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Apparatus and method are described for a data communication network which has topological independence, low variance service time distributions, potentially guaranteed maximum time to transmit, easy expansion and high error tolerance. The network access control is fundamentally a permit (token) base

Apparatus and method are described for a data communication network which has topological independence, low variance service time distributions, potentially guaranteed maximum time to transmit, easy expansion and high error tolerance. The network access control is fundamentally a permit (token) based system. This yields highly efficient utilization of the channel and powerful control over priorities on access to the network. In addition, a contention based scheme is provided to enable error recovery, startup, and restart to be fast and reliable.

대표청구항 ▼

1. A data communication system comprising: a communication medium including a plurality of taps for making connection therewith, said medium providing for the coupling of signals along said taps; a plurality of transceivers connected by respective ones of said taps to said medium, each of said t

1. A data communication system comprising: a communication medium including a plurality of taps for making connection therewith, said medium providing for the coupling of signals along said taps; a plurality of transceivers connected by respective ones of said taps to said medium, each of said transceivers including means for transmitting a signal into said medium and means for receiving a signal communicated via said medium, said transceivers and said medium constituting a communication network; interface means coupled to respective ones of said transceivers for interfacing said transceivers with utilization devices; each of said transceivers including permit means comprising circuitry for generating a network-access permit in the form of a digital signal, and means for passing the permit via said transmitting means and said medium from one of said transceivers to another of said transceivers; each of said transceivers further comprising permit-checking means for enabling transmission by said transmission means, in any one of said transceivers said enabling of said transmission being in response to the presence of said permit at said one transceiver; each of said transceivers further comprising means for detecting errors when more than one transceiver attempts to utilize said medium at the same time, said error detecting means signaling when a transceiver assumes ownership of the permit, and logic means including means to reestablish error free network communication; said logic means in each of said transceivers designating a sequence of communication among the transceivers while permitting an addition and a deletion of transceivers to the network without need to reinitialize other ones of the transceivers in the network whereby any one of said transceivers is enabled to transmit a message to another of said transceivers only upon the presence of said permit at said one transceiver so as to prevent a concurrent transmission of messages by more than one receiver. 2. A data communication system comprising: a communication medium including a plurality of taps for making connection therewith, said medium providing for the coupling of signals along said taps; a plurality of transceivers connected by respective ones of said taps to said medium, each of said transceivers including means for transmitting a signal into said medium and means for receiving a signal communicated via said medium, said transceivers and said medium constituting a communication network; interface means coupled to respective ones of said transceivers for interfacing said transceivers with utilization devices; each of said transceivers including permit means comprising circuitry for generating a network-access permit in the form of a digital signal, and means for passing the permit via said transmitting means and said medium from one of said transceivers to another of said transceivers; each of said transceivers further comprising permit-checking means for enabling transmission by said transition means, in any one of said transceivers said enabling of said transmission being in response to the presence of said permit at said one transceiver; whereby any one of said transceivers is enabled to transmit a message to another of said transceivers only upon the presence of said permit at said one transceiver so as to prevent a concurrent transmission of messages by more than one receiver; and wherein any one of said transceivers, said permit means comprises: activity sensing means for sensing the presence of a signal propagating in said medium, said sensing means being responsive to the absence of a permit transmission in said medium during a predetermined interval of time to designate the failure of a transceiver to pass the permit; said sensing means including collision detecting means coupled to said transmitting means for detecting the simultaneous presence of both a transmitted signal of said transmitting means and a medium signal propagating in said medium, said simultaneous presence being a collision, said collision detecting means providing a collision signal upon detection of a collision, and wherein such collision occurs during a contention mode of access to said network initiated by said sensing means upon said designation of the failure, and during which mode of access said permit circuitry is generating a permit, said permit means including collision logic means for interrupting generation of a permit by said circuitry in response to said collision signal. 3. A system according to claim 2 wherein said permit passing means includes means for selecting one or more of said plurality of transceivers for receipt of the permit in accordance with a predesignated scheme of priority. 4. A system according to claim 1 wherein said permit-passing means of one of said transceivers addresses a plurality of other ones of said transceivers, sequentially, for receiving said permit on a non-priority basis upon the conclusion of a transmission by said transmitting means. 5. A data communication system comprising: a communication medium including a plurality of taps for making connection therewith, said medium providing for the coupling of signals along said taps; a plurality of transceivers connected by respective ones of said taps to said medium, each of said transceivers including means for transmitting a signal into said medium and means for receiving a signal communicated via said medium, said transceivers and said medium constituting a communication network; interface means coupled to respective ones of said transceivers for interfacing said transceivers with utilization devices; each of said transceivers including permit means comprising circuitry for generating a network-access permit in the form of a digital signal, and means for passing the permit via said transmitting means and said medium from one of said transceivers to another of said transceivers; each of said transceivers further comprising permit-checking means for enabling transmission by said transition means, in any one of said transceivers said enabling of said transmission being in response to the presence of said permit at said one transceiver; whereby any one of said transceivers is enabled to transmit a message to another of said transceivers only upon the presence of said permit at said one transceiver so as to prevent a concurrent transmission of messages by more than one receiver; and wherein said permit-passing means of one of said transceivers addresses a predesignated one of said transceivers for receiving said permit on a priority basis transfer upon the conclusion of a transmission by said transmitting means, thereby providing a prioritized access to said communication medium by utilization devices which may be coupled to said transceivers. 6. A data communication system comprising: a communication medium including a plurality of taps for making connection therewith, said medium providing for the coupling of signals along said taps; a plurality of transceivers connected by respective ones of said taps to said medium, each of said transceivers including means for transmitting a signal into said medium and means for receiving a signal communicated via said medium, said transceivers and said medium constituting a communication network; interface means coupled to respective ones of said transceivers for interfacing said transceivers with utilization devices; each of said transceivers including permit means comprising circuitry for generating a network-access permit in the form of a digital signal, and means for passing the permit via said transmitting means and said medium from one of said transceivers to another of said transceivers; each of said transceivers further comprising permit-checking means for enabling transmission by said transition means, in any one of said transceivers said enabling of said transmission being in response to the presence of said permit at said one transceiver; whereby any one of said transceivers is enabled to transmit a message to another of said transceivers only upon the presence of said permit at said one transceiver so as to prevent a concurrent transmission of messages by more than one receiver; and wherein each of said transceivers includes acknowledgement means coupled to said receiving means for generating an acknowledgement signal upon receipt of the permit; and wherein upon the failure of an addressed receiver to acknowledge receipt of the permit within a predesignated amount of time, said permit passing means addresses another of said transceivers. 7. A system according to claim 1 further comprising timing means coupled between said transmitting means and said permit passing means for enabling said transmitting means to transmit data during an interval of time of predetermined duration followed by activation of said permit passing means to pass the permit. 8. A system according to claim 7 wherein said timing means includes means for adjusting said predetermined duration of said interval. 9. A system according to claim 1 wherein each of said transceivers includes buffer storage means for storing data provided by a utilization device prior to transmission of such data via said medium, thereby providing an asynchronous communication capability. 10. A data communication system comprising: a communication medium including a plurality of taps for making connection therewith, said medium providing for the coupling of signals along said taps; a plurality of transceivers connected by respective ones of said taps to said medium, each of said transceivers including means for transmitting a signal into said medium and means for receiving a signal communicated via said medium, said transceivers and said medium constituting a communication network; interface means coupled to respective ones of said transceivers for interfacing said transceivers with utilization devices; each of said transceivers including permit means comprising circuitry for generating a network-access permit in the form of a digital signal, and means for passing the permit via said transmitting means and said medium from one of said transceivers to another of said transceivers; each of said transceivers further comprising permit-checking means for enabling transmission by said transmission means, in any one of said transceivers said enabling of said transmission being in response to the presence of said permit at said one transceiver; whereby any one of said transceivers is enabled to transmit a message to another of said transceivers only upon the presence of said permit at said one transceiver so as to prevent a concurrent transmission of messages by more than one receiver; and wherein each of said transceivers includes acknowledgement means coupled to said receiving means for generating an acknowledgement signal at the conclusion of the reception of a message. 11. A data communication system comprising: a communication medium including a plurality of taps for making connection therewith, said medium providing for the coupling of signals along said taps; a plurality of transceivers connected by respective ones of said taps to said medium, each of said transceivers including means for transmitting a signal into said medium and means for receiving a signal communicated via said medium, said transceivers and said medium constituting a communication network; interface means coupled to respective ones of said transceivers for interfacing said transceivers with utilization devices; each of said transceivers including permit means comprising circuitry for generating a network-access permit in the form of a digital signal, and means for passing the permit via said transmitting means and said medium from one of said transceivers to another of said transceivers; each of said transceivers further comprising permit-checking means for enabling transmission by said transition means, in any one of said transceivers said enabling of said transmission being in response to the presence of said permit at said one transceiver; whereby any one of said transceivers is enabled to transmit a message to another of said transceivers only upon the presence of said permit at said one transceiver so as to prevent a concurrent transmission of messages by more than one receiver; and wherein a common address is provided for the simultaneous addressing of a plurality of said transceivers, and wherein said permit-passing means includes means for inserting said common address in a digital signal packet including said permit. 12. A system according to claim 11 wherein said plurality of transceivers includes all of said transceivers. 13. A data communication system comprising: a communication medium including a plurality of taps for making connection therewith, said medium providing for the coupling of signals along said taps; a plurality of transceivers connected by respective ones of said taps to said medium, each of said transceivers including means for transmitting a signal into said medium and means for receiving a signal communicated via said medium, said transceivers and said medium constituting a communication network; interface means coupled to respective ones of said transceivers for interfacing said transceivers with utilization devices; each of said transceivers including permit means comprising circuitry for generating a network-access permit in the form of a digital signal, and means for passing the permit via said transmitting means and said medium from one of said transceivers to another of said transceivers; each of said transceivers further comprising permit-checking means for enabling transmission by said transition means, in any one of said transceivers said enabling of said transmission being in response to the presence of said permit at said one transceiver; whereby any one of said transceivers is enabled to transmit a message to another of said transceivers only upon the presence of said permit at said one transceiver so as to prevent a concurrent transmission of messages by more than one receiver; and wherein a first of said transceivers comprises multifunction circuitry utilized via a time shared process in the performance of each of a plurality of functions, the permit means in a second of said transceivers comprising means for inserting a "request-to-submit" signal in a packet containing said permit, said packet further including the address of said first transceiver, and wherein said first transceiver includes means for generating a "ready-to-receive" signal in reponse to receipt of the "request-to-transmit" signal when said multifunction circuitry is available for receiving a message from said second transceiver. 14. A system according to claim 13 wherein said multifunction circuitry is a memory time-shared among a plurality of functions. 15. A communication system comprising: a set of stations; a communication medium interconnecting said stations, each of said stations including transceiver means for transmitting signals on said medium to other ones of said stations and for receiving signals via said medium from other ones of said stations; each of said transceiver means including enabling means responsive to a permit signal for the enabling of the transmission of a signal into said medium by the transceiver; and wherein said system further comprises means for passing said permit signal from station to station among said set of stations to insure transmission of signals via said medium by only one station at a time; means for detecting failures wherein multiple stations attempt to use the system, and also failures characterized by a lack of attempt by any station to use said system, and logic means coupled to said failure detecting means including means to reestablish error-free communication; and said logic means designating a sequence of communication among the stations while permitting an addition and a deletion of stations on the system without need to reinitialize other ones of the stations. 16. A system according to claim 15 further comprising timing means for activating said passing means at the conclusion of an interval of transmission by one of said stations. 17. A system according to claim 15 wherein one of said transceiver means includes means for generating a permit signal for transference of a permit signal to another of said stations. 18. A data communication system comprising: a set of stations; a communication medium interconnecting said stations, each of said stations including transceiver means for transmitting signals on said medium to other ones of said stations and for receiving signals via said medium from other ones of said stations; each of said transceiver means including enabling means responsive to a permit signal for the enabling of the transmission of a signal into said medium by the transceiver; and wherein said system further comprises means for passing said permit signal from station to station among said set of stations to insure transmission of signals via said medium by only one station at a time, one of said transceiver means including means for generating a permit signal for transference of a permit signal to another of said stations; and wherein each of said transceiver means includes means for addressing another of said stations and means for decoding an address to enable the passing of a permit signal to a predesignated station on a priority basis. 19. A fault-tolerant method of communicating data signals in a network of stations that is easily expanded or altered, and is connected by a communication medium comprising: generating a permit; passing said permit via said medium to various ones of said station; retaining said permit at a station from which a data transmission is to be made via said medium to another of said stations; enabling said transmission via said permit; releasing said permit to another station; detecting errors when multiple stations attempt to use the network and establishing sole ownership of the permit; detecting errors when no station attempts to use the network and establishing a permit with a single station; detecting the addition of a new station to the network and passing the permit to said new station at an appropriate time; detecting a deletion of a station from the network and passing the permit to the next appropriate station in the network; whereby each of a plurality of said stations is enabled to transmit, one-by-one so as to avoid collision among data transmissions from respective ones of said stations. 20. A method according to claim 19 further comprising the storing of data prior to a transmission so as to have the data ready for transmission when the permit is received. 21. A method of communicating data signals in a network of stations connected by a communication medium comprising: generating a permit; passing said permit via said medium to various ones of said station; retaining said permit at a station from which a data transmission is to be made via said medium to another of said stations; enabling said transmission via said permit; releasing said permit to another station, whereby each of a plurality of said stations is enabled to transmit, one-by-one so as to avoid collision among data transmissions from respective ones of said stations; and further comprising a step of addressing a specific one of said stations for receipt of the permit in a priority sequence of data transmissions.