US Patent 7739437 Access arbiter and arbitrable condition verification device

A priority control value, which is smaller as the priority of access by each of requesters is higher, decreases with the lapse of time when an access request is issued. When the access is completed, the priority control value increases by a priority decrease value (PERIOD). When there is no access request, the priority control value decreases to a reference priority value (TMIN) and is then maintained at the reference priority value. Access permission is given to the one of the requesters issuing requests which has the smallest priority control value. As a result, proper arbitration is performed at a high speed with a simple hardware configuration.