Interfacing Kepware KEPServerEX with SIMATIC PCS 7 - Integrated WinCC OPC vs OpenPCS 7 Architecture

Interfacing Kepware KEPServerEX with SIMATIC PCS 7 - Integrated WinCC OPC vs OpenPCS 7 Architecture

Connecting a third-party software client such as Kepware KEPServerEX v6 to a SIMATIC PCS 7 v8.2 system across a network can be achieved using two distinct architectural methods: the native WinCC OPC Server or the dedicated OpenPCS 7 station. For classic OPC Data Access (OPC DA), the integrated WinCC OPC DA server ('OPCServer.WinCC') executes automatically whenever WinCC runtime is active, requiring zero additional software licenses or configuration beyond Windows DCOM security settings. However, for platform-independent, cross-network OPC Unified Architecture (OPC UA) without DCOM vulnerabilities, or when extracting historical archives (OPC HDA) and alarms (OPC A&E), Siemens officially recommends deploying OpenPCS 7.

Table of Contents

• OPC Integration Architectures in SIMATIC PCS 7 v8.2
• Option 1: The Native Integrated WinCC OPC DA/UA Server
• Option 2: The Enterprise OpenPCS 7 Station
• Comparative Matrix: WinCC Integrated OPC vs OpenPCS 7
• Step-by-Step Procedure: Connecting Kepware to WinCC OPC DA
• Windows DCOM Security and Network Configuration
• Verification
• Limitations and Operational Precautions
• Engineer FAQ
• Technical References
• Related Articles
• Related Tags

OPC Integration Architectures in SIMATIC PCS 7 v8.2

Industrial plants frequently require bi-directional data exchange between SIMATIC PCS 7 and external enterprise software, manufacturing execution systems (MES), or third-party SCADA packages via OPC (Open Platform Communications).

Kepware KEPServerEX v6 is commonly deployed as an OPC client or gateway bridging corporate IT networks with plant automation. In PCS 7 v8.2, two primary OPC server foundations exist:
1. Integrated WinCC OPC Server: Embedded natively inside WinCC. It provides OPC DA (Data Access 2.05a / 3.0), OPC XML-DA, and native OPC UA Server capabilities running directly on the OS Server.
2. OpenPCS 7: A specialized, decoupled PCS 7 PC station. It queries OS Servers and Historians across the terminal bus, exposing unified OPC DA, OPC HDA, and OPC A&E interfaces to external clients.

Option 1: The Native Integrated WinCC OPC DA/UA Server

The integrated WinCC OPC server is ideal for direct, cost-effective integrations:
- Zero Licensing Costs: Included automatically with any WinCC Runtime license.
- Automatic Execution: The service starts automatically when WinCC Runtime activates.
- ProgID: External OPC DA clients connect to ProgID OPCServer.WinCC.1.
- OPC UA Interface: In PCS 7 v8.2 / WinCC v7.4, the WinCC OPC UA Server can be enabled in WinCC Explorer, communicating over TCP port 4862 with certificate-based authentication, bypassing Microsoft DCOM completely.

Option 2: The Enterprise OpenPCS 7 Station

For large-scale, high-security multi-project architectures:
- Decoupled Gateway: Installed on a standalone PC station connected to the terminal bus.
- Multi-Server Aggregation: Collects tags and messages from all OS servers in the plant, presenting a single unified address space to KEPServerEX.
- Historical and Alarm Access: Fully supports OPC HDA (historical trends) and OPC A&E (alarm journals).
- Licensing: Requires the OpenPCS 7 software package license (6ES7658-7...) scaled by client connections.

Comparative Matrix: WinCC Integrated OPC vs OpenPCS 7

The table below compares the two OPC server options:

Step-by-Step Procedure: Connecting Kepware to WinCC OPC DA

Follow this procedure to connect KEPServerEX v6 to the WinCC OPC DA Server:

Step 1: Configure DCOM on Both Workstations

1. On both the WinCC OS Server and the KEPServerEX machine, open Windows Run and execute dcomcnfg.
2. Navigate to Component Services > Computers > My Computer.
3. Right-click My Computer and select Properties:
   - In Default Properties, set Default Authentication Level to Connect and Default Impersonation Level to Identify.
   - In COM Security, grant Remote Access, Remote Launch, and Remote Activation to user ANONYMOUS LOGON, Everyone, and SIMATIC HMI.
4. Under DCOM Config, locate OPCServer.WinCC and grant full launch and access rights.

Step 2: Configure KEPServerEX OPC DA Client Driver

1. In KEPServerEX v6, click Click to add a channel.
2. Select channel type: OPC DA Client.
3. In the connection dialog, enter the IP address or host name of the WinCC OS Server.
4. Select OPC Server Name: OPCServer.WinCC.1.
5. Test the connection; verify that status indicates Connected.

Step 3: Browse and Import PCS 7 Tags

1. In KEPServerEX, right-click the device and select Tag Generation or browse OPC items.
2. The hierarchical WinCC tag tree is displayed. Select the desired technological variables (e.g., FIC_101/PV_Out.Value).
3. Launch the KEPServerEX OPC Quick Client; confirm that tags display live numeric values with quality Good.

Windows DCOM Security and Network Configuration

To maintain security and prevent communication timeouts:
- Ensure both machines share identical local user accounts with identical passwords if operating in a workgroup, or belong to the same Active Directory domain.
- In Windows Firewall, create inbound rules opening TCP Port 135 (RPC Endpoint Mapper) and allow program execution for OPCServer.exe and opcenum.exe.

Verification

To confirm that the Kepware OPC link is fully operational:
1. Quick Client Quality Check: Open Kepware OPC Quick Client; confirm that all imported tags display quality code Good (0xC0).
2. Data Update Test: Force an analog value change in CFC or on the WinCC faceplate; verify that KEPServerEX updates within the configured poll interval (< 200 ms).
3. Channel Diagnostics: In WinCC Channel Diagnosis, verify that the OPC channel indicates active client connection count 1.

Limitations and Operational Precautions

Engineering teams must observe the following precautions:
- Classic OPC DA relies on Microsoft DCOM, which is vulnerable to network latency and firewall blocks; where possible, deploy OPC UA to eliminate DCOM complexity.
- High-frequency polling (> 1000 tags at < 100 ms) directly against an OS Server can degrade operator screen update speeds; tune KEPServerEX poll rates to 500 ms - 1000 ms.
- Always validate final license quantities and MLFBs against the applicable Siemens catalog and authorized distributor quotation when procuring OpenPCS 7 licenses.

Engineer FAQ

Does the WinCC OPC DA Server require an OpenPCS 7 license?

No. The built-in WinCC OPC DA Server (OPCServer.WinCC.1) is included with the base WinCC Runtime software and does not require an OpenPCS 7 license.

How do I connect via OPC UA without using DCOM?

In WinCC Explorer, open the OPC UA configuration, enable the server on TCP port 4862, export the security certificate, and import it into KEPServerEX's OPC UA Client driver.

Can Kepware write setpoint values back into PCS 7?

Yes. Provided the user account has write permissions in WinCC and the S7 block parameter is not set to read-only in CFC.

Technical References

• WinCC OpenPCS 7 Interface Description and Manual (A5E36987622)
• WinCC Communication Manual: OPC Channel and Servers (A5E37536440)
• Kepware KEPServerEX OPC DA Client Driver Manual

Related Articles

• Exporting SIMATIC PCS 7 Process Data to External Relational Databases - WinCC IndustrialDataBridge vs OpenPCS 7
• Bridging External OPC Data from WinCC into S7-400 CFC Control Logic in SIMATIC PCS 7
• Configuring AS-OS Communication and Redundant WinCC Servers in SIMATIC PCS 7

Related Tags

• OPC DA
• OPC UA
• KEPServerEX
• OpenPCS 7
• DCOM