C135 PCS 7 (PCS7)
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Establishing Cross-Version AS-to-AS and OS Communication Between Independent SIMATIC PCS 7 Systems

Establishing Cross-Version AS-to-AS and OS Communication Between Independent SIMATIC PCS 7 Systems

To establish robust Ethernet communication between two independent SIMATIC PCS 7 systems operating different software releases (such as a PCS 7 V7.1 multiproject and a PCS 7 V8.1 system with APL), two primary architectures exist. For direct controller-to-controller data exchange via CP 443-1, configure an S7 Connection to an 'Unspecified' partner in NetPro on both systems, defining the partner's IP address and TSAP; deploy BSEND/BRECV or technological blocks Send_BO/Recv_BO and Send_R/Recv_R in CFC without requiring dummy stations. Alternatively, for supervisory data sharing, configure the WinCC OPC DA/UA Server on one system and the native WinCC OPC Client Channel on the other.

Table of Contents

Executive Summary

Industrial processing plants frequently expand over decades, resulting in distinct manufacturing areas automated with different generations of SIMATIC PCS 7. A classic scenario involves linking an established facility running PCS 7 V7.1 (utilizing the classic standard library) with a newly commissioned expansion running PCS 7 V8.1 (standardized on the Advanced Process Library). Because the two systems reside in separate, independently maintained multiprojects with different database schemas, engineers cannot merge them into a single project. Automation leads routinely ask whether a 'dummy AS station' must be created in NetPro, or whether OPC is the only viable mechanism. Understanding how to configure 'Unspecified' S7 Connections in NetPro enables direct, high-speed AS-to-AS communication across independent PCS 7 systems without architectural compromise.

Cross-Multiproject and Cross-Version Communication Challenges

Interconnecting separate PCS 7 multiprojects requires decoupling configuration databases:

  • Multiproject Isolation: Each multiproject has its own Master Data Library, plant hierarchy, and network ID mappings.
  • Version Mismatches: PCS 7 V8.1 engineering tools cannot be installed alongside V7.1 on the same OS, precluding direct cross-project linking.
  • The 'Unspecified' Connection Solution: NetPro provides the 'Unspecified' partner type, allowing an S7 connection to be configured with arbitrary destination IP addresses and TSAPs (Transport Service Access Points) without requiring the partner project to be imported or modeled as a dummy station.

Direct AS-AS Coupling via NetPro 'Unspecified' S7 Connections

An Unspecified S7 Connection operates symmetrically:

  • On System 1 (PCS 7 V7.1 AS): Insert an S7 connection pointing to 'Unspecified'. Enter the IP address of System 2's CP 443-1. Assign a local TSAP (e.g. 10.02) and remote TSAP (e.g. 11.02).
  • On System 2 (PCS 7 V8.1 AS): Insert an identical connection pointing to 'Unspecified'. Enter the IP address of System 1's CP 443-1, mirroring the TSAPs (local 11.02, remote 10.02).
  • This establishes an authentic, bidirectional S7 protocol channel over Industrial Ethernet.

CFC Block Selection: BSEND/BRECV vs Send_BO/Send_R Technological Blocks

Inside the CFC program, data is exchanged using standard communication blocks:

  • BSEND (FB12) / BRECV (FB13): Designed for bulk raw data transmission. Transfers large data blocks (up to 64 KB) asynchronously with transmission acknowledgment.
  • Send_BO / Recv_BO and Send_R / Recv_R: Standard PCS 7 Basis Library blocks that serialize up to 128 discrete binary flags or 32 real variables into a compact telegram. They handle communication handshakes, watchdog timeouts, and quality codes automatically, providing superior diagnostics over raw BSEND.

Cross-System Integration Architecture Matrix

The following table compares integration methods between disparate PCS 7 installations:

Integration ArchitectureCoupling LayerDeterminism / SpeedEngineering ComplexityController WorkloadAS-AS 'Unspecified' S7 ConnController (CP 443-1)High (< 100 ms)Low (NetPro TSAP Mapping)Low (Handled by CP)WinCC OPC Server / ClientSupervisory (OS Server)Moderate (500 - 1000 ms)Low (WinCC OPC Channel)Zero CPU impact (Handled by OS)Open User Comm (TCP/IP)Controller (T-Blocks)High (< 50 ms)High (Custom SCL serialization)Moderate CPU overheadHardwired Inter-AS I/OField WiringInstantaneousExtremely High (Cabling / I/O)Negligible

Step-by-Step Procedure to Configure 'Unspecified' S7 Connections in NetPro

Method 1: Configuring AS1 (System 1 - PCS 7 V7.1)

  1. Open NetPro in the PCS 7 V7.1 multiproject.
  2. Select the CPU of the transmitting S7-400 controller.
  3. In the connection table, insert a new connection: Set Partner to (Unspecified) and Type to S7 connection.
  4. In Properties, enter the static IP address of the target System 2 CP 443-1 (e.g. 192.168.1.50).
  5. Switch to the Address Details tab. Note the Local TSAP (e.g. Rack 0, Slot 4, Sub-address 10.02).
  6. Configure the Remote TSAP to match System 2 (e.g. Rack 0, Slot 4, Sub-address 11.02).
  7. Note the assigned Connection ID (e.g. W#16#0001).
  8. Save, compile, and download NetPro to CPU 1.

Method 2: Configuring AS2 (System 2 - PCS 7 V8.1)

  1. Open NetPro in the PCS 7 V8.1 multiproject.
  2. Select the target CPU; insert an S7 connection to (Unspecified).
  3. Enter the IP address of System 1 CP 443-1 (e.g. 192.168.1.20).
  4. Under Address Details, invert the TSAP assignments: Local TSAP becomes 11.02, Remote TSAP becomes 10.02.
  5. Save, compile, and download NetPro to CPU 2.

Method 3: Programming CFC Data Exchange

  1. In System 1 CFC, insert Send_R (FB115). Assign parameter ID to the connection ID and link process values to input pins.
  2. In System 2 CFC, insert Recv_R (FB116). Assign matching ID and R_ID parameters.
  3. Compile CFC charts and download to both controllers.

Verification

To verify cross-version AS-to-AS communication:

  1. NetPro Online Diagnostics: In NetPro, select the CPU and go online. Confirm that the S7 connection status indicates 'Configured and Active'.
  2. CFC Test Mode Inspection: In CFC Test Mode on both systems, monitor Send_R and Recv_R. Confirm that output ERROR = 0 and STATUS = 0.
  3. Dynamic Value Tracking: Change a REAL variable in System 1. Verify that System 2's Recv_R reflects the updated value within 100 milliseconds.

Limitations and Operational Precautions

  • TSAP Inversion Mandatory: The most frequent error in 'Unspecified' connections is mismatched TSAPs; ensure Local and Remote TSAPs mirror each other precisely across both projects.
  • R_ID Coordination: Parameter R_ID must match exactly on paired Send and Recv blocks to ensure telegram routing within the same connection.
  • Network Routing: Ensure the two CP 443-1 modules reside on the same IP subnet or that corporate switches route TCP port 102.

Engineer FAQ

Do I need to buy an extra license for AS-AS S7 connections?

No. Standard S7 communication over CP 443-1 utilizes native firmware resources and requires no additional software licenses.

What happens if System 1 is powered off?

The Recv block on System 2 will assert output QERR = 1 after the communication watchdog timeout, outputting bad quality status.

Can safety data (PROFIsafe) be exchanged between different PCS 7 versions this way?

No. Exchanging safety data between independent S7 F-Systems controllers requires dedicated F_SEND_S / F_RCV_S blocks with safety signatures.

Technical References

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  • https://industrialautomation.net/search?query=as-as-communication
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