Resolving PCS7 V9.0 'Generate Module Driver' CH_AI Library Error

When a legacy SIMATIC PCS 7 multiproject (originally compiled with PCS 7 V7.x driver blocks) is opened on a freshly installed PCS 7 V9.0 engineering station, the chart compile step frequently aborts with "Generate module driver" in the progress log and a dialog stating "Necessary files are missing for block CH_AI. Please note that you have to install exactly the same version of the library as the one this block was imported from." This article documents the root cause, the library architecture behind it, and the field-proven procedure to clear the error without having to migrate the program to the Advanced Process Library (APL).

1. Problem Description

The reported symptom chain is reproducible on any V9.0 station that does not have the legacy PCS 7 V7.1 library stack installed:

1. Engineer retrieves a customer PCS 7 V7.1 multiproject onto a brand-new V9.0 station.
2. Project opens, CFC/SFC editors, OS pictures and the simulation all work as expected.
3. Engineer modifies any chart and triggers Chart → Compile → Charts as Program (or Scope → Compile).
4. The compiler progress dialog displays "Generate module driver" and then halts.
5. Compass log or the Module Driver tab inside the compile result reports:
   Necessary files are missing for block CH_AI. Please note that you have to install exactly the same version of the library as the one this block was imported from.
6. The chart is not regenerated; @CH_AI driver charts are missing or empty, which causes AS-OS download inconsistencies downstream.

The same error appears in the catalog whenever the project contains any of the legacy driver blocks from the pre-APL family: CH_AI, CH_AO, CH_DI, CH_DO, CH_CNT, CH_MS, CH_UDT, MOT_SPEED, VALVE_ANA, PID_FM, etc.

2. Root Cause Analysis

The PCS 7 driver generator (the "@chart" wizard that lives inside the CFC compiler) requires additional metadata about every driver block it must instantiate:

• The driver block's interface signature (IN/OUT/STAT declarations) — this is stored in the project, in the S7 program / block container.
• Wizard metadata — the rules that tell the driver generator how to wire the channel to the user-placed driver block, which I/O signals to connect, and which faceplate to bind. This metadata is not stored in the project. It is added to the engineering station by the library setup.

PCS 7 V9.0 Setup, by default, installs only the APL (Advanced Process Library) — the post-V8.0 architecture where the library is split into a Basic Library (basis blocks) and an Advanced Process Library (driver, control and faceplate blocks). The legacy "Library Vx.y" that shipped with PCS 7 V6/V7 is no longer part of V9.0 media. When the driver wizard encounters a CH_AI in the project, it cannot find the corresponding wizard description and aborts with the "missing files" error.

3. Library Architecture — Pre-APL vs APL

Understanding the library split is essential to choosing the correct installer and avoiding version mismatches later.

The non-APL library has no "Basis Library" counterpart. Before the APL architecture (V8.0) there was a single Library V7.1 SPx that contained both the basic blocks and the driver/control/faceplate blocks. Only the APL era introduced the split.

4. Affected Versions & Compatibility

• Engineering station: PCS 7 V9.0, V9.0 SP1, V9.0 SP2, V9.0 SP3, V9.0 SP4 and later V9.0.x updates (the issue is reproducible on every V9.0 update because none of them re-includes the legacy V7.1 library stack).
• Project origin: PCS 7 V6.0, V6.1, V7.0, V7.1, V7.1 SP1, V7.1 SP2, V7.1 SP3, V7.1 SP4, V8.0 — all use the same non-APL "Library V7.1" blocks.
• Block family: All CH_* driver blocks plus their associated technological blocks (MOT_SP, VALVE_ANA, PID_FM, ...).
• OS components: Projects with WinCC faceplates from the V7.1 era additionally require the Library Faceplates V7.1 SP3 Upd1 on the OS engineering side, otherwise OS compile will fail with the same "missing files" class of error.

5. Solution — Install the Legacy Library Stack

The complete fix has three installation steps. All three are required when the project contains pre-APL technological blocks with faceplates. If the project only contains CH_* driver blocks, the first two steps are sufficient.

5.1 Step 1 — Install Library V7.1 SP3 Upd4 (driver + control blocks)

1. Close SIMATIC Manager / PCS 7 Engineering on the engineering station.
2. Open the Siemens Industry Online Support entry 109757344 — "PCS 7 Library V7.1 SP3 Upd4" and download the package.
3. Unpack the ZIP and run setup.exe as administrator.
4. Follow the installer; the package deploys the legacy Library V7.1 blocks plus the driver wizard metadata into the PCS 7 catalog.
5. Restart the engineering station when the installer prompts to do so.

5.2 Step 2 — Install Library Faceplates V7.1 SP3 Upd1 (OS faceplates)

Required only if the project contains pre-APL technological blocks (motors, valves, PID controllers) that own a faceplate.

1. Navigate to the V8.2 Update page of the Siemens support portal. The faceplates package is no longer linked from the V9.0 update pages, but it is still hosted under the V8.2 entry. Search the support portal for "PCS 7 Library Faceplates V7.1 SP3 Upd1".
2. Download and run the setup. The faceplates are deployed into the WinCC picture catalog.
3. Restart SIMATIC Manager so the new picture objects become available.

5.3 Step 3 — Reopen and re-verify the project

1. Re-open the multiproject in PCS 7 V9.0.
2. Right-click the AS → Compile → Charts as Program.
3. Confirm that the "Generate module driver" step completes without aborting.
4. Open the Module Driver tab of the compile result — it should be empty (no missing-file entries).

6. Locating the Installer on a PCS 7 Media DVD

If the support portal is not reachable (off-site plant, locked-down ES), the legacy stack may still be present on the original PCS 7 V8.x media DVD or on the V9.0 DVD under Additional Tools:

• Mount the PCS 7 DVD and browse the root directory.
• Open the Additional_Tools folder.
• Look for PCS7_Library_V71_SP3_Upd4.exe (or similar).
• Look for PCS7_Library_Faceplates_V71_SP3_Upd1.exe.

7. Verification Procedure

After installing the legacy library, perform the following checklist:

8. Troubleshooting Matrix

9. Why the Project Cannot Be Self-Contained

Engineers frequently ask why Siemens did not bundle the wizard metadata into the project itself. The architectural reasons are documented in the PCS 7 engineering manual and worth restating for the field:

• Catalog size: The wizard metadata for every driver and technological block would inflate the project archive by hundreds of megabytes.
• Version coupling: A library fix (e.g. addressing a connection bug) must be deployable to the engineering station without re-opening the project.
• Multi-ES consistency: Multiple engineers on the same multiproject must have the identical library stack; installing it once per ES (and not per project) guarantees that.

For all these reasons, the Library V7.1 is an engineering-station-level dependency, not a project-level artifact. It must be installed on every ES that opens the project, including contractor laptops and FAT rigs.

10. Best Practices for Mixed-Vintage PCS 7 Fleets

1. Maintain a documented Library Reference Sheet per project, listing the exact library versions used (e.g. Library V7.1 SP3 Upd4 + Faceplates V7.1 SP3 Upd1).
2. Build a standardized ES image (Windows + PCS 7 + required legacy libraries) and image new ES laptops from it instead of installing libraries piecemeal.
3. Run SIMATIC Manager → Options → PCS 7 → Library Readme after every library install to confirm version and date.
4. When migrating to APL, follow the Siemens Library Migration Guide; do not run a mixed project on a V9.0 station without first reconciling the driver block versions in IMAP.
5. Keep a copy of the legacy installers in a project-archive folder so the dependency can be re-satisfied years later when the original DVD is no longer readable.

11. Frequently Asked Questions