Method and apparatus for detecting a faulty computer in a multicomputer system

Abstract

In a method of controlling a multicomputer system which includes a plurality of computers connected to a common transfer bus, each of the plurality of computers decides whether or not the adjacent computer is abnormal, and the computer which has decided that the adjacent computer is abnormal cuts off this adjacent computer from the transfer bus.

We claim: 
     
       1. A multicomputer system comprising: (a) first and second computers, each of which includes a processor for controlling transmission and reception of data, and a memory for storing data received and to be transmitted;   (b) a common transmission bus;   (c) first and second bus connector means, which are respectively connected to one of said first and second computers and to said common transmission bus and each of which includes gate means for selectively passing a signal to the corresponding computer from said common transmission bus and a signal to be delivered from said corresponding computer to said common transmission bus;   (d) means including at least one first connection line for transmitting data or control signals and which connects said first computer with said first bus connector means;   (e) means including at least one second connection line for transmitting data or control signals and which connects said second computer with said second bus connector means, said gate means in each of said first and second bus connector means being controlled by control signals which are applied from the respective computers to said bus connector means through the respective first and second connection lines, and data delivered from said first computer being transmitted to said second computer through said first connection line, said first bus connector means, said common transmission bus, said second bus connector means and said second connection line;   (f) a third connection line which connects said first computer with said second computer; and   (g) means for transmitting a signal for checking the operative condition of said first and second computers along a closed loop which includes said first computer, said third connection line, said second computer, said second connection line, said second bus connector means, said common transmission bus, said first bus connector means and said first connection line.   
     
     
       2. A multicomputer system according to claim 1, wherein said memory of said each computer has an area for storing a status flag, and said gate means of each bus connector means is controlled by a control signal corresponding to said status flag. 
     
     
       3. A multicomputer system according to claim 1, wherein said memory of said each computer has an area for storing a value corresponding to a predetermined time period, said each computer further includes first timer means for counting a .Iadd.determined lapse .Iaddend.period of time from the reception of a transmission request signal .Iadd.from another computer.Iaddend., and means for sensing a fault in the .Iadd.other .Iaddend.computer on the basis of a comparison between an output of said first timer means and said value corresponding to the predetermined time period. 
     
     
       4. A multicomputer system according to claim 1, wherein said memory of each computer has an area for storing a value corresponding to a predetermined time, and each computer further includes first timer means for counting a time interval from the time that predetermined data is delivered onto said connection line to the time that the data returns back to the same computer, and means for controlling said gate means of each bus connector so that, when an output of said timer means has become greater than the value stored in said area of said memory, no data may be delivered from the particular computer to said common data transmission bus. 
     
     
       5. A multicomputer system according to claim 1, wherein said memory of each computer has an area for storing a value corresponding to a predetermined time, and each computer further includes second timer means for counting a time interval from the time that the signal is delivered to said third connection line of said closed loop to the time that the signal returns back to the same computer, and means for controlling said gate means of said each bus connector so that, when an output of said timer means has become greater than the value stored in said area of said memory, no data may enter the particular computer from at least one direction of said common data transmission bus. 
     
     
       6. A multicomputer system comprising: (a) first and second data transmission buses;   (b) a plurality of computers, each of which includes first and second processors for controlling transmission and reception of data, and a memory for storing data received and to be transmitted;   (c) a group of first bus connector means which are connected respectively to said plurality of computers and to said first data transmission bus, and each of which includes first gate means for controlling passage of data to said first processor of one of said computers from said first data transmission bus and data to be delivered from said first processor to said first data transmission bus;   (d) a group of second bus connector means which are connected respectively to said plurality of computers and to said second data transmission bus, and each of which includes second gate means for controlling passage of data to said second processor of one of said computers from said second data transmission bus and data to be delivered from said second processor to said second data transmission bus;   (e) means including at least one first connection line for transmitting said data or control signals and which connects said first bus connector means with said first processor of one of said computers;   (f) means including at least one second connection line for transmitting said data or control signals and which connects said second bus connector means with said second processor of one of said computers;   (g) a plurality of third connection lines each of which connects a respective first processor of one of said computers with a first processor of another computer;   (h) a plurality of fourth connection lines each of which connects a respective second processor of one of said computers with a second processor of another computer; and   (i) means forming first and second closed loops for checking the operative condition of a computer, each first closed loop including the first processors of two of said computers and the first bus connector means and third connection lines connected to the respective processors, each second closed loop including the second processors of two of said computers and the second bus connector means and fourth connection lines connected to the respective processors.   
     
     
       7. A multicomputer system according to claim 6, wherein said memory of each computer has an area for storing a transfer direction flag, and means for controlling said first gate means or second gate means so as to deliver data from the computer to said first data transmission bus or second data transmission bus in correspondence with said flag. 
     
     
       8. A multicomputer system according to claim 6, wherein said memory of said each computer has a data buffer area, and data received through said first connection line is stored in said area and is thereafter delivered from the computer through said second connection line. 
     
     
       9. In a multicomputer system including a plurality of computers each of which has a processor for controlling transmission and reception of data and a memory which stores data received and to be transmitted, a common transmission bus, gate means which is connected between each computer and said common transmission bus, and a connection line which connects .[.the.]. respective adjacent computers; a transmission control method comprising the steps of: counting.Iadd., in each computer, .Iaddend.a time interval in which predetermined data delivered from .[.any desired one of said computers reaches another.]. .Iadd.that computer returns from an adjacent .Iaddend.computer; controlling.Iadd., in each computer, .Iaddend.said gate means when said time interval is greater than a predetermined time, so that no data may be delivered from said .[.one.]. .Iadd.adjacent .Iaddend.computer to said common transmission bus; delivering.Iadd., in each computer, .Iaddend.a fault check signal from .[.one of said computers.]. .Iadd.its own computer .Iaddend.to the adjacent computer through said connection line; counting.Iadd., in each computer, .Iaddend.a time interval in which the delivered fault check signal returns to .[.the original.]. .Iadd.its own .Iaddend.computer through the adjacent computer, said common transmission bus and said gate means; and controlling.Iadd., in each computer, .Iaddend.said gate means connected .[.between.]. .Iadd.to .Iaddend.said common transmission bus .[.and the computer which has delivered said fault check signal.]., so as to be in  .[.the.]. .Iadd.a .Iaddend.cut off state when said time interval is greater than a predetermined time. .Iadd.10. A data transmission system comprising: .Iadd.at least one transmission medium; and   .Iadd.a plurality of equipments which are connected to said transmission medium and each of which has (A) connector means connected through said transmission medium to other equipments and including at least one gate means for selectively passing a signal from one of the equipments to another one and, (B) processing means connected to said connector means and including (B1) means for checking a condition of a path including at least one of said other equipments and said transmission medium connected thereto to detect a fault in the path at any time independently of operations of and in parallel with other equipments and (B2) means responsive to said checking means for controlling said gate means of said connector means independently of other equipments so as to prevent said signal from passing through at least one of said gate means when a fault is detected as a result of the checking by said checking means. .Iaddend.   
     
     
        .Iadd.11.  A data transmission system according to claim 10 in which said gate means includes means for selectively receiving a signal from one of said other equipments and said controlling means includes means for controlling said gate means of said connector means so as to prevent said signal from being received when a fault is detected as a result of the 
     
     
        checking by said checking means. .Iaddend. .Iadd.12.  A data transmission system according to claim 10 or 11 wherein, a plurality of transmission mediums are connected to each of said plurality of equipments and in which said gate means includes means for selectively transmitting data to said transmission mediums and said processing means includes means for controlling said gate means so that, when the fault of a path including one of said plurality of transmission medium is detected as a result of the checking by said checking means, said signal is transmitted to another 
     
     
        one of said plurality of transmission mediums. .Iaddend. .Iadd.13.  A data transmission system according to claim 10 in which said means for checking delivers a loop check message which passes a loop which comprises said one of other equipments and said transmission medium connected thereto and 
     
     
        returns back to said means for checking. .Iaddend. .Iadd.14.  A method of controlling a multicomputer system having first and second computers, each of which includes a processor for controlling transmission and reception of data, and a memory for storing data received and to be transmitted; a common transmission bus; first and second bus connector means, which are respectively connected to one of said first and second computers and to said common transmission bus and each of which includes gate means for selectively passing a signal to the corresponding computer from said common transmission bus and a signal to be delivered from said corresponding computer to said common transmission bus; means including at least one first connection line for transmitting data or control signals and which connects said first computer to said first bus connector means; at least one second connection line for transmitting data or control signals and which connects said second computer to said second bus connector means; and a third connection line which connects said first computer to said second computer; said method performed in each computer independently comprising the steps of: controlling said gate means in each of said first and second bus connector means by applying control signals from the respective computers to said bus connector means through the respective first and second connection lines;   transmitting data delivered from said first computer to said second computer through said first connection line, said first bus connector means, said common transmission bus, said second bus connector means and said second connection line; and   transmitting a signal for checking the operative condition of said first and second computers along a closed loop which includes said first computer, said third connection line, said second computer, said second connection line, said second bus connector means, said common transmission bus, said first bus connector means and said first connection line.   
     
     
        .Iaddend. .Iadd.15.  A method of controlling data transmission system having at least one transmission medium, and a plurality of equipments which are connected to said transmission medium and each of which has (1) connector means connected through said transmission medium to other equipments and including at least one gate means and (2) control means for controlling operation of said gate means, said method performed in each equipment at any time independently of the operations of and in parallel with other equipments including the steps of: selectively passing a signal from one of the equipments to another one in at least one direction thereof via said transmission medium;   checking a path including at least one of said other equipments and said transmission medium connected thereto and producing a control signal when a fault is detected; and   controlling said gate means of said connector means by said control means in response to said control signal so as to prevent said signal from passing through at least one of said gate means when a fault is detected   
     
     
        as a result of said checking step. .Iaddend. .Iadd.16.  The method according to claim 15 in which said gate means includes means for selectively receiving a signal from one of said other equipments, and said controlling step comprises controlling said gate means of said connector means so as to prevent said signal receiving by said gate means when a 
     
     
        fault is detected as a result of said checking step. .Iaddend. .Iadd.17. A data transmission system according to claim 15 or 16 wherein, a plurality of transmission mediums are connected to each of said plurality of equipments and in which said gate means includes means for selectively transmitting data to said transmission mediums, and wherein said controlling step includes controlling said gate means so that, when the fault of a path including one of said plurality of transmission medium is detected as a result of the checking step, said signal is transmitted to another one of said plurality of transmission mediums. .Iaddend. 
     
     
        .Iadd.     A data transmission system according to claim 15 in which said checking step includes sending a loop check message which passes a loop which comprises said one of the other equipments and said transmission 
     
     
        medium connected thereto. .Iaddend. .Iadd.19.  The method according to claims 14 or 15, in which respective steps in each equipment are performed 
     
     
        in parallel with those in other equipment. .Iaddend. .Iadd.20.  A method of controlling a multicomputer system having a plurality of equipments, each of which includes a computer and connecting means for transmission and reception of data, and a transmission medium connecting said equipments, said method comprising the following steps performed in each computer means in each equipment: transmitting a signal for transmission request through said connecting means to said transmission medium;   receiving a signal for transmission request from at least one of the other equipments through said connecting means;   determining whether the computer has the right of data transmission based on signals for transmission request of its own equipment and from other equipment; and   transmitting data through said connecting means to said transmission medium when it has the right of data transmission;   wherein each equipment operates independently to each other and respective operations in each equipment are performed in parallel with those in each   
     
     
        other equipment. .Iaddend. .Iadd.21.  A multicomputer system comprising: (a) first and second computers, each of which includes a processor for controlling transmission and reception of data;   (b) a transmission line;   (c) first and second connector means, which are respectively connected to said first and second computers and to said transmission line and each of which includes gate means, for selectively passing a signal to the corresponding computer from said transmission line and a signal to be delivered from said corresponding computer to said transmission line;   (d) means including at least one first connection line for transmitting data or control signals and which connects said first computer with said first connector means;   (e) means including at least one second connection line for transmitting data or control signals and which connects said second computer with said second connector means, said gate means in each of said first and second connector means being controlled by signals which are applied from the respective computers to said connector means through the respective first and second connection lines, and data delivered from said first computer being transmitted to said second computer through said first connection line, said first bus connector means, said transmission line, said second bus connector means and said second connection line; and   (f) means for transmitting a signal for checking the condition of said first and second computers along a route which includes said second computer, said second connection line, said second connector means, said transmission line, said first bus connector means, said first connection line and said first computer. .Iaddend.