An integrated circuit includes a volatile memory, a central processing unit that normally operates on a first clock, and an input-output circuit that transfers data in synchronization with a second clock having a lower frequency than the first clock. The integrated circuit has a power-saving mode in which the volatile memory loses its data and the central processing unit stops operating. The power-saving mode is preceded and followed by transitional periods during which the central processing unit uses the input-output circuit to save data from the volatile memory to an external memory device and restore the data from the external memory device to the volatile memory. During these transitional periods, the central processing unit operates on the second clock to conserve power.