PURPOSE: To easily test the functions of a microcomputer by providing a circuit which converts a clock inputted to a 2nd input terminal into an opposite-phase clock as a 2nd clock opposite in phase from a 1st clock regarding a clock inputted to a 1st input terminal.

CONSTITUTION: When the clock is inputted to the 1st input terminal 3, the 1st clock regarding the clock is outputted. When the clock is inputted to the 2nd input terminal 4, the clock is converted into the 2nd opposite-phase clock. Therefore, even when the clock inputted to the 1st input terminal is in phase with the clock inputted to the 2nd input terminal 4, the phase of an oscillation output is the same. Consequently, the function test can be conducted without altering a test program for the function test.