A debug circuit of a microcomputer, providing an on-chip debug function, is provided as a measurement permission circuit for outputting a measurement permission signal to a timer that measures, as a measurement object, a time period between two events in a program execution period of the CPU, according to a user-specified condition. The measurement permission circuit includes an interrupt level register for setting an interrupt level that either permits or prohibits a time measurement operation of the timer, and a comparator for determining by comparison a high-low relationship between an interrupt level of an interrupt process executed by the CPU and an interrupt level set in the interrupt level register, and a determination result of the comparator is specified as the measurement permission signal.