A method for determining connection of an external device to a mobile communication terminal is provided. The method comprises detecting connection of an external device to a mobile communication terminal based on a signal generated by a first operation module of the mobile communication terminal; activating a connection interrupt routine, in response to the signal generated by the first operation module; controlling an active status of a second operation module by way of the first operation module to switch system operations from a first clock speed to a second clock speed; and establishing a signal transfer path between the mobile communication terminal and the external device.