Siemens S7-300 Installation And Operating Manual page 75

"Provide 0 value"
The value "0" is returned to the safety program in the F-CPU as soon as discrepancy is
detected between the signals of two input channels.
The sensor-actuator response time is not influenced by the discrepancy time if the "Provide 0
value" parameter is set.
Discrepancy analysis at redundant digital input modules (only in fail-safe S7 F/FH systems)
See Chapter "Configuring redundant F-I/O" in the
Programming
Parameter assignment
Open the object properties catalog of the fail-safe signal module in
discrepancy time and behavior (for information on the parameters, refer to the chapters
dealing with the digital input modules).
Fail-safe signal modules
Installation and Operating Manual, 01/2010, A5E00085586-10
8.2 Discrepancy analysis at the fail-safe digital input modules
operating instructions.
S7 F/FH Systems Configuring and
HW Config
Digital modules
to assign the
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