| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a clock input circuit capable of performing noise removal with high accuracy without depending upon the power supply voltage of a microcomputer. <P>SOLUTION: This clock input circuit is provided with a switch circuit 4 for performing switching control on the basis of the level of the power supply voltage of the microcomputer, a switching circuit 5 and a programmable register 7. When the power supply voltage of the microcomputer is equal to or greater than a predetermined value, normal noise removal that uses Schmitt trigger circuits 2 and 3 and a capacitor 6 is performed. Meanwhile, when the power supply voltage of the microcomputer is lower than the predetermined value, noise removal that uses the Schmitt trigger circuit 2 and flip-flops 8 and 9 is performed. Then, highly accurate noise removal that does not depend upon the power supply voltage of the microcomputer is realized. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
