The hardware timed send feature allows cyclic frame sending exactly at starting KPA EtherCAT Master cycle without any jitters.
Usually, KPA EtherCAT Master begins preparing cyclic frame at starting its cycle. That is why actual time of frame sending is delayed for the time of its preparation.
When hardware timed send is enabled, KPA EtherCAT Master prepares frame in advance, before starting the cycle and passes them to a hardware module (HW module) on the target. Therefore, when the cycle starts, the HW module just sends prepared frames with no delays.