The above is the description in our manual.
MF is what we often call ENA, that is, enable.
Generally speaking, enabling can control whether the motor is controlled.
If the motor is controlled and the controller sends pulses, the motor will respond accordingly.
If the motor is not controlled, the drive will not energize the motor, and the motor will have no response when the controller sends pulses. At this time, the motor shaft is free because there is no current.
When MF+ and MF- are not connected, the motor is enabled, which means that the motor is controlled. If MF+ and MF- are connected, the user will control whether the motor is enabled.
PEND is an in-position signal. When the in-position signal is valid, after the driver completes the given pulse (under normal circumstances, it can also be considered as the motor completes the given action), PEND will send out a signal.
I don't know why arduino doesn't receive any signal, I'm out of thoughts..