Local Data Requirement for the Automatically Added F-Blocks According to
Local Data Requirement of User Safety Program
The information below must be taken into account only if the amount of local
data available for your safety program is insufficient and you received a
message from S7 Distributed Safety to that effect.
You can estimate the probable local data requirement for the automatically added
F-blocks as follows:
Determine the local data requirement for each call hierarchy (path starting from the
F-PB across all nesting levels down to the lowest) of your safety program:
Local data requirement for a call hierarchy (path local data requirement in
bytes) =
2 x amount of all local data of F-FBs/F-FCs of data type BOOL in the path
+ 4 x amount of all local data of F-FBs/F-FCs of data type INT in the path
+ 6 x amount of all local data of F-FBs/F-FCs of data type TIME in the
path
+ 22 x number of nesting levels in which an F-application block is called
+ 42 x number of nesting levels
+ 14 x number of nesting levels in which a fixed-point function is
programmed
The estimated local data requirement for the automatically added F-blocks is thus
equivalent to the maximum of the path local data requirement of all paths.
Note
If you are unable to provide a sufficient amount of local data for the automatically
added F-blocks, we recommend that you reduce the local data requirement of
your safety program, by reducing nesting depth, for example.
Product Information for the S7 Distributed Safety, Configuring and Programming Manual
26 A5E00169432-02
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