JP2000316017A - Optical dual loop network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical dual loop network system that reduces the number of times of incidence of interrupted system operations and decreases an interrupting time on the occurrence of a fault. SOLUTION: In the system where a plurality of nodes 8 are connected in duplicate as rings by optical fibers 9 and a signal is transmitted around one direction and other direction through sequential repetition by the nodes 8, a ring master node 10 predetermined among the nodes 8 acts like a termination node when all of the nodes 8 are able to send the signal like ring, and a last node able to transmit the signal acts like a termination node when any of the nodes 8 cannot transmit the signal like ring, when two adjacent nodes 8 confirm an adjacent node as to whether or not a fault is in existence, a node address of its own station is added to a transmission control signal, a receiver side of the transmission control signal discriminates whether or not the node address is normal, and only when the receiver side discriminates that the address is normal, the receiver side node informs the ring master node about adjacent node confirmed information through repetition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical duplex system in which a plurality of nodes (stations) are connected in a ring shape, and adjacent nodes among them are double-connected by optical fibers so that two-way communication is possible. Related to loop network systems.

[0002]

2. Description of the Related Art In this type of optical double loop network system using an optical fiber as a transmission line, one of a plurality of nodes is a ring master node (hereinafter, also simply referred to as a ring master) and the other nodes are adjacent to each other. An information frame received from one of the nodes (hereinafter, simply referred to as a frame) is transmitted to the other adjacent node, and an information frame received from the other adjacent node is transmitted to the adjacent one node. In the flow of the information frame, the ring master receives the information frame from the upstream but does not transmit it to the downstream. In this case, the information frame is repeated (relayed) at each node, but the communication in the form of a bus is practically possible.

[0003]

In the communication system as described above, if the communication becomes impossible at any one place due to disconnection or the like, the ring master receives the information frame from the upstream but does not transmit the information frame to the downstream. , The terminal cannot communicate with the downstream node. Conventionally, when such a communication-disabled state occurs, or when a node is added or removed, the ring master sends a reset notification to all nodes connected to it and suspends system operation. Then, the ring master itself determines whether or not to repeat, and in the case of repeating, performs communication processing with respect to a downstream node.

However, when the adjacent nodes cannot communicate with each other properly in a state where normal communication cannot be performed, when the abnormality is transmitted to a ring master or an upper node, incorrect address information may be used due to the influence of noise or the like. Alternatively, there is a problem that the operation of the system is frequently interrupted due to a delay in the abnormality diagnosis.

[0005] In addition, when the system operation is interrupted, a large amount of time is required for abnormality diagnosis, so that there is a problem that the system is interrupted for a long time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical double loop network system capable of reducing the number of interruptions of system operation due to occurrence of an abnormality.

Another object of the present invention is to provide an optical double loop network system capable of shortening the interruption time of system operation due to occurrence of an abnormality.

Another object of the present invention is to provide an optical double loop network system which can reduce malfunction due to noise.

Still another object of the present invention is to provide an optical double loop network system capable of reducing the load of control software.

Another object of the present invention is to provide an optical double loop network system capable of suppressing the occurrence of island conditions in the system.

[0011]

The invention according to claim 1 is
A plurality of nodes are connected in a ring by an optical fiber, and adjacent nodes are doubly connected to perform signal transmission around one direction and signal transmission around the other direction by repeating sequentially, In a state where all of the nodes can transmit a signal in a ring shape, in a state where only one ring master node in the node is terminated and all of the nodes cannot transmit a signal in a ring shape. An optical node that terminates at the last node capable of transmitting a signal, and transmits and receives a control signal not to be repeated between two adjacent nodes to confirm whether or not the adjacent node is abnormal. In a double loop network system, the node address of the own station is added to the transmission signal of the control signal at the time of confirming the adjacent node, and De address is equal to or normal, only if it is determined to be normal, it is characterized by notifying the adjacent node confirmation information to the ring master node by repeat.

According to a second aspect of the present invention, in the optical dual loop network system according to the first aspect, the ring master node can transmit signals in a ring shape to all nodes connected thereto. Notify each node other than the ring master node of whether or not each node detects a communication failure with an adjacent node when a ring-shaped signal can be transmitted. Each node indicates a suspension of system operation. Using a signal to notify the ring master node of the occurrence of an error by repeat, and when a node in the middle of the repeat detects an error in information, the repeat of the signal indicating the suspension of the system operation is aborted and the signal can be transmitted in a ring shape. If it is impossible to detect communication failure with the adjacent node, each node shall notify the other node of the occurrence of an error in the information frame. It is characterized.

According to a third aspect of the present invention, in the optical dual loop network system according to the second aspect, each node generates a control signal not to be repeated, a signal indicating interruption of system operation, and occurrence of an abnormality in the ring master node. The transmission intervals of the information frames to be notified are kept constant.

According to a fourth aspect of the present invention, in the optical dual loop network system according to any one of the first to third aspects, each node stores a node address for each control signal type.

According to a fifth aspect of the present invention, in the optical dual loop network system according to the fourth aspect, when the control code type does not change and the node address information changes, it is detected that an event change has occurred, It is characterized in that node address information is stored with a changed value.

According to a sixth aspect of the present invention, a plurality of nodes are connected in a ring by an optical fiber, and signal transmission around one direction of the ring and signal transmission around the other direction are performed by successively repeating adjacent nodes. In a state where all nodes are capable of transmitting signals in a ring shape, only one ring master node in the nodes is terminated and all nodes are ring-shaped. In the state where it is impossible to transmit a signal to the other node, the last node that can transmit the signal is the terminal, and the adjacent node is abnormal due to transmission and reception of a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system for confirming the presence or absence of an adjacent node, each node includes means for generating a return instruction for a transmission signal. In response to the occurrence of the folded instruction, it is characterized in that the received signal by folding the transmission signal.

According to a seventh aspect of the present invention, a plurality of nodes are connected in a ring by an optical fiber, and signal transmission around one direction of the ring and signal transmission around the other direction are performed by successively repeating adjacent nodes. In a state where all nodes are capable of transmitting signals in a ring shape, only one ring master node in the nodes is terminated and all nodes are ring-shaped. In the state where it is impossible to transmit a signal to the other node, the last node that can transmit the signal is the terminal, and the adjacent node is abnormal due to transmission and reception of a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system for confirming the presence or absence of an adjacent node, each node includes means for generating a return instruction for a transmission signal. In response to the occurrence of the folded instruction, it is characterized in that the input signal to the local node does not transmit the transmission signal to the next node.

According to an eighth aspect of the present invention, a plurality of nodes are connected in a ring shape by an optical fiber, and signal transmission around one direction of the ring and signal transmission around the other direction are performed by successively repeating adjacent nodes. In a state where all nodes are capable of transmitting signals in a ring shape, only one ring master node in the nodes is terminated and all nodes are ring-shaped. In the state where it is impossible to transmit a signal to the other node, the last node that can transmit the signal is the terminal, and the adjacent node is abnormal due to transmission and reception of a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks the presence or absence of an adjacent node, when the initial system configuration of a plurality of nodes and the connection node configuration change, It is characterized by sharing de connection information.

According to a ninth aspect of the present invention, a plurality of nodes are connected in a ring by an optical fiber, and signal transmission around one direction of the ring and signal transmission around the other direction are performed by successively repeating adjacent nodes. In a state where all nodes are capable of transmitting signals in a ring shape, only one ring master node in the nodes is terminated and all nodes are ring-shaped. In the state where it is impossible to transmit a signal to the other node, the last node that can transmit the signal is the terminal, and the adjacent node is abnormal due to transmission and reception of a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks whether or not there is an adjacent node, check the connection node address with the ring master node at initialization, It is characterized in that to check the address of the node adjacent to the node of interest when confirmation.

According to a tenth aspect of the present invention, a plurality of nodes are connected in a ring shape by an optical fiber, and adjacent nodes sequentially repeat to transmit a signal around one direction of the ring and a signal around the other direction. In a state where all nodes are capable of transmitting signals in a ring shape, only one ring master node in the nodes is terminated and all nodes are ring-shaped. In the state where it is impossible to transmit a signal to the other node, the last node that can transmit the signal is the terminal, and the adjacent node is abnormal due to transmission and reception of a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks the presence or absence of an adjacent node, this command is used to instruct each node to initialize the system when an error occurs. The loop initialization request control code is characterized by sequentially relaying transmission hardware.

According to an eleventh aspect of the present invention, a plurality of nodes are connected in a ring by an optical fiber, and adjacent nodes sequentially repeat to transmit a signal in one direction and a signal in another direction. In a state where all nodes are capable of transmitting signals in a ring shape, only one ring master node in the nodes is terminated and all nodes are ring-shaped. In the state where it is impossible to transmit a signal to the other node, the last node that can transmit the signal is the terminal, and the adjacent node is abnormal due to transmission and reception of a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks the presence or absence of an adjacent node, the presence or absence of an abnormality is checked for each direction of signal transmission, and It is characterized by counting the number of occurrences of going on data.

According to a twelfth aspect of the present invention, a plurality of nodes are connected in a ring shape by optical fibers, and adjacent nodes sequentially repeat to transmit a signal in one direction and a signal in another direction. In a state where all nodes are capable of transmitting signals in a ring shape, only one ring master node in the nodes is terminated and all nodes are ring-shaped. In the state where it is impossible to transmit a signal to the other node, the last node that can transmit the signal is the terminal, and the adjacent node is abnormal due to transmission and reception of a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system for confirming whether or not there is an adjacent node, a connection request control code at the time of an initial connection confirmation operation between adjacent nodes, It is characterized in that the notification control code after connection abnormality after connection completion with the same code.

According to a thirteenth aspect of the present invention, a plurality of nodes are connected in a ring shape by an optical fiber, and adjacent nodes sequentially repeat to transmit a signal in one direction and a signal in another direction. In a state where all nodes are capable of transmitting signals in a ring shape, only one ring master node in the nodes is terminated and all nodes are ring-shaped. In the state where it is impossible to transmit a signal to the other node, the last node that can transmit the signal is the terminal, and the adjacent node is abnormal due to transmission and reception of a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks the presence or absence of an adjacent node, when one of the doubly connected optical fibers becomes abnormal, Separate the connected other optical fiber to heavy from normal signal transmission system is characterized by comprising a switching means for switching connections between nodes became line abnormality.

According to a fourteenth aspect of the present invention, in the optical double loop network system according to the thirteenth aspect, when a line abnormality occurs at two or more locations of the optical fiber connected doubly, the optical fiber loop around one direction of the ring. The optical fiber is switched and connected so that a signal can be transmitted.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 1 is a system diagram showing an overall configuration of an embodiment of an optical double loop network system according to the present invention. In this optical double loop network system, adjacent nodes use a LAN (Local Area
The optical fiber 9 is doubly connected by two optical fibers 9 forming a network, and the whole is connected in a ring shape. One of these nodes is a ring master 10 and the other is a node 8. Each of the node 8 and the ring master 10 includes a communication module 7, and has a function of sequentially transmitting information frames clockwise as shown in the drawing and a function of sequentially transmitting information frames counterclockwise.

FIG. 2 is a block diagram showing a detailed configuration of the communication module 7. The transmission / reception control circuit 5, the CPU 11, and the memory circuit 13, which will be described in detail later, respectively,
, Among which the transmission / reception control circuit 5 and C
The switch circuit 6 is connected to the PU 11, and further,
The host interface circuit 14 is connected to the transmission / reception control circuit 5.

FIG. 3 is a functional block diagram of the communication module 7 shown in FIG.
It has functions of a network management means 2, a data link layer means 3, and a transmission / reception driver 4. here,
The transmission / reception driver 4 passes the information frame requested to be transmitted from the data link layer means 3 or the information frame requested to be transmitted from the loop management means 1 to the transmission / reception control circuit 5, and receives the information frame via the transmission / reception control circuit 5. The information frame is transferred to the data link layer means 3 or the loop management means 1
Hand over to The switch circuit 6 also has a function of generating, transmitting, and receiving a control signal exchanged between two adjacent stations and not set as a repeat target. The control signal transmission instruction is issued by the loop management means 1. The received control signal is not confirmed as a received frame by the transmission / reception control circuit 5, and is not notified through the transmission / reception control circuit 5. When receiving the control code signal, the switch circuit 6 notifies the CPU 11 by an interrupt. When this interrupt occurs, the loop management means 1 performs processing according to the reception control code signal and the state of the loop management.

FIG. 4 is a functional block diagram showing a detailed configuration of the switch circuit 6, and the CPU interface circuit 1
5, a transmission / reception control circuit interface circuit 16, an A-system transmission unit 17, a B-system transmission unit 18, an A-system reception unit 19, a B-system reception unit 20, and a LAN interface circuit 21. Here, a system for transmitting and receiving to and from a node adjacent in the clockwise direction in the drawing is referred to as an A system, and a system for transmitting and receiving to and from a node adjacent in a counterclockwise direction is referred to as a B system.

The LAN interface circuit 21 has a LAN
Is received, and is extracted as a LAN reception signal 29 and transmitted to the A-system receiving unit 19 and the B-system receiving unit 20. LAN interface circuit 2
1 sends out the signals received from the A-system transmitting unit 17 and the B-system transmitting unit 18 as LAN transmission signals 28 on the LAN. When the LAN interface circuit 21 receives the return instruction 30 from the CPU interface circuit 15, the LAN interface circuit 21
A process of returning the received signal as it is as the LAN transmission signal 28 is also performed.

The A-system receiving section 19 and the B-system receiving section 20 perform control code discrimination, frame synchronization, reception error processing, and frame extraction processing. The signal is transmitted to the circuit 15. Also, the A-system receiving unit 19, B
The received frame signal 25 extracted from the system receiving unit 20 is transmitted to the transmission / reception control circuit interface circuit 16. Further, the A-system receiving unit 19 switches to the B-system transmitting unit 18.
Then, the repeat reception signal 27 is transmitted from the B-system receiving unit 20 to the A-system transmitting unit 17, respectively.

The transmission / reception control circuit interface circuit 16 transmits the reception frame signal 25 from the A-system reception unit 19 and the B-system reception unit 20 to the transmission / reception control circuit 5. Further, it receives the transmission signal transmitted from the transmission / reception control circuit 5 and transmits it to the A-system transmission unit 17 and the B-system transmission unit 18 as a transmission frame signal 26. In the present embodiment, the signals for the A system and the B system are connected to the transmission / reception control circuit 5 as separate systems. Also,
When the return instruction 30 is sent from the CPU interface circuit 15, the transmission signal is transmitted to the transmission / reception control circuit 5 as a return reception signal.

The CPU interface circuit 15 receives the reception status 24 from the A-system receiving unit 19 and the B-system receiving unit 20 and notifies the CPU 11 of the reception status. Further, the CPU interface circuit 15 receives the transmission status 23 from the A-system transmitting unit 17 and the
Notify 11 Further, the CPU interface circuit 1
5 transmits the repeat control signal and the control code transmission signal received from the CPU 11 to the A-system transmission unit 17 and the B-system transmission unit 18 as a transmission control command 22. Further, the CPU interface circuit 15 transmits a return instruction 30 to the transmission / reception control circuit interface circuit 16 and the LAN interface circuit 21.

The A-system transmission unit 17 and the B-system transmission unit 18 transmit control commands from the CPU interface circuit 15, repeat reception data from the A-system reception unit 19 and the B-system reception unit 20, respectively, And transmits a LAN transmission signal 28 to the LAN interface circuit 21.

FIG. 5 is a block diagram showing a detailed configuration of the A-system transmitting unit 17 and the B-system transmitting unit 18. A transmission unit 17,
The B-system transmission unit 18 includes a transmission frame selection circuit 32,
FIFO (First In First Out) circuit 33, transmission selection circuit 34, transmission control circuit 35, and control code generation circuit 36
It is constituted by.

The transmission frame selection circuit 32 transmits the transmission frame signal 26 from the transmission / reception control circuit interface circuit 16 to the A-system receiving section 19 or the B-system receiving section 20.
Receiving the repeat reception signal 27 (frame) from
The transmission frame selection result signal 37 is sent to the FIFO circuit 33. The transmission status 23 is transmitted to the CPU interface circuit 15.

In accordance with the FIFO output control signal 38 from the transmission control circuit 35, the FIFO circuit 33 converts the transmission frame selection result signal 37 previously fetched from the transmission frame selection circuit 32 into an output frame signal 40 in the order received. The signal is transmitted to the transmission selection circuit 34. Also FIFO
The transmission control circuit 3 determines whether or not there is information stored in the circuit 33.
5 as a FIFO status signal 39.

In the transmission selection circuit 34, in accordance with the transmission selection signal 44 transmitted from the transmission control circuit 35, the FIFO circuit 3
3 to output either the FIFO output frame signal 40 sent from the control code generation circuit 3 or the control code generation result signal 43 sent from the control code generation circuit 36.
The N transmission signal 28 is transmitted to the LAN interface circuit 21.

In the transmission control circuit 35, the transmission control command 22 from the CPU interface circuit 15 and the A-system receiving unit 1
9 or a repeat reception signal 27 from the B-system reception unit 20
(Code) and the FIFO state signal 39 from the FIFO circuit 33, and the transmission state is determined. When it is determined that the output is the FIFO output, a FIFO output control signal 38 is output to the FIFO circuit 33. If it is determined that the control code is to be transmitted, the control code generation circuit 36 sends the control code generation control signal 4
Transmit 1. Further, it takes in the FIFO status signal 39 and the control code generation status signal 42 from the control code generation circuit 36, and performs the switching operation of the output destination. Also,
The type of the transmission data is transmitted to the transmission selection circuit 34 as a transmission selection signal 44.

The control code generation circuit 36 receives the control code generation control signal 41 from the transmission control circuit 35 and transmits a control code generation result signal 43 to the transmission selection circuit 34. In addition, a result indicating whether or not control code generation has been completed is transmitted to the transmission control circuit 35 as a control code generation status signal 42. In the case of a repeat control code,
Based on the repeat reception signal 27 from the A-system receiving unit 19 or the B-system receiving unit 20, transmission control code information is created inside the control code. In the case of another control code transmission request, C
Transmission control command 2 from PU interface circuit 15
2 is used.

FIG. 6 is a block diagram showing a detailed configuration of the A-system receiving section 19 and the B-system receiving section 20. This A-system receiving unit 1
9, the B-system receiving unit 20 includes a reception control code detection circuit 46, a reception frame check circuit 47, a frame synchronization detection circuit 48, an information frame detection circuit 49, and a reception FIFO.
It comprises a circuit 50 and a reception abnormality detection circuit 51.

The reception control code detection circuit 46 receives the LAN reception signal 29 and detects the control code. In the case of detecting the synchronization processing control code, the synchronization code detection signal 52 is transmitted to the frame synchronization detection circuit 48. Also,
The synchronization code receiving signal 53 is transmitted to the information frame detection circuit 49.
To communicate. Further, the reception control code detection circuit 46 transmits the control code type signal 54 to the reception abnormality detection circuit 51.

When the control code is detected, the reception control code detection circuit 46 determines whether or not the information code following the control code is data having no problem. 24
To communicate. Further, the synchronous frame receiving signal 56 is received from the information frame detecting circuit 49, and the control code discrimination timing is distinguished. As for the break reception signal, the repeat reception signal 27 is transmitted to the A-system transmission unit 17 and the B-system reception unit 18.

The frame synchronization detection circuit 48 receives the synchronization code detection signal 52 from the reception control code detection circuit 46 and transmits a frame synchronization establishment signal 58 to the information frame detection circuit 49. The information frame detection circuit 49 uses a LAN
The LAN reception signal 29 is received from the interface circuit 21, and frame reception is started using the time interval obtained from the frame synchronization establishment signal 58 from the frame synchronization detection circuit 48 and the synchronization code receiving signal 53 from the reception control code detection circuit 46. To detect. When the start of frame reception is detected, the synchronization frame receiving signal 56 is transmitted to the reception control code detection circuit 46, the reception frame check circuit 47, and the reception FIFO circuit 50. Further, a reception frame extraction signal 57 is generated and a reception frame check circuit 47 is generated.
And to the reception FIFO circuit 50.

The reception FIFO circuit 50 receives the synchronization frame receiving signal 56 and the reception frame extraction signal 57 from the information frame detection circuit 49, and transmits the reception frame signal 25 to the transmission / reception control circuit interface circuit 16 in the order of reception. Further, it transmits the repeat reception signal 27 (frame) to the transmission units 17 and 18. The reception frame check circuit 47 receives a synchronization frame receiving signal 56 and a reception frame extraction signal 57 from the information frame detection circuit 49.
Received and a CRC check (Cyclic Redundancy Chec
Check the frame contents such as k). The check result is transmitted to the CPU interface circuit 15 as the reception status 24. The reception abnormality detection circuit 51 receives the LAN reception signal 29 from the LAN interface circuit 21 and detects abnormal data. If an abnormality has occurred, the reception status 24 is transmitted to the CPU interface circuit 15.

FIG. 7 shows control codes used in this embodiment. The Quiet signal 60 is used as a connection request to an adjacent node. The Ack signal 61 is used as a connection acceptance response to the Quiet signal 60. Break
The k signal 62 is used as a disconnection request due to the occurrence of an abnormality. The above three types of control codes have a format of a head code + code type code + code information. A header code indicates a control code, a code type indicates a control code type, and necessary information is included in the code information. (Such as a control code transmission source address). Idle signal 6
Reference numeral 3 denotes a signal synchronization establishment signal at the time of establishing the connection. This control code is composed of only an Idle identification code.

FIG. 8 shows the structure of the information frame. The information frame has a plurality of recognition codes, that is, Pre codes at the beginning, and a control code indicating a frame type;
It is composed of a destination address code, a source address code, data, a data check code, and the like.

FIG. 9 shows an example of a transaction for confirming an adjacent node in this embodiment. The adjacent node confirmation is a process performed by the loop management unit 1, and is performed when the node starts up or when communication with the adjacent node cannot be performed due to a signal interruption or the like.

The Quiet signal 60, the Ack signal 61, and the Idle signal 63 are control signals that are exchanged between two adjacent stations and are not repeated. Ack signal 61
Is a response to the Quiet signal 60. During normal operation, the idle signal 63 is transmitted when there is nothing to transmit or repeat the frame. Quiet signal 60
Ack signal 61 is added with information and transmitted. The information is set in the switch circuit 6 by the loop management means 1. In the adjacent node confirmation, the node address of the own station is set as information. When the Ack signal 61 corresponding to the Quiet signal 60 is obtained, the loop management unit 1 determines that communication with the adjacent node is possible, and the Idle signal 6
Send 3. The Idle signal 63 is a signal that flows after the confirmation of the adjacent node is performed.

The following operation is performed inside the switch circuit 6. First, the loop management means 1 of the N1 node sets its own address value and a Quiet signal transmission request to the N2 node on the B-system side of the CPU interface circuit 15, for example. The CPU interface circuit 15 transmits a Quiet signal transmission request transmission control command 22 to the B-system transmission unit 18. The transmission control circuit 35 in the B transmission section 18 receives the transmission control command 22 and sends a control code generation control signal 41 for a Quiet signal transmission request to the control code generation circuit 36. Further, it sends a transmission selection signal 44 of control code transmission selection to the transmission selection circuit 34.
In the control code generation circuit 36, the Qui
The transmission data of the et signal is generated as a control code generation result signal 43 and transmitted to the transmission selection circuit 34. Transmission selection circuit 3
4, the received control code generation result signal 43 is transmitted to the LAN.
The transmission signal 28 is sent to the LAN interface circuit 21. The LAN interface circuit 21 sends a LAN transmission signal 28 as B-system transmission data.

In the N2 node, Qu is placed on the LANA system.
The iet signal is sent. LA signal on system A is LA
The N interface circuit 21 receives the signal,
As a LAN reception signal 29. A system receiver 19
In the reception control code detection circuit 46, the LAN reception signal 2
9, the Quiet code included in the connection status is determined. If the Quiet code matches the Quiet code requested to be connected, and if there is no abnormality in the address data portion, the reception status 2
4, the Quiet signal is received, and the CPU interface circuit 15 is notified. The loop management means 1 of the N2 node determines from the information output from the CPU interface circuit 15 that the A system has received the Quiet signal.

In response to this, the loop management means 1 of the N2 node transmits the Ack signal 61 to the A system. The loop management means 1 of the N2 node includes a CPU interface circuit 15
, Set its own address value and Ack signal transmission request to the N1 system side (in this case, the A system side). Ack from the CPU interface circuit 15 to the A-system transmitting unit 17
The transmission control command 22 of the signal transmission request is transmitted. After that, the same as the transmission of the Quiet signal 60, the A
The ck signal 61 is transmitted.

Thereafter, the LAN interface circuit 21 of the N1 node receives the Ack signal 61 and
0 is sent as a LAN reception signal 29. B-system receiver 2
The Ack code included in the LAN reception signal 29 is discriminated by the reception control code detection circuit 46 within 0.
Notify the interface circuit 15. From the information output by the CPU interface circuit 15, the loop management means 1 of the N1 node determines that the B system has received the Ack signal.

In response to this, the loop management means 1 of the N1 node transmits an Idle code to the B system. The N1 node sets an Idle signal transmission request to the B side. From the CPU interface circuit 15, the B transmission unit 1
8 for the transmission control command 2 of the idle signal transmission request.
Tell 2 In this case, only the idle code is transmitted.

In the N2 node, I
The dle signal 63 is sent. The LAN interface circuit 21 receives the LAN signal on the A-system and sends it to the A-system receiving unit 19 as a LAN reception signal 29. The reception control code detection circuit 46 in the A-system receiving unit 19 determines the Idle identification code included in the LAN reception signal 29, and if the same as the transmitted Idle code, puts the Idle signal reception code in the reception status 24. The CPU interface circuit 15 is notified. From the information output by the CPU interface circuit 15, the loop management means 1 of the N2 node
Determines that the A system is receiving an Idle signal. Here, the N2 node completes the confirmation that the N1 node is adjacent to the A-system side.

Finally, Idl is sent from the N1 node to the N2 node.
The e signal 63 is sent, and the confirmation that the N1 node is adjacent to the B system as the N2 node is completed. At this point, the idle signal 63 is sent to both sides.

The detailed operation when the Idle signal 63 is received will be described below. When the reception control code detection circuit 46 detects the idle code, a synchronization code detection signal 52 is sent to the frame synchronization detection circuit 48. The frame synchronization detection circuit 48 confirms that the synchronization code detection signal 52 is sent periodically at the idle signal reception timing, and sends a frame synchronization establishment signal 58 to the information frame detection circuit 49. This frame synchronization establishment signal 58 is used when receiving a frame.

The N1 node notifies the ring master by transmitting the information frame 64 that the confirmation of the adjacent station is completed.

The detailed operation of the switch circuit 6 in this case will be described below. The loop management means 1 transmits a frame to the system participating in the system operation, that is, in this case, the system A side. Transmission frame data is sent from the transmission / reception control circuit 5 to the switch circuit 6 via the network management means 2. The transmission / reception control circuit interface circuit 16 converts the received transmission frame data into a transmission frame signal 26.
To the transmission frame selection circuit 32. The transmission frame selection circuit 32 inputs a signal to the FIFO circuit 33. FI
The FO circuit 33 sends to the transmission control circuit 35 a FIFO status signal 39 indicating that there is a FIFO input. Transmission control circuit 35
Then, the FIFO output control signal 38 is transmitted to the FIFO circuit 33 as FIFO output permission. Also, the transmission control circuit 3
5 transmits the transmission selection signal 44 to the transmission selection circuit 34 as a FIFO output. Here, the FIFO circuit 33 is
It receives the output control signal 38 as output permission and sends a FIFO output frame signal 40 to the transmission selection circuit 34. The transmission selection circuit 34 creates the LAN transmission signal 28 and transmits it to the LAN interface circuit 21. The frame is transmitted from the LAN interface circuit 21 to the A system.

The ring master receives the information frame sent from the system B side. The signal received by the LAN interface circuit 21 is transmitted to the B-system receiving unit 20 as a LAN reception signal 29. The information frame detection circuit 49 inside the B-system receiving section 20 detects a received frame by detecting a Pre code match. This coincidence detection is performed using the timing of the frame synchronization establishment signal 58 output from the frame synchronization detection circuit 48. When a received frame is detected, a synchronous frame receiving signal 56 and a received frame extracting signal 57 are sent to the receiving FIFO circuit 50. The reception FIFO circuit 50 sends the received signal as a reception frame signal 25 to the transmission / reception control circuit interface circuit 16. Transmission / reception control circuit interface circuit 1
A reception signal is sent from 6 to the transmission / reception control circuit 5, the transmission / reception control circuit 5 receives a frame, and notifies the CPU 11 of the reception. Adjacent node confirmation information is transmitted to the loop management means 1 via the transmission / reception driver 4 and the data link layer means 3.

At the node between the N1 node and the ring master, the adjacent station confirmation frame is repeated (relayed). B
The data received by the system is transmitted from the B-system receiving unit 20 to the A-system transmitting unit 17 as a repeat reception signal 27. The data is received by the transmission frame selection circuit 32 inside the A-system transmission unit 17, is processed in the same manner as the transmission frame signal 26 from the transmission / reception control circuit interface circuit 16, and is sent to the A-system side.

The above-mentioned adjacent node check is performed independently for each system. Even if only one system is operating and terminated in the system operation, the other system may operate in the other system. Can be performed without affecting the Also, the ring master loop management means 1
Can be notified via the data link layer means 3 that the communication with the adjacent node is possible together with the address of the adjacent node using the system participating in the system operation. Notification can be executed without affecting the system operation.

Further, the address information is checked at the time of checking the control code. In the case of an abnormal address, the upper CPU is not notified of the occurrence of the control code, so that the reading of the control code due to the influence of noise or the like is not performed. Is less likely to occur, whereby the interruption time of the system operation can be reduced.

FIG. 10 shows a case where ring-shaped signal transmission is possible in this embodiment, that is, a communication disabled notification in the case of a ring. FIG. 11 shows a case where ring-shaped signal transmission is impossible in this embodiment. That is, a communication disable notification in the case of a bus.

The loop management means 1 of the ring master 10
By creating the node arrangement tables 65A and 65B shown in FIG. 12, it is determined whether the ring is a ring terminated by a ring master or a bus terminated by another node, and the loop management of all nodes connecting this is performed. The means 1 is notified by a broadcast frame. As a result, all nodes memorize the current ring or bus.

When each node detects that communication with an adjacent node is impossible during a ring, as shown in FIG. 10, it transmits a Break signal 62 having a signal disconnection identifier and a source node address as information. Break signal 6
2 flows from the ring master to the N2 node B
Stop for requesting stop of transmission of leak signal Break
k. a req signal, and the N2 node responds to the request to stop transmission in response thereto. Break. rsp
A signal is returned, and finally, a system which means restarting the system operation from the ring master The system operation is suspended until the Start broadcast frame flows.

The detailed operation inside the switch circuit 6 in this case will be described below. Switch circuit 6 of N2 node
The reception abnormality detection circuit 51 detects that the communication is disabled by the B-system receiving unit 19. Specifically, the LAN reception signal 29
Is monitored, and if no signal continues for a certain period of time or more, the reception status 24 is notified to the CPU interface circuit 15 as occurrence of signal interruption. This status is transmitted from the CPU interface circuit 15 to the CPU 11, and the loop management unit 1 performs signal disconnection processing.

In the case of a ring configuration, the loop management means 1 of the N2 node receives this signal and sends a Break signal 62 to the A system.
Is sent. The loop management means 1 of the N2 node is a CPU
It sets its own address value and a Break signal transmission request to the N1 node on the A-system side of the interface circuit 15. The CPU interface circuit 15 transmits a transmission control command 22 for a Break signal transmission request to the A-system transmission unit 17. After that, the Quiet signal and Ack
A Break signal 62 is transmitted on the LAN in the same manner as the signal transmission. In addition, repeat transmission of control codes and information frames at the N2 node is stopped.

The Break signal 62 is repeated from the node N2 to a node in the middle of the ring master. The B-system LAN signal is input from the LAN interface circuit 21 and transmitted to the B-system receiving unit 20. The reception control code detection circuit 46 in the B-system receiving unit 20 detects the Break code, and sends the Break reception condition and the code information including the address N2 in the reception control code to the A-system transmitting unit 17 in the repeat reception signal 27. introduce. The Break signal reception status is reset when the Break signal reception is completed. In the A-system transmission section 17, the repeat reception signal 27 is passed to the transmission control circuit 35 and the control code generation circuit 36. In the transmission control circuit 35, the control code generation control signal 41
Is set to the Break signal repeat transmission and sent to the control code generation circuit 36. The control code generation circuit 36 creates a Break signal including the control code information, and sends it to the transmission selection circuit 34 as a control code generation result signal 43. In the transmission selection circuit 34, the LAN transmission signal 2
8 to send a Break signal to the LAN interface circuit 2
1 is sent to the A side of the LAN.

The case where there is no error in the control code information has been described above. If the reception control code detection circuit 46 detects that there is an error in the control code information, the repeat reception signal 27 is transmitted to the A-system. The operation is not transmitted to the unit 17.

The ring master receives the break control code transmitted in a repeated manner, and performs the above bus change processing, that is, Stop. Break. Frame transmission after the transmission of the req signal is performed.

On the other hand, if it is detected that communication with the adjacent node is impossible when the connection configuration is a bus, as shown in FIG. 11, the N2 node is terminated, and transmission and reception of frames are limited to only the N1 node side system. Further, the report that notifies only the ring master loop management means 1 of the state of the signal interruption, which has information indicating that the communication between the N2 node and the N3 node has been disabled, as the information. Status. transmission of the req signal
Request to data link layer means 3. In response, the ring master reports the bus connection terminating at the N2 node. Status. Transmit the rsp signal to the N2 node.

By having the transmission function and the switching function as described above, the communication disabled state can be processed without interrupting the system operation, and the code information in the Break code is incorrect due to noise or the like. In this case, since no repeat signal is transmitted, erroneous information is not transmitted to the next node. As a result, it is possible to reduce the rate of occurrence of malfunction when noise occurs, and reduce interruption of system operation.

FIG. 13 is a time chart for explaining a process for securing a control code and a transmission frame interval. A period a indicates a state in which a control code signal is waiting during transmission of a frame. During the period b, the frame transmission is completed,
This shows a state where the Idle signal is being transmitted. Period c is I
This shows a state in which a Break signal request due to a higher priority repeat is received and transmitted during transmission of the dle signal. The period d indicates a state in which the break signal transmission by the repeat is completed and the idle signal transmission that has been waiting is performed. In this case, there is a frame transmission request, but the control code transmission is completed.

First, the signal operation inside the A-system transmitting unit 17 and the B-system transmitting unit 18 during the period a will be described. FI
The transmission frame selection result signal 37 is output from the transmission frame selection circuit 32 to the FO circuit 33. In the FIFO circuit 33, since a transmission frame has been generated, the FIFO
Set frame presence in the status signal 39, and
Data is stored in the O circuit 33. The transmission control circuit 35 determines the transmission control in accordance with the transmission synchronization timing (（in FIG. 13), accepts the FIFO transmission request, and turns on the FIFO output control signal 38 (FIFO output permission). The transmission selection signal 44 is a FIFO transmission selection. In the FIFO circuit 33, the transmission frame data stored in the FIFO output frame signal 40 due to the FIFO status signal 39 being enabled for FIFO output is input. The transmission selection circuit 34 selects the FIFO output frame signal 40 and
An N transmission signal 28 is output. When all the frame signals stored in the FIFO circuit 33 have been output, the FIFO status signal 39 becomes no frame. Upon receiving this signal, the transmission control circuit 35 disables the output from the FIFO state signal 39. While the frame transmission is being performed, the transmission control command 22 indicates that the idle code is transmitted, but waits until the frame transmission is completed.

Next, the operation in the period b will be described.
The transmission control circuit 35 transmits the control code generation control signal 41 to the control code generation circuit 36 at the timing when the frame transmission ends, in the form of the idle code transmission. In response to this, the control code generation circuit 36 creates an Idle code and outputs it to the control code generation result signal 43. Also,
The transmission control circuit 35 sets the transmission selection signal 44 to control code transmission selection. At the timing of transmitting the next Idle signal 63, a request to transmit a Break signal by a high-priority repeat is entered in the repeat reception signal 27, and the transmission control circuit 35 stops transmitting the Idle signal 63.

Next, the operation in the period c will be described.
The transmission control circuit 35 transmits the control code generation control signal 41 to the control code generation circuit 36 at the timing when the transmission of the Idle signal is stopped, by using the transmission content of the Break signal by the repeat. In response to this, the control code generation circuit 36 creates a Break signal by repeat and adds it to the control code generation result signal 43. The transmission control circuit 35 continues the transmission selection signal 44 with the content of the control code transmission selection. When the control code generation status signal 42 indicates that the control code generation has been completed, the transmission control circuit 35 stops transmitting the Break signal by repeat.

Finally, the operation in the period d will be described. In the transmission control circuit 35, at the timing when the transmission of the Break signal by the repeat is stopped, the control code generation circuit 3
6, the control code generation control signal 41 is transmitted as the content of the idle signal transmission. In response to this, the control code generation circuit 36 generates an Idle signal and supplies the control code generation result signal 43 to the transmission selection circuit 34. The transmission control circuit 35 supplies a transmission selection signal 44 to the transmission selection circuit 34. When the next Idle signal 63 is transmitted, FI
Since a request for the presence of a high-priority information frame is included in the FO state signal 39, the transmission control circuit 35 stops transmitting the Idle signal. Thereafter, transmission of the information frame is started.

By performing the above-described control processing, even if the transmission control code data and the information frame are mixed, it is possible to transmit the information while keeping the information at a constant interval. As a result, when an abnormality occurs, each node operates independently, and confusion does not occur even if the Break signal 62 and the information frame 64 coexist, eliminating the possibility of causing an error in the termination change timing on the ring master. Can be.

As described above, by providing the function of keeping the transmission interval of the transmission control code and the information frame constant, the termination change timing can be determined, so that the interruption of the system operation can be reduced.

FIG. 14 is a time chart for explaining the storage operation of the node address. A of the switch circuit 6
In each of the system receiving unit 19 and the B system receiving unit 20, the LAN reception signal 29 is received by the reception control code detection circuit 46,
After the control code determination is performed and the control code information reception is completed, the control code type is output as control code information in the reception status 24 and transmitted to the CPU interface circuit 15.

The CPU interface circuit 15 receives this, stores therein the generated control code type every time the control code type content changes, and stores the control code information for each generated control code type. Further, it notifies the CPU of the occurrence of the control code reception.

By taking this measure, it is possible to receive the reception control code type and the control code information in a consistent manner even if the reception processing of the CPU is delayed. If the control code type does not match the control code information due to a delay in the reception process, the contents of the loop connection information may be inconsistent, and the system operation may be interrupted.

As described above, a control signal transmitted between adjacent nodes is transmitted with the own node address added thereto, and the node address signal is stored for each control signal type. It is possible to reduce interruption of system operation caused by missed address information that may occur.

FIG. 15 is a time chart for explaining the node address storage operation when the control code type does not change and only the address value changes. In each of the A-system receiving unit 19 and the B-system receiving unit 20 of the switch circuit 6, the LAN
The reception signal 29 is received by the reception control code detection circuit 46, the control code discrimination is performed, and after the control code information reception is completed, the control code type and the control code information are output in the reception status 24, and the CPU interface circuit 15
To communicate.

However, when only the control code information (address value) changes without changing the content of the control code type, the control code information is transmitted and changed once so that the control code type is not detected. The control code type value is transmitted.

Next, a case where a Break code is received twice consecutively as shown in FIG. 15 will be described. CPU
The interface circuit 15 receives this, stores the generated control code type therein whenever the content of the control code type changes, and stores control code information for each generated control code type. Further, the occurrence of the control code
Notify PU11.

As described above, when the control code type does not change and the address value changes, the occurrence of information change is detected, and the node address information is stored with the changed value, thereby reducing the load on the control software. can do.

FIG. 16 is a time chart for explaining the frame return operation. In the switch circuit 6, the CP
When there is no return request from U11, the transmission frame from the transmission / reception control circuit 5 is accepted, and the transmission / reception control circuit interface circuit 16 sends the A-system transmission unit 17, the B-system transmission unit 1
8 synchronizes the timing with the control code signal sent as the transmission frame signal 26 to the LAN interface circuit 2.
Sent from one. Further, the reception frame signal 25 received from the A-system receiving unit 19 and the B-system receiving unit 20 is transmitted to the transmission / reception control circuit 5 as a frame reception signal.

When there is a return request, a return instruction 30 is sent from the CPU interface circuit 15 to the transmission / reception control circuit interface circuit 16, and in response to this, the transmission / reception control circuit interface circuit 16 sends the return command 30
Is transmitted to the transmission / reception control circuit 5 without being transmitted to the A-system transmission unit 17 and the B-system transmission unit 18 of the switch circuit 6. Further, even if the received frame signal 25 is sent from the A-system receiving unit 19 and the B-system receiving unit 20, it is not accepted.

With this function, it is possible to completely separate the operation status from the transmission / reception units of the A-system and B-system inside the switch circuit. It is possible to easily determine whether or not an abnormality has occurred.

As described above, the transmission / reception control circuit 5
By returning the transmission signal from the receiver as it is as the return reception signal, it is possible to quickly detect the location where the abnormality has occurred, and to eliminate interruption of the system operation caused by erroneous reception control code due to the influence of signal noise or the like.

FIG. 17 is a time chart for explaining the folding operation in the switch circuit. Hereinafter, the operation of the switch circuit 6 will be described with reference to this time chart.

When there is no return request from the CPU 11, the switch circuit 6 accepts a transmission frame from the transmission / reception control circuit 5, and the transmission / reception control circuit interface circuit 1
6 is synchronized with the transmission frame signal 26 sent to the A-system transmission unit 17 and the B-system transmission unit 18 and sent out from the LAN interface circuit 21 as a transmission signal on the LAN. Further, the reception frame signal 25 received by the A-system reception unit 19 and the B-system reception unit 20 is transmitted to the transmission / reception control circuit 5 as a reception frame signal.

When there is a return request, a return instruction 30 is sent from the transmission / reception control circuit interface circuit 16 to the LAN.
Sent to the interface circuit 21 and received
The interface circuit 21 returns the LAN transmission signals from the A-system transmission unit 17 and the B-system transmission unit 18 to the A-system reception unit 19 and the B-system reception unit 20 without transmitting them to the LAN.

Further, even if a received signal on the LAN is sent from the next stage, it is not accepted. With this function, it is possible to completely separate the operation components and the components after the switch circuit, and if a transmission operation error occurs, it is easy to determine which part has an error. It can be implemented. As described above, by returning the transmission signal at its own stage as it is and returning it as a reception signal, the location where the abnormality has occurred can be quickly detected, and the error occurs due to the wrong reception control code due to the influence of signal noise etc. Interruption of system operation can be eliminated.

FIG. 18 shows an example of a transaction when a node is added (terminated connection). The ring master loop management means 1 includes, as information, a report indicating that the connection was confirmed from the N2 node to the N3 node. St
atus. When r eq is received, Re addressed to the N2 node
port Status. A request is sent to the data link layer means 3 for res. Further, it notifies the network management means 2 that the N3 node has been confirmed.

When receiving an instruction from the network management means 2 to connect to the N3 node, the loop management means 1 requests a terminating connection, and sends a Link to the loop management means 1 of the N2 node. Connect. req
Is transmitted to the data link layer means 3. The loop management means 1 of the N2 node sends L
inc Connect. When receiving the req, the Link master destined for the loop management means 1 of the ring master Conne
ct. A request for transmission of rsp to the data link layer means 3 is made, and a termination connection process is executed for the system on the N3 node side.

As shown in FIG. 18, when the terminating connection terminates normally with connection possible, the N2 node stops the termination and repeats, and both systems can transmit and receive frames. Re for the ring master addressed to the loop management means 1 having connection completion as information
port Status. The transmission request is sent to the data link layer means 3 for req. The loop management means 1 of the ring master uses this Report Status. Upon receiving the req, it is confirmed that the N3 node has been connected, and the report addressed to the loop management means 1 of the node N2 is received. Stat
us. A request for transmission of rsp to the data link layer means 3 is made. After that, the System including the node connection information
The Conf message is transmitted as a format addressed to all nodes. Other nodes receive and store this message.

FIG. 19 shows an example of a transaction for adding a node (repeat-through connection). When the N3 node is connected with the terminating connection as shown in FIG. 18, the loop management means 1 of the ring master acquires the node arrangement table 65A65B (see FIG. 12) held by the N3 node. Get addressed to means 1
Table. The transmission request is sent to the data link layer means 3 for req. Upon receiving this, the loop management unit 1 of the N3 node receives a Get to the ring management unit 1 of the ring master having the node array table 65 as information. Tab
le. A request for transmission of rsp is sent to the data link layer means 3.

The loop management means 1 of the ring master
t Table. If a new node that is not connected can be confirmed in the node array information in the rsp, Li to the loop management means 1 of the N3 node requesting a repeat-through connection in order to connect those nodes collectively.
nc Connect. The transmission request is sent to the data link layer means 3. The loop management means 1 of the N3 node includes:
Link that requires repeat-through connection Connect
t. When receiving the req, the Link master destined for the loop management means 1 of the ring master Connect. A request for transmission of rsp to the data link layer means 3 is made, and a repeat-through connection process is executed for the system on the N4 node side.

As shown in FIG. 19, when the repeat-through connection ends normally with connection possible, the N3 node stops terminating and repeats.
In addition, both systems can transmit and receive frames, and report to the loop management means 1 of the ring master having connection completion as information. Status. The transmission request is sent to the data link layer means 3 for req. The loop management means 1 of the ring master uses this Report Status. When receiving the req, it is confirmed that the N4 node and the like are connected,
Report addressed to loop management means 1 of N3 node S
status. A request for transmission of rsp to the data link layer means 3 is made. Then, Sys containing the node connection information
tem The Conf message is transmitted as a format addressed to all nodes. Other nodes receive and store this message.

FIG. 20 shows an example of a system in which an island is formed.
When communication between the N2 node and the N3 node and between the N7 node and the N6 node cannot be performed, the nodes N3, N4,
There is an island that can communicate between N5 and N6. When the ring master (node N0) knows that the adjacent node confirmation processing has been completed between the N2 node and the N3 node, the ring master (node N0) notifies the network management means 2 of the completion. Instruct the N2 node to terminate the connection with the N3 node. If the connection is successful, the node arrangement table 65 is obtained from the N3 node, and there are unconnected nodes N4, N5, and N6 among them. Is confirmed, a repeat-through connection is instructed to the N3 node to connect a plurality of nodes at once. In this way, the newly confirmed multiple nodes are
Connections can be made at once without affecting system operation.

The node array tables 65A, 65B
Is created as follows. FIG. 21 shows an example of a transaction for acquiring a node array in the present invention. After completing the adjacent node confirmation processing, the ring master loop management means 1 requests the next node address to the loop management means 1 of the adjacent N1 node whose processing has been found.
Address. Send the req signal. The loop management means 1 of the N1 node uses the node address (N2) of the adjacent node (N2 node) in the system on the opposite side of the system that has received it.
N which responds to the next node address having
ext Address. Return rsp to the ring master.
The ring master further includes a loop management unit 1 of the node N2.
Next requesting the next node address to Ad
ress. Nex that transmitted a req signal and responded to the next-stage node address having the node address N3 as information.
t Address. res signal is received, and so on. Address. Next, receiving the rsp, or not knowing the adjacent node address, that is, Next Address.
Next until the rsp signal is received. Address.
The transmission of the req signal is repeated. By confirming the addresses in this manner, erroneous detection can be made when node addresses are erroneously registered overlappingly, and the system downtime in such a case is reduced.

Here, the example of the node array table shown in FIG. 12 will be described in more detail. This is the next-stage address request Next Address. req, Atres response Next Address. It is a table which stores the node address confirmed by the processing of res. It is composed of the number of nodes, ring / bus, and address. The ring master writes addresses in the order in which the nodes are arranged. Is the ring / bus a ring terminated by a ring master,
Indicates whether another node has become a terminating bus. In the case of a bus terminated by another node, a node arrangement table can be created for both the A-system side and the B-system side. When the ring master creates the node array table, it notifies all connected nodes of this. When an island is formed as shown in FIG. 20, the node with the smallest address among the nodes N3, N4, N5, and N6 becomes the ring master, and the node array table 65 is created similarly.

According to the above procedure, every time a node is added, the node array table is updated and transmitted to nodes other than the ring master. If the ring master stops operating due to some abnormality, the configuration is newly renewed using the node array information table 65 held in each node. For this reason, new connection confirmation is not required, and system transmission is resumed in a short time.

As described above, by maintaining the in-loop connection information at a plurality of stations, the interruption time of the system operation caused by the failure of the ring master can be shortened. Also, when the ring master checks the address of the connecting station at initialization, the address of the adjacent station is checked, so that errors in the set station address value can be easily detected. Can be shortened.

FIG. 22 shows an example of a transaction for transmitting an initialization command. When a system initialization operation occurs due to a system error or a command from a higher system, a system initialization command is transmitted from the ring master. In this case, the control code (Break)
Signal).

A normal Break signal sends a node address value at which an error has occurred as control code information. In this case, a value dedicated to initialization is transmitted as control code information (a value not used as a node address is used). By using this method, the time required for software can be reduced.

As described above, since the network initialization command can be relayed and transmitted by hardware, the interruption time of the system operation when the network initialization operation occurs can be shortened.

FIG. 23 is a timing chart of the frame check operation. The LAN reception signal is received by the LAN interface circuit 21 and passed to the A-system reception unit 19 and the B-system reception unit 20 as a LAN reception signal. An information frame is detected by an information frame detecting circuit 49 in these receiving sections, and the received frame is detected as a received frame extracting signal 57 by the receiving FIFO circuit 5.
0 and send it to the received frame check circuit 47. Receive FI
In the FO circuit 50, the transmission / reception control circuit interface circuit 1
6 is sent to the receiving frame signal 25. The received frame check circuit 47 checks whether the frame is correct by using a check signal in the frame. A CRC check is used as a check method. The check result is stored in the reception status 24 and the CPU interface circuit 15
To communicate. The check result has the contents of check normal / check abnormal.

As shown in the figure, the CPU interface circuit 15 increases the normal counter from n to n + 1 when the content of the reception status 24 is normal, and increases the abnormal counter from m to m + 1 when the content of the reception status 24 is abnormal.

The value of the normal / abnormal counter is read from the CPU circuit to obtain the number of normally received frames and the number of abnormally received frames. Using this count number, the status of the network can be confirmed.

This counting function is provided on both sides of the A-system and the B-system. It is also possible to compare the quality of the network based on the frequency of occurrence of an abnormality.

As described above, the above check is performed for each system that receives an information frame, and by counting the number of abnormal data occurrences, it is possible to grasp the state of the network. It is possible to speed up the abnormality diagnosis and shorten the loop interruption time.

FIG. 24 shows an example of a transaction for confirming the return state of an abnormality that has occurred after confirmation of an adjacent node according to the present embodiment. The adjacent node confirmation is a process performed by the loop management unit 1, and is performed when the node starts up or when communication with the adjacent node cannot be performed due to a signal interruption or the like. Quiet signal 60, Ack signal 6
1. The Idle signal 63 is a non-repeat control signal exchanged between two adjacent stations. Ack signal 6
1 is a response to the Quiet signal 60. During normal operation, the idle signal 63 is transmitted when there is nothing to transmit or repeat the frame. Quiet signal 60
Ack signal 61 is added with information and transmitted. The information is set in the switch circuit 6 by the loop management means 1. In the adjacent node confirmation, the node address of the own station is set as information. When the Ack signal 61 corresponding to the Quiet signal 60 is obtained, the loop management unit 1 determines that communication with the adjacent node is possible, and the Idle signal 6
Send 3. The Idle signal 63 is a signal that flows after the confirmation of the adjacent node is performed.

The information frame 64 for performing the confirmation in the above operation and notifying the connection completion is sent to the ring master, and the connection is confirmed. Thereafter, if any transmission abnormality occurs during the transmission operation and it is necessary to reconfirm the connection, the N1 node sends the connection abnormality occurrence notification control code to the N2 node again. In this case, the connection is confirmed again in the same procedure as in the initial connection. After the reconfirmation, it is possible to return to the state before the occurrence of the abnormality.

Considering the time required for reconnection, the N1 side
Since the same procedure can be used for both the N2 side and the initialization, the extra judgment can be reduced and the processing time can be shortened.

As described above, the control code type is reduced by setting the connection request control code at the time of the initial connection confirmation operation between adjacent stations and the connection error occurrence notification control code after the connection is completed to the same control code. However, by simplifying the control processing, the interruption time of the system operation when an abnormality occurs can be shortened.

FIG. 25 shows a communication module 7 according to another embodiment of the optical double loop network system according to the present invention.
FIG. In the figure, the upper configuration is the same as that shown in FIGS. The configuration is such that a LAN switch circuit 66 is added to the communication module of FIG. The LAN switch circuit 66 is used for switching connection of input / output signals on the LAN, and is connected to both sides of the A system and the B system and used for two circuits.

FIG. 26 is a block diagram showing a detailed configuration of the LAN switch circuit 66 and a connection configuration thereof. For the sake of explanation, a transmission path connecting the N1 node and the N2 node is taken out. The LAN switch circuit 66 includes a transmission switch circuit (SW-a) 69 and a reception switch circuit (SW-a).
b) 70, and a transmission / reception connection switch (SW-c) 71. The system connection is switched by turning on and off these switches.

FIG. 27 shows a normal connection state. In this case, the transmission / reception connection switch 71 in the LAN switch circuit 66
Is off and no signal is passed. The transmission switch circuit 69 and the reception switch circuit 70 are in the ON state, and the signal passes. The transmission signal from the N1 node side switch circuit 6 is transmitted to the transmission switch circuit 6 in the LAN switch circuit 66.
9, through the optical fiber 9, to the switch circuit 6 via the reception switch circuit 70 in the N2 node side LAN switch circuit 66.

Conversely, the transmission signal from the N2 node side switch circuit 6 passes through the transmission switch circuit 69 in the LAN switch circuit 66, passes through the optical fiber 9, and passes through the N1 node side L
The signal reaches the switch circuit 6 via the reception switch circuit 70 in the AN switch circuit 66.

FIG. 28 shows an example of the situation at the time of the connection switching operation. In this case, an abnormality occurs in the optical fiber from the N1 node to the N2 node, and the connection of the LAN switch circuit 66 is switched to secure the transmission in the transmission direction.

In this case, the transmission switch circuit 69 and the transmission / reception connection switch 71 in the N1 node side LAN switch circuit
Is in the ON state, and the reception switch circuit 70 is in the OFF state. The reception switch circuit 70 and the transmission / reception connection switch 71 in the LAN switch circuit on the N2 node side are in the ON state, and the transmission switch circuit 69 is in the OFF state.

The transmission signal from the N1 node side switch 6 passes through the transmission switch circuit 69 and the transmission / reception connection switch 71 in the LAN switch circuit 66, passes through the optical fiber 9 in a direction opposite to the normal direction, and returns to the N2 node side LAN switch circuit 66. It reaches the switch circuit 6 via the transmission / reception connection switch 71 and the reception switch circuit 70 in the inside. Receiving switch circuit 70
The N2 node side transmission switch circuit 69 is turned off to prevent a signal from flowing in an extra direction.

By controlling the LAN switch circuit 66, even if one system of the double optical cable is disconnected or becomes abnormal, the information transmission direction is reversed so as to prevent the information from being disconnected. can do. As a result, even when an abnormality occurs, transmission of system information and the like is quickly performed.

As described above, when one side of the double loop is broken, the connection direction is switched, it is possible to prevent the line through which information flows, and to shorten the system operation interruption time when an abnormality occurs. .

FIG. 29 shows an example of a system in which islands of a connection state are formed by disconnection of an input signal. From the island side of node N3-node N4-node N5-node N6, node N0
-Although information can be output to the islands of the node N1-the node N2-the node N7, the information on the opposite side cannot be exchanged and the system is separated into two islands.

FIG. 30 shows a signal connection between the LAN switch circuit 6
This is a system in which the island is eliminated by switching at 6. When it is determined at the system configuration that the information transmission breaks at both ends of the island are in the same direction on only one side as shown in FIG. 29, the LAN switch connection of the same part on both islands is switched, and the signal connection direction is changed. Reverse. As a result, information can be exchanged between both islands. As a result, the "island" in the system is eliminated, and the system can be operated for all nodes.

An operation procedure when a disconnection occurs between the nodes N6 and N7 and a new disconnection occurs between the nodes N2 and N3 will be described below.

(1) The node N6-N7 is disconnected, and the system is operated with a bus connection having the nodes N6 and N7 at both ends. However, it has been detected that only information from the node N7 to the node N6 cannot be transmitted, and all the nodes hold this information.

(2) Information cannot be transmitted from the node N2 to the node N3.

The node N3 notifies the node N2 of the occurrence of an abnormality, and attempts to reconnect, but cannot connect.

(3) Since a certain time has elapsed, the node N
3. Node N2 also determines that a disconnection has occurred, and node N2 notifies the ring master. The ring master determines that the island configuration has been established, and issues a reverse connection command to the node N2. Nodes N4 and N indicate that the island has changed from node N3.
5, N6, and the node N3 becomes the temporary ring master.

(4) Both the nodes N2 and N3 switch the LAN switch to reverse the connection.

(5) The node N3 confirms that the connection from the node N2 to the node N3 has become possible, and the node N6
To the ring master of the node N0 via the node N7.

(6) The ring master notifies other nodes that the single ring configuration has been formed. Thereafter, the system operates as a single loop.

As described above, the occurrence of the "island" situation in the system can be reduced by switching the route through which the information flows and detecting the information of the stations as much as possible.

[0139]

As is apparent from the above description, according to the first aspect of the present invention, the node address of the own station is added to the transmission signal of the control signal at the time of confirming the adjacent node, and the node address becomes normal on the receiving side. Is determined, and only when it is determined to be normal, the ring master node is notified of the adjacent node confirmation information by repeat, so that the number of interruptions of the system operation due to the occurrence of the abnormality can be reduced. it can.

According to the second aspect of the present invention, the ring master node notifies other nodes of information as to whether or not it is possible to transmit a signal in a ring shape. When a communication failure with a node is detected, a ring master node is notified of the occurrence of an error by a repeat, and when a node in the middle of the repeat detects an error in information, the signal repeat indicating a system operation interruption is aborted. Therefore, it is possible to reduce the number of times the system operation is interrupted due to the occurrence of an abnormality, and it is possible to reduce malfunctions due to noise.

According to the third aspect of the invention, each node keeps the transmission intervals of the control signal not to be repeated, the signal indicating the suspension of the system operation, and the information frame for notifying the ring master node of the occurrence of the abnormality constant. Because we hold
It is possible to reduce the number of times the system operation is interrupted due to the occurrence of an abnormality.

According to the fourth aspect of the present invention, each node stores the node address for each control signal type, so that the system operation caused by missing address information which may be caused by the operation delay of the CPU. Interruptions can be reduced.

According to the invention of claim 5, when the control code type does not change and the node address information changes,
Since the occurrence of the event change is detected and the node address information is stored with the changed value, the effect of reducing the load on the control software can be obtained.

According to the sixth aspect of the present invention, the transmission signal is looped back to the reception signal in response to the generation of the loopback command, so that the interruption time of the system operation due to the occurrence of the abnormality can be reduced. can get.

According to the seventh aspect of the present invention, the transmission signal is not transmitted to the next-stage node but is used as the input signal to the own node in response to the generation of the return instruction. The effect that the interruption time of the operation can be reduced can also be obtained.

According to the eighth aspect of the present invention, the node connection information is shared at the time of the initial system configuration of a plurality of nodes and at the time of changing the connection node configuration, so that the interruption time of the system operation due to the occurrence of an abnormality can be reduced. The effect that can be obtained is also obtained.

According to the ninth aspect of the present invention, at the time of initialization, the connection node address is confirmed by the ring master node, and at the time of this confirmation, the address of the node adjacent to the target node is confirmed. There is also an effect that the interruption time of the system operation at the time can be reduced.

According to the tenth aspect of the present invention, the loop initialization request control code used to instruct each node to perform system initialization when an abnormality occurs is sequentially relayed and transmitted by hardware. There is also an effect that the interruption time of the system operation when the operation occurs can be reduced.

According to the eleventh aspect, the presence or absence of an abnormality is checked for each direction in which a signal is transmitted, and the number of occurrences of abnormal data is counted. It is possible to grasp using a stochastic method, thereby obtaining an effect that the abnormality diagnosis can be speeded up and the reap interruption time can be reduced.

According to the twelfth aspect, when one of the doubly connected optical fibers becomes abnormal, the other doubly connected optical fiber is disconnected from the normal signal transmission system. Since the switching means is provided for switching between nodes in which a line abnormality has occurred, the interruption time of system operation when an abnormality occurs can be shortened.

According to the thirteenth and fourteenth aspects,
When a line error occurs at two or more locations in the double-connected optical fiber, the optical fiber is switched so that the signal can be transmitted around one direction of the ring, reducing the occurrence of island conditions in the system. There is also obtained an effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an entire configuration of an embodiment of an optical double loop network system according to the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a communication module constituting the embodiment shown in FIG. 1;

FIG. 3 is a functional block diagram of the communication module shown in FIG. 2;

FIG. 4 is a functional block diagram showing a detailed configuration of a switch circuit shown in FIG. 2;

FIG. 5 is a block diagram showing a detailed configuration of each of the A-system and B-system transmission units shown in FIG. 4;

FIG. 6 is a block diagram showing a detailed configuration of each of the A-system and B-system receiving units shown in FIG. 4;

FIG. 7 is a diagram showing a configuration of a control code used in the embodiment shown in FIG. 1;

FIG. 8 is a diagram showing a configuration of an information frame used in the embodiment shown in FIG. 1;

FIG. 9 is an example of an adjacent code confirmation transaction used in the embodiment shown in FIG. 1;

FIG. 10 is a communication disable notification example in the case where ring-shaped signal transmission is possible in the embodiment shown in FIG. 1;

FIG. 11 is an example of a communication disable notification in the case where ring-shaped signal transmission is impossible in the embodiment shown in FIG. 1;

FIG. 12 is a diagram showing a configuration example of a node array table in the embodiment shown in FIG. 1;

FIG. 13 is a time chart for explaining a process for securing a control code and a transmission frame interval in the embodiment shown in FIG. 1;

FIG. 14 is a time chart for explaining a storage operation of a node address in the embodiment shown in FIG. 1;

FIG. 15 is a time chart for explaining a node address storage operation when the control code type does not change and only the address value changes in the embodiment shown in FIG. 1;

FIG. 16 is a time chart for explaining a frame return operation in the embodiment shown in FIG. 1;

FIG. 17 is a time chart for explaining a folding operation in the switch circuit in the embodiment shown in FIG. 1;

FIG. 18 shows an example of a transaction when a node is added (terminated) in the embodiment shown in FIG. 1;

FIG. 19 is a transaction example of node addition (repeat-through connection) in the embodiment shown in FIG. 1;

FIG. 20 is a system configuration diagram in which an island is formed in a ring connection node.

FIG. 21 is an example of a transaction when creating the node array table shown in FIG. 12;

FIG. 22 is a transaction example of transmitting an initialization command in the embodiment shown in FIG. 1;

FIG. 23 is a timing chart of a frame check operation in the embodiment shown in FIG. 1;

FIG. 24 is an example of a transaction for confirming a return state with respect to an abnormality occurring after confirmation of an adjacent node in the embodiment shown in FIG. 1;

FIG. 25 is a block diagram showing a configuration of a communication module according to another embodiment of the optical dual loop network system according to the present invention.

26 is a block diagram showing a detailed configuration and a connection configuration of the LAN switch circuit shown in FIG.

FIG. 27 is a diagram showing a normal connection state of the LAN switch circuit shown in FIG. 25;

FIG. 28 is a diagram showing an example of a situation at the time of a connection switching operation of the LAN switch circuit shown in FIG. 25;

FIG. 29 is an example of a system in which an island of a connection state is formed by disconnection of an input signal according to the embodiment shown in FIG. 25;

FIG. 30 is a switching state diagram of the LAN switch circuit for eliminating the island of FIG. 25;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Loop management means 2 Network management means 3 Data link layer means 4 Transmission / reception driver 5 Transmission / reception control circuit 6 Switch circuit 7 Communication module 8 Node 9 Optical fiber 10 Ring master node 11 CPU 12 Internal bus 13 Memory circuit 14 Host interface circuit 15 CPU interface Circuit 16 Transmission / reception control circuit interface circuit 17 A-system transmission unit 18 B-system transmission unit 19 A-system reception unit 20 B-system reception unit 21 LAN interface circuit 32 Transmission frame selection circuit 33 FIFO circuit 34 Transmission selection circuit 35 Transmission control circuit 36 Control code Generation circuit 46 Reception control code detection circuit 47 Reception frame check circuit 48 Frame synchronization detection circuit 49 Information frame detection circuit 50 Reception FIFO circuit 51 Reception error detection circuit 65A, 65B Node array table 66 LAN switch circuit

Claims (14)

[Claims] A plurality of nodes are connected in a ring shape by an optical fiber, and adjacent nodes sequentially repeat to transmit a signal in one direction and a signal in another direction. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the termination, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In the optical duplex loop network system that confirms the neighboring nodes, the node address of the own station is added to the control signal transmission signal when confirming the neighboring nodes Then, it is determined whether or not the node address is normal on the receiving side of the transmission signal, and only when it is determined to be normal, the adjacent node confirmation information is notified to the ring master node by repeat, Optical double loop network system. 2. The ring master node notifies each node other than the ring master node whether all nodes connected thereto can transmit a signal in a ring shape. If the communication failure with the adjacent node is detected when ring-shaped signal transmission is possible, each node notifies the ring master node of the occurrence of an abnormality by repeating using a signal indicating suspension of system operation, When the node in the middle of the repeat detects an error in the information, discontinues the repeat of the signal indicating the interruption of the system operation, and detects that communication with the adjacent node is impossible when it is impossible to transmit the signal in a ring shape. 2. The optical duplex loop network system according to claim 1, wherein each node informs another node of the occurrence of an abnormality using an information frame. 3. The communication system according to claim 1, wherein each of the nodes keeps a constant transmission interval of a control signal not to be repeated, a signal indicating a suspension of system operation, and an information frame for notifying the ring master node of occurrence of an abnormality. The optical double loop network system according to claim 2. 4. The optical double loop network system according to claim 1, wherein each node stores a node address for each control signal type. 5. The method according to claim 4, wherein when the control code type does not change and the node address information changes, it is detected that an event change has occurred, and the node address information is stored with the changed value. 2. The optical double loop network system according to item 1. 6. A method in which a plurality of nodes are connected in a ring by an optical fiber, and adjacent nodes successively repeat to transmit a signal in one direction and a signal in another direction. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the terminal, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In the optical double loop network system for confirming adjacent nodes, each of the nodes includes means for generating a return instruction for a transmission signal, An optical double-loop network system, wherein a transmission signal is turned back to a reception signal in response to the generation of a return command. 7. A method in which a plurality of nodes are connected in a ring shape by an optical fiber, and adjacent nodes successively repeat to perform signal transmission around one direction of the ring and signal transmission around the other direction. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the terminal, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In the optical double loop network system for confirming adjacent nodes, each of the nodes includes means for generating a return instruction for a transmission signal, An optical double-loop network system, wherein a transmission signal is not transmitted to a next-stage node but is used as an input signal to the own node in response to a return command. 8. A method in which a plurality of nodes are connected in a ring by an optical fiber, and adjacent nodes perform signal transmission in one direction and signal transmission in the other direction by repeating sequentially. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the termination, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks two adjacent nodes, the node connection information is used when the initial system configuration of multiple nodes and when the connection node configuration is changed. An optical duplex loop network system for sharing information. 9. A system in which a plurality of nodes are connected in a ring by an optical fiber, and adjacent nodes repeat signal transmission in one direction and signal transmission in another direction by repeating sequentially. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the termination, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks the neighboring nodes, the node address of the connecting node is checked by the ring master node during initialization. An optical double-loop network system, wherein the address of a node adjacent to the target node is confirmed. 10. A system in which a plurality of nodes are connected in a ring by an optical fiber, and adjacent nodes perform signal transmission in one direction and signal transmission in the other direction by repeating sequentially. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the termination, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks for adjacent nodes, the first loop used to command each node to initialize the system when an error occurs An optical double-loop network system, wherein the initialization request control code is sequentially relayed and transmitted by hardware. 11. A method in which a plurality of nodes are connected in a ring shape by an optical fiber, and adjacent nodes perform signal transmission in one direction and signal transmission in the other direction by repeating sequentially. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the termination, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks the neighboring nodes, the presence or absence of an abnormality is checked for each direction of signal transmission, and An optical double loop network system, which counts the number of times data is generated. 12. A system in which a plurality of nodes are connected in a ring by an optical fiber, and adjacent nodes successively repeat so as to perform signal transmission around one direction of the ring and signal transmission around the other direction. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the terminal, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks the neighboring nodes, the connection request control code for the initial connection confirmation operation between adjacent nodes and the An optical double-loop network system, wherein the same code as the notification control code after the occurrence of the connection abnormality is used. 13. A method in which a plurality of nodes are connected in a ring by an optical fiber, and adjacent nodes sequentially repeat to transmit a signal in one direction and a signal in another direction. In a state in which all the nodes are capable of transmitting signals in a ring shape, only one ring master node defined in the nodes is terminated, and all of the nodes transmit signals in a ring shape. In the state where it is impossible to perform the operation, it is determined whether the last node capable of transmitting a signal is the termination, and the adjacent node is abnormal by transmitting and receiving a control signal not to be repeated between two adjacent nodes. In an optical duplex loop network system that checks the neighboring nodes, if one of the duplexed optical fibers becomes abnormal, the duplex connection is made. An optical double loop network system, comprising: switch means for disconnecting the other optical fiber from the normal signal transmission system and switching connection between nodes having an abnormal line. 14. The optical fiber according to claim 13, wherein when a line abnormality occurs at two or more locations of the double-connected optical fiber, the optical fiber is switched and connected so that a signal can be transmitted around one direction of the ring. 2. The optical double loop network system according to item 1.