Abstract: A clock switching circuit comprises: a composite clock generation circuit, which is to receive a first clock, a second clock, and a clock switching execution signal for switching between the first clock and the second clock, and to make a level of the clock fixed to be a second level and to output the clock as a composite clock for clock switching, for a specified period including one of a leading edge and a trailing edge of the clock as well as additional time before and after the edge, when the signal becomes active while the clock is at a first level; a switching demand signal generation circuit that receives the clock and the signal, and outputs a clock switching demand signal; a clock selection signal generation circuit that changes a level of a first clock selection signal when the signal becomes active; and a first selector that selects one of the clock and the clock, according to the level of the signal, and outputs the selected clock.

Abstract: A clock switching circuit comprises: a composite clock generation circuit, which is to receive a first clock, a second clock, and a clock switching execution signal for switching between the first clock and the second clock, and to make a level of the clock fixed to be a second level and to output the clock as a composite clock for clock switching, for a specified period including one of a leading edge and a trailing edge of the clock as well as additional time before and after the edge, when the signal becomes active while the clock is at a first level; a switching demand signal generation circuit that receives the clock and the signal, and outputs a clock switching demand signal; a clock selection signal generation circuit that changes a level of a first clock selection signal when the signal becomes active; and a first selector that selects one of the clock and the clock, according to the level of the signal, and outputs the selected clock.

Abstract: The present invention provides a debug function built-in type microcomputer that is capable of restricting outputs only to necessary information to prevent necessary information from being terminated halfway and performing a more accurate tracing in real time, when an output signal line having a bit width fewer than a bit width of an inner bus is used for tracing information on the inner bus. The debug function built-in type microcomputer can be provided with registers that temporarily store bus information prepared for each target bus to be traced, a register writing condition judgment circuit that controls temporary storage of the bus information in the registers according to a trace condition stored in a setting register, and a multiplexer that selects and outputs the bus information temporarily stored in the registers.

Abstract: The invention provides a debug function built-in type microcomputer that is capable of creating a readily analyzable debug environment and compressing output information, even when an output signal line having a bit width fewer than a bit width of a command bus is used to trace contents on the command bus. In a debug function built-in type microcomputer, a DBG (debug unit) outputs information to be traced, and status information indicative of contents of the information to be traced from a status generation circuit.