| 摘要 |
<p>PURPOSE:To reduce the contention arbitration time with respect to an access request by providing this time a border placing lowest priority to a request occurrence source obtaining precedingly access permission and dividing the arrangement of priority classes into two groups. CONSTITUTION:Selection priority of access request occurrence sources R1-R16 is arranged fixedly in advance in a ring form and the arrangement is divided into two groups A,B by providing a border setting the priority of any of the access request occurrence sources R1-R16 obtaining an access right just precedingly to a lowest priority. First arbitration circuits CT1-CT16 select a request with higher priority for each time slot in each of the groups A, B. Second arbitration circuits CTa1-CTa4, CTb1-CTb4 select a highest priority for each time slot and give an access light thereto by taking it into account that a source obtaining an access right just precedingly corresponding to a ring whose request is selected by any of the circuits CT1-CT16 is set to a source with a lowest priority. Thus, the access request is subjected to parallel processing while being divided in this way to reduce the contention arbitration time.</p> |
