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Configuring Fault-Tolerant Named Connections Between PCS 7 WinCC and External S7-400H Controllers Across Separate Projects

Configuring Fault-Tolerant Named Connections Between PCS 7 WinCC and External S7-400H Controllers Across Separate Projects

In SIMATIC PCS 7, establishing a high-availability 'S7 connection fault-tolerant' (Named Connection) between a WinCC OS Server and a redundant S7-400H controller residing in a separate external STEP 7 project (or a different supplier's multiproject) requires precise cross-project network modeling in NetPro. Because the two systems do not share an integrated database, engineers cannot use automated OS compilation. Instead, the connection must be engineered by configuring an 'Other Station' or 'SIMATIC 400 Station' proxy in NetPro representing the partner controller, defining redundant IP addresses and Transport Service Access Points (TSAPs), loading the connection table into the PC Station Configuration Editor, and manually creating the Named Connection tags in WinCC Tag Management.

Table of Contents

Cross-Project Fault-Tolerant Communication Architecture

In large industrial complexes, distinct process packages are frequently engineered by independent system integrators using separate STEP 7 / PCS 7 multiprojects:
- Package A: Central plant supervisory WinCC OS Server (PCS 7).
- Package B: Third-party vendor package (e.g., Turbocompressor, Boiler, or Flare system) running a redundant S7-400H controller.

To achieve continuous high-availability monitoring:
- A standard S7 connection is inadequate because failure of a single CP 443-1 or fiber cable terminates communication.
- An 'S7 connection fault-tolerant' manages multiple redundant communication paths across 4 physical routes (WinCC CP 1623 -> CP 443-1 Subrack 0, CP 443-1 Subrack 1, and cross-routes).
- The low-level SIMATIC NET software layer executes automated, bumpless route failover (< 100 ms) without disturbing the WinCC runtime application.

Understanding TSAPs and Redundant Routing in S7-400H

In cross-project S7 connections, connection endpoints cannot be resolved automatically by symbolic names; they must be bound using TSAP (Transport Service Access Point) addresses:
- Local TSAP (WinCC): Identifies the WinCC application in the Station Configurator (e.g., 10.01 for Rack 0, Slot 1).
- Remote TSAP (S7-400H): Encodes the CPU position and connection resource:
- Format: <Resource_ID>.<Subrack_Rack><Slot>
- Example for CPU in Slot 3: 12.03 (Subrack 0, Slot 3) and 12.13 (Subrack 1, Slot 3).
- In NetPro, identical TSAPs must be configured on both the WinCC OS station and the partner S7-400H station.

Prerequisites: Hardware Modules and SIMATIC NET Licenses

Deploying fault-tolerant named connections requires verified hardware and software prerequisites:
1. On the WinCC OS Server:
- High-performance communications processor: CP 1623 (6GK1162-3AA00) or CP 1613.
- Software package: S7-REDCONNECT (e.g., 6GK1716-0HB...) installed via Automation License Manager.
2. On the S7-400H Controller:
- Two Industrial Ethernet communications processors (CP 443-1 Standard / Advanced): one in Subrack 0, one in Subrack 1.
- S7-400H CPU firmware supporting fault-tolerant S7 communication.

Step-by-Step Configuration Procedure in NetPro and WinCC

Follow this procedure to establish cross-project fault-tolerant communication:

Step 1: Model the External S7-400H in NetPro

  1. In the PCS 7 project, open NetPro.
  2. From the catalog, drag and drop an 'Other Station' (or insert a SIMATIC 400 Station) onto the plant bus.
  3. Open properties of the station; add two network interfaces representing the supplier's CP 443-1 modules:
    - Interface 1: IP address of CP 443-1 in Subrack 0 (e.g., 192.168.1.10).
    - Interface 2: IP address of CP 443-1 in Subrack 1 (e.g., 192.168.1.11).

Step 2: Create the Fault-Tolerant S7 Connection

  1. In NetPro, select the WinCC Appl. on the OS Server.
  2. In the lower connection table, right-click an empty row and select Insert New Connection.
  3. Select partner: 'Other Station'.
  4. Connection Type: Select S7 connection fault-tolerant.
  5. In the connection properties dialog:
    - Assign a unique Connection Name: e.g., S7400H_PackageB.
    - Specify the Local and Remote TSAPs matching the supplier's configuration.
    - Enable path redundancy across both CP 443-1 IP addresses.
  6. Click Save and Compile in NetPro.

Step 3: Download Connection to Station Configurator

  1. Right-click the OS PC Station in NetPro and select PLC > Download to Current Station > Connections and Gateways.
  2. The Station Configuration Editor updates its internal connection routing table.

Step 4: Map Connection in WinCC Tag Management

  1. Open the WinCC project in WinCC Explorer.
  2. Open Tag Management > SIMATIC S7 Protocol Suite.
  3. Right-click Named Connections and select New Connection.
  4. Enter the exact connection name defined in NetPro: S7400H_PackageB.
  5. Open connection properties; verify that the connection status points to the Station Configurator virtual rack.
  6. Create process tags referencing the supplier's data blocks (e.g., DB100.DBD0).

Comparative Connection Matrix: S7 Protocol Profiles

The table below compares connection types between PC stations and S7-400H CPUs:

Connection ProfileNetwork RedundancyFailover TimeRequired LicenseRecommended Use CaseStandard S7 Connection (TCP)None (Single IP)N/A (Session Drops)Standard WinCCNon-critical auxiliary systemsFault-Tolerant S7 ConnectionFull 4-Way RedundancyBumpless (< 100 ms)S7-REDCONNECTMission-critical vendor packagesOpenPCS 7 GatewayHandled by Server1-2 secondsOpenPCS 7 LicenseThird-party OPC client integration

Verification

To confirm that the fault-tolerant connection is operational:
1. WinCC Channel Diagnosis Health Check: Open WinCC Channel Diagnosis; expand Named Connections > S7400H_PackageB; verify that connection status indicates Ready / Operational with green checkmark.
2. Tag Communication Check: In WinCC Runtime, monitor tags mapped to the external S7-400H DBs; confirm that live values update cyclically with valid quality.
3. Bumpless Failover Test: Disconnect the network cable from CP 443-1 in Subrack 0; verify that Channel Diagnosis logs an automatic route switchover to Subrack 1 without tags displaying invalid quality or process interruption.

Limitations and Operational Precautions

Engineering teams must observe the following precautions:
- S7-REDCONNECT licenses are mandatory for fault-tolerant connections on the OS Server; missing licenses cause WinCC to drop the redundant route after demo timeouts.
- Both CP 443-1 IP addresses on the external S7-400H must reside in the same IP subnet as the WinCC CP 1623 card unless industrial routers supporting fault-tolerant routing are deployed.
- Always validate final license quantities and MLFBs against the applicable Siemens catalog and authorized distributor quotation when procuring SIMATIC NET communication software.

Engineer FAQ

Can standard commercial network cards (IE General) support fault-tolerant S7 connections?

Yes, with limitations. Using SIMATIC NET SOFTNET-S7 RedConnect VM, standard network cards can form fault-tolerant connections, but failover relies on software polling. For high-speed hardware-deterministic failover, Siemens recommends dedicated CP 1623 / CP 1613 cards with Hardnet.

Why did OS Compilation fail to create tags for this connection?

Automated OS compilation works exclusively within a unified Multiproject. Connections to external 'Other Stations' must have their tags created manually in WinCC Tag Management or imported via CSV/Excel.

What is the maximum number of fault-tolerant connections a CP 1623 can handle?

A CP 1623 running S7-REDCONNECT supports up to 120 concurrent fault-tolerant S7 connections.

Technical References

Related Articles

Related Tags

  • Fault-Tolerant Connection
  • S7-400H
  • Named Connections
  • S7-REDCONNECT
  • NetPro
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