CLOCK SWITCHING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a clock switching apparatus suitable for a microcomputer to be used for a system in which variation of power supply voltage is large and capable of suppressing the generation of whiskers at the time of switching clock signals without using a complicated and expensive circuit such as a PLL circuit and capable of accurately detecting the switching timing of two clock signals.

SOLUTION: The clock switching apparatus is provided with the microcomputer 26, a monitoring circuit 22 for monitoring the power supply voltage of the microcomputer 26, a circuit 12 for generating a second clock whose frequency is lower than that of a first clock of high frequency and a switching circuit 24 for switching the first and second clocks and outputting the switched clock to the microcomputer 26 and constituted so as to supply the first clock or the 2nd clock to the microcomputer 26 in accordance with a state that power supply voltage to the microcomputer 26 is a prescribed value and more or less than the prescribed value at the timing that the phase of the first clock coincides with the phase of the second clock.

COPYRIGHT: (C)2005,JPO&NCIPI