Siemens SIMATIC S7 F Manual page 153

Programming
As with the offline Block View, a window shows any blocks whose signatures differ.
View option "Show unconnected F-FB input parameter differences:
This option forces a complete comparison of values of constants connected to the
inputs of F-Blocks between the online and an offline program, and displays
differences in an upper pane in the dialog.
Note that normally this option is only used when the overall signatures already
match, indicating that the offline program has not changed since the last download
to the F-CPU. Checking this option allows the more thorough check for any
parameters that may have been changed online by a method other than compile
and download.
View option "Filter F-System checksums
This option suppresses the display of expected differences that will occur when the
F-CPU writes to input parameters of certain F-Blocks (e.g. checksum values at
inputs of F_PLK, F_PLK_O). This option is only valid when you have checked the
option for "Show unconnected F-FB input parameter differences.
Fail-Safe Systems
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