3.3 Fail-Safe Blocks
F-blocks of an F-runtime group
The following table shows the F-blocks that you use in an F-runtime group:
F-block Function
Main safety block The first step in programming of the safety program is the main safety block.
In F‑CPU S7‑1500, the main safety block is an F‑FC or F‑FB (with instance‑DB), which is called by the
F‑OB.
F‑FB/F‑FC Both in the main safety block as well as additional F-FBs and F-FCs, you can perform the following:
● Program the safety program with the instructions available for F-blocks in FBD or LAD
● Call other created F-FBs/F-FCs for structuring the safety program
● Insert F-blocks from the project library or global libraries
F-DB Optional failsafe data blocks that can be read- and write-accessed within the entire safety program.
F-I/O DB An F-I/O DB is automatically generated for each F-I/O when it is configured. You can or you must
access the tags of the F‑I/O DB in conjunction with F‑I/O accesses.
F-runtime group infor‐
mation DB
An F-runtime group information DB is created when you create an F-runtime group.
The F-runtime group information DB provides information on the F-runtime group and on the safety
program as a whole.
Note
You are not permitted to insert F-system blocks from the "System blocks" folder in a main safety
block/F-FB/F-FC.
Instructions for the safety program
In task card "Instructions", depending on the F-CPU being used, you can find instructions that
you can use to program the safety program.
You can find instructions that you know from the standard user program, such as bit logic
operations, mathematical functions, functions for program control, and word logic operations.
Moreover, there are instructions with safety functions, e.g., for two-hand monitoring,
discrepancy analysis, muting, emergency STOP/emergency OFF, safety door monitoring,
feedback monitoring and instructions for safety-related communication between F-CPUs.
Additional information
For a detailed description of the instructions for the safety program, refer to Overview of
instructions (Page 71).
Safety program of the F-PLC
3.3 Fail-Safe Blocks
Safety Integrated (with SINAMICS S120)
Commissioning Manual, 02/2020, A5E46305916B AB 59
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