PURPOSE: To eliminate the complication of the operation for initialization, by initializing a device only when data in a specific area of an RAM does not coincide with initializing pattern data at the time when an initializing pulse inputted.

CONSTITUTION: The initializing pulse is given when an electric power is supplied to an LSI, and the initializing operation is performed by an initializing circuit 3 when initializing pattern data does not coincide with data in an area A of an RAM1, and a normal control operation is started after initializing pattern data is written in the area A. Hereafter, when the initializing pulse is inputted by a sudden change of the power source voltage or a noise pulse, read data from the area A and input pattern data are compared with each other. If they do not coincide each other, the initializing operation is performed and data is written; but if they coincide each other, the initializing operation is performed only when it is required. Consequently, since the time set is not performed as long as data is held in the RAM after the device is initialized once, the time set is not performed more than needs.