JP2024004705A - Network system and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dual-loop network system that makes it possible to transmit information without delay and detect the occurrence of abnormality in transmission paths and the occurrence sources thereof.

SOLUTION: A transmission device comprises: a CPU that is capable of processing relay information and that constitutes a control unit; a network controller that controls transmission paths therebelow; an interface unit that transmits information processed by the CPU to downstream transmission devices therebelow; a downstream abnormality information transmission unit that generates and transmits abnormality detection information upon detecting abnormality; an alert issuance unit that presents the abnormality detection information to master station transmission devices or users, explicitly indicating the transmission device having received said information first as the source of alert issuance; and a selector that selects a through or an S-F communication mode in accordance with the received information. In the through communication mode, the relay information is latched into the CPU and a receive process is performed after being transmitted to the downstream first; in the S-F communication mode, the relay information is latched into the CPU first and then transmitted to the downstream after the receive process is completed.

SELECTED DRAWING: Figure 13

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a network system and its control method.

Various types of double loop network systems have been considered, but the basic configuration is one in which one master station transmission device and multiple slave station transmission devices are connected to a double loop transmission path. The transmission paths are configured such that the transmission directions are opposite to each other in consideration of loopback.

Normally, as a method for detecting an abnormality in the transmission path, each slave station transmission device imports the received information into its control unit and makes a judgment, and when an information abnormality occurs, it sends abnormality information to the master station transmission device. . At the same time, once a slave station transmission device receives abnormal information, it is common to discard it and prevent it from being transmitted to the next transmission device.

Furthermore, Patent Document 1 describes a method for detecting an abnormality in a transmission path by expanding the transmission data control function, adding information for error detection, and transmitting the data at regular intervals to downstream devices. An abnormality in the transmission path is detected by monitoring the reception status at the master station, and the transmission equipment that detects the abnormality sets additional information and sends it downstream, allowing the master station transmission equipment to detect the occurrence and location of the abnormality in the line. However, it has been proposed to issue a loop replacement or loopback instruction.

Japanese Patent Application Publication No. 8-65328

The loop communication system disclosed in Patent Document 1 can only determine an abnormality when no abnormality detection data is received, so it can detect only simple failures such as complete interruption of information transmission. can. However, the current state of this type of loop communication system is that there are many facilities that are close to the end of their useful life, and these facilities are becoming increasingly obsolete, and new problems are occurring as a result.

Specifically, in an aging loop communication system, the transmitted information is weakened or lost, some of the transmitted information is abnormal, the integrity of the transmitted information cannot be maintained, and the transmitted information is half-finished. This is a problem with sending and receiving information. In this case, a problem has frequently occurred in recent years in which human labor is required to check communication logs and operation logs for each transmission device in order to identify the location of the failure.

In addition, although examples of literature are omitted, in the method of determining the presence or absence of an abnormality after receiving received information into the control unit, each transmission device performs reception processing for monitoring each time it receives information. A delay occurs in transmission, impairing real-time performance. Therefore, the technique of monitoring each time reception cannot be applied to a network system where real-time performance is important.

The present invention has been made in view of the above-mentioned problems, and its purpose is to enable each transmission device connected to a network to transmit information without delay, and to detect whether or not an abnormality has occurred in the transmission route, and if any, to correct it. The purpose is to provide a double-loop network system that can detect the source of the problem.

The present invention, which solves the above problems, is a double-loop network system in which a master station transmission device and a plurality of slave station transmission devices are connected to a transmission path, and these master stations and slave stations are configured. A transmission device consists of a CPU (Central Processing Unit) that can process information transmitted over a transmission route and forms the upper level of the control unit, a network controller that controls the transmission route that is lower than the CPU, and a CPU that is lower than the network controller. an interface section that sends information processed by An alarm unit that clearly indicates the transmission device as the alarm source and presents it to the master transmission device or the user from any transmission device, and a through communication mode and S&F (Store & In the through communication mode, the information to be relayed is first transmitted to the downstream transmission device and then taken into the CPU for reception processing, and in the S&F communication mode, the information is relayed. After the information is first input to the CPU and the reception process is completed, it is transmitted to the downstream transmission device.

According to the present invention, a double-loop network system is provided that allows each transmission device connected to the network to transmit information without delay, and also detects whether or not an abnormality has occurred in the transmission path, and if so, the source of the abnormality. can be provided.

1 is a schematic configuration diagram of a double loop type network system (hereinafter also referred to as "this network system") according to an embodiment of the present invention. FIG. 2 is an internal configuration diagram of a transmission device (master device or processor device). FIG. 2 is an internal configuration diagram of an interface unit (NIF). FIG. 3 is a diagram showing a data format of transmitted and received data. FIG. 3 is a diagram showing a data reception path in a transmission device. FIG. 3 is a diagram showing a data reception path inside the interface unit (NIF). FIG. 3 is a diagram showing a data format of abnormality detection information. FIG. 3 is a diagram showing a data transmission route in a transmission device. FIG. 3 is a diagram showing the flow of data when data is returned in the transmission device. FIG. 3 is a diagram showing the flow of data in the S&F communication mode inside the interface unit (NIF). FIG. 3 is a diagram showing the flow of data in the S&F communication mode in the transmission device. FIG. 3 is a diagram showing the flow of data on the transmission path L during normal operation. FIG. 3 is a diagram showing the flow of abnormality detection information on the transmission path L when an abnormality occurs. It is a flowchart which shows the processing procedure of the abnormality detection means in a master device. FIG. 6 is a diagram illustrating a process in which an abnormality detection means locates a device in which an abnormality has occurred.

Embodiments of the present invention will be described below with reference to the drawings. This network system exemplifies a network system in which a plurality of transmission devices are connected to a double loop-shaped transmission path L, and a technique for identifying a device on the network system that generates abnormal information.

FIG. 1 is a schematic configuration diagram of this network system. In this network system, one master device 1 is installed as a master station transmission device M, and five processor devices 2 to 6 are installed as slave station transmission devices P1 to P5. , are connected by transmission paths L1 and L2 (collectively referred to as L if there is no need to distinguish) which are configured in a double loop type with transmission directions in opposite directions.

Note that the number of processor devices is not limited to five, but may be two or more. Furthermore, in the following description, the master device M is assumed to be the master device 1, and the processor devices P1 to P5 are assumed to be the processor devices 2 to 6, respectively.

FIG. 2 is an internal configuration diagram of a transmission device that is a master device 1 or processor devices 2 to 6. These transmission devices 1 to 6 are composed of a CPU (Central Processing Unit) 20A of the 1st system, a CPU 20B of the 2nd system (Summary). network controllers NCP22A, 22B (collectively NCP22) connected to CPU20A, NCP22C, 22D connected to CPU20B, interface unit NIF24A connected to NCP22A, NCP22B, and connected to NCP22C and NCP22D. It is equipped with NIF24B (collectively NIF24).

The CPUs 20A and 20B are upper control units that execute application processing, and are connected to each other via an inter-CPU communication path 21 to exchange status information or control information and execute dual system functions. NCP22A to NCP22D are network controllers 22 that perform communication control of transmission route L, NCP22A and 22C control transmission route L1, and NCP22B and 22D control transmission route L2, respectively.

Further, the NCPs 22A and 22B are connected by an inter-NCP communication path 23A, and the NCPs 22C and 22D are connected by an inter-NCP communication path 23B, and each transmits and receives information bidirectionally. The NIFs 24A and 24B are interface units that control input and output to the transmission paths L1 and L2, respectively.

In the following description, the CPUs 20A and 20B will be collectively referred to as the CPU 20, the NCPs 22A to 22D will be collectively referred to as the NCP 22 or the network controller 22, and the NIFs 24A and 24B will be collectively referred to as the NIF 24 or the interface unit 24.

FIG. 3 is an internal configuration diagram of the NIF 24. The NIF 24 includes an NCP I/F 31, a selector 32, a receiver 33, and a driver 34. The NCP I/F 31 is connected to the NCP 22 (NCP 22A, 22C and NCP 22B, 22D), and has data transmission/reception, mode setting, and monitoring functions.

The receiver 33 and driver 34 are connected to the transmission paths L1 and L2, and control data reception and transmission, respectively. The selector 32 has a function of selectively selecting data received from the receiver 33 or data transmitted from the NCP I/F 31 under control of the NCP I/F 31 and outputting the selected data to the driver 34 .

FIG. 4 is a diagram showing a transmission/reception data format. As shown in FIG. 4, the transmitted and received data includes a start flag 40 for bit synchronization, a source address 410, a function code 42, a data section 43, a frame check sequence (FCS) 44, and an end flag 45. It is configured.

Note that FCS is a code added to communication protocol frames for error detection. A loopback is the flow of an electronic signal, digital data stream, or item back to its source without intentional processing or modification. It is primarily used as a means of testing power transmission and transportation infrastructure.

Next, the operation of this network system will be explained. Specifically, the procedure for receiving data from another device will be explained using FIGS. 5 and 6. FIG. 5 is a diagram showing data reception paths in transmission devices 1 to 6. FIG. 6 is a diagram showing a data reception path inside the interface unit (NIF) 24.

When the NCP 22 is not performing transmission processing, the NCP 22 sets the selector 32 of the NIF 24 to a through communication mode in which data received from the receiver 33 is selected. The NIF 24 electrically relays the received data and transmits it to the transmission path L1 or L2 via the driver 34, and simultaneously sends the received data to the NCP 22 via the NCP I/F 31.

The NCP 22 performs a frame check of the received data that has been sent, and if the frame is normal, checks the function code, searches a preset function code table, and if they match, stores the received data in the CPU shared memory. Set.

Then, if the frame of the received data is abnormal or the function code does not match, the received data is discarded. Furthermore, when a frame abnormality occurs in the received data, abnormality detection information (function code 72 in FIG. 7) in which an abnormality detection code is set as a function code is generated and transmitted.

FIG. 7 is a diagram showing the data format of the abnormality detection information. In order from the left in FIG. 7, a start flag 70, a source address 71, a function code (abnormality detection) 72, a reserve 73, an FCS 74, and an end flag 75 are formed.

The data transmission procedure will be shown using FIGS. 8 to 11. When receiving a transmission request from the CPU 20, the NCP 22 sets the selector 32 of the NIF 24 to a mode (S&F mode) in which received data is blocked and transmission data from the NCP I/F 31 is selected.

Furthermore, S&F refers to a method in which, when performing telecommunications via a relay station, information is temporarily stored at the relay point and then transferred to the final destination or another relay station. This S&F is also called store and forward switching. Relay stations and computer network nodes use S&F to confirm whether the transmitted information maintains its integrity before transmitting the information.

S&F is a method generally used in networks with intermittent connections, and is often used in harsh conditions or when communicating while moving. S&F is suitable when a long delay is acceptable, when the error rate is high, when communication is impossible without relaying, etc.

FIG. 8 is a diagram showing a data transmission path in the transmission device. After confirming the switching of the selector 32, the NCP 22 starts the feedback monitoring timer T1 and sends the transmission data to the NIF 24.

FIG. 9 is a diagram showing the flow of data when data is returned in the transmission device. When the transmitted data goes around the loop transmission path L (transmission path L1 here) and returns to the source, the data is sent from the NIF 24 to the NCP 22.

The NCP 22 checks the source address of the received data, and if it is the address of its own device, determines that it is the return of the transmitted data, returns the selector 32 of the NIF 24 to the through communication mode, cancels the feedback monitoring timer T1, Terminate the sending process normally. If the feedback monitoring timer T1 times out without the transmitted data being returned, the NCP 22 abnormally terminates the transmission process as the transmitted data is not returned.

FIG. 10 is a diagram showing the flow of data within the interface section (NIF) 24 in the S&F communication mode. FIG. 11 is a diagram showing the flow of data in the S&F communication mode in the transmission devices 1 to 6.

Since the selector 32 of the NIF 24 is held in the S&F mode, the data received by the NCP 22 during the transmission process is pulled into the NCP 22 without being electrically relayed (FIGS. 10 and 11). The NCP 22 performs a frame check on data received in S&F mode, and if the frame is abnormal, discards the received data. As a result of the frame check, if the frame is normal, it is retransmitted following the data currently being transmitted.

Further, if the frame is normal, the function code is checked, and a function code table set in advance by the CPU 20 is searched, and if they match, the received data is set in the CPU shared memory.

Next, an abnormality detection procedure when a data frame is destroyed and a data abnormality occurs due to an abnormality in the transmission path L or an abnormality in the transmission device will be explained using FIGS. 12 to 15.

FIG. 12 is a diagram showing the flow of data on the transmission path L during normal operation. Regarding data transmission during normal operation, as shown by the broken line in FIG. 12, the data is transmitted from the source transmission device 1, passes through each downstream transmission device 2 to 6, and goes around the transmission path L (L1, L2). It returns to the source transmission device and ends data transmission. The broken line in FIG. 12 indicates the direction in which data flows in the transmission path L1, and in the opposite direction in the transmission path L2.

FIG. 13 is a diagram showing the flow of abnormality detection information on the transmission path L when an abnormality occurs. Here, if an abnormality in the transmission path L or an abnormality in the transmission device destroys the data frame and causes a data abnormality, for example, in FIG. 13, after data is transmitted from the master device 1, an abnormality occurs in the processor device 4. When this occurs, the processor devices 5 and 6 relay the corresponding abnormality data and then transmit abnormality detection information, respectively.

Next, when receiving the abnormality detection information transmitted from the processor devices 5 and 6, the master device 1 checks the function code included in the abnormality detection information, and the abnormality detection code set in the corresponding function code is Since the preset function code tables match, the received abnormality detection information is set in the shared memory of the CPU 20 and reception processing is performed.

FIG. 14 is a flowchart showing the processing procedure of the abnormality detection means in the master device 1. As shown in FIG. 14, after receiving the abnormality detection information, the CPU 20 of the master device 1 determines whether the FCSs match or not. (S1). If NO in step S1, the sender address is recorded as the next abnormality detection message (S5) and the process ends. If YES in step S1, the source address is searched from the connection order table (S2).

In this step S2, the transmission source addresses set in the relevant abnormality detection information are scanned from a preset connection order table (Table 1) in the reverse order of the transmission route L that received the relevant abnormality detection information. Is the source address set in the relevant abnormality detection information an upstream device? (S3).

If NO in step S3, the source address is a downstream device, so it is discarded and the process ends. If YES in step S3, the sender address is overwritten and recorded (S4) and the process ends.

According to this network system, information can be transmitted without delay and it can be automatically determined that an abnormality has occurred in the transmission path L. More specifically, the following effects can be expected.

FIG. 15 is a diagram illustrating a process in which the abnormality detection means finds out which device has experienced an abnormality. As shown by α in FIG. 15, the source address of the abnormality detection information recorded first is 51, which corresponds to the most downstream transmission device 6. As shown by β in FIG. 15, the second recorded source address of the abnormality detection information is 31, which corresponds to the next upstream transmission device 5. After the abnormality occurs, the master device 1 repeatedly executes the process shown in FIG. 14, so that the source address of the finally recorded abnormality detection information indicated by γ in FIG. 15 is 31, which corresponds to the most upstream transmission device 4. do.

As a result, according to this network system, it is automatically detected that an abnormality has occurred in the transmission device 3 one upstream of these transmission devices 4 or in the transmission path L between the transmission device 3 one upstream. It's clear. Further, in this network system, each of the transmission devices 1 to 3, 5, and 6 other than the transmission device 4 transmitting the abnormality detection information operates in the through communication mode, thereby maintaining real-time information transmission.

This network system can be summarized as follows from the viewpoints of configuration, operation, and effects.
[1] This network system includes one master station transmission device 1 and a plurality of slave station transmission devices 2 to 6 on double-loop transmission paths L1 and L2 (collectively L) whose transmission directions are opposite to each other. This is a double loop type network system in which various transmission devices 1 to 6 are connected.

The various transmission devices constituting the master station M1 and the slave stations 2 to 6 include a CPU 20, a network controller 22 below it, an interface section 24 below it, an abnormality information transmitting section for downstream belonging to it, and a network controller 22 below it. The communication mode includes an alarm unit that presents the abnormality detection information received from the master station transmission device 1 or the user, and a selector 32 that switches and selects a communication mode between through and S&F.

The CPU 20 forms a higher level of the control unit and is capable of generating and processing information transmitted through the transmission path L. A network controller 22 controlled by the CPU 20 controls the transmission path L. The interface section 24 controlled by the network controller 22 transmits the information processed by the CPU 20 to a downstream transmission device.

As shown in the order of reference numerals 1 to 6 in FIG. , an abnormality may occur in the slave station transmission devices 2 to 6. When an abnormality is detected, the downstream abnormality information transmitting unit controlled by the interface unit 24 generates abnormality detection information and transmits it to the downstream transmission device 5 .

The alarm unit of the transmission device 5 presents the abnormality detection information to the master station transmission device 1 or the user from the transmission device 5 that received the abnormality detection information first, clearly indicating that transmission device 5 as the alarm source. Therefore, the user can know that an abnormality has occurred in the slave station transmission device 4 one upstream of the transmission device 5 or in the transmission path immediately after it. Furthermore, since this network system can monitor and detect abnormalities at one location in the master station transmission device 1, it can be more convenient not only in the case of remote monitoring.

Further, for example, depending on the information received from the upstream transmission device 4, the selector 32 provided in the one downstream transmission device 5 switches between the through communication mode and the S&F communication mode. Note that the selector 32 is provided in the interface section 24 of all the transmission devices 1 to 6.

In this network system, for example, if the information received from the upstream transmission device 4 includes abnormality detection information, the selector 32 provided in the transmission device 5 performs through communication as shown in [2] below. mode to S&F communication mode.

Normally, in the through communication mode, the information to be relayed is first transmitted to the downstream transmission device and then taken into the CPU 20 for reception processing, so there is no monitoring and there is less delay. On the other hand, in the S&F communication mode, the information to be relayed is first input to the CPU 20 and after the reception process is completed, it is transmitted to the downstream transmission device, so instead of a delay, an abnormality can be detected and abnormality detection information can be generated. Can be done.

However, if the S&F communication mode is used infrequently, for example, once a year, there will be no problem even if there is some delay in the communication state at that time. Furthermore, the CPU 20 of the master station transmission device 1 that has detected the abnormal state switches the active system and standby system in the double-loop type transmission paths L1 and L2. That is, if there is an abnormality in the active system, it is replaced with a standby system with no abnormality.

In this way, if abnormal information is detected, this network system not only discards it, but also switches the primary and secondary of the double-loop transmission paths L1 and L2, as shown in [2] below. control can be quickly executed to maintain availability.

Conventionally, in a double loop type network system, when an abnormality occurs in data flowing on the transmission path L due to an abnormality in the transmission device or the transmission path L, the source of the data abnormality cannot be detected. On the other hand, in this network system, automatically determined abnormality detection information is transmitted to the master station transmission device 1 as if the source of the abnormality were to self-report. Further, the abnormality detection information can be presented to the user via the terminal type slave station transmission device shown in [4] below.

This network system is suitable for, for example, security systems for infrastructure, transportation, and railways, and is also useful for wide-ranging displays at large railway stations and other control objects.

[2] In the present network system of [1] above, the control unit of the transmission device may set the through communication mode as the reference state when there is no abnormality, and if there is an abnormality, control as follows. The control unit switches to the S&F communication mode when transmitting information suggesting an abnormality from the transmission device itself based on the abnormality detection information. After the transmitted information indicating an abnormality travels around the transmission path L, the control unit receives and discards the information.

After discarding the information suggesting an abnormality, the control unit returns from the S&F communication mode for abnormal situations to the through communication mode for normal conditions. According to this network system, each transmission device other than the transmission device transmitting information operates in the through communication mode, so that real-time information transmission can be maintained. Moreover, this network system switches to the S&F communication mode only when there is information suggesting an abnormality, and brings the abnormal situation to an end.

[3] In this network system of [1] above, the control unit of the master station transmission device 1 sets the S&F communication mode as the reference state and receives and processes all information transmitted from the slave station transmission devices 2 to 6. It may be controlled to

In this network system, the master station transmission device 1 always operates in the S&F communication mode, and the slave station transmission devices 2 to 6 always operate in the through communication mode, thereby transmitting information on the transmission path L. At the same time, the reception processing time of each slave station transmission device 2 to 6 can be omitted, and the real-time nature of information transmission can be greatly improved.

[4] In the present network system of [1] above, the control unit of the master station transmission device 1 sets in advance the connection order to the transmission path L for the transmission devices starting from the master station transmission device 1, It is best to control it as follows. When receiving the abnormality detection information, the control unit searches for the addresses of the transmission devices included in the abnormality detection information in the order of connection.

The control unit transmits the name of the transmission device corresponding to the address as the abnormality generating device name to the terminal-type slave station transmission device connected to the network in accordance with the connection order searched in this way. Note that a terminal-type slave station transmission device is a terminal device that is equipped with a monitor that can display a screen, a keyboard that can input and output, etc., and that allows the user to recognize the status of information being transmitted in this network system. be.

The control unit presents the abnormality detection information received by the terminal-type slave station transmission device and the name of the abnormality generating device so that the user can recognize them. As an example of notification to the user, at least one of a monitor screen display, blinking of a dedicated lamp, and audio notification can be considered. Further, the control unit causes the network controller 22 to add address information of the transmission device to which the network controller 22 belongs as part of the abnormality detection information.

This network system can transmit automatically determined abnormality detection information with an address to the downstream transmission device 5 or the master station transmission device 1, and present it to the user. In this way, the present network system can detect whether an abnormality has occurred on the transmission path L and its source and present it to the user while transmitting information without delay. In addition, if the abnormality response of this network system is configured to be completely automatically executed by the master station transmission device 1 that receives the abnormality detection information and does not require presentation to the user, the terminal-type slave station transmission device is unnecessary. It is.

[5] In the network system described in [4] above, the control unit of the master station transmission device 1 calculates the connection order for the transmission devices starting from the master station transmission device 1 to the transmission path L at the time of system startup. It is recommended that you set it accordingly. According to this, the master station transmission device 1 calculates and stores the order in which all the transmission devices 1 to 6 are connected to the transmission path L when starting up the network system.

By doing so, when this network system receives abnormality detection information including the address of the abnormality generating device 4 from the slave station transmission devices 2 to 6, it searches for the corresponding address 31 from the connection order of the transmission devices 1 to 6. do. As a result, as shown in FIG. 13, the location where the abnormality has occurred can be quickly identified as the transmission device 3 or the transmission path L immediately following it.

1 Master device, 2 to 6 Processor device, 1 to 6 Transmission device, L, L1, L2 Loop type transmission path, 20, 20A, 20B CPU (forming the upper layer of the control unit), 21 Inter-CPU transmission path, 22, 22A ~22D Network controller NCP, 23, 23A, 23B NCP transmission path, 24, 24A, 24B Interface section NIF, 30 NCP I/F, 32 Selector, 33 Receiver, 34 Driver, 44, 74 FCS, 70 Start flag, 71 Sender address, 72 Function code (abnormality detection), 73 Reserve, 75 End flag

Claims (6)

A double loop type network system in which a master station transmission device and a plurality of slave station transmission devices are connected to a transmission path,
The transmission equipment that constitutes these master stations and slave stations is
a CPU (Central Processing Unit) capable of processing information transmitted through the transmission path and forming a higher level of the control unit;
a network controller that controls the transmission path below the CPU;
an interface unit that transmits information processed by the CPU at a lower level of the network controller to the downstream transmission device;
a downstream abnormality information transmitting unit that belongs to the interface unit and generates and transmits abnormality detection information when an abnormality is detected;
a reporting unit that clearly indicates the transmission device as the transmission source from any of the transmission devices that first received the abnormality detection information and presents the information to the master transmission device or the user;
a selector that switches between a through communication mode and an S&F (Store & Forward) communication mode according to information received from an upstream transmission device;
Equipped with
In the through communication mode, the information to be relayed is first transmitted to the downstream transmission device, and then taken into the CPU and processed for reception,
In the S&F communication mode, the information to be relayed is first taken into the CPU, and after the reception process is completed, the information is transmitted to the downstream transmission device.
network system. The control unit of the transmission device includes:
The through communication mode is set as a reference state,
switching to S&F communication mode when transmitting the abnormality detection information from the transmission device itself;
After the transmitted information has gone around the transmission path, receiving and discarding the information;
After the discard, returning from the S&F communication mode to the through communication mode;
The network system according to claim 1. The control unit of the master station transmission device includes:
The S&F communication mode is set as a reference state,
receiving and processing all information transmitted from the slave station transmission device;
The network system according to claim 1. The control unit of the master station transmission device includes:
A transmission device having the master station transmission device as a starting point is configured to set in advance the order of connection to the transmission path,
When the abnormality detection information is received, searching for addresses of the transmission devices included in the abnormality detection information in the connection order;
In the searched connection order, transmitting the name of the transmission device corresponding to the address as the abnormality generating device to the terminal type slave station transmission device connected to the network,
The terminal type slave station transmission device presents the received abnormality detection information and the name of the abnormality generating device to the user,
The network controller adds address information of the transmission device to which the network controller belongs to the abnormality detection information.
The network system according to claim 1. The control unit of the master station transmission device includes:
causing a transmission device whose starting point is the master station transmission device to calculate and set a connection order to the transmission path at the time of system startup;
The network system according to claim 4. A double-loop type network system control method in which a master station transmission device and a plurality of slave station transmission devices are connected to a transmission path, and control units provided in the transmission devices constituting the master station and slave stations control the system. And,
A CPU forming a higher level of the control unit is also capable of processing transmitted information,
A network controller below the CPU controls the transmission path,
a lower interface unit of the network controller transmits the information processed by the CPU to the downstream transmission device;
When a downstream abnormality information transmission unit belonging to the interface unit detects an abnormality, it generates and transmits abnormality detection information,
An alarm unit of one of the transmission devices that first receives the abnormality detection information clearly indicates the transmission device as the alarm source and presents the abnormality detection information to the master transmission device or the user,
a selector belonging to the interface unit switches and selects a through communication mode and an S&F communication mode according to information received from the upstream transmission device;
In the through communication mode, the information to be relayed is first transmitted to the downstream transmission device, and then taken into the CPU and processed for reception,
In the S&F communication mode, the information to be relayed is first taken into the CPU, and after the reception process is completed, the information is transmitted to the downstream transmission device.
Network system control method.

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