F_Testc - Siemens SIMATIC S7 F Manual

Fail-Safe Blocks
8.6.11

F_TESTC

Function
This block checks whether the background self-tests of the CPU have been carried
out fully and without errors and that this did not take place more than 24 hours ago.
The tests must not be switched off by the SFC 90.
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_TEST.
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#...)
75DAH
75E1H
...
75E1H
8-78
Description
Error in the safety data format of the input F_CNT_W (error due to online
modification of the Safety Program or internal CPU fault)
Errors at CPU self-tests or error due to online modification of the Safety
Program or internal CPU fault
Fail-Safe Systems
A5E00085588-03