Expanding Interlock Capacity in SIMATIC PCS 7 APL Faceplates: Upgrading Intlk02/04 to Intlk08 and WinCC Tag Integration

To add three additional interlock conditions to an existing motor or valve in SIMATIC PCS 7 APL, replace the existing Intlk02 or Intlk04 block in CFC with an Intlk08 block. Reconnect the existing inputs and wire the new interlocks to In05, In06, and In07. Connect the Out pin of Intlk08 to the drive's interlock input (e.g., Permit, Intlock, or Protect), and reconnect the drive's LockAct output to Intlk08.LockAct. Execute a CFC compilation with 'Generate Module Drivers' and run Compile OS. The WinCC APL drive faceplate dynamically adapts its Interlock view to display all eight interlocks without manual PDL graphic editing.

APL Dynamic Interlock Architecture and Faceplate Adaptation

In traditional DCS graphics, modifying an interlock display required manually editing graphic screens (.pdl), adding text fields, and binding new tags to screen objects. In the SIMATIC PCS 7 Advanced Process Library (APL), faceplates are completely dynamic and data-driven.

APL drive blocks (MotL, MotRevL, MotSpdL, VlvL, Vlv2WayL) feature dedicated interlock inputs: Permit (start permissive), Intlock (interlock without reset), and Protect (interlock with reset / protection). When an APL interlock block (Intlk02, Intlk04, Intlk08, Intlk16) is connected to one of these inputs, the OS compilation engine automatically structures the WinCC tags so that the drive faceplate reads the interlock block's configuration and dynamically renders the exact number of active input rows.

Block Type Selection: When to Migrate from Intlk04 to Intlk08

Standard equipment templates often ship configured with an Intlk04 block (providing 4 inputs: In01 through In04). When process modifications demand additional trip criteria (such as adding high bearing temperature, seal water pressure low, and motor winding vibration), the 4-input capacity is exceeded.

Instead of cascading multiple Intlk04 blocks (which complicates faceplate navigation and requires operators to drill through nested faceplates), the recommended engineering practice is to replace Intlk04 with a single Intlk08 block. This keeps all interlock statuses consolidated on a single, clean faceplate screen.

CFC Engineering Workflow: Block Replacement and Pin Reconnection

Follow this procedure in Continuous Function Chart (CFC) to upgrade the interlock block:

Document Existing Parameters: Open the CFC chart containing the motor drive and existing Intlk04. Note down inverted pins (InvIn01..04), configured text strings (OS_Perm, custom texts), and Feature bit settings (e.g., Feature.Bit31 for First-In).
Insert Intlk08: Drag Intlk08 (FB1825) from the APL library catalog into the CFC chart.
Reconnect Existing Signals: Reconnect field digital signals to In01 through In04. Wire the three new trip signals into In05, In06, and In07. Set InvInxx parameters for any normally closed (NC) fail-safe inputs.
Reconnect Drive Handshake Pins:
- Connect Intlk08.Out to MotL.Intlock (or Permit / Protect).
- Connect MotL.LockAct to Intlk08.LockAct (essential for interlock feedback processing).
Configure Feature Bits: Enable Feature.Bit31 if First-In alarm latching is required.
Delete Obsolete Intlk04: Delete the old Intlk04 block from the chart.

WinCC Tag Management and OS Compile Synchronization

After logic modification in CFC, the operator station database must be synchronized:

CFC Compile: Compile the CFC charts. A delta compile is permitted if the AS remains in RUN.
Execute OS Compile: In SIMATIC Manager, right-click the OS project and select Compile. Choose 'Changes' (Delta Compile) or 'Entire project'.
Tag Generation: The compiler updates the WinCC Tag Management database, creating the new tag structure for Intlk08 and updating the internal pointer on the motor drive block.
No Graphic Editing Required: You do not need to open Graphics Designer or edit @PG_MotL_Interlock.pdl. When the faceplate opens at runtime, the standard APL C-script reads the interconnected block type and renders eight rows with live status LEDs.

APL Interlock Block Migration Comparison

The following table compares parameters between Intlk04 and Intlk08 during block migration:

Block AttributeIntlk04 (FB1824)Intlk08 (FB1825)Migration Requirement / ActionInput Pin Count4 (In01..In04)8 (In01..In08)Rewire In01..04; connect new signals to In05..07Inversion PinsInvIn01..InvIn04InvIn01..InvIn08Match inversion settings on migrated pinsOutput PinOutOutConnect to drive Permit, Intlock, or ProtectFeedback InputLockActLockActConnect from drive LockAct outputFirst-In OutputFirstIn1 (DWORD)FirstIn1 (DWORD)Enable via Feature.Bit31 = TRUEMemory Footprint~1.2 KB AS work memory~1.8 KB AS work memoryNegligible AS memory difference

Verification

Verify the expanded interlocks through the following procedure:

Open the CFC chart online and verify that inputs In01 through In07 display active live statuses (16#80).
Verify that Intlk08.Out = 1 and MotL.Intlock = 1.
In WinCC Runtime, open the motor faceplate. Click the Interlock button to open the Interlock view.
Confirm that the faceplate displays all eight input rows, with the new interlock descriptions clearly visible.
Trip one of the newly added inputs (e.g., In06). Confirm that the motor stops immediately and that the faceplate indicates the tripped condition on line 6.

Limitations and Operational Precautions

Consider these operational rules when expanding interlocks:

Never Leave Unused Inputs Floating: On Intlk08, if input In08 is unused, ensure it defaults to 1 (healthy) and is not inverted (InvIn08 = 0); otherwise, the block will permanently remain tripped.
Online Delta Download Safety: In older PCS 7 versions (prior to V8.0), replacing a block type in CFC could require an AS stop. In PCS 7 V8.1 and V8.2, deleting an Intlk04 and inserting an Intlk08 can be performed via Delta Download in RUN, provided work memory and block numbers are available.
Signal Status Processing: Always ensure analog threshold comparisons (from MonAnL or CompAn02) provide valid signal status (ST = 16#80) into Intlk08 to prevent nuisance trips.

Engineer FAQ

Can I assign custom text labels to each interlock input on the faceplate?

Yes, in CFC open block properties, navigate to inputs In01..In08, and configure the 'Identifier' or 'OS Additional Text' attribute to display custom field instrument tag names.

How do I add more than 8 interlocks if Intlk08 is full?

You can migrate to Intlk16 (FB1826) which provides 16 inputs, or cascade two Intlk08 blocks by connecting the Out of the first into In01 of the second.

Does changing from Intlk04 to Intlk08 require updating the Master Data Library?

No, both Intlk04 and Intlk08 are standard blocks already present in the PCS 7 APL library. Simply place Intlk08 from the library into the chart.