MICROCOMPUTER OPERATING BY A PLURALITY OF POWER SOURCES AND STARTING METHOD FOR MICROCOMPUTER

摘要

PPROBLEM TO BE SOLVED: To provide a technology allowing supply of voltage from each power source to a microcomputer separately supplied with the voltage from the plurality of the power sources at an interval of a prescribed period. PSOLUTION: This microcomputer has: an internal circuit operating by a first power source; a port circuit part operating by a second power source, and performing input/output of a signal between the outside and the internal circuit; a switching circuit switching the voltage supply to the port circuit part from the second power source; a voltage detection circuit detecting power-on of the first power source, and supplying a power-on detection signal to the switching circuit according to a detection resu and a time measurement circuit counting a lapsed time after the power-on of the first power source, and supplying a time lapse signal to the switching circuit after a prescribed first time lapses. The switching circuit permits the voltage supply to the port circuit part from the second power source on and after the first time lapses after the power-on of the first power source based on the time lapse signal and a voltage detection signal. PCOPYRIGHT: (C)2009,JPO&INPIT