Siemens SIMATIC S7 F Manual page 185

Safety
You can obtain the overall signature of the program and the signatures of the
blocks in the CPU by choosing the Options > Edit Safety Program menu
command. When a comparison with the online program is made, it is indicated
whether the source, load memory and working memory match up (this enables
impermissible data manipulation to non-interconnected fail-safe input parameters
in the working memory to be detected).
You can check whether a Safety Program in the CPU is really the one you
expected by carrying out the following steps:
1. Choose the Options > Edit Safety Program menu command in SIMATIC
Manager and activate "Online" in the dialog box. The signature displayed in the
dialog box must match the signatures in the accepted printout (in the text and
in the footer).
2. To detect impermissible manipulation (e.g. via test mode in CFC) in the
working memory of the CPU, choose "Compare..." and compare the accepted
program with the online program in the dialog box. Any manipulated
parameters are displayed there. This step is imperative for acceptance.
3. In the case of fault-tolerant S7 FH systems, the above steps must be carried
out for both CPUs in the online view of SIMATIC Manager.
When you repeat downloading or repeat checks of the Safety Program, carry
out this overall signature check again.
Please note that the overall signature is also available from "F_PRG_SI input the
F_SHUTDN function block within the @F_ShutDn CFC.
Fail-Safe Systems
A5E00085588-03
7-19