A storage medium including a first transmittal module and a control module. The first transmittal module includes a plurality of first transmittal pads. The control module determines whether a level state of the first transmittal module is equal to a pre-determined state. When the level state is equal to the pre-determined state, the control module operates in a secure digital (SD) mode. When the level state is not equal to the pre-determined state, the control module operates in an embedded multimedia card (eMMC) mode.