Siemens SIMATIC FM 452 Manual page 100

Settings
9.1 Influence of Settings on the Switching Response of Time Cams
Actual Value Changes
A time cam can be skipped by the following settings that change the actual value:
Set actual value
Set actual value on-the-fly
Zero offset
Retrigger reference point
Switching a Time Cam
If you skip the start of a time cam due to one of the settings listed above, this cam
is activated as long as the actual direction in which the axis is moving matches the
activation direction set for the cam. The set on time runs until it expires.
Note
If the axis is stationary, the direction of movement depends on fluctuations in the
actual value.
If you want the direction of movement to be taken into account when the axis is
stationary, you must set a hysteresis that is greater than the fluctuations in the
actual value when the axis is stationary.
If the axis is not moving, the last detected direction of movement is retained.
Warning
!
Injury to persons or damage to equipment can occur.
With a rotary axis, settings that modify the actual value can led to accidental
activation of time cams.
You should always set the time cams of a rotary axis to "invalid" if you want to
modify the actual value using the settings listed above.
9-2
FM 452 Electronic Cam Controller
C79000-G7076-C452-04