Data transmission system of the star type with enablement passing
First Claim
1. A data communication system comprising a plurality of stations between which communication is to take place and coupling means,each station being connected to the coupling means by an inward channel for the transmission of data from the station to the coupling means and an outward channel for the transmission of data from the coupling means to the station, the channels of each station being distinct from those of every other station,each station having means for detecting an entitlement indication received over its inward channel, which indication confers an entitlement on the station to transmit user data,user data being transmitted in frames, the stations being in a predetermined cyclic sequence in which each station has a successor station, andthe coupling means comprising:
- means responsive to receipt of a frame over the inward channel from any station for retransmitting that frame on to the outward channels of the other stations, whereby the frame is broadcast to those other stations, andmeans responsive to receipt of an indication from any station, indicating that the station is relinquishing its entitlement to transmit user data, for transmitting an entitlement indication solely on to the outward channel of that station'"'"'s successor station.
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Accused Products
Abstract
A network provides communication between end units (1). Each end unit (1) received an entitlement to transmit in the form of a go-ahead. It is then able to transmit a frame of user data, which is broadcast by a central unit (7) to all other end units (1). When the end unit (1) transmitting the frame wishes to relinquish its entitlement to transmit it regenerats the go-ahead, which is passed by the central unit (7) to the next end unit (1) taking them in a predtermined cyclic sequence. The system allows frames to be acknowledged: the central unit (7) collects acknowledgements from end units (1) receiving the frame successfully, and when every expected station has acknowledged, returns an acknowledgement to the source end unit (1). Central units (1) may be combined to form larger systems.
35 Citations
11 Claims
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1. A data communication system comprising a plurality of stations between which communication is to take place and coupling means,
each station being connected to the coupling means by an inward channel for the transmission of data from the station to the coupling means and an outward channel for the transmission of data from the coupling means to the station, the channels of each station being distinct from those of every other station, each station having means for detecting an entitlement indication received over its inward channel, which indication confers an entitlement on the station to transmit user data, user data being transmitted in frames, the stations being in a predetermined cyclic sequence in which each station has a successor station, and the coupling means comprising: -
means responsive to receipt of a frame over the inward channel from any station for retransmitting that frame on to the outward channels of the other stations, whereby the frame is broadcast to those other stations, and means responsive to receipt of an indication from any station, indicating that the station is relinquishing its entitlement to transmit user data, for transmitting an entitlement indication solely on to the outward channel of that station'"'"'s successor station. - View Dependent Claims (2, 3, 4)
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- 5. A coupling element for a data communications system comprising a plurality of ports each comprising an input for connection to an inward channel for transmitting data to the coupling element and an output for connection to an outward channel for transmitting data from the coupling element, the element comprising means for retransmitting a frame received at any input from the output of every other port in a predetermined group of ports the said group including the port at whose input the frame is received and means for transmitting, on receipt of an indication derived from any of the said inputs that an entitlement to transmit has been relinguished, an indication of an entitlement to transmit from a predertermined successor port in the said group.
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11. A method of data communication between a pluraltiy of stations, the stations receiving in turn an entitlement indication which indication confer an entitlement on the station to transmit user data, the said entitlement being passed from station to station in a predetermined sequence in such a manner that each of the said stations periodically receives the said entitlement and user data being transmitted in frames each of which is received by all other of the said stations in which method:
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each station is connected for data transmission to a common coupling means, which means is capable of distinguishing between a frame containing user data and an indication provided by a station that it relinquishes an entitlement to transmit, the coupling means distributes a separate copy of a frame received from any station to every other of the said stations, and the coupling means on receipt of the said indication of relinquishment of entitlement from any station transmits the said entitlement indication solely to a predetermined successor station among the said stations.
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Specification