An electronic device maintains data utilizing a ferroelectric memory, not requiring a backup power source voltage. Data such as schedule data and telephone number data is stored in a ferroelectric RAM which switches between a dynamic mode and a nonvolatile mode. When a clock mode is designated by a "CLK" key, a memory control circuit causes the ferroelectric RAM to be switched to the nonvolatile mode to maintain the data stored therein. When a schedule mode or a telephone mode is designated by means of a "Sch" key or a "Tel" key, the ferroelectric RAM is switched to the nonvolatile mode to write/read data therein/therefrom. When it is detected that a battery voltage is lowered or the battery is removed from the electronic device, the ferroelectric RAM is switched to the nonvolatile mode to protect the stored data.