Function Blocks (Fb) - Siemens S7-1200 Programming Manualline

3 General Programming
3.2 Program blocks
3.2.3

Function blocks (FB)

Figure 3-6: "Add new block" dialog (FB)
FBs are blocks with cyclic data storage, in which values are permanently stored.
The cyclic data storage is realized in an instance DB.
Figure 3-7: Calling a function block
Properties
FBs are blocks with cyclic data storage.
Temporary and out tags are undefined when called in non-optimized blocks. In
optimized blocks, the values are always preset to the default value (S7-1500
and S7-1200 Firmware V4). Thus, the resulting behavior is not accidental but
reproducible.
Static tags keep the value from cycle to cycle
Recommendation
Use the function blocks in order to create subprograms and structure the user
program. A function block can also be called several times in different locations
of the user program. This makes programming of frequently recurring program
parts easier.
If function blocks are applied multiply in the user program, use separate
instances, preferably multi-instances.
Programming Guideline for S7-1200/1500
V1.2, Entry ID: 81318674
Instance DB
Call of a function block in the
block editor
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