US 4,190,821 AGranted

Self-healing loop communications system

AssigneeBurroughs Corporation

InventorThomas R. Woodward

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Abstract

Primary and back-up closed loop unidirectional transmission lines transmit self-clocking data streams and null data, respectively, in opposite directions to a plurality of loop interface units (LIUs) connected to the primary and back-up lines. To protect against failure of the entire system due to a break in the primary and/or back-up lines or failure of one of the loop interface units, each loop interface unit can detect a signal loss on the primary or back-up transmission line and wrap signal flow to bypass the detected fault. After wrapping around a detected fault, an LIU then creates a failure on the non-failing line causing an analogous wraparound in the LIU on the other side of the actual failure. After error recovery, there is then a complete loop connecting all non-failing loop interface units, although it is twice as long as before the signal loss was detected. Also disclosed is an alternate embodiment in which a microprocessor and attached external device are interconnected to a similar loop structure.

Claims24

Dependent claims

A self-healing loop communications system comprising:

a primary closed loop unidirectional transmission line for transmitting signals in a first direction;
a back-up closed loop unidirectional transmission line for transmitting signals in a second direction opposite to said first direction;
first means coupled to said primary and back-up lines for providing on one of said primary and back-up lines a serial data stream in a self-clocking code and further for providing on said other of said primary and back-up lines a stream of self-clocking idle data;
and
a plurality of loop interface units coupled to said primary and back-up lines, each of said loop interface units including
second means connected to said one of said primary and back-up lines for detecting a first fault in said one of said primary and back-up lines,
third means connected to said other of said primary and back-up lines and said second means and responsive to said second means for switching between a first state wherein that one of said loop interface units is coupled to said other of said primary and back-up lines and a second state wherein that one of said loop interface units is uncoupled from said other of said primary and back-up lines, and
fourth means connected to said one of said primary and back-up lines and said second and third means and responsive to said second means for switching between a third state wherein that one of said loop interface units is coupled to said one of said primary and back-up lines and a fourth state wherein that one of said loop interface units is uncoupled from said one of said primary and back-up lines and said primary and back-up lines are interconnected and transferring said signals on said back-up and primary lines to the other of said back-up and primary lines, said primary and back-up lines thereby cooperating to provide a first new closed loop unidirectional transmission line to bypass said first fault.

5 more elements

A self-healing loop communications system for interfacing a plurality of external devices to each other in a loop structure, comprising:

a primary closed loop unidirectional transmission line for transmitting signals in a first direction;
a back-up closed loop unidirectional transmission line for transmitting signals in a second direction opposite to said first direction;
first means coupled to said primary and back-up lines for providing on one of said primary and back-up lines a serial data stream in a self-clocking code and further for providing on said other of said primary and back-up lines a stream of self-clocking idle data;
and
a plurality of nodes coupled to said primary and back-up lines, each of said nodes including
loop interface means for transferring digital information to and from said primary and back-up lines,
processor means connected to said loop interface means for processing said digital information and further for controlling said loop interface means,
memory means connected to said processor means for storing programs and data for use by said processor means, and
device interface means connected to said processor means and one of said external devices for interfacing said processor means with said external device.

6 more elements

Dependencies are inferred from the claim text.