Siemens SINUMERIK 840D Function Manual page 401

Linear axes
The switching edges of the cam signals are generated as a function of the axis traversing
direction:
● The minus cam signal switches from 1 to 0 when the axis traverses the minus cam in the
positive axis direction.
● The plus cam signal switches from 0 to 1 when the axis traverses the plus cam in the positive
direction.
Figure 13-1
Note
If the axis is positioned exactly at the output cam position (plus or minus), the defined output
flickers. If the axis moves one increment further, the output becomes a definite zero or one.
Flickering of the actual position causes the signals to flicker in this manner.
The actual position is evaluated.
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
Software cams for linear axis (minus cam < plus cam)
N3: Software cams, position switching signals
13.2 Cam signals and cam positions
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