F_Test - Siemens SIMATIC S7 F Manual

Fail-Safe Blocks
8.6.10

F_TEST

Function
This block executes a command test.
At compilation, the block is inserted automatically into a F-run-time group named
@F_CycCo-OB3x, where x is 0 through 8 that correspond to the OB3x containing
F-Blocks, that contain the blocks F_CYC_CO and F_TESTC.
Note
A project based on Fail-safe Blocks (V1_1) the user must follow the manual
procedure for creating a CFC chart with the F_CYC_CO function block. A Run-
time group must also be created and the user must place the F_CYC_CO function
block within this new Run-time group.
Again, for a project based on Fail-safe Blocks (V1_2) or higher the manual
procedure has been eliminated. The user is no longer allowed to manually place
the F_CYC_CO function blocks – it is now a system function.
I/Os
The inputs and outputs will not be explained here since this is logic that the system
automatically generates.
Error Handling
In the event of an error that is critical to safety, the system function SFC F_CTRL
is called. This records the event in the Diagnostic Buffer and requests a switch to
the reserve CPU if the error occurred only on the master CPU. For non-redundant
systems or a common-cause error occurring in both CPUs, the shutdown logic can
be configured to either disable the F-run-time group with the error or the entire
Safety Program.
Error Information in Diagnostic Buffer
Error Code (W#16#...)
75E1H
Fail-Safe Systems
A5E00085588-03
Description
Internal CPU fault
8-77