A memory device includes a group of memory cells organized in rows and columns and a first addressing circuit for addressing said memory cells of said group on the basis of a cell address. For this purpose, under condition that a communication area covered by a base station is variable, notification of spread code reassignment is issued while communication is being made between the base station and a mobile terminal. the switching transistor supplies a corresponding one of the pixel electrodes with a low electric potential signal or a high electric potential signal supplied from a signal line.