Operand area Description
● F-DB
Data blocks store information for the program. They can either be de‐
fined as global data blocks such that all F-FBs, F-FCs, or main safety
blocks can access them or assigned to a particular F-FB or main safety
block (instance DB). A tag of a shared DB can only be accessed from
one F-runtime group, and an instance DB only from the F-runtime group
in which the corresponding F-FB/instruction is called.
● DB
This area is used for data exchange with the standard user program.
In addition, read access requires a process-specific validity check.
For a tag of a DB, either read access or write access is possible in the
safety program.
Transfer to IN_OUT parameters of an F-FB or F-FC is therefore not valid
either.
Please note that the tags of a DB can only be used for transferring data
between the standard user program and the safety program; DBs must
not be used as a buffer for F-data
.
Temporary local data This memory area holds the temporary tags of a block (or F‑block) while
the (F-) block is being executed. The local data stack also provides
memory for transferring block parameters and for saving intermediate
results.
File type conversion
Just as with the standard user program, there are two possibilities for file type conversion in the
safety program.
● Implicit conversion
The implicit conversion is executed as in the standard user program with the following
restrictions: The bit length of the source data type has to match the bit length of the
destination data type.
● Explicit conversion
You use an explicit conversion instruction before the actual instruction is carried out.
Slice access
Slice access is not possible in the safety program.
Non-permitted operand areas
Access via units other than those listed in the table above is not permitted. The same applies
to access to operand areas not listed, in particular:
● Data blocks that were automatically added
Exception: certain variables in the F-I/O DB and in the F-runtime group information DB
● I/O area: Inputs
● I/O area: Outputs
Safety program of the F-PLC
3.5 Restrictions in the programming languages FBD/LAD
Safety Integrated (with SINAMICS S120)
66 Commissioning Manual, 02/2020, A5E46305916B AB
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