| 摘要 |
A ring topology based architecture for a local area network. The transmission medium is unshielded twisted-pair wire. A set of two such twisted-pairs are used to connect the nodes of the network together, with the transmit twisted-pair wires from one node being connected to the receive twisted-pair wires of the next node. When a node of the network is powered up, a relay is opened which disconnects the incoming receive lines from the outgoing transmit lines. This brings the node on line. The relay is controlled via software command and a timer which is used to take a preceding node off-line for a predetermined period in the event jabber from that node is detected. A 16 byte FIFO bypass built into the medium access control hardware of the system is used to reduce the ring latency which normally results from the need to store entire data packets at each node, prior to the packet being forwarded. The FIFO bypass is used to detect the source and destination addresses for the data packets, and to determine if a packet should be forwarded along the ring. If a node is transmitting a packet when it receives a new packet, the incoming data is buffered until the current transmission is completed. This avoids the collision problem common in bus topologies.
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