Selecting and Migrating Block Libraries for SIMATIC PCS 7 V8.1: APL vs. Standard Library

When upgrading a legacy SIMATIC PCS 7 V7.0 plant to PCS 7 V8.1 with WinCC V7.3, automation engineers must select between retaining the legacy PCS 7 Standard Library (V7.1) or migrating to the modern PCS 7 Advanced Process Library (APL V8.1). APL V8.1 is the latest, standard, and officially recommended library for all new engineering and modernizations. However, direct library replacement in existing charts is not automatic; because APL introduces structured variables (STRUCT with signal status ST) and redesigned faceplates, migration requires systematic block replacement or running both libraries side-by-side during phased upgrades.

The Evolution of PCS 7 Libraries: Standard Library vs. APL

When planning a software upgrade from PCS 7 V7.0 to V8.1, one of the most critical decisions facing lead control engineers is library architecture:
* Classic PCS 7 Standard Library:
- The historical foundation of PCS 7 (V4.x through V7.0).
- Built around classic blocks: MEAS_MON (FB 64), MOTOR (FB 66), VALVE (FB 73), CTRL_PID (FB 61).
- While maintained for backward compatibility in PCS 7 V8.1, the Standard Library is in Phase-Out status and receives zero new functional development.
* PCS 7 Advanced Process Library (APL):
- Introduced in V7.1 and perfected in V8.0/V8.1/V8.2.
- Built around modern technological objects: MonAnL (FB 1845), MotL (FB 1850), VlvL (FB 1899), PIDConL (FB 1874).
- Incorporates NAMUR NE 107 diagnostics, high-performance ergonomic OS faceplates, unified operating modes, and integrated asset management.

Key Architectural Differences: Elementary vs. Structured Data Types

The transition from Standard Library to APL is not a simple block name alias; it represents a fundamental data structure revolution:
1. Elementary vs. Structured Pins:
- In the classic Standard Library, process values and commands were raw data types (REAL, BOOL).
- In APL, almost all interconnectable signals are STRUCT (Value + ST), where ST carries the 8-bit NAMUR signal status.
2. Channel Driver Coupling:
- Standard Library utilized CH_AI, CH_DI, CH_AO, CH_DO.
- APL utilizes Pcs7AnIn, Pcs7DiIn, Pcs7AnOu, Pcs7DiOu.
- APL channel drivers communicate directly with module diagnostic blocks to propagate wire-break and sensor-fault statuses into technological blocks.
3. WinCC Faceplate Technology:
- Standard Library faceplates use legacy C-script popups.
- APL faceplates use high-performance vector graphics, unified color schemes, multi-tab operational views, and integrated trend windows.

Can Legacy Standard Library and Modern APL Coexist in PCS 7 V8.1?

Yes, 100% supported!
A major strength of SIMATIC PCS 7 V8.1 is Coexistence Support:
* An S7-400 CPU can execute both classic Standard Library blocks (MOTOR, VALVE) and modern APL blocks (MotL, VlvL) within the same controller simultaneously.
* WinCC OS V7.3 seamlessly hosts both classic faceplates and APL faceplates concurrently.
* Migration Strategy: Plants do not need to rewrite thousands of charts during a single turnaround. The existing plant can run on the upgraded Standard Library V7.1 in PCS 7 V8.1, while new plant expansions or modernized skids are engineered natively in APL.

PCS 7 Library Feature and Lifecycle Comparison Matrix

The following matrix compares library options available in SIMATIC PCS 7 V8.1:

Architectural FeatureClassic Standard LibraryAdvanced Process Library (APL)Industry Library (IL)Current Lifecycle StatusLegacy / Phase-OutActive Standard ProductionActive Specialized Add-onData Type ArchitectureElementary (REAL, BOOL)Structured (STRUCT with ST)Structured (APL Compatible)NAMUR NE 107 SupportNoneNative StandardNative StandardFaceplate ErgonomicsClassic WinCCModern APL Vector LayoutAPL Look & Feel + PanelsSIMATIC Comfort Panel SupportNoneNone (OS Server/Client only)Native via TIA PortalDriver Generator SupportClassic CH_ Driver BlocksModern Pcs7 Channel DriversAPL Channel DriversLicense RequirementStandard PCS 7 AS/OS POStandard PCS 7 AS/OS PODedicated IL License

Step-by-Step Strategy for Library Selection and Migration

To execute a clean library strategy during an upgrade to PCS 7 V8.1:
1. Determine the Modernization Scope:
- Option A (Fast Track - Upgrade in Place): Keep existing logic in the Standard Library. Install the PCS 7 Standard Library V7.1 SP3 for PCS 7 V8.1 package. Charts require zero re-wiring.
- Option B (Full Modernization - APL Migration): Replace classic blocks with APL equivalents to benefit from modern faceplates and asset management.
2. If Migrating to APL: Build Model Charts in Master Data Library:
- Do not replace blocks directly in production charts.
- In the Master Data Library, create new Control Module Types (CMTs) using APL blocks (MotL, VlvL, MonAnL).
3. Use Automated Migration Tools:
- Siemens provides the APL Migration Assistant to assist in translating classic block parameters to APL structured pins.
4. Update Channel Drivers:
- In HW Config and CFC, replace legacy CH_AI / CH_DI blocks with Pcs7AnIn / Pcs7DiIn.
- Recompile CFC with Generate module drivers enabled.
5. Compile OS and Update Block Icons:
- Compile the OS: In Graphics Designer, update block icons to @PCS7TypicalsAPLV8.pdl.

Verification

Verify library operational health after upgrade:
1. In SIMATIC Manager, check the Master Data Library: Verify that all instantiated block types report version APL V8.1 or Standard Library V7.1.
2. Execute a CFC compilation (Scope: Entire program): Verify that compilation finishes with 0 Errors and 0 block number collisions.
3. Open WinCC Runtime:
- For APL blocks: Verify that clicking the block icon opens the modern APL faceplate.
- For retained classic blocks: Verify that clicking the block icon opens the classic faceplate.
4. Confirm that alarms from both libraries display seamlessly in the unified WinCC alarm banner.

Limitations and Operational Precautions

Never attempt to connect a raw elementary address (REAL / BOOL) directly to an APL structured input without an APL converter block (StrgToBy, etc.); doing so causes Signal Status compilation errors.
The classic Standard Library does not receive new functional features or cyber-security enhancements; plan phased migration to APL for long-term supportability.
Commercial licensing note: Standard APL is included in base PCS 7 PO licensing, whereas the Industry Library requires separate software licenses; validate with an authorized Siemens distributor.

Engineer FAQ

What is the latest library version for SIMATIC PCS 7 V8.1?

For PCS 7 V8.1, the latest certified process library is SIMATIC PCS 7 Advanced Process Library (APL) V8.1 SP1. For plants utilizing Comfort Panels, the companion library is PCS 7 Industry Library (IL) V8.1.

Can I upgrade to PCS 7 V8.1 without converting my charts to APL?

Yes. By installing the 'PCS 7 Standard Library for PCS 7 V8.1' compatibility package, you can upgrade your engineering station and OS servers to V8.1 while leaving all existing S7 charts running classic Standard Library blocks.

Does APL consume more CPU memory than the classic Standard Library?

Yes. Because APL blocks feature extensive internal algorithms, interlock handling, and structured signal statuses, an APL block instance consumes approximately 25% to 40% more work memory than a classic block.