Local area data communication network
First Claim
1. A data communication network over which data handling devices connected thereto can transmit and receive messages among themselves, comprisingbus means, anda plurality of subnetworks, each subnetwork comprisinginterface means for connecting a plurality of said devices to said subnetwork, andconcentrator means for connecting said interface means to said bus means,said interface means and said concentrator means further comprisingtransceiver means for transmitting, to said bus means and to devices connected to said subnetwork, messages originating from devices connected to said subnetwork, and for receiving from said bus means messages originating from other said subnetworks,collision avoidance means for monitoring transmission attempts by said devices connected to said subnetwork, detecting competing such transmission attempts that would create a collision on said subnetwork, and, upon such detection, permitting a selected such attempt to enter said subnetwork while preventing other such attempts from entering said subnetwork, andcollision detection means for monitoring said bus means and preventing all said attempted transmissions from entering said bus means when a message from another said subnetwork is present on said bus means.
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Accused Products
Abstract
A data communication network over which data handling devices can transmit and receive packets among themselves having a bus, a number of subnetworks (each having interfaces for connecting a number of devices to each subnetwork), a concentrator for connecting each interface to the bus, each concentrator having a transceiver for transmitting, to the bus and to devices connected to each subnetwork, packets originating from devices within a subnetwork (transmitted packets), and for receiving from the bus packets originating from other subnetworks (received packets), collision avoidance circuitry for monitoring transmission attempts by devices connected to the subnetwork, for detecting competing transmission attempts that would create a collision on the subnetwork, and, upon such detection, permitting a selected attempt to enter the subnetwork, while preventing other attempts from entering it, collision detection circuitry for monitoring the bus and preventing all attempted transmissions from entering the bus whenever a packet from another subnetwork is present on the bus. In another aspect the interface means and the concentrator means include a network interface unit and a further interface unit.
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Citations
13 Claims
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1. A data communication network over which data handling devices connected thereto can transmit and receive messages among themselves, comprising
bus means, and a plurality of subnetworks, each subnetwork comprising interface means for connecting a plurality of said devices to said subnetwork, and concentrator means for connecting said interface means to said bus means, said interface means and said concentrator means further comprising transceiver means for transmitting, to said bus means and to devices connected to said subnetwork, messages originating from devices connected to said subnetwork, and for receiving from said bus means messages originating from other said subnetworks, collision avoidance means for monitoring transmission attempts by said devices connected to said subnetwork, detecting competing such transmission attempts that would create a collision on said subnetwork, and, upon such detection, permitting a selected such attempt to enter said subnetwork while preventing other such attempts from entering said subnetwork, and collision detection means for monitoring said bus means and preventing all said attempted transmissions from entering said bus means when a message from another said subnetwork is present on said bus means.
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11. A data communication network over which data handling devices connected thereto can transmit and receive messages among themselves, comprising
bus means, and a plurality of subnetworks, each subnetwork comprising interface means for connecting a plurality of said devices to said subnetwork, and concentrator means for connecting said interface means to said bus means, said interface means and said concentrator means further comprising transceiver means for transmitting, to said bus means and to devices connected to said subnetwork, messages originating from devices connected to said subnetwork, and for receiving from said bus means messages originating from other said subnetworks, collision avoidance means for monitoring transmission attempts by said devices connected to said subnetwork, for detecting competing such transmission attempts that would create a collision on said subnetwork, collision signal generating means for generating a collision signal upon detecting competing transmission attempts, and a network interface unit associated with each said device to cause withdrawal of an attempted transmission by said device upon receipt of a said collision signal, and a transmit channel over which messages originating with said subnetwork are transmitted to said bus, a receive channel over which received messages are transmitted to devices connected to said subnetwork, a further interface unit intermediate said network interface unit and said concentrator, said network further comprising a first transmit connector over which transmitted messages pass from said network interface unit to said further interface unit, a receive connector over which received messages pass from said further interface unit to said network interface unit, a collision signal connector over which said collision signals pass from said further interface unit to said network interface unit, a second transmit connector over which transmitted messages pass from said further interface unit to said transmit channel, a combined receive and collison signal connector over which said collision signals pass from said concentrator to said further interface unit, and over which said received messages pass from said receive channel to said further interface unit, and demultiplexing means in said further interface unit for routing collison signals to said collision signal connector and received messages to said receive connector.
Specification