Has the priority mediation which is improved the bus master mediation circuit

摘要

PURPOSE: To enable a retrieved request to have high priority through the next mediation by not changing the priority which is interrupted although access to a bus has been permitted. ;CONSTITUTION: When retrying a master, a saved priority bit is saved into a flip-flop 616. When the master is not retried, however, that master loses the priority over all the masters. Therefore, when it is necessary to retry the master, the priority over all the other masters is held and in order to recover the bus at the next request time, priority access is provided. When that master is not retrieved, however, the priority is abandoned for all the masters. A priority decode logic corrected by AND and OR gates 624, 626, 628 and 630 is used, so that only the requested master is allowed to participate in the mediation.;COPYRIGHT: (C)1995,JPO