Resolving 'RT Station Not Obtainable' Errors During PCS 7 OS Project Downloads

The error 'RT Station not obtainable' during an OS download in SIMATIC PCS 7 indicates that the Engineering Station cannot establish remote administrative communication with the target PC station over the Terminal Bus. The most common root causes are: mismatched Simatic Shell encrypted communication passphrases (in PCS 7 V9.0+), the target PC network adapter not being assigned in Simatic Shell settings, the logged-in Windows user missing from the local 'SIMATIC HMI' security group on the target PC, or Windows Defender Firewall blocking RPC/DCOM (TCP port 135) and SMB (TCP port 445).

Executive Summary

During commissioning, project download, or server-client synchronization in SIMATIC PCS 7, automation engineers frequently face the dreaded error dialog: 'RT Station not obtainable. The target station cannot be reached or is not ready for download.' Engineers often spend hours reinstalling software or rebooting PCs in vain. In reality, remote OS downloads depend on a precise chain of network discovery services, security groups, and encryption keys. This article provides a comprehensive troubleshooting guide to diagnose and resolve this error permanently.

Architecture and Fundamental Mechanics

Remote OS Download Architecture and Communication Requirements:

The Engineering Download Pipeline:
1. Name Resolution & Simatic Shell Multicast: SIMATIC Manager uses Simatic Shell multicast (UDP ports 5222/5223) to discover target PC stations by their Windows computer name.
2. Encrypted Handshake (PCS 7 V9.0+): Simatic Shell validates communication using an encrypted passphrase configured across all stations.
3. RPC / DCOM Remote Management: The ES commands the target station's CCRemoteService via Remote Procedure Calls (TCP port 135) to verify runtime status.
4. SMB File Share Transfer: The ES connects to the target station's shared project directory (<TargetDir>) over SMB (TCP port 445) to copy database files.
Failure Bottlenecks:
If Simatic Shell is bound to the wrong network adapter (e.g., an inactive Wi-Fi card or Plant Bus adapter instead of the Terminal Bus), discovery fails.
If the Windows user account executing the download does not have administrative rights and membership in SIMATIC HMI on the target PC, access is denied.

Step-by-Step Implementation Procedure

Systematic Troubleshooting Procedure for 'RT Station Not Obtainable':

Verify Simatic Shell Binding and Network Visibility:
- On both the ES and the target OS: Open Windows File Explorer -> expand 'This PC' -> right-click Simatic Shell -> select Settings....
- Ensure the selected network adapter is the Terminal Bus network card on both machines.
- In Simatic Shell, verify that all networked PCs (ES, OS Servers, OS Clients) appear in the tree without red cross icons.
Synchronize Encrypted Communication Settings (PCS 7 V9.0+):
- In Simatic Shell Settings -> check 'Encrypted communication'.
- Ensure that the encryption migration key / passphrase is 100% identical across all stations, or disabled across all stations for testing.
Verify Windows Security Group Memberships:
- On the target OS station: Open Computer Management (compmgmt.msc) -> Local Users and Groups -> Groups.
- Ensure your domain or local user account is an explicit member of:
- Administrators
- SIMATIC HMI
- SIMATIC NET
Verify Windows Firewall Rules:
- On the target PC, verify that the Siemens 'PCS 7 Firewall' exceptions are active.
- Confirm inbound rules permit TCP port 135 (RPC Endpoint Mapper) and TCP port 445 (SMB File Sharing).
Verify Network Share Permissions:
- On the target PC, ensure the target destination folder is shared over the network with 'Full Control' permissions granted to SIMATIC HMI and Everyone.
Re-Attempt OS Download:
- In SIMATIC Manager on the ES, right-click the OS -> Target System -> Download.
- Select target path via UNC (\\TargetPC\SharedFolder\...); complete download.

Verification

To verify communication restoration:
1. On the ES, open Windows Command Prompt; ping the target station by Windows Computer Name (e.g., ping OS_SRV01); verify reply without packet loss.
2. In Windows Explorer on the ES, navigate to \\OS_SRV01\ProjectShare; confirm you can create and delete a test text file.
3. Open Simatic Shell on the ES; verify the target station shows status 'Activated' or 'Deactivated' (not 'Unavailable').
4. Initiate the OS download in SIMATIC Manager; confirm progress bar begins transferring files immediately.

Limitations and Operational Precautions

Operational precautions:
- Never attempt an OS download while the target OS project is actively running in WinCC Runtime, unless performing an explicit 'Download Changes only' on supported server configurations.
- Do not disable Windows Firewall completely on production control systems; configure port exceptions rather than removing perimeter security.
- Ensure both computers share identical system date and time synchronization via NTP.

Engineer FAQ

What does 'RT Station not obtainable' mean?

It means the Engineering Station cannot establish remote RPC or network share communication with the target PC over the Terminal Bus.

Why did this error start happening after upgrading to PCS 7 V9.0?

PCS 7 V9.0 introduced encrypted Simatic Shell communication. If the encryption passphrase does not match between ES and OS, communication is rejected.

What network ports must be open for OS downloads?

TCP port 135 (RPC), TCP port 445 (SMB), and UDP ports 5222/5223 (Simatic Shell multicast).

Does the user downloading the project need to be an Administrator?

Yes, the user account must have administrative privileges and belong to the SIMATIC HMI group on both the ES and the target PC.

What tool configures the Terminal Bus network binding?

Simatic Shell, accessed via Windows File Explorer.

Technical References

Related Tags

RT Station Not Obtainable
Simatic Shell
OS Download
Terminal Bus
Firewall Ports

RT Station Not Obtainable

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Resolving 'RT Station Not Obtainable' Errors During PCS 7 OS Project Downloads