Patent ID: 7657681

Claim:
An arbitration circuit, comprising: a plurality of function processing circuits; a shared circuit shared among the function processing circuits; and a shared-circuit-use-arbitrating circuit, wherein the shared circuit is used exclusively by one of the function processing circuits at a time, each of the function processing circuits issues a usual use request to use the shared circuit and a use reservation request prior to the usual use request, and further issues a sporadic access request without issuing the use reservation request, the shared-circuit-use-arbitrating circuit receives the usual use requests, the sporadic access requests, and the use reservation requests from the function processing circuits, arbitrates between a use reservation request from one of the function processing circuits and a sporadic access request from another function processing circuit, and preferentially allows either one of the usual use request to be issued after the use reservation request, and the sporadic access request, to use the shared circuit, the shared-circuit-use-arbitrating circuit includes an automatic reservation issuing circuit for automatically issuing a use reservation request at established periods for one of the function processing circuits periodically using the shared circuit, and after one of the function processing circuits has accessed the shared circuit, the shared-circuit-use-arbitrating circuit reduces a priority level of this function processing circuit which has accessed the shared circuit, and then, when an access request from this function processing circuit is reserved, the shared-circuit-use-arbitrating circuit increases the priority level of this function processing circuit.