Siemens SINUMERIK 840D Description Of Functions page 459

11.03
The levels of the SN signals change as follows:
Fig. 8-9
Because of the modulo correction and the associated level changes of the safe
cams, the above method of rounding would have the effect that "position
detection 0 degrees" would always be a low signal.
This problem can be solved by negating signal SN1+ in the machine data
parameterization and OR'ing it with signal SN1-.
© Siemens AG 2003 All Rights Reserved
SINUMERIK 840D/SIMODRIVE 611 digital SINUMERIK Safety Integrated (FBSI) - Edition 11.03
359.5° 0° 0.5°
SN1+
SN1-
Modulo
correction
Position detection
to be implemented
SN1+
Position detection
0 degrees
&
SN1-
Signal generation for modulo cam 1
8 Application examples
8.4 Safe cams at the modulo limit
8-459