Resolving WinCC Runtime Communication Loss with CP 1623 on PCS 7 Operator Stations

When a SIMATIC PCS 7 Operator Station (OS) with an Industrial Ethernet communications processor (CP 1623) successfully downloads from an Engineering Station (ES) and responds to ICMP pings but WinCC Runtime fails to communicate with S7-400 or CPU 410 controllers, the failure is caused by an invalid Access Point mapping in "Set PG/PC Interface" or IP address contention across dual network stacks. In a PCS 7 PC Station, the WinCC Named Connections channel does not connect directly to CP1623.ISO.3. Instead, the access point S7ONLINE must be configured to point to PC internal.local.1, enabling the Station Configuration Editor (SCE) to route communication internally between the WinCC Application and the CP 1623.

PCS 7 PC Station Architecture: CP 1623 and WinCC Routing

In a SIMATIC PCS 7 distributed control system, an Operator Station (OS Single Station or OS Server) relies on dedicated communications processors—such as the CP 1623 (6GK1162-3AA00) or CP 1628 (6GK1162-8AA00)—to communicate over Industrial Ethernet with automation controllers.

The CP 1623 incorporates an onboard microprocessor that offloads protocol handling (ISO and ISO-on-TCP) from the Windows operating system. However, engineers new to PCS 7 frequently treat the CP 1623 as a simple commercial NIC, mapping the WinCC communication driver directly to the card's physical interface in 'Set PG/PC Interface'.

In a standard PCS 7 PC Station, communications do not flow directly from WinCC to the network adapter. Instead, SIMATIC NET establishes a virtual software rack managed by the Station Configuration Editor (SCE). In this architecture, WinCC Application and the CP 1623 reside in virtual slots, communicating via internal software routers.

Root Causes of CP 1623 Runtime Communication Failure

When an OS station can be downloaded from the ES and responds to network pings, yet displays blank values or disconnected block icons in WinCC Runtime, the communication failure typically stems from three root causes:

Failure ModeConfiguration DefectSymptom in StationResolutionAccess Point MisdirectionS7ONLINE pointed directly to CP1623(ISO) or TCPIPWinCC channel status displays disconnectedSet S7ONLINE to PC internal.local.1IP Subnet ConflictNDIS commercial IP and Industrial Ethernet IP set to same subnetDriver contention, download packet failuresAssign separate IP subnets or disable NDISSCE Configuration MismatchVirtual rack in SCE does not match NetPro hardware configurationStation Configurator shows red wrench or missing componentDownload PC Station configuration from ES via NetProWinCC Logical Device NameLogical device in S7 Protocol Suite set to wrong access pointNamed Connections channel cannot establish linkVerify Logical Device Name is set to PC internal.local.1

A particularly damaging error is configuring the CP 1623's NDIS IP address (used for Windows networking) to the exact same IP address as the Industrial Ethernet IP configured in NetPro. This creates a routing collision within the Windows IP stack.

Correcting Set PG/PC Interface to PC internal.local.1

To establish proper communication between WinCC and the controllers:

On the OS computer, open Windows Control Panel.
Open Set PG/PC Interface.
Under Access Point of the Application, select S7ONLINE (STEP 7).
In the list of available interface parameters, locate and select:
PC internal.local.1
Do NOT select CP1623.ISO.1, CP1623.TCPIP.1, or TCP/IP -> Intel Network Connection.
Click OK to apply.
In WinCC Explorer, expand Tag Management -> SIMATIC S7 Protocol Suite -> Named Connections. Right-click Named Connections and select System Parameters. Confirm that the Logical Device Name is configured as PC internal.local.1.

Station Configuration Editor and NetPro Downloading

The virtual rack inside the Station Configuration Editor must be synchronized with the engineering project:

Open the Station Configuration Editor from the Windows taskbar tray on the OS computer.
Confirm that the Station Name matches the PC Station name configured in SIMATIC Manager.
Verify that Slot 1 hosts the WinCC Application and Slot 2 (or matching NetPro slot) hosts the CP 1623.
In SIMATIC Manager on the Engineering Station, open NetPro.
Select the OS PC Station, click PLC -> Download -> Selected Stations.
This downloads the communication database (.xdb), establishing the internal routing linkages between WinCC and the physical CP 1623.

Verification

To verify that WinCC communication is operational:
1. In WinCC Explorer, activate Runtime.
2. Open the WinCC Channel Diagnosis utility (C:\Program Files (x86)\Siemens\WinCC\bin\WinCCChannelDiagnosis.exe).
3. Under SIMATIC S7 Protocol Suite -> Named Connections, verify that the connection status to each CPU displays a green checkmark with status Connected.
4. Verify that process graphics display live dynamic data and that all @NC_CONNECT_FAILED system alarms clear.

Limitations and Operational Precautions

Never modify Station Configuration Editor slot assignments while WinCC Runtime is active. Reconfiguring virtual slots breaks active shared memory queues and can terminate WinCC communication daemons (s7oiehsx.exe). Always deactivate WinCC Runtime before downloading PC Station hardware configurations from NetPro.

Engineer FAQ

Why must S7ONLINE be set to PC internal.local.1 instead of the CP 1623 directly?

PC internal.local.1 routes requests through the Station Configuration Editor virtual backplane. This allows multiple applications (WinCC, STEP 7, BATCH) to share the CP 1623 simultaneously using configured Named Connections.

What is the difference between NDIS IP and Industrial IP on CP 1623?

NDIS IP is a standard Windows network adapter binding for general office/Terminal Bus traffic. Industrial IP is used by SIMATIC NET for deterministic controller communication. They must not share the same IP address.

Can an Engineering Station use ISO while the OS uses TCP/IP?

Yes. Each PC station can utilize either ISO transport protocol (layer 2 MAC-based) or ISO-on-TCP (layer 4 TCP/IP) as configured in its respective NetPro hardware settings.