Patent ID: 6973583

Claim:
An information processing apparatus that can perform an interruption function comprising: a central processing unit that operates with one of a first clock and a second clock, the second clock having a shorter period than the first clock; a clock generating circuit for generating the second clock upon receiving a start signal; a clock switching circuit for normally supplying the first clock to the central processing unit to cause the central processing unit to operate with the first clock, and for supplying the second clock, instead of the first clock, to the central processing unit to cause the central processing unit to operate with the second clock when a predetermined condition is present; and an interrupt control circuit for supplying the start signal substantially simultaneously to both the central processing unit and the clock generating circuit when the interrupt control circuit receives an interrupt request signal, the start signal being supplied to the clock generating circuit without passing through the central processing circuit, the start signal causing the central processing unit to start preparation for the interruption and additionally causing the clock generating circuit to start producing the second clock while the central processing unit is starting preparation for the interruption, so that stabilization of oscillation of the second clock proceeds as the central processing unit is preparing for the interruption.