According to one embodiment, an electronic device forming a first communication path which couples a first interface of a high-rank unit and a second interface of a mid-rank unit and a second communication path which couples a third interface of the mid-rank unit and a fourth interface of a low-rank unit, while cutting off a third communication path which couples the first interface and the fourth interface, in an ordinary state. When data needs to be write from the high-rank unit to the low-rank unit, the electronic device forming the third communication path and cutting off the first communication path and the second communication path.