Yaskawa MP940 Reference Manual - Manual (Page 420)

MotionSuite™ MP940 Machine Controller Reference Manual Control Mode
11-23
Although the example above of the run command (Dwg H04) is extremely
simplified, in reality each of the register types can be freely controlled by the
user program.
Zero-point Return Mode
The zero-point return operation returns the machine to a fixed zero-point.
When an incremental encoder is used, the system zero-point position data is
deleted if power is cut off. Therefore a new system zero point must be
determined after power ON. Generally this zero-point is determined by using
an encoder with a zero pulse and a limit switch showing the zero-point range.
There are two methods of zero-point return operation: the zero-return mode,
and the motion commands. Keep in mind that these zero-point return
operations differ.
When an absolute encoder is used, position control with a position reference
of 0 results upon selecting “Zero-point Return”.
Detailed Description
The order of operations for zero-point return is shown in the following
figure.