PCS 7 PLCSIM: Migrating Named Connection Tags to Ethernet TCP/IP

Problem Overview

When commissioning a SIMATIC PCS 7 V8.x project (including V8.0 SP1 and V8.2) against S7-PLCSIM, engineers frequently encounter the runtime alarm "TERMINAL ADAPTER DISCONNECTED" in WinCC Explorer. The alarm appears in Tools > Status of Driver Connections, even though the OS compiles successfully, the PC station downloads without obvious fault, and PLCSIM is already in RUN. The same symptom occurs when the CFC blocks generated by the PCS 7 master data library were originally tied to a Named Connection in NetPro rather than a TCP/IP, MPI, or Industrial Ethernet (ISO) subnet.

The symptom is independent of the OS server target: it reproduces on single-station AS-OS, on distributed OS servers, and on WinCC clients used for OS simulation. The fault is not in the application code, the CFC chart logic, or the WinCC picture hierarchy - it is a binding mismatch between the connection type that PLCSIM can carry and the connection type that PCS 7 inserts by default when the engineer first drags the AS into the PC station.

Root Cause Analysis

PLCSIM is a virtual S7-CPU stub. It implements the S7 communication stack only over the S7-on-TCP transport (RFC 1006) and over the ISO transport (ISO-on-TCP / ISO 8073). It does not implement the Named Connection S7 service that PCS 7 uses internally when no explicit transport subnet is referenced in NetPro. A Named Connection is a symbolic, transport-agnostic S7 connection that the WinCC Channel "SIMATIC S7 Protocol Suite" resolves at runtime by looking up the connection partner in the S7 project. PLCSIM never receives an S7 connect request on the corresponding slot, so the connection stays in DISCONNECTED state and the runtime surfaces "TERMINAL ADAPTER DISCONNECTED" on the affected channel unit.

The two contributing defects in the typical "Colour Project" getting-started workflow are:

1. The PC/PG interface is still set to PC internal (visible as a yellow arrow in the Set PC/PG Interface dialog) instead of PLCSIM.TCPIP.1.
2. The OS has been compiled against the Named Connection logical transport rather than an explicit Ethernet subnet. All CFC block tags therefore end up under the SIMATIC S7 Protocol Suite > Named Connections channel in WinCC Tag Management, where PLCSIM cannot service them.

Additional secondary causes observed in the field:

• PC station configuration in the SIMATIC Station Configurator is stale relative to NetPro (component count or IE address drift).
• Hardware in HW Config was added on the engineering station but is not registered on the PC station, producing a download error during station configure.
• The Windows computer name contains characters that WinCC rejects (the documented restriction excludes dashes).

Prerequisites and Environment

Step-by-Step Migration Procedure

The procedure migrates all CFC block tags from a Named Connection to an Ethernet TCP/IP connection and re-establishes the OS simulation channel.

Step 1 - Switch the PC/PG Interface to PLCSIM

1. Open SIMATIC Manager.
2. Select Options > Set PC/PG Interface...
3. In the Interface Parameter Assignment Used list, select the access point S7ONLINE.
4. Change the interface from PC internal to PLCSIM.TCPIP.1 for Ethernet or PLCSIM.MPI.1 for MPI.
5. Confirm with OK. The yellow arrow in the dialog confirms the active selection.

This step is mandatory - if the PC/PG interface stays on PC internal, every download and every NetPro compile will resolve against the loopback rather than PLCSIM, regardless of subsequent settings.

Step 2 - Insert a TCP/IP Subnet in NetPro

1. In SIMATIC Manager, right-click the project and choose Open NetPro (or use Options > Configure Network).
2. Insert a new Ethernet subnet: right-click in the network area > Insert New Subnet > Industrial Ethernet.
3. Assign an IP address range; 192.168.0.1 for the AS and 192.168.0.2 for the OS server is conventional for a simulation-only project.
4. Drag the AS station (e.g. AS01) onto the Ethernet subnet to bind its IE interface.

Step 3 - Create an S7 Connection via TCP/IP

1. Select the AS station in NetPro.
2. Right-click > Insert New Connection.
3. In the partner dialog choose the OS server / PC station (e.g. WALIDAE).
4. Set the connection type to S7 Connection and check the box "Use TCP/IP". The connection now references the Ethernet subnet instead of being a Named Connection.
5. Compile and save NetPro.

Step 4 - Download to PLCSIM

1. Open PLCSIM and power on the simulated CPU.
2. In SIMATIC Manager, select the AS and choose PLC > Download (or right-click > Download to Target System).
3. Place PLCSIM in RUN-P.

Step 5 - Recompile the OS Against the Ethernet Transport

1. In the PCS 7 plant view, right-click the OS (e.g. OS01) and choose Compile OS (full compilation).
2. In the OS compilation wizard, navigate to the Network page.
3. From the dropdown, select TCP/IP or Industrial Ethernet explicitly. Do not leave it on "Name network" or "Named Connection".
4. For PLCSIM-only simulation, the documented supported transports are TCP/IP (RFC 1006) or MPI - PLCSIM cannot connect over Named Connections regardless of NetPro wiring.
5. Complete the wizard. The CFC tags will now appear under SIMATIC S7 Protocol Suite > TCP/IP instead of under Named Connections.

Step 6 - Bind the WinCC Channel Unit to PLCSIM

1. Open WinCC Explorer.
2. Navigate to Tag Management > SIMATIC S7 Protocol Suite > TCP/IP.
3. Right-click the TCP/IP driver > System Parameters.
4. On the Unit tab, change the unit assignment from S7ONLINE / Real Ethernet to PLCSIM.TCPIP.1.
5. Click OK.

Step 7 - Download the PC Station

1. Right-click the PC station in the PCS 7 component view.
2. Choose PLC > Compile and Download.
3. If a "component not found on PC station" error appears, edit the PC station to remove the offending module and retry.
4. Confirm that the Station Configurator icon turns green after download.

Alternative Protocol Configurations

PLCSIM supports three transports in PCS 7 environments. Choose based on the existing NetPro wiring and on whether the production system uses ISO or TCP/IP.

Verification Procedure

After completing the migration, verify the OS-PLCSIM handshake in three stages.

1. Static check: In WinCC Explorer, right-click TCP/IP > System Parameters > Unit tab. The selected unit must be PLCSIM.TCPIP.1 (or PLCSIM.ISO.1 / PLCSIM.MPI.1).
2. Runtime check: Start WinCC Runtime, then select Tools > Status of Driver Connections. Each connection associated with a CFC block must show status Connected rather than Disconnected.
3. Tag check: Open a WinCC picture with a process tag (e.g. a motor block from the Colour Project). Force a value in PLCSIM via the monitor/modify table and confirm that the picture element reflects the change.

If a connection reports "Disconnected" while the unit and the OS compile are correct, check that PLCSIM is in RUN-P (not STOP) and that the simulated CPU has not raised an SF (system fault) due to a missing hardware configuration.

PC Station Configuration

The PC station is the NetPro counterpart of the OS server. It must be reconfigured whenever NetPro is changed so that the Station Configurator runtime service stays in sync.

1. Right-click the PC station in SIMATIC Manager > PLC > Configure...
2. Select the local PC station and click Configure.
3. Validate that all components referenced in NetPro (WinCC Application, S7-Communication, IE General) appear with matching slot indices.
4. If a component shows an error ("Component not found on PC station"), remove it from the PC station, recompile NetPro, then re-add it once the OS has been recompiled.

The Station Configurator dialog indicates the running state of the service. A green check on every component is required before the OS runtime can establish S7 connections.

Troubleshooting Matrix

Best Practices and Field Notes

• Always store the "Colour Project" and any subsequent training project under a path that contains no spaces and no Unicode characters. PCS 7 V8.x SIMATIC Manager is sensitive to paths containing extended characters and to UNC paths with embedded dashes.
• Keep a working backup of the project before each OS recompile. A failed OS compile in PCS 7 V8.x can corrupt the WinCC database; recovering from a clean backup is faster than repairing the database.
• When porting a working OS simulation to a production OS server, revert the WinCC TCP/IP unit from PLCSIM.TCPIP.1 back to S7ONLINE / the real Ethernet adapter. Forgetting this step is the most common cause of "works in simulation, fails on plant" commissioning delays.
• Reserve a dedicated Ethernet adapter (or virtual loopback) for the PLCSIM path on engineering workstations that also host plant VPNs - simultaneous binding to a VPN tunnel and the PLCSIM virtual stack has been observed to drop S7 connections after a few minutes.
• Document the PLCSIM unit assignment next to the OS server in the project README; this prevents the next engineer from spending an hour re-discovering that the OS must be compiled against TCP/IP rather than the default Named Connection.
• For multi-station projects, perform Steps 1-7 on each PC station in the project - clients, servers, and standalone OS stations each need their own PC/PG interface switch and their own WinCC unit binding.

Differences Between PCS 7 V8.0 SP1 and V8.2

The procedure is functionally identical between V8.0 SP1 and V8.2. Two menu paths differ:

• In V8.0 SP1, the OS compile wizard exposes the network selection as a separate dialog page. In V8.2, the selection moved into the Connections page of the same wizard.
• The PC station component "S7-Communication" was renamed to "S7 Communication (PROFIBUS/MPI/Ethernet)" in V8.2; the slot position and NetPro semantics are unchanged.
• PLCSIM V5.4 SP5 (bundled with V8.2) supports parallel simulation of up to 8 virtual CPUs; older V8.0 SP1 PLCSIM V5.4 SP3 supports 4. Both versions refuse to service Named Connections identically.

Frequently Asked Questions