When the reference cam is reached, the NCK is signaled which coded reference cam is actuated.
The interface signal:
DB31, ... DBX2.4 - DBX2.7 (reference point values 1 to 4)
must remain set until the reference point is reached,
or until a new coded reference cam is actuated.
If the machine axis has reached the reference point (axis stationary) then using the reference point
value pre-selected using
IS "reference point values 1 to 4" from the machine data:
MD34100 $MA_REFP_SET_POS (reference point value)
is transferred into the control as the new reference position.On a machine tool with large traversing distances, four coded reference cams can be distributed
over the entire distance traveled by the axis, four different reference points approached and the time required to reach a valid referenced point reduced.If the machine axis has arrived at the reference point and none of the four "reference point value 1 to 4" interface signals has been set, the value of the reference point is automatically set to 1.

实际就是选择MD34100中那个参考点坐标生效。
一般我们的机床回参考点后都是0，所以可以不用。