Siemens SIMATIC S7 F Manual page 88

Programming
Notes on Working With CFC
Safety Note – Compression Changes Signature
!
Compressing CFC programs changes the overall signature of the program!
If the program has to be compressed, carry out the compression before it is
accepted.
The fail-safe blocks in the Fail-safe Blocks library are highlighted in color in the
CFC chart. They are colored yellow to indicate that it is a safety program.
The CFC charts and run-time groups with F-Blocks are yellow and marked with an
"F" to differentiate them from the charts and run-time groups of the standard
program.
5-6
Fail-Safe Systems
A5E00085588-03