Converting STEP 5 to STEP 7: S5/S7 Converter and TIA Portal

Siemens SIMATIC S5 controllers (S5-90U, S5-95U, S5-100U, S5-115U, S5-135U, S5-155U) reached end-of-life decades ago, but a large installed base still runs STEP 5 programs written in STL, LAD, CSF, or SCL. Modern S7-300, S7-400, and TIA Portal controllers require STEP 7 (SIMATIC Manager) or TIA Portal projects. Migrating legacy code therefore involves two distinct toolchains: the S5/S7 Converter (ships with STEP 7 classic) for the first hop into STEP 7, and the TIA Portal migration tool for the second hop into the current engineering framework. This reference documents both stages, the conversion errors you will hit, and the manual fix-up steps required when automated conversion cannot resolve them.

1. Migration Path Overview

A STEP 5 project does not become a TIA Portal project in a single operation. Siemens defines the canonical path as two sequential transformations:

1. STEP 5 → STEP 7 (classic): Performed by the S5/S7 Converter that ships with STEP 7 V5.x. The tool reads *.S5D files and emits a STEP 7 project consumable by SIMATIC Manager.
2. STEP 7 (classic) → TIA Portal: Performed by the TIA Portal migration tool, which reads the STEP 7 V5.x project and produces a *.ap20 / *.am20 migration project that TIA Portal V20 (or the target version) opens and converts.

Per the official Siemens migration documentation, the TIA Portal migration tool produces an initial migration project (*.am20) that the user must open, review, recompile, and save as a regular TIA Portal project. No fully automatic "one-click" path exists for STEP 5 → TIA Portal.

2. Prerequisites and Tool Versions

Install STEP 7 V5.x first and confirm the S5/S7 Converter is present in the Windows Start menu. Verify Windows file association for *.S5D opens the converter rather than a text editor. The conversion manual STEP 7 From S5 to S7 is available on Siemens Industry Online Support as a PDF (entry ID 45531547) and should be downloaded before starting.

3. S5/S7 Converter Workflow

3.1 Launch and select source

1. Start → SIMATIC → STEP 7 → S5 Converter.
2. Select File → Open and navigate to the STEP 5 project (*.S5D or unpacked directory containing S5DAT.A0D, S5DAT.A1D, ... S5DAT.A7D).
3. The converter parses the S5 program and displays the FB/FC/PB/OB structure in a tree view.

3.2 Configure target S7 CPU

The S5/S7 Converter requires a target S7-300 or S7-400 CPU to be selected because the address space, organization blocks, and I/O layout differ from the S5 source. Typical mappings:

3.3 Run conversion

Select Convert → Start Conversion. The S5/S7 Converter performs the following sequence internally:

1. Parses STEP 5 STL statements and translates to STEP 7 STL (AWL) and SCL equivalents.
2. Maps S5 bit memory, timers, counters, and I/O to S7 equivalent areas:

The conversion manual STEP 7 From S5 to S7 (Siemens entry 45531547) explicitly notes: "The S5/S7 Converter uses STEP 7 instructions to convert indirect addressing with DO FW and DO DW. The instruction sequence generated is generally very extensive." In practice, a single S5 DO FW loop may expand to dozens of STEP 7 STL statements using pointer arithmetic and indirect addressing.

4. STEP 5 vs STEP 7 Instruction Mapping

The S5/S7 Converter handles a large portion of the standard instruction set automatically, but several S5 constructs require manual review. The table below summarizes the principal mappings; a complete list is in the conversion manual.

5. Handling Conversion Errors and Warnings

When the S5/S7 Converter completes, it produces a diagnostic log. Errors block compilation of the STEP 7 program; warnings do not block but indicate code that requires manual review.

5.1 Common errors

If errors persist after the converter has produced its best-effort output, manual intervention is required. There is no fully automatic recovery path; users must open the resulting STEP 7 blocks in SIMATIC Manager and edit them directly.

5.2 Common warnings

6. Manual Conversion Approach

When the S5/S7 Converter fails or yields code that cannot be salvaged, the only remaining path is manual conversion. The recommended procedure is:

1. Document the S5 program: Print the STL listing with cross-references; record all FB/FC/PB/DB numbers, the cyclic OB structure, and the I/O map.
2. Build a new STEP 7 project: In SIMATIC Manager, insert a new S7-300 or S7-400 station, insert the target CPU, and create the OB1 cyclic, OB100 warm restart, OB101 hot restart, OB102 cold restart, and any required error OBs (OB80-OB87) to match the S5 program structure.
3. Re-create the symbol table: In S7, edit the symbol table (S7 Program → Symbols) and add every S5 symbolic name. This is critical for readability and for the TIA Portal migration step.
4. Port FBs block by block: Open the S5 STL listing side by side with a new STEP 7 STL source file. Re-translate each instruction. Replace S5 timers/counters with multi-instance IEC blocks within the FB; this requires adding VAR / END_VAR declarations.
5. Port DBs as UDTs first when shapes repeat: If multiple DBs share the same structure, define a UDT and instantiate it, mirroring S5 DX practice.
6. Compile, download, and test in PLCSIM: Before touching a real CPU, install S7-PLCSIM V5.x and run the OB1 in simulation against simulated I/O. Walk through the original S5 program state table and confirm each step.

For a 1000-line S5 program, manual conversion typically consumes 2-5 engineering days; for 10,000+ line programs expect several weeks and consider whether a full PLC replacement is more economical.

7. Migrating STEP 7 to TIA Portal

Once a STEP 7 V5.x project compiles cleanly, it can be migrated to TIA Portal. The official Siemens procedure is documented in the TIA Portal help under Migration of STEP 7 projects (S7-300, S7-400):

1. Open TIA Portal V20 (or target version).
2. Select Project → Migrate project.
3. Browse to the STEP 7 V5.x project file (*.S7P).
4. TIA Portal produces a migration file (*.am20) and opens it. At this stage the project is read-only and displays conversion diagnostics.
5. Review the migration log. The tool highlights unsupported hardware (e.g., older CP 443-1), unsupported blocks, and licensing notes.
6. Resolve the migration diagnostics: replace obsolete CPs with current models (e.g., CP 443-1 EX30, 6GK7443-1EX30-0XE0), recompile the SCL and STL sources, and migrate any HMI ProTool projects to WinCC Unified.
7. Save the result as a normal TIA Portal project (*.ap20).

After the STEP 7 V5.x project migrates, every S7-300/S7-400 station and program is visible in the TIA Portal project tree. The HMI connection data, network configuration, and user program are preserved with the diagnostic warnings noted in the migration log.

8. Common Conversion Issues and Diagnostics

9. Verification and Commissioning

Before downloading the converted STEP 7 or TIA Portal program to a real CPU, perform the following verification sequence:

1. Static checks: Compile in STEP 7 / TIA Portal with no errors and no warnings unresolved.
2. Cross-reference review: In SIMATIC Manager Options → Reference Data → Display (or TIA Portal Tools → Cross-reference), verify that every input, output, flag, timer, counter, and DB used in the original S5 program has a counterpart in the converted program.
3. Simulation: Run the program in S7-PLCSIM (STEP 7) or PLCSIM Advanced (TIA Portal). Drive inputs, observe outputs, and compare to the S5 simulation trace if available.
4. Fatigue test: Run for 24-72 hours of simulated time covering all sequences, fault paths, and operator modes.
5. Field validation: With the plant in a safe state, download to the real CPU in STOP mode, perform a warm restart (OB100), and step through the first cycle manually with the operator station in hand-control.
6. Parallel run: If downtime is critical, run the S5 and S7 CPUs in parallel for a defined window and compare outputs via a Y-cable on the field wiring before final cutover.

10. Key Documentation References

• STEP 7 From S5 to S7 conversion manual (Siemens, entry 45531547)
• Migration of STEP 7 projects (S7-300, S7-400) to TIA Portal

Both references are official Siemens documentation and should be cross-checked against the installed TIA Portal version, as the migration tool behavior is updated between major releases (V15, V16, V17, V18, V19, V20).