CLOCK INPUT DEVICE FOR SEMICONDUCTOR INTEGRATED CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a clock input circuit with which unnecessary high frequency radiation noises can be reduced at the time of ordinary operation of a semiconductor integrated circuit(LSI), and further the LSI can be checked at high speed without deteriorating characteristics at the time of a synchronous LSI check. SOLUTION: In an LSI 1, a selector circuit 7 can select either a clock CK1 outputted from a clock generating circuit 4 or inputted from outside while containing a high frequency component or a clock CK2 from which an unnecessary high frequency component is excluded, based on a select signal 8 to be changed only at the time of the synchronous LSI check. In an ordinary operation of the LSI, the clock CK2, from which the unnecessary high frequency component is excluded, is selected. Thus, malfunction or characteristic degradation of the set caused by unnecessary high frequency radiation noises to be a problem especially when mounting the LSI on communication equipment can be canceled.