How to Connect Two PCS 7 V9.0 OS Stations to an S7-400H System

Two independent PCS 7 OS stations can each have their own WinCC application and OS–AS connection to an H station. For PCS 7 V9.0, Siemens specifies an S7 connection fault-tolerant for an OS connection to an H station and says to repeat the connection setup for the other operator stations. Download those configured connections to the H-system CPU as connection data. Configure and download each CP1623/PC-station configuration to its own OS computer; do not treat that as a CPU hardware-configuration download.

First Decide Whether the OS Stations Are Independent or Redundant

The described setup has two OS stations, each with its own PC station, CP1623, and WinCC application. If both stations are intended to operate independently, each needs its own OS–AS connection. PCS 7 V9.0 standard architectures document systems with multiple OS single stations, including configurations with up to eight OS single-user stations.

A master/standby OS server pair is a different arrangement: the stations are explicitly configured as an OS server and its redundant partner, with OS redundancy properties. Do not configure two independent operator stations as a redundant pair merely because one loses communication after a download.

Create a Separate OS–H-Station Connection for Each WinCC Application

Siemens' PCS 7 V9.0 Operator Station manual describes the following NetPro sequence and explicitly says to repeat it for all other operator stations.

In SIMATIC Manager, confirm both OS stations and the SIMATIC H station have been inserted in the same project. Each OS PC station must contain its own WinCC application and its actual CP/network configuration.
Open NetPro with Options > Configure Network.
Select the first OS station's WinCC application and choose Insert > New Connection in its connection table.
Select the CPU in the H station whose data the OS must display.
Select S7 connection fault-tolerant as the connection type for an H station. Enter the local/named connection ID used by that OS configuration.
Repeat the steps for the second OS WinCC application, creating its own OS–AS connection to the H station. Confirm the local ID referenced by each WinCC application matches that connection's configuration.
Save and compile the network configuration. Review both OS connections and their H-station partner before downloading.

The fault-tolerant connection uses the applicable high-availability communication support; Siemens states that S7-REDConnect licensing is required for high-availability S7 connections. Confirm that the installed CPs, CPU firmware, and licenses support the intended path.

Download Connection Data to the H Station

After creating or changing OS–AS connections, download the connection configuration to the H-system CPU. The PCS 7 V9.0 High Availability manual describes selecting the connection in NetPro and using the selected-connections download command; it notes that process interfacing by an OS is unavailable until the AS knows the connection.

For an initial or changed configuration, select the required OS–AS connection entries and download the complete set needed by both OS stations to the AS. Verify the target shown in the download dialog is the H-station CPU. A replacement prompt is consequential: it can mean that system data on the AS are being replaced. Do not accept it as if it were merely a download of the PC's CP1623 hardware.

Download Each PC Station to Its Own OS Computer

The PC-station/CP1623 configuration is configured in the SIMATIC PC station's HW Config and belongs to the OS computer. PCS 7's Operator Station manual provides a separate Component View workflow: select the OS PC station, configure its target, then use PLC > Download...; check the Station Configuration Editor on that OS computer for Component is ready for operation.

Keep these operations distinct:

Data being transferredTargetPurposeOS–AS connection configurationH-station CPUMakes the configured communication connection known to the ASPC-station hardware/network configurationIts corresponding OS PCApplies that computer's CP1623/PC-station setupWinCC OS runtime projectIts configured OS target pathTransfers the compiled operator project

Do not direct the PC-station hardware download to the H CPU. Do not expect transferring a WinCC runtime project to create the missing AS-side NetPro connection.

Why the Last Download Can Leave Only One OS Online

The observation that the last OS downloaded is online while the other disconnects is consistent with checking whether the AS still contains both required OS connection definitions after the operation, but the source does not prove that this is the root cause. The user's description does not include the NetPro connection table, exact menu/target used for each download, the CPU/CP topology, or the replacement dialog details.

Inspect the H station's current connection configuration and confirm both WinCC applications have entries for their intended H-station connections. If downloading PC-station hardware, verify its target is the matching OS computer. If downloading connection data, select the intended AS-side connection records rather than treating the OS hardware configuration as CPU data.

Verification

With both OS computers running, verify the following separately:

Each PC station reports ready in its own Station Configuration Editor.
The H station has the required OS–AS connection definitions loaded for both WinCC applications.
Both OS applications show active process communication at the same time, with valid values and status indications.
If a connection fails, inspect the H CPU diagnostics and the connection status for that specific OS instead of inferring the cause from which OS was downloaded last.

The source provides no screenshots or diagnostic traces, so these checks are needed to establish whether the fault is a missing AS connection, a PC-station target/configuration issue, a communication-resource/licensing limit, or another configuration problem.

Limitations and Operational Precautions

The documented connection steps are from PCS 7 V9.0 manuals and match the reported PCS 7 V9.0 SP3 context. Exact CPU firmware, CP443 configuration, plant-bus topology, S7-REDConnect license state, local connection IDs, and download dialogs are not shown. Confirm applicability to the actual hardware and installed updates.

Downloading connection data to an operating H system can change active communications. Coordinate the change, preserve the project, and verify the intended connection records before accepting a replacement or download prompt. Never download PC-station hardware configuration to an AS CPU.

Engineer FAQ

What connection type does PCS 7 V9.0 specify for an OS connected to an H station?

The Operator Station manual specifies S7 connection fault-tolerant for an H-station partner.

Do two independent OS stations share one WinCC application connection?

No. Each WinCC application has its own connection table and should have its own configured OS–AS connection.

Is a redundant OS server pair the same as two independent single stations?

No. A redundant pair uses master/standby OS server configuration and redundancy settings; independent stations have separate OS applications and connections.

Where should the CP1623 configuration be downloaded?

To the corresponding OS PC station target, using the PC-station configuration procedure. The OS–AS connection definition is downloaded to the AS separately.

Why might PCS 7 show a replace-configuration prompt?

It indicates that the operation is replacing existing target configuration data. Check whether the selected target is an AS CPU or PC station and whether the intended data are hardware, connection, or OS runtime data before continuing.

Technical References

Siemens, Operator Station (V9.0), Configuration Manual, 05/2017, A5E39219159-AA: §§6.1–6.2, PC-station/OS configuration, NetPro OS–AS connections, connection type for an H station, and downloading selected stations. https://cache.industry.siemens.com/dl/files/516/109746516/att_923912/v1/ps7phosb_en-US.pdf
Siemens, High Availability Process Control Systems (V9.0), Function Manual, 05/2017, A5E39221836-AA: §§4.3 and 5.3, high-availability connection support, licensing, and downloading selected connection configurations to the AS. https://cache.industry.siemens.com/dl/files/538/109746538/att_923931/v1/ps7red_b_en-US.pdf
Siemens, SIMATIC PCS 7 V9.0 Standard Architectures, 11/2017, Entry ID 109751791: §5.3, multiple OS single stations (up to eight) in a configuration without an OS server. https://cache.industry.siemens.com/dl/files/791/109751791/att_933116/v1/109751791_PCS_7_Architectures_V90_en.pdf

How to Connect Two PCS 7 V9.0 OS Stations to an S7-400H System