A memory device is provided which is connected to operate with power and clocks supplied from a host apparatus. The memory device includes external terminals, a flash memory chip to store data, an IC chip to process data; and a controller chip connected with the external terminals, the flash memory chip and the IC chip, wherein, the flash memory chip, the IC chip and the controller chip are discrete chips. The controller chip writes data inputted from the host apparatus into the flash memory chip or the IC chip and transfers data read from the flash memory chip or the IC chip to the host apparatus, based upon commands from the host apparatus.