Some of our company's digital I/O board has the function of monitoring output ports.
This function read ouput data from software is called Echo Back.
In the case of board which has the function of monitoring output ports, Echo Back function returns the input data from hardware.
In the case of board which doesn't have the function of monitoring output ports, Echo Back function returns the data stored in driver work.
Whether the board has the function of monitoring output ports, you can refer to the hardware specification of each device.