Device configuration
6.6 Configuring the operation of the CPU
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
173
The default filter time for the digital inputs is 6.4 ms. You can select a filter time from the
Input filters drop-down list. Valid filter times range from 0.1 us to 20.0 ms.
Risks with changes to filter time for digital input channel
If you change the filter time for a digital input channel from a previous setting, a new "0"
level input value may need to stay at "0" for up to 20.0 ms before the filter becomes fully
responsive to new inputs. During this time, short "0" pulse events of duration less than 20.0
ms may not be detected or counted.
This changing of filter times can result in unexpected machine or process operation, which
may cause death or serious injury to personnel, and/or damage to equipment.
To ensure that a new filter time goes immediately into effect, a power cycle of the CPU
must be applied.
Configuring filter times for digital inputs used as HSCs
For inputs that you use as high-speed counters (HSCs), change the input filter time to an
appropriate value to avoid missing counts.
Siemens recommends the following settings:
Recommended input filter time
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