3.1.4 F-suitable PLC data type
For safety programs, too, it is possible to optimally structure data using PLC data
types.
F-suitable PLC data types have the following features:
F-suitable PLC data types are declared and used in the same way as PLC data
types.
All data types that are allowed in the safety program can be used in F-suitable
PLC data types.
Nesting F-suitable PLC data types within other F-suitable PLC data types is not
supported.
F-suitable PLC data types can be used both in the safety program and in the
standard user program.
Recommendation
Create F-suitable PLC data types to structure data also in the safety program.
Use F-suitable PLC data types to transfer large numbers of variables to blocks.
Use F-suitable PLC data types for access to I/O ranges.
In this context, follow the below rules:
– The structure of the tags of the F-suitable PLC data type must match the
channel structure of the F-I/O.
– Example of an F-suitable PLC data type for an F-I/O with 8 channels:
8 BOOL variables (channel value) or
16 BOOL variables (channel value + value status)
– Access to F-I/O is only allowed for activated channels. When configuring a
1oo2 evaluation, the higher-level channel is always deactivated.
Advantages
A change in a PLC data type is automatically updated in all points of use in the
user program.
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