Siemens SIMATIC S7 F Manual page 135

Programming
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Deletion of run-time groups: If a run-time group is moved to another task, you
must not delete the run-time group of the F_CYC_CO in the old task at the
same time. If you want to do that in order to delete the old task completely, for
example, proceed as follows in two steps:
- Move, compile and download the run-time group to the new task.
- Then delete, compile and download the run-time group of the F_CYC_CO
from the old task.
Impermissible Changes
Some changes must not be carried out even when safety mode is deactivated,
because continuous (bumpless) execution of the user program cannot be
guaranteed. The following changes can cause the execution of the user program to
be interrupted or the Safety Program to shutdown, or even prevent the changes to
the Safety Program from being downloaded:
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Changes to the parameter assignment of F-I/Os are not possible during
operation in the current product version. The modules can only receive the
modified parameter assignment in the S7 FH System as well after removal and
insertion. The F-I/Os detect a CRC error after the first change has been
downloaded and output substitute values.
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Like parameter changes in HWCONFIG, changes to the properties of existing
CPU-CPU connections are not bumpless if properties are modified that go to
the network addresses. In this case, as well, substitute values are output until
the state of the F communication blocks is consistent. It is, possible to achieve
this in several steps by means of an additional connection (see
"Communication Between Run-Time Groups or CPUs"). Changing the ID and
R_ID I/Os of the F-SENDR/BO and F-RCVR/BO is not permitted.
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Deletion and reinsertion of the automatically inserted F control blocks and the
F_CYC_CO F-system block will result in Safety Program disable.
•
The same thing applies to
reinserted and interconnected, the associated F_R_BO or F_R_R F-Block
outputs substitute values.
•
Moving an F-run-time group to another priority class is not permitted.
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Interface changes to fail-safe blocks cause the Safety Program to disable.
Fail-Safe Systems
A5E00085588-03
If such an F-Block is deleted,
F_S_BO and F_S_R:
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