Look-ahead priority arbitration system and method
First Claim
1. An arbitration system for selecting a single request for transmission to one output node from multiple such requests for transfer made by contending input nodes, said arbitration system comprising:
- a plurality of input queues one associated with each of said contending input nodes, each such input queue for storing, in a plurality of stages, requests from its associated input node, at least two of said stages in each queue being separately accessible output stages, one stage being a head of queue stage and another stage being a next to head of queue stage;
arbitration means connected to both output stages of each queue for selecting, during a single selection cycle, a request from either a head of queue stage or a next to head of queue stage of one of said queues in accordance with a selection algorithm, said arbitration means including primary selection means for selecting a request from a head of queue stage if such a request is present in any said head of queue stage and secondary selection means for selecting a request from a next to head of queue stage in a queue selected by said algorithm in the absence, during said selection cycle, of any such request in any head of queue stage of said queues.
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Abstract
An improved arbitration system is disclosed for arbitrating signals at a plurality of input nodes to output nodes where each input node can access any output node. The system includes a FIFO (first-in-first-out) input queue for each node and means for arbitrating the top of each queue for providing the arbitrated output to a given node and means when the top of the input queue has no request for a given node arbitrating the requests from the next to the top entry of the input queues and providing the data from the next to top entry associated with the arbitrated request to the given node.
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Citations
9 Claims
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1. An arbitration system for selecting a single request for transmission to one output node from multiple such requests for transfer made by contending input nodes, said arbitration system comprising:
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a plurality of input queues one associated with each of said contending input nodes, each such input queue for storing, in a plurality of stages, requests from its associated input node, at least two of said stages in each queue being separately accessible output stages, one stage being a head of queue stage and another stage being a next to head of queue stage; arbitration means connected to both output stages of each queue for selecting, during a single selection cycle, a request from either a head of queue stage or a next to head of queue stage of one of said queues in accordance with a selection algorithm, said arbitration means including primary selection means for selecting a request from a head of queue stage if such a request is present in any said head of queue stage and secondary selection means for selecting a request from a next to head of queue stage in a queue selected by said algorithm in the absence, during said selection cycle, of any such request in any head of queue stage of said queues. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for transferring, one at a time, to a single output node, sets of signals, made up of a request signal and data signals, said sets of signals being supplied by a plurality of requesting nodes contending for such transfer said method comprising the steps of:
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a) placing said sets from each requesting node in stages of separate queues in the order in which said sets are to be transferred to the output node; b) simultaneously selecting for transfer from said queues a first output from stages containing highest order requests for transfer to said one output node and a second output from stages containing next highest order requests for transfer to said one output node; c) detecting the presence or absence of a request for transfer in any of said stages of said queues for containing the highest order requests; d) transferring to said one output node data signals in said first output if the presence of a request for transfer to said one output node is detected by step c) and transferring to the output node data signals in said second output if the presence of a request is not detected by step c). - View Dependent Claims (8, 9)
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Specification