / Ethernet via TCP RFC1006) and the online block transfer format were also frozen. The only practical caveat is the firmware version of the CPU: very old CPUs (e.g., CPU 312 IFM, CPU 314 IFM, early CPU 413/414/416) may require the matching old firmware be present, but this is independent of the STEP 7 editor used to compile.

Prerequisites Before Touching the Plant Project

1. Install SIMATIC STEP 7 V5.5 SP4 on an engineering PG/PC. The trial package is referenced under Siemens support entry 109761045; for full functionality the plant must hold a valid V5.5 SP4 license (floating or single).
2. Install S7-PLCSIM V5.4 SP5 if offline simulation is desired before the live plant download.
3. Confirm the CPU order number and firmware version by reading the online diagnostic buffer of the plant CPU. STEP 7 V5.5 SP4 ships a hardware catalog that lists every S7-300/400 CPU that shipped up to 2013.
4. Take a full backup of the live CPU using STEP 7: PLC > Upload Station to PG. Save the upload as a separate project, do not overwrite the 2006 archive.
5. Capture the symbol table and the source files (if any exist) from the original archive: Options > Manage STL/SCL Source Files.
6. Document the version of the 2006 archive. Open the .s7p file and read the Project > Properties dialog. If it reports V5.0 service pack 1 or V5.0 SP2, write it down — it tells you which optional packages (CFC, SCL, Graph, S7-GRAPH) must also be installed in V5.5 SP4 for the project to open without errors.

Procedure: Modify the 2006 Archive in V5.5 SP4 and Download Only the Changed Blocks

1. Open the V5.0 archive. Launch SIMATIC Manager, choose File > Open > User Projects, and select the .s7p file. SIMATIC Manager will detect the older format and display a compatibility banner; accept it. No data loss is expected for plain STL/LAD/FBD blocks, but optional packages (CFC, S7-SCL, S7-Graph) must be installed or the corresponding subtrees will appear greyed out.
2. Resolve HW Config mismatches. If the HW Config tree shows a yellow triangle because V5.5 SP4 has a newer version of the hardware catalog than the one originally used, do not force a hardware upgrade. The version stamped in the project is the version the live CPU runs. Re-select the original order number / firmware combination from the catalog; do not allow STEP 7 to re-write the HW Config silently.
3. Edit the logic. Open the relevant FB, FC, or OB. Edit in LAD/FBD/STL as usual. Save with Ctrl+S. Recompile the changed block (Edit > Compile or right-click Compile).
4. Recompile the entire program to refresh the system data (SDB): PLC > Compile and Download Objects. This regenerates SDBs that the CPU needs for hardware parameter assignment. Skipping this step is the most common cause of online faults after a partial edit.
5. Consistency check before going online: PLC > Check Consistency. Resolve any errors relating to block interface changes; downstream blocks referencing the changed interface must be updated and recompiled in the same work session.
6. Connect online via the configured MPI/PROFIBUS/Ethernet interface. The online view of the block list shows the timestamps of blocks currently in the CPU versus blocks in your PG project.
7. Download only the changed blocks: Select the modified FB/FC/OB in the offline project tree, then PLC > Download. STEP 7 will prompt for STOP/RUN transitions on FBs that affect cyclic OB1; on S7-300/400 this is generally required for FB/FC/OB changes and is acceptable for short plant interruptions.
8. Verify SDB download: After the logic blocks finish downloading, PLC > Download User Program to Memory Card is not what you want; instead, check PLC > Compare to confirm the online SDBs match the offline SDBs. If they do not, repeat step 4.

Cross-Version Library Strategy: S7 Source Files Instead of Compiled Blocks

If the field engineer at the plant only owns STEP 7 V5.0 (no upgrade budget, no spare license seat), a source-file approach is the only sustainable transfer method:

1. In V5.5 SP4, mark the changed FB/FC/OB and generate an STL or SCL source file: Options > Manage STL Source Files > Generate Source. The file is plain text and can be opened in Notepad.
2. Copy the generated *.awl or *.scl file to the plant PC on a USB stick or via shared drive.
3. On the plant PC running STEP 7 V5.0, Options > Manage STL Source Files > Insert the source file into the S7 program container.
4. Right-click the source file and choose Compile. STEP 7 will produce a compiled block in the offline program that is bit-identical to the one produced under V5.5 SP4 — STL source files are version-stable across all V5.x releases because the compiler recognises the original syntax dialect.
5. Download the compiled block as in the previous procedure.

Inline Visual: Decision Flow for the Legacy Project

WinCC V6.0: Why It Cannot Be Downloaded and What Replaces It

WinCC V6.0 (and V6.2) installers are not hosted by Siemens on the public support portal. Trial downloads start at WinCC V11 SP2 (TIA Portal) and go up through the latest TIA release. A V6.0 project cannot be opened by WinCC V7.0 or later without an in-place migration. The supported migration path is:

1. Install WinCC V7.0 SP3 (or V7.2/V7.3 — V7.x has a built-in migration wizard that ingests V6.x projects).
2. Open the V6.0 project under V7.x; the migration wizard runs and rewrites the project database.
3. Run a full compile and tag-export round-trip to surface any orphaned tags or broken picture references.
4. After V7.x, further migration to TIA WinCC Professional is a separate, non-reversible step.

If the 2006 plant still runs a WinCC V6.0 runtime, the HMI PC must continue to run V6.0 RT. You cannot push V7.x compiled RT files into a V6.0 runtime; they are incompatible binaries. For minor HMI changes on a V6.0 system, the only path is a WinCC V6.0 installation on the engineering PC, which requires a support request through your Siemens representative for the legacy media.

Hardware-Compatibility Check for Old S7 CPUs Under V5.5 SP4

Verification note: the exact "latest firmware supported" figures should be cross-checked against the STEP 7 V5.5 SP4 readme (file Readme.rtf in the installation root). Siemens periodically updates the readme between service packs; the readme is the binding source for support claims.

Verification Procedure After the Plant Download

1. Force the CPU into STOP from the online panel: PLC > Operating Mode > STOP. Observe the STOP LED; on a 2006 S7-300/400 this is reliable.
2. Compare offline vs online block list: PLC > Compare. Every block timestamp and CRC must match between PG and CPU.
3. Read the diagnostic buffer: PLC > Diagnostic/Setting > Diagnostic Buffer. Look for entries of class "IO Configuration Error" or "Parameter Assignment Error" — these indicate that the SDB did not download cleanly.
4. Switch to RUN: PLC > Operating Mode > RUN. Watch the SF/BF LEDs; clean status is RUN-only with green RUN LED.
5. Single-step the modified logic: Debug > Monitor/Modify. Force the inputs to the modified FB and confirm the new branch executes exactly as the offline simulation predicted. Release the force flags before leaving site.
6. Take a fresh full upload: PLC > Upload Station to PG. Archive this as the new plant baseline. This file now reflects the V5.5 SP4 compile and supersedes the 2006 archive.

License and Authorisation Considerations

• A STEP 7 V5.5 SP4 license is required even when opening a V5.0 project. The license key (a USB-style "Authorisation" or the newer softkey on a 7mm dongle) must be present on the engineering PC for the offline editor and online download to function.
• If the engineering PC is borrowed and the license must be returned, do Automation License Manager > Transfer License back to the original owner. Do not deinstall STEP 7 without first returning the license — the licence becomes orphaned and requires Siemens support to recover.
• STEP 7 V5.5 SP4 and TIA Portal can co-exist on the same Windows PC; they do not share authorisation files. A V5.5 SP4 license does not enable TIA Portal.

Troubleshooting Matrix

Field-Commissioning Notes for a 2006 Plant

• Take a screenshot of every HMI screen before starting. WinCC V6.0 archives often contain graphics that are not part of the project file but live in the runtime cache.
• Capture the active connection list from the live CPU (PLC > Connections) before touching HW Config. Removing an unused connection in V5.5 SP4 can break a partner CPU the engineer forgot about.
• If the plant CPU sits behind a router or NAT on TCP, verify that the TSAP and rack/slot match the partner's online view; V5.5 SP4 added stricter TSAP validation that older online projects sometimes did not store.
• Bring a working MPI cable (6ES7 972-0BA12-0XA0 or equivalent) as a fallback. Many 2006 cabinets still expose only the MPI port; Ethernet modules were rare before 2008.

When You Cannot Avoid the Original V5.0 Installer

If the project contains:

• CFC (Continuous Function Chart) charts that must remain editable,
• S7-PLCSIM V5.0 simulation models embedded in the project,
• ProAgent diagnostic wiring that is no longer shipped after V5.4,
• HiGraph graphs that require a specific HiGraph version,

then a one-time support request to your Siemens representative for the V5.0 media is the only legal path. The request must reference the plant's Siemens customer number and the original sales order number to receive the legacy media under contract.

Escalation Path: Getting Old Media Through Siemens

1. Open a support request via Siemens Industry Online Support with category "Automation / SIMATIC / STEP 7 / Older versions".
2. Reference the project date, original order number, and the customer's SAP/SD customer number.
3. Siemens will provide a quote for the legacy media (typically a USB drive or download link with a one-time activation key). Lead time is typically 5-10 business days in EMEA; longer in regions where legacy media must be shipped physically.
4. Activate the media with the legacy license key (if still owned) or purchase a fresh STEP 7 V5.5 SP4 license and use it as the migration target instead — V5.5 SP4 is cheaper and faster than restoring V5.0.

FAQ