A method of reducing power consumption without increasing the load of a host apparatus. A media controller connected to a system bus is provided in an external apparatus, such media controller being provided with, for example, a camera controlling circuit, a GPS controlling circuit and an interface connecting to an electronic apparatus. The electronic apparatus may include, for example, a GPS function block, a camera shooting function block and a memory function block. Such function blocks are connected to the interface through a register, thus exchanging data with the external apparatus. In addition, each of the function blocks has a power controlling unit and a power controlling signal is supplied from a system controlling circuit of the electronic apparatus to each of the power controlling units.