How to Configure SIMIT as an OPC Server to Exchange Simulation Data with SIMATIC PCS 7

To connect SIMIT as an OPC Server to SIMATIC PCS 7, configure the SIMIT simulation project with an OPC Server coupling to publish process variables over standard OPC DA. In PCS 7 WinCC, insert the OPC communication channel under Tag Management, browse for the local or remote SIMIT.OPCServer.1 COM/DCOMProgID, and create AS-OS tag interconnections to map simulated transmitter values and actuator commands. Alternatively, configure SIMIT as an OPC Client connecting directly to the OpenPCS 7 OPC Server across the terminal bus, or utilize native SIMIT Virtual Controller (VC) couplings for high-speed simulation without DCOM overhead.

Architectural Coupling Pathways Between SIMIT and SIMATIC PCS 7

In process automation virtual commissioning, SIMIT simulates plant behaviors—including hydraulic pressure dynamics, valve opening characteristics, reaction vessel temperatures, and motor electrical loads—to validate automation software prior to physical site deployment.

When connecting SIMIT to a SIMATIC PCS 7 environment, engineers can select from several communication architectures depending on the validation scope:
1. SIMIT as OPC Server: SIMIT hosts an OPC DA 2.05a server (SIMIT.OPCServer). PCS 7 components (such as WinCC OS stations or OpenPCS 7) act as OPC clients, reading simulated plant states and writing operator setpoints.
2. SIMIT as OPC Client: SIMIT connects as a client to an external OPC server hosted by PCS 7 (such as OpenPCS 7 or the local WinCC OPC DA server). SIMIT subscribes to controller outputs and writes simulated input values back into the control system.
3. SIMIT Virtual Controller (VC) Coupling: SIMIT emulates the controller firmware internally, executing compiled PCS 7 S7 programs directly in memory without physical networking or DCOM delays.
4. Hardware-in-the-Loop (HiL): SIMIT communicates with physical S7-400 or CPU 410 hardware via a SIMIT UNIT (PROFINET) or SIMBA box (PROFIBUS DP).

Configuring SIMIT as an OPC DA Server

To configure SIMIT to publish simulated variables as an OPC Data Access (DA) Server:

Create the OPC Coupling in SIMIT:
* Open the SIMIT project.
* In the Project Tree, expand Couplings, right-click, and select New coupling.
* In the selection dialog, choose OPC Server and assign a name (e.g., PCS7_Coupling).
Define Simulation Signals:
* In the Coupling editor, create the input and output signal lists:
- Inputs (from PCS 7): Actuator control signals (e.g., Valve_Open_Cmd, Pump_Run_Cmd).
- Outputs (to PCS 7): Simulated field measurements (e.g., Tank_Level_PV, Flow_Rate_PV, Limit_Switches).
- Define appropriate data types: REAL for analog flows/levels, BOOL for digital limit switches and valve feedbacks.
Configure COM/DCOM Settings:
* When SIMIT operates on a separate workstation from PCS 7, Windows DCOM security must be configured:
* Open dcomcnfg.exe on both PCs.
* Under DCOM Config, locate SIMIT.OPCServer.1.
* Set Launch and Activation Permissions to allow the common SIMATIC user account.
* Enable TCP port 135 and dynamic RPC ports across local firewalls.

Establishing the WinCC OPC Channel Connection in PCS 7

Once the SIMIT OPC Server is active, configure WinCC OS to acquire simulation tags:

Add the OPC Driver in WinCC Explorer:
* Open the WinCC project on the Engineering Station (or OS Single Station).
* In WinCC Explorer, right-click Tag Management and select Add new driver....
* Select OPC.chn (OPC Communication Channel) and click Open.
Create Connection to SIMIT:
* Expand Tag Management > OPC > OPC Groups (OPCHNServer.wincc).
* Right-click and select System Parameter.
* Under the OPC Server tab, click Browse Server.
* If SIMIT is running locally on the same PC, select SIMIT.OPCServer.1 under Local Servers.
* If SIMIT is running on a remote simulation workstation, enter the remote computer name or IP, click browse, and select SIMIT.OPCServer.1.
Tag Import and Interconnection:
* In the WinCC Tag Management tree under the newly created SIMIT connection, right-click and select Open OPC Driver Browser.
* The hierarchical tag tree defined in SIMIT will appear.
* Select the required signals and click Add Tags to import them into the WinCC tag database.
* Connect these tags to Graphics Designer process objects or use WinCC internal scripts to route data into the AS image.

Alternative Coupling: SIMIT OPC Client vs Virtual Controller (VC)

While using SIMIT as an OPC Server provides flexible access for third-party systems, other coupling types offer superior engineering efficiency for pure PCS 7 validation:

SIMIT as OPC Client:
If PCS 7 already has OpenPCS 7 installed, configuring SIMIT as an OPC Client is often simpler. In SIMIT, create an OPC Client coupling, browse for the OpenPCS7.OPCServer, and map signals directly. OpenPCS 7 automatically resolves AS tag structures and redundant OS server pairs.
SIMIT Virtual Controller (VC):
For full automation software testing without physical PLCs, the SIMIT Virtual Controller is the industry standard.
In SIMIT, create a Virtual Controller coupling and import the PCS 7 project directly (.s7p file).
SIMIT imports the complete hardware configuration, I/O symbol table, and communication links automatically, eliminating manual tag creation and DCOM configuration entirely.

Comparison of SIMIT to PCS 7 Interface Technologies

The table below compares the primary interface options for connecting SIMIT simulation models to SIMATIC PCS 7.

Coupling MethodProtocol / LayerTarget StationEngineering EffortSimulation Speed / Real-TimeSIMIT as OPC ServerOPC DA (COM/DCOM)WinCC OS / Third-Party HMIModerate (Manual tag mapping & DCOM)Cycle rates ~250 ms to 1000 msSIMIT as OPC ClientOPC DA / OPC UAOpenPCS 7 / WinCC ServerModerate (Connects to plant bus)Cycle rates ~200 ms to 500 msSIMIT Virtual ControllerDirect Memory PipeEmulated S7-400 CPULow (Automated project import)High-speed, cycle-synchronousSIMIT UNIT (Hardware)PROFINET / PROFIBUSPhysical S7-400 / CPU 410 ASLow (Hardware-in-the-Loop)Real-time fieldbus speed (1 ms - 10 ms)

Verification

To confirm that the SIMIT OPC Server coupling is communicating properly with PCS 7:
1. In SIMIT, click the Start button to place the simulation into RUN mode. Verify that the simulation time counter increments smoothly.
2. In WinCC Explorer, launch WinCC Channel Diagnosis. Check the status of the OPC.chn driver: the connection state to SIMIT.OPCServer.1 must show State: OK with a green indicator.
3. In SIMIT, manually force a simulated analog transmitter output (e.g., set Tank_Level_PV to 75.5).
4. In WinCC Runtime, open the tank overview graphic: verify that the bar graph and numeric display update immediately to 75.5.
5. Toggle an actuator control command in WinCC: confirm that the corresponding input signal in SIMIT transitions state within 500 ms.

Limitations and Operational Precautions

Never attempt to connect a SIMIT simulation OPC coupling to a live, operating production plant bus; simulated signals can overwrite physical field data, causing uncommanded equipment movements.
OPC DA relies on Microsoft DCOM; when crossing network subnets or operating across Windows Workgroups, ensure DCOM security policies (such as RPC packet integrity) are harmonized across both machines.
OPC DA communication is not deterministic; avoid using OPC couplings to test high-speed turbine safety trip logic or sub-millisecond fast interlocks.
SIMIT simulation models must be paused or stopped prior to compiling or downloading changes in HW Config or WinCC.

Engineer FAQ

Why does WinCC fail to browse the remote SIMIT OPC Server?

Remote OPC browsing failures almost always stem from Windows DCOM security barriers or firewalls. Windows blocks TCP port 135 and dynamic RPC ports by default. Ensure the OPC Enumerator service (OpcEnum.exe) is running on the SIMIT machine and that both machines share identical local user credentials.

Can SIMIT simulate both the PLC and the field instrumentation simultaneously?

Yes. When using the SIMIT Virtual Controller (VC) option, SIMIT emulates the S7-400 controller execution internally while simultaneously running the mathematical process model (valves, pipes, tanks), providing an all-software virtual testing environment on a single PC.

What is the difference between OPC DA and OPC UA in SIMIT?

OPC DA (Data Access) is based on legacy Microsoft COM/DCOM technology and is restricted to Windows operating systems. Modern SIMIT releases support OPC UA (Unified Architecture), which uses cross-platform TCP/IP communication with built-in SSL/TLS encryption, eliminating all DCOM configuration headaches.