Most of the times, the D.M.A. software is used. D.M.A. i.e. direct memory access uses a technique of waiting until the data gets copied in the form of loop and it even interrupts to signify that it is not done as yet.
So the most common method or technique that central processing units apply is that, it puts the data in buffer state and then the D.M.A. is activated and is out to action.
At this point, the central processing unit can even work in the form of a bus master. However to speed up the overall processed the central processing unit can speed up the overall process and chained form or command enhancement can be used.