Interrupt control unit

An interrupt control unit for use with interrupt sources, comprising:

• a plurality of interrupt memory circuits each for storing data representing a state of an interrupt processing request for each interrupt source,
• interrupt request circuits each being provided for and operatively coupled to each interrupt request memory circuit,
• interrupt processing mode indication circuits each being provided for and operatively coupled to each interrupt request circuit for storing interrupt processing mode information,
• priority level indication circuits each being provided for and operatively coupled to each interrupt request circuit, for storing acknowledgement order information representing priority level data,
• a plurality of search information generating circuits, operatively coupled to said interrupt request circuits, each for generating search information, said search information including interrupt processing mode search information and priority order search information for each of said interrupt request circuits,
• a search information comparison circuit, operatively coupled to the interrupt processing mode indication circuits, the priority level indication circuits and the search information generating circuits, for detecting a state of the interrupt request circuit provided for each interrupt request memory circuit, and for comparing the interrupt processing mode information stored in the interrupt processing mode indication circuits and the acknowledgement order information stored in the priority level indication circuits with the search information generated by the search information generating circuits, by extending a comparison range step by step from a first range including only the interrupt processing mode information, the search information comparison circuit generating an internal interrupt request signal when a coincidence is obtained in the comparison range, and
• control means, operatively coupled to said search information comparison circuit and the search information generating circuit, for updating the interrupt processing mode search information and the priority order search information in the search information generating circuit in accordance with a result of the comparison by the search information comparison circuit, an output of the search information comparison circuit being monitored by said control means, and
• when data of the interrupt processing mode search information of the search information generating circuit coincides with data of one of the interrupt processing mode indication circuits, an internal interrupt receipt signal is generated by said control means in response to the interrupt request signal generated by the search information comparison circuit, and
• when data of the interrupt processing mode search information of the search information generating circuit does not coincide with data of any one of the interrupt processing mode indication circuits, the interrupt processing mode search information is updated and an internal interrupt receipt signal is generated by said control means in response to the internal interrupt request signal generated by the search information comparison circuit when data of the priority order search information of the search information generating circuit perfectly coincides with data of the acknowledgement order information of one of the priority order indication circuits,
• wherein said search information generating circuit includes means for discriminating said interrupt processing mode search information prior to the priority order search information.