Siemens SINUMERIK 840D sl Function Manual page 168

Safety functions integrated in the system/drive
7.8 Safety software cams and safety cam track (SN)
Synchronization
The synchronization of the cam SGA is carried out between the NCK and PLC. Both the SGA
"cam track" as well as the SGA "cam range" must be synchronized.
The SGA "cam track" is synchronized by AND'ing the two signals from the NCK and drive
monitoring channels. The logic operation is carried out for all 4 cam positions.
The 4-bit SGA "cam range" (value range 0...15) is synchronized according to the following rule:
If the SGA "cam range" as well as the SGA "cam track" is different in both monitoring channels
and the SGA "cam track" of its own channel has a value of "1", then the SGA "cam range" of
the other channel must be used.
Alternative evaluation of the cam signals
In order to simplify the evaluation of cam signals, the cam signals "cam track" and "cam range",
generated from the axis monitoring channels NCK and drive, can be mapped to 15 "cam range
bits" for each cam track (for the cam ranges 0 ... 14).
The "cam range bits" are generated by logically combining the "cam track" and "cam range"
signals in the NCK and in the PLC. If the axis is positioned at a cam, then the cam range bit
of the cam range assigned to this cam is set to 1.
The SGA "cam track", "cam range" and "cam range bit" are shown in the following diagram
using an example:
168
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety Integrated