Semiconductor integrated circuit

A semiconductor integrated circuit comprising a clock generator receiving input of a reference clock so as to generate a modulated clock based on the input reference clock, and a diagnostic circuit;

• wherein said clock generator includes:
• a phase comparator comparing the phase of said reference clock with that of a feedback clock;
• an oscillator receiving input of said modulated clock of which the oscillating frequency is controlled based on output from said phase comparator, and
• a modulation circuit receiving input of said modulated clock so as to output said feedback clock;
• wherein said modulation circuit includes a frequency divider, and a division ratio modulation circuit supplying a division ratio to said frequency divider;
• wherein said frequency divider outputs said feedback clock by dividing the output of said oscillator by said division ratio;
• wherein said division ratio modulation circuit is fed with a multiplication count and has at least one of two periods, one of the two periods being one in which said division ratio modulation circuit outputs a value larger than said modulation count as said division ratio, the other period being one in which said division ratio modulation circuit outputs a value smaller than said modulation circuit as said division ratio, said division ratio modulation circuit further outputting a magnitude relationship between said division ratio and said multiplication count in the form of a spread direction identification signal, and
• wherein said diagnostic circuit includes a first counter counting said reference clock, and a second counter counting said modulated clock based on said spread direction identification signal.