Abstract: When controlling a clock to a central processing unit, it is naturally preferable not to change existing circuits which are not related to the control of the clock. A clock control circuit inputs a clock input CLK, and generates a clock output CLKOUT for the central processing unit. In the clock control circuit, CLK is masked by a write operation to an internal register. CLKOUT is stopped by the mask operation. The mask operation is carefully designed to be initiated when the internal cycle of the central processing unit is detected. The resumption of the clock is initiated by interrupts.

Abstract: There are provided a plurality of priority register circuits which specify respective priorities for a plurality of logical regions, so that the priority of the logical regions can be varied. Even if there is a change in a memory map, the degree of freedom for setting changes is high compared to a case when the priority is fixed. Thus, the purpose can be attained more likely by a processing of changing the priority where the processing involves comparatively low number of bits.

Abstract: When controlling a clock to a central processing unit, it is naturally preferable not to change existing circuits which are not related to the control of the clock. A clock control circuit inputs a clock input CLK, and generates a clock output CLKOUT for the central processing unit. In the clock control circuit, CLK is masked by a write operation to an internal register. CLKOUT is stopped by the mask operation. The mask operation is carefully designed to be initiated when the internal cycle of the central processing unit is detected. The resumption of the clock is initiated by interrupts.

Abstract: There are provided a plurality of priority register circuits which specify respective priorities for a plurality of logical regions, so that the priority of the logical regions can be varied. Even if there is a change in a memory map, the degree of freedom for setting changes is high compared to a case when the priority is fixed. Thus, the purpose can be attained more likely by a processing of changing the priority where the processing involves comparatively low number of bits.