| 摘要 |
A common electrical bus for coupling a plurality of units in a data processing system for the transfer of information therebetween. The units are coupled in a priority arrangement which is distributed thereby providing priority logic in each of the units and allowing bus transfer cycles to be generated in an asynchronous manner. Each of the units includes priority logic which includes logic elements for requesting a bus cycle, such request being granted if no other higher priority unit has also requested a bus cycle. The request for and an indication of the grant of the bus cycle are stored in each unit so requesting and being granted the bus cycle respectively, only one such unit being capable of having the grant of a bus cycle at any given time, whereas any number of such units may have its request pending at any particular time. Upon completion of the bus cycle, the priority logic is coupled to deactivate the indication of the grant of the bus cycle, and in response thereto, to deactivate the request of the particular unit which has just had access to the bus.
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