Siemens Industry Online Support
Siemens AG
Entry type: FAQ, Entry ID: 109761403, Entry date: 10/24/2018

When changes are made in the standard user program, why do you have to load in the STOP mode with fail-safe S7-1200F/S7-1500F CPUs?

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The following three scenarios describe the cause and remedy for avoiding loading in the STOP mode.

Scenario 1

If you exchange data between the standard user program and the safety program, in the case of standard changes the system sometimes requires loading in STOP mode.

In the safety program, read access from the standard user program to the static tag of an instance block is programmed. This data block is therefore relevant for the safety program for compiling and downloading. Now, if you change the interface of the associated function block and thus the instance block, then the safety program also has to be compiled. As a consequence, the "safety-relevant" change makes it necessary to load in STOP mode.

For data exchange between the standard user program and the safety program we recommend that you define special data blocks (transfer data blocks) in which the data to be exchanged is stored. This decouples the blocks of the standard and safety programs. As long as these data blocks are not changed changes in the standard program do not affect the safety program and vice versa.

Further Information
More information is available in the Programming Guideline Safety for SIMATIC S7-1200/1500 and in section 3.9 "Data exchange between standard user program and safety program".

Scenario 2

If you are working on a safety program in a multiuser environment, a download in STOP might occur through the following procedure with standard changes.

You make changes to the safety program in the local multiuser session. Then you load these changes directly into the controller and then synchronize the changes with the multiuser server project. You cannot mark the generated F system blocks and they are therefore not transferred into the server project.

The next time you compile and load standard changes in the multiuser server project, you have to change the F system blocks once more for the changed and this leads to loading in the STOP mode.

Load the changes in the safety program only from the multiuser server project.

Scenario 3

If your project has multiple project languages and you have installed your project on another PC with different installed STEP 7 (TIA Portal) project languages, when changes are made in the standard environment the system does a download in STOP with safety controllers.

You project has multiple project languages (German, English, for example).

  • User A has only English project languages installed and stores the project completely compiled.
  • User B has German project languages installed.

During processing, the safety program is compiled again with change of signature, but loading in STOP mode is necessary.  

All users have to select the same project languages. You can add more project languages in the TIA Portal.

Further Information
More information is available via the links in the following table:

Entry type Link 
ManualMultilingual support (S7-1500) 
Manual Basics for compiling and downloading PLC programs 
FAQIn STEP 7 (TIA Portal), why are the display texts, titles and comments no longer displayed after opening the project in the block editor?