FAQ00268 of Programmable Controllers FAQ

The XSOUT signal (SEN signal) is used to load the present motor position when connecting OMRON Drivers that support absolute values (R88).
(By using Motion Controllers with OMRON Servo Drivers/Servomotors, an absolute system that does not need to search for the origin can be easily constructed.)

Therefore, the XSOUT signal (SEN signal) is not required when connecting servo drivers from another company. As for the timing, the SEN signal will turn ON when Motion Control Units power supplies are turned ON (i.e., when power supplies for Programmable Controllers are turned ON). The SEN signal will turn OFF when Servomotors are locked.