Siemens SINUMERIK 840D sl Function Manual page 717

Figure 9-2
Extended Functions
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Note
Position switching signals:
If the axis is positioned exactly on the cam (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.
Software cams for linear axis (plus cam < minus cam)
Software Cams, Position Switching Signals (N3)
Cam signals and cam positions
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