Siemens SIMATIC PCS 7 Configuration Manual page 121

Note
It is generally practical to initially assign all modules to a medium program cycle (e.g. 500 ms
or 1,000 ms) for a complete process consisting of a few fast and slow parts.
You then only have to assign the appropriate process image partition of the given cyclic
interrupt to the modules containing the signals for fast controlling or interlocking (e.g. 50 ms
or 100 ms).
This procedure saves configuration time.
Redundant I/O modules
In PCS 7, fault tolerance is realized on the field level by means of the redundant distributed I/
O, using ET 200M modules.
Note
Information on setting up, wiring and configuring can be found in the document "Configuration
of Redundant I/O Modules in SIMATIC PCS 7"
en/view/28430682).
Compendium Part A - Configuration Guidelines (V8.2)
Configuration Manual, 08/2016, A5E38166869-AA
Configuration of the hardware (AS and I/O)
6.5 Configuration of the I/O devices
(https://support.industry.siemens.com/cs/ww/
121