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Lockhead bus arbitration system with override of conditional access grants by bus cycle extensions for multicycle data transfers

  • US 5,034,883 A
  • Filed: 02/23/1990
  • Issued: 07/23/1991
  • Est. Priority Date: 05/01/1987
  • Status: Expired due to Term
First Claim
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1. A node, coupled to a plurality of request lines corresponding exclusively to the node, and coupled to each of a plurality of other nodes by a pended bus, wherein a node becomes a transmitter in order to transfer a message, including a command or including return data, on the pended bus during one or more cycles of the bus, wherein a commander node initiates a transaction on the pended bus by making a command transfer, wherein a responder node completes the transaction on the pended bus by making a return data transfer in response to the command transfer, and wherein a node can access the pended bus after the commander node initiates a transaction and before the responder node completes the transaction, the node comprising:

  • bus request means, coupled to the plurality of request lines corresponding exclusively to the node, for generating a bus request and transmitting the bus request on one of the corresponding plurality of request lines at times when a command is to be transferred from the node onto the bus, and for generating a bus request and transmitting the bus request on another one of the corresponding plurality of request lines at times when return data is to be transferred from the node onto the bus;

    extend request means for generating an extend request for the node at times when the node requires more than one bus cycle to transfer a message;

    extend cycle means, coupled to the extend request means, for activating an extend bus cycle signal when the node becomes a transmitter at times when the extend request for the node is present; and

    bus access means, for obtaining control of the pended bus to enable the node to become a transmitter during an initial access cycle, in response to receipt of a conditional bus grant, at times when an extend bus cycle signal is not activated by any of the other nodes, and for maintaining control of the pended bus to enable the node to remain the transmitter during bus cycles succeeding the initial access cycle at times when the extend bus cycle signal is activated by the node.

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