Siemens SINUMERIK 840D Function Manual page 403

Modulo rotary axes
The switching edges of the cam signals are generated as a function of the rotary axis traversing
direction:
● The plus cam signal switches from 0 to 1 when the axis traverses the minus cam in a positive
axis direction and from 1 back to 0 when it traverses the plus cam.
● The minus cam signal changes level in response to every positive edge of the plus cam
signal.
Note
The described response of the plus cam applies on conditionthat:
plus cam - minus cam < 180 degrees
Figure 13-3
The signal change of the minus cam makes it possible to detect traversal of the cam even if the
cam range is set so small that the PLC cannot detect it reliably.
Both cam signals can be output to the PLC and to the NC I/O. Separate output of the plus and
minus cam signals makes it easy to detect whether the axis is within or outside the plus or minus
cam range.
If this condition (plus cam - minus cam < 180 degrees) is not fulfilled or if the minus cam is set
to a greater value than the plus cam, then the response of the plus cam signal is inverted. The
response of the minus cam signal remains unchanged.
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
Software cams for modulo rotary axis (plus cam - minus cam < 180 degrees)
N3: Software cams, position switching signals
13.2 Cam signals and cam positions
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