Siemens SIMATIC S7-300 - Manual (Page 43)

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SIMATIC S7-300 Getting Started for First Time Users
Getting Started, 04/2007, 6ZB5310-0NC02-0BA0
Setting the parameters of the CPU 312C
You can set numerous parameters for each of the modules. As an example, we
will modify the retention behavior of the CPU 312C.
1. Set the amount of retentive bit memory to “0”.
The retention behavior of the
CPU 312C determines
whether or not the values of
internal memory bits are
retained after a power failure
or memory reset on the
CPU 312C.
You can use the retention
behavior to ensure that the
motor does not start up in an
uncontrolled manner after a
power failure.