A controller for transferring data between a host and a storage medium includes a data transfer unit and a control unit. The data transfer unit transfers data according to control commands from the host if the data transfer unit is enabled. The control unit coupled to the data transfer unit receives a status signal indicating whether the storage medium is coupled to a socket of the controller. The control unit provides interruption signals to the host. Power and a clock signal for the control unit are disabled if the status signal indicates that the storage medium is decoupled from the controller.