F-Shutdown Groups - Siemens SIMATIC PCS 7 Operating Manual

7.2.6

F-shutdown groups

An F-shutdown group is a self-contained unit in your safety program. It contains user logic
which is executed or shut down simultaneously. The F-shutdown group contains one or a
number of F-runtime groups which are assigned to a common cyclic interrupt OB. You can
choose whether an error during execution of the safety program causes a full shutdown or a
partial shutdown of the safety program. With a partial shutdown, only the F-shutdown group
in which the error occurred is shut down.
Rules for F-shutdown groups in the safety program
You are not permitted to directly interconnect F-blocks in different F-shutdown groups. Data
can only be exchanged between F-shutdown groups using special communication blocks
(F_S_xx, F_R_xx for F_BOOL and F_REAL data structures). Therefore, all F-channel drivers
in an F-signal module must be in the same F-shutdown group, together with the module
driver of the F-signal module.
Defining F-shutdown groups
As soon as you place F-blocks in the CFC editor for the first time, all of the F-runtime groups
in a single cyclic interrupt OB will form an F-shutdown group.
You can configure each F-runtime group as the last F-runtime group in an F-shutdown group
by placing the F_PSG_M "selection block". The F-system then creates a new F-shutdown
group for all subsequent F-runtime groups until another F_PSG_M block is found.
Distribution/Combination by means of manual placing of F_PSG_M
If you add or delete one or a number of F_PSG_M blocks in your project, the order of your F-
shutdown groups will change. If you make a change to the layout of your F-shutdown
groups, you must make sure that the F-module drivers and all assigned F-channel drivers
are integrated in the same F-shutdown group.
You can split one F-shutdown group into two F-shutdown groups.
To do this, in the CFC editor's runtime editor, place the F_PSG_M block in the last F-runtime
group which is to be assigned to the first F-shutdown group. All subsequent F-runtime
groups will then be assigned to the second F-shutdown group.
The number of F-shutdown groups is limited to 110 in all cyclic interrupt OBs. The system
restricts the number of F-runtime groups in an F-shutdown group.
You have the option of combining two F-shutdown groups. To do this, in the runtime editor of
the CFC editor, delete the F_PSG_M block between the F-shutdown groups.
If you combine a number of F-shutdown groups which exchange data via F-communication
blocks in a single F-shutdown group, you need to remove these F-communications blocks
and replace them with direct interconnections.
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB
Configuring the safety program
7.2 Creating the safety program
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