| 摘要 |
An improved arbitration technique for a computer network system in which multiple nodes communicate using a shared bus. Each node in the system is assigned an initial arbitration number, N+1, where N is the node number assigned to the node. The arbitration number is the number of quiet slots a node must count before trying to transmit on the system bus. The length of a quiet slot is determined by a particular system's electrical characteristics. Each node in the system monitors a carrier signal on the system bus, the presence of which indicates that a node is transmitting on the bus. Upon detecting the absence of the carrier signal, each node in the system begins to count quiet slots. Every time a node counts an additional quiet slot, it checks to see if the count matches its arbitration number. If the two values are equal, the node checks to see if it has a transmit request, and begins to transmit a message on the system bus if a transmit request is present. If a node detects the presence of the carrier signal before the number of counted quiet slots equals its arbitration number, a different node has won the arbitration for the system bus. All other nodes therefore stop counting quiet slots and change their arbitration numbers. The arbitration number is changed by subtracting from a node's arbitration number either the number of quiet slots counted by a winning node or the node number of the winning node, and performing modulo (M) on the result, where M is the number of nodes in the system.
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