Programming
Fail-Safe Systems
5-24 A5E00085588-03
5.3.6 Passivation and Reintegration of the Input and Output Channels
Passivation
Passivation means that, in the event of a fault/error, one or more channels of an F-
I/O are switched to the safe state.
When a channel fault occurs (e.g. sensor defective), only the affected channel is
passivated. In the event of a module fault/error (e.g. communication error), all the
channels of the F-I/O are passivated. The messages on the ES/OS indicate
whether all channels or only specific channels of a fail-safe module are passivated.
Passivation can be triggered by the F-I/O, the F module driver or F channel driver
or by the user in the safety program.
If an F-I/O detects a fault/error, it switches the affected channel or all its channels
to the safe state. In other words, channels of this module are passivated. The F-I/O
reports detected error to the F driver block.
• Passivation of output channels means that the outputs are de-energized.
The F channel driver of a passivated digital output channel outputs a substitute
value with the quality code (QUALITY) 16#48 and the output QBAD = 1 is set.
• Passivation of input channels means that substitute values are forwarded to
the safety program regardless of the current process signal. The F channel
driver of a passivated digital input channel outputs the substitute value 0 with
the quality code (QUALITY) 16#48 and the output QBAD = 1 is set. Depending
on the parameterization at the input SUBS_ON, the F channel driver of an
analog input channel outputs a substitute value with the quality code
(QUALITY) 16#48 or the last valid value with the quality code (QUALITY)
16#44 . In addition, the output QBAD = 1 is set and, if a substitute value is
output, the output QSUBS = 1 is set as well.
Via the input PASS_ON, you can also switch the passivation of a channel on and
off in the safety program (e.g. depending on certain conditions in the execution of
the program). If PASS_ON = 1 is set, the channel is passivated as described
above. If PASS_ON = 0, passivation is canceled.
Group Passivation
In the event of a fault or error, other channels (of the same or different modules)
can be passivated by interconnecting the input PASS_ON with the output
PASS_OUT of another channel. For a group shutdown of several channels, all the
PASS_OUT outputs of the channels in this group are ORed, and the result is sent
to the PASS_ON inputs of all the channels in this group.
A group shutdown by means of PASS_OUT/PASS_ON can also be used to force a
simultaneous switchover to process values after a startup (cold or warm restart).
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