C135 PCS 7 (PCS7)
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Troubleshooting OS Simulation Connection Failures Over PLCSIM.TCPIP.1 After Upgrading to PCS 7 V9.0 SP2 UC3

Troubleshooting OS Simulation Connection Failures Over PLCSIM.TCPIP.1 After Upgrading to PCS 7 V9.0 SP2 UC3

In SIMATIC PCS 7, when OS Simulation fails to connect to S7-PLCSIM over the virtual channel PLCSIM.TCPIP.1 following an update to PCS 7 V9.0 SP2 UC3, the cause is an uncoordinated S7DOS communication driver update or an active WinCC Service Mode configuration. S7-PLCSIM operates strictly as a local simulation engine and cannot bind to WinCC if the OS project is set to Service Mode or if S7DOS communication endpoints retain obsolete physical network bindings. To restore simulation connectivity, switch the WinCC project from Service Mode to Standard Mode, verify that the PG/PC Interface is set to 'PLCSIM.TCPIP.1', and re-initialize the S7DOS communication subsystem using the 's7epaImp.exe' utility.

Table of Contents

Executive Summary

Testing operator screens, alarm cascades, and sequence logic using OS Simulation connected to S7-PLCSIM on an Engineering Station (ES) is an essential commissioning practice. After applying Update Collection 3 (UC3) to PCS 7 V9.0 SP2, engineers frequently report that OS Simulation launches, but all faceplates and process values display disconnected # symbols and PLCSIM.TCPIP.1 returns quality code 0x01 (No Connection). This breakdown is caused by updated S7DOS security and driver components introduced in UC3 that alter local named pipe and TCP loopback handling, especially when WinCC projects are configured for Service Mode. This guide provides the recovery workflow to restore local PLCSIM simulation.

Architecture and Fundamental Mechanics

The communication architecture between WinCC OS Simulation and S7-PLCSIM relies on local S7DOS loopback drivers:
1. The PLCSIM Communication Interface (PLCSIM.TCPIP.1):
In classical S7-PLCSIM (V5.4 SP8), the simulator does not open real physical Ethernet ports. Instead, it creates a local virtual driver device (PLCSIM.TCPIP.1) managed by the Siemens Communication Layer (S7DOS). When WinCC launches under OS Simulation, the SIMATIC S7 Protocol Suite -> TCP/IP channel driver binds to this virtual device name.
2. Root Cause A: WinCC Service Mode Restrictions:
In PCS 7 V9.0 SP2 UC3, enhanced security policies isolate Windows services from user desktop sessions. If a WinCC project is configured as a 'Service Project', WinCC runtime processes (CCProjectMgr.exe, CCWinCCStoreSvc.exe) run in Session 0. Because S7-PLCSIM runs in the interactive user desktop (Session 1), Session 0 services are blocked by Windows from opening communication pipes to desktop applications. The connection immediately reports 'Disconnected'.
3. Root Cause B: S7DOS Endpoint Registration Desynchronization:
Installing UC3 updates low-level S7DOS system libraries (s7oiehsx.exe). If the communication registry is not cleanly refreshed, the logical device name PLCSIM.TCPIP.1 in the PG/PC interface fails to map to the updated S7DOS virtual TCP loopback adapter.

Step-by-Step Implementation Procedure

  1. Verify WinCC Project Operating Mode (Disable Service Mode for Simulation):
    a. Open the OS project in WinCC Explorer on the Engineering Station.
    b. Right-click the project root in the left pane and select 'Properties'.
    c. Under the 'General' tab, locate the project operating mode.
    d. If the project is configured as a 'Service Project', change the mode to 'Standard Project'.
    e. Close WinCC Explorer.

  2. Reconfigure the PG/PC Interface to PLCSIM.TCPIP.1:
    a. Open Windows Control Panel and launch 'Set PG/PC Interface (32-bit)'.
    b. In the 'Access Point of the Application' dropdown, select 'S7ONLINE (STEP 7)'.
    c. In the interface parameter assignment list, select 'PLCSIM.TCPIP.1'.
    d. Click OK to save.

  3. Re-initialize S7DOS Communication Subsystem:
    a. Close all Siemens software (SIMATIC Manager, S7-PLCSIM, WinCC).
    b. Open Windows Command Prompt as Administrator.
    c. Execute the following commands to restart S7DOS helper services:
    cmd net stop s7oiehsx net start s7oiehsx
    d. Alternatively, restart the Engineering Station.

  4. Synchronize Download to S7-PLCSIM:
    a. Launch S7-PLCSIM (Start -> Siemens Automation -> S7-PLCSIM).
    b. In the S7-PLCSIM window, select 'TCP/IP' from the connection dropdown.
    c. In SIMATIC Manager, open HW Config and download the station hardware configuration to PLCSIM.
    d. Open NetPro and download 'Connections and Gateways' to PLCSIM.
    e. Download the CFC charts to PLCSIM and switch the simulated CPU to 'RUN-P'.

  5. Launch OS Simulation:
    a. In SIMATIC Manager, select the OS object.
    b. Select Options -> OS -> Start OS Simulation.
    c. Confirm that WinCC Runtime launches in standard desktop mode.

Verification

  1. In WinCC Explorer during OS Simulation, open 'Channel Diagnosis' under Tools.
  2. In Channel Diagnosis, select SIMATIC S7 PROTOCOL SUITE -> TCP/IP.
  3. Verify that the connection status reports a green checkmark with status 'Ready / Connected'.
  4. Open a process screen: verify that analog trends and digital block icons display live simulated values without # symbols.

Limitations and Operational Precautions

S7-PLCSIM V5.4 only supports local simulation on the same physical PC; it cannot accept remote connections from standalone OS servers over the network without third-party network bridging utilities.

Engineer FAQ

Why did OS Simulation stop working after applying PCS 7 V9.0 SP2 UC3?

UC3 updated S7DOS communication drivers and tightened session security. Running WinCC in Service Mode blocks communication between Session 0 services and desktop S7-PLCSIM.

How do I change a WinCC project from Service Mode to Standard Mode?

In WinCC Explorer, open Project Properties under the General tab and switch the project type to 'Standard Project'.

What access point must S7ONLINE be set to for PLCSIM?

It must be set to PLCSIM.TCPIP.1 (or PLCSIM.ISO.1 if using ISO transport protocol).

Can S7-PLCSIM simulate S7-400H redundant CPU synchronization?

No. Classic S7-PLCSIM V5.4 simulates a single S7-400 CPU; it does not simulate dual-chassis fiber-optic redundancy failovers.

Where can I check if WinCC is communicating with PLCSIM?

Open the WinCC Channel Diagnosis tool (WinCCChannelDiagnosis.exe) and check the status under the TCP/IP channel.

Technical References

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Related Tags

  • OS Simulation
  • S7-PLCSIM
  • PLCSIM.TCPIP.1
  • PCS 7 V9.0 SP2
  • WinCC Channel Diagnosis
  • S7DOS
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