This is one of a servo motor control signals and is output from a motor driver.
In the servo motor control with pulse-train input, the motor operation is delayed than the accumulated position of the pulse train.
Therefore, when the pulse train stops, the motor does not stop immediately.
This signal is output when the motor reached almost the specified position.
The control LSI can delay the timing for changing the operation status monitor to the stop status until this signal is input after the pulse train output is completed.