Maintenance
12.8 Reaction to faults in fail-safe modules and fail-safe motor starters
Distributed I/O system
System Manual, 12/2016, A5E03576849-AG
257
Substitute value output for fail-safe modules
In the case of F-modules
, if there is passivation, the F-system provides substitute
values (0) for the safety program instead of the process data pending at the fail-safe inputs.
In the case of F-modules with outputs
, if there is passivation, the F-system transfers
substitute values (0) to the fail-safe outputs instead of the output values provided by the
safety program. The output channels are de-energized. This also applies when the F-CPU
goes into STOP mode. Assignment of substitute values is not possible.
Depending on which F-system you are using and the type of fault that occurred (F-I/O fault,
channel fault or communication error), substitute values are used either for the relevant
channel only or for all channels of the relevant fail-safe module.
Reintegration of a fail-safe module
The system changes from fail-safe to process values (reintegration of an F-module) either
automatically or only after user acknowledgment in the safety program. If channel faults
occur, it may be necessary to remove and reinsert the F-module. A detailed listing of faults
requiring removal and insertion of the F-module can be found in the section Diagnostic
messages of the respective F-module.
After reintegration, the following occurs:
● In the case of an F-module with inputs, the process data pending at the fail-safe inputs is
made available to the safety program again
● In the case of an F-module with outputs, the output values provided in the safety program
are transferred to the fail-safe outputs again
Additional information on passivation and reintegration
For additional information on passivation and reintegration of F-I/O, refer to the SIMATIC
Safety, Configuring and Programming
(http://support.automation.siemens.com/WW/view/en/54110126) manual.
Behavior of the fail-safe module with inputs in the event of a communication disruption
F-modules with inputs respond differently to communication errors compared to other errors.
If a communication error is detected, the current process values remain set at the inputs of
the F-module. There is no passivation of the channels. The current process values are
passivated in the F-CPU.
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