Siemens SINUMERIK 840D sl Function Manual page 697

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
● The minus cam signal changes level in response to every positive edge of the plus cam
Figure 9-3
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 NCK I/Os. 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°) 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.
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
positive axis direction and from 1 back to 0 when it traverses the plus cam.
signal.
Note
The described response of the plus cam applies on condition that:
plus cam - minus cam < 180 degrees
Software cams for modulo rotary axis (plus cam - minus cam < 180°)
N3: Software cams, position switching cycles - only 840D sl
9.2 Cam signals and cam positions
697