SEMICONDUCTOR INTEGRATED CIRCUIT

An SSCG generating a center-spread modulated clock centering on a frequency obtained by multiplying an input reference clock frequency by a predetermined number is configured to include a phase comparator, a VCO, and a modulation circuit formed by a frequency divider and a division ratio modulation circuit. The division ratio modulation circuit supplies the frequency divider with a division ratio modulated above and below the predetermined multiplication number, and outputs a magnitude relationship involved as a spread direction identification signal. The diagnostic circuit includes a counter that counts the modulated clock and, based on the spread direction identification signal, performs counting operations during an up-spread or down-spread period. Based on the values counted for a predetermined period, the operating status of the SSCG is diagnosed for the presence or absence of a failure, for example.