Siemens SIMATIC PCS 7 Operating Manual page 79

During compilation, specific functions for detecting and reacting to errors are automatically
added to the F-program. The S7 F-System optional package also features functions for
comparing F-programs and providing support for the acceptance and approval procedure for
F-programs, such as functions for generating a signature via the F-program which can be
used to detect changes to functions and parameters. This signature is saved during the plant
acceptance procedure.
Program structure of the safety program
The figure below shows a diagram illustrating the structure of a safety program comprising
CFC charts with F-blocks which are assigned to F-runtime groups.
Some of the properties possessed by the various components are:
● The safety program contains F-runtime groups and the charts assigned to them. The
charts contain F-blocks with their parameter settings and interconnection.
● The F-runtime groups are added to one or more cyclic interrupt OBs.
● F-runtime groups can be combined in F-shutdown groups (F-SG).
● The cyclic interrupt OB can also contain standard runtime groups.
● The F-blocks in the S7 F-Systems F-library appear in yellow on the CFC chart in order to
highlight the fact that there is a safety program involved.
● The CFC charts and F-runtime groups with F-blocks appear in yellow and are marked "F"
in order to distinguish them from charts and runtime groups associated with the standard
user program.
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB
Configuring the safety program
7.1 Introduction
79