Siemens S7-300 Installation And Operating Manual page 251

Discrepancy analysis for fail-safe analog input modules
If you have configured 1oo2 evaluation, you can configure a discrepancy time and an
absolute and a relative tolerance window for each channel pair of the module. In addition,
configure the standard value (MIN = lower value / MAX = higher value) to be applied and
transferred to the F-CPU.
If the difference between the two redundant input channels of the channel pair exists longer
than the configured discrepancy time, an error is signaled and the fail-safe value (7FFF
transferred. In
program in place of 7FFF
SUBS_V of the channel driver will be provided in the PII.
Fail-safe signal modules
Installation and Operating Manual, 01/2010, A5E00085586-10
S7 Distributed Safety
, the fail-safe value 0 is provided in the PII for the safety
S7 F/FH Systems
. In
H
9.3 SM 336; F-AI 6 x 0/4 ... 20 mA HART
the fail-safe value assigned at the input
Analog modules
) is
H
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