JP2022082276A - Slave device, network system, slave device control method and control program - Google Patents

Abstract

To provide a slave device that allows a failure place of a communication cable in a network system to be easily known.SOLUTION: A slave device (21c) is connected to a slave device 21b with a communication cable (30c), and includes: a first communication unit (220) that diagnoses failure of the communication cable (30c) when link down with the slave device (21b) occurs; and a control unit (210) that controls notification of a failure diagnosis result of the communication cable (30c) to the outside.SELECTED DRAWING: Figure 1

Description

The present invention relates to a slave device, a network system, a control method and a control program of the slave device.

In the field of factory automation (FA), various types of devices that share work processes are controlled. In order to operate various controllers, remote I / O, and manufacturing equipment used for work in a certain area such as factory facilities in cooperation, an industrial network system called a field network that connects these equipments has been constructed. ing.

In a general industrial network system, a master-slave network composed of various slave devices and a master device is used. A slave device is a device that controls equipment installed in a factory or collects data. The master device is a device called (PLC: Programmable Logic Controller) that centrally manages these slaves. EtherCAT® or Ethernet / IP is an example of such an industrial network system scheme (ETHERNET: Registered Trademark). In such an industrial network system, a communication cable is laid between each device to construct a network.

Japanese Unexamined Patent Publication No. 2013-236162

If a failure such as a disconnection occurs in the communication cable connecting the slave devices, the communication between the slave devices is cut off. In the industrial network system as described above, the link-off information notifying the communication blackout between the slave devices can be notified from the slave device to the master device. Therefore, the administrator can know through the master device that some kind of communication abnormality has occurred between specific slave devices. However, it is not possible to know whether the cause of the communication interruption is a failure of the communication cable. Also, it is not possible to know where the location of the failure is on the communication cable.

On the other hand, according to Patent Document 1, a technique is disclosed in which a communication terminal is provided with a function of determining a failure state of a communication cable. However, it is only possible to determine the failure state of the communication cable connected to the specific communication terminal from the specific communication terminal.

The present invention has been made in view of the above problems, and the administrator can easily identify the faulty part of the communication cable in the industrial network system, and thus the maintenance work of the communication cable can be performed. The purpose is to realize a slave device that can be executed efficiently.

The present invention adopts the following configuration in order to solve the above-mentioned problems.

The slave device according to one aspect of the present invention is connected to the first other device by the first communication cable, and when a link down occurs between the first other device, a failure diagnosis of the first communication cable occurs. It is provided with a first communication unit for performing the above and a control unit for controlling the external notification of the failure diagnosis result of the first communication cable.

According to the above configuration, the administrator can easily identify the faulty part of the communication cable in the industrial network system. Therefore, it is possible to realize a slave device that enables efficient execution of maintenance work of the communication cable.

In the slave device according to the above aspect, the slave device is further connected to the second other device by the second communication cable, and when a link down occurs between the second other device, the second communication cable is used. The second communication unit is provided, and the control unit controls the external notification of the failure diagnosis result of the first communication cable or the failure diagnosis result of the second communication cable.

According to the above configuration, the administrator can easily identify the faulty part of the communication cable in the industrial network system. Therefore, it is possible to realize a slave device that enables efficient execution of maintenance work of the communication cable.

In the slave device according to the above aspect, the first communication unit determines whether or not a link down has occurred with the first other device after a predetermined time set in advance has elapsed from the power-on of the slave device. do.

According to the above configuration, after a predetermined time has elapsed from turning on the power of the slave device, it is determined whether or not a link down has occurred with the first other device. Therefore, if a link down has occurred, it is determined. , The first communication cable can be automatically diagnosed.

In the slave device according to the above aspect, the first communication unit calculates the length of the first communication cable from the slave device to the failure point from the failure diagnosis result of the first communication cable.

According to the above configuration, since the faulty part of the first communication cable is shown as the distance from the slave device, the faulty part of the cable abnormality can be easily known.

In the slave device according to the above aspect, the second communication unit determines whether or not a link down has occurred with the second other device after a predetermined time has elapsed from the power-on of the slave device. do.

According to the above configuration, after a predetermined time has elapsed from turning on the power of the slave device, it is determined whether or not a link down has occurred with the second other device. Therefore, if a link down has occurred, it is determined. , The second communication cable can be automatically diagnosed.

In the slave device according to the above aspect, the second communication unit calculates the length of the second communication cable from the slave device to the failure point from the failure diagnosis result of the second communication cable.

According to the above configuration, since the faulty part of the second communication cable is shown as the distance from the slave device, the faulty part of the cable abnormality can be easily known.

In the slave device according to the above aspect, the control unit transmits the failure diagnosis result of the first communication cable or the failure diagnosis result of the second communication cable to the master device or the external via the first communication unit or the second communication unit. Notify the device.

According to the above configuration, the master device or the external device can acquire the failure diagnosis result of the communication cable connected to the slave device, and the administrator can easily find the failure location of the communication cable in the industrial network system. You will be able to identify.

In the slave device according to the one aspect, the first other machine is arranged on the master device side, and the second other machine is arranged on the opposite side of the master device.

The network system according to one aspect of the present invention is a network system in which a master device and a plurality of slave devices are connected, and each of the plurality of slave devices is a first other device and a first device on the master device side. When a link down occurs between the first communication cable and the first other device, the first communication unit that performs failure diagnosis of the first communication cable and the master of the failure diagnosis result of the first communication cable. Includes a control unit that controls transmission to the device.

According to the above configuration, the administrator can easily identify the faulty part of the communication cable in the industrial network system. Therefore, it is possible to realize a slave device that enables efficient execution of maintenance work of the communication cable.

The network system according to one aspect of the present invention is a network system in which a master device and a plurality of slave devices are connected, and when the master device detects a communication abnormality, the master device diagnoses cables for the plurality of slave devices. Each of the plurality of slave devices is connected to the first other device on the master device side by the first communication cable, and when the execution instruction of the cable diagnosis is received, the first communication cable is transmitted. It includes a first communication unit that performs failure diagnosis of the above, and a control unit that controls notification of the failure diagnosis result of the first communication cable to the master device.

According to the above configuration, the administrator can easily identify the faulty part of the communication cable in the industrial network system. Therefore, it is possible to realize a network system that enables efficient execution of maintenance work of the communication cable.

The method for controlling a slave device according to one aspect of the present invention includes a step of determining whether or not the slave device has a link down with a first other device connected by a first communication cable. When a link down occurs with the first other device, the step includes a step of performing a failure diagnosis of the first communication cable and a step of notifying the failure diagnosis result of the first communication cable to the outside.

According to the above configuration, the administrator can easily identify the faulty part of the communication cable in the industrial network system. Therefore, it is possible to realize a control device that enables efficient execution of maintenance work of the communication cable.

The control program according to one aspect of the present invention is a computer program for causing a computer to execute a control method of a slave device, and links down with a first other device connected by a first communication cable. The step of determining whether or not it has occurred, the step of performing a failure diagnosis of the first communication cable when a link down occurs between the first other device, and the failure diagnosis result of the first communication cable are shown. Includes a step to notify the outside.

According to the above configuration, the administrator can easily identify the faulty part of the communication cable in the industrial network system. Therefore, it is possible to realize a control device that enables efficient execution of maintenance work of the communication cable.

Management according to any one of the slave device according to one aspect of the present invention, the network system according to one aspect of the present invention, the control method of the slave device according to one aspect of the present invention, and the control program according to one aspect of the present invention. It will be possible for a person to easily identify the faulty part of the communication cable in the industrial network system, and thus it will be possible to efficiently carry out the maintenance work of the communication cable.

It is a block diagram which shows the outline of the functional structure of the slave apparatus which concerns on Embodiment 1 of this invention. It is a schematic block diagram which shows the network system provided with the slave apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the detail of the functional configuration of the slave apparatus which concerns on Embodiment 1 of this invention. It is a flowchart for demonstrating the processing procedure of PC. It is a flowchart for demonstrating the processing procedure of a slave device. It is a flowchart for demonstrating the processing procedure of the network system which concerns on Embodiment 2 of this invention.

[Embodiment 1]
Hereinafter, embodiments according to one aspect of the present invention (hereinafter, also referred to as “the present embodiment”) will be described with reference to the drawings.

§1 Application example FIG. 1 is a block diagram showing an outline of a functional configuration of a slave device 21c included in the network system 1 according to the first embodiment of the present invention. The network system 1 includes an HMI (Human Machine Interface) 11, a master device 20, and slave devices 21a to 21d. The slave devices 21a to 21d each have the same configuration and function.

As shown in FIG. 1, the master device 20 and the slave device 21a are connected by a communication cable 30a. Similarly, the slave device 21a and the slave device 21b are connected by the communication cable 30b, and the slave device 21b and the slave device 21c are connected by the communication cable 30c. Further, the slave device 21c and the slave device 21d are connected by a communication cable 30d. The slave devices 21a to 21d are connected by a daisy chain connection.

The slave device 21c includes a control unit 210, a first communication unit 220, and a second communication unit 230. The first communication unit 220 is connected to the slave device (first other device) 21b on the master device 20 side by a communication cable (first communication cable) 30c. When communication is interrupted (link down) with the slave device 21b, the first communication unit 220 performs a failure diagnosis including detection of a failure location of the communication cable 30c.

The second communication unit 230 is connected to the slave device (second other device) 21d on the opposite side of the master device 20 by a communication cable (second communication cable) 30d. When a link down occurs with the slave device 21d, the second communication unit 230 performs a failure diagnosis including detection of a failure location of the communication cable 30d.

The control unit 210 controls the first communication unit 220 and the second communication unit 230, and when a link down occurs between the first communication unit 220 and the slave device 21b, the first communication unit 220 communicates with each other. Receive the failure diagnosis result including the failure location detection of the cable 30c.

Further, when a link down occurs between the second communication unit 230 and the slave device 21d, the control unit 210 receives a failure diagnosis result including detection of a failure location of the communication cable 30d from the second communication unit 230.

The control unit 210 notifies the master device 20 of the failure diagnosis result from the first communication unit 220 and / or the failure diagnosis result from the second communication unit 230 via the first communication unit 220. Further, the control unit 210 may make an LED (Light Emitting Diode) or the like emit light to notify the outside (network administrator).

As described above, according to the slave device 21c according to the first embodiment of the present invention, the control unit 210 obtains the failure diagnosis result from the first communication unit 220 and / or the failure diagnosis result from the second communication unit 230. Since the notification is given to the master device 20 and the like, the user can identify the failure location in the required communication cable by reading the failure diagnosis result from the master device 20 and the like. Therefore, the administrator of the network system can easily identify the faulty part in the communication cable stretched in the network system. Therefore, the administrator of the network system can efficiently perform maintenance work such as removal and replacement of the location where the cable failure occurs in the field network, identification of the location where the cable abnormality frequently occurs, and countermeasures.

§2 Configuration example (Overview of network system 1)
FIG. 2 is a schematic configuration diagram showing a network system 1 including slave devices 21a to 21d, 22a to 22c, and 23a to 23c according to the first embodiment. The network system 1 includes a server 10, an HMI (terminal device) 11, a master device 20, slave devices 21a to 21d, 22a to 22c and 23a to 23c, hub devices 32a and 32b, a hub device 33, and a PC. (Personal Computer) 50-52 and the like. As a specific example, EtherCAT (registered trademark) or Ethernet / IP is applied to the network system 1 (ETHERNET: registered trademark).

The server 10, the HMI (terminal device) 11 and the PC 50 are connected to the master device 20, and the master device 20 can be controlled by transmitting an instruction from these devices to the master device 20.

The master device 20 is connected to the hub device 32b, the slave devices 21a to 21d, and the PC 51 via the hub device 32a. Further, the hub device 32a is connected to the slave devices 22a to 22c, the hub device 33, and the PC 52 via the hub device 32b. Further, the hub device 33 is connected to the slave devices 23a to 23c.

The hub device 33 corresponds to the slave devices 23a to 23c connected in a ring shape, and controls communication with each device on the upstream side. The configuration of the network system shown in FIG. 2 is an example, and is not limited thereto.

(Slave device configuration)
FIG. 3 is a block diagram showing details of the functional configuration of the slave device 21c. The slave device 21c includes a control unit 210, a first communication unit 220, and a second communication unit 230. Further, the first communication unit 220 includes a first communication control unit 221, a first communication execution unit 222, a first detection unit 223, and a first recording unit 224.

The first communication control unit 221 is a functional block that controls the entire first communication unit 220 and controls the communication by the first communication unit 220. The first communication execution unit 222 is a functional block that executes communication packet exchange with another device 21b through the communication cable 30c based on the instruction of the first communication control unit 221.

The first detection unit 223 is a functional block that executes a failure diagnosis of the communication cable 30c based on the instruction of the first communication control unit 221. The first recording unit 224 is a register that records the result of the failure diagnosis acquired by the first detection unit 223. In the failure diagnosis, at least the presence or absence of a failure and the distance information that correlates with the length from the first communication unit 220 to the failure point in the communication cable 30c when there is a failure are detected.

When executing the failure diagnosis, the first detection unit 223 sends out a specific signal waveform to the connected communication cable 30c and detects the reflected signal. As a result, the first detection unit 223 detects the distance information that correlates with the length of the communication cable 30c to the failure point. Further, a failure determination may be performed to determine the state of the communication cable 30c, that is, whether it is normal, disconnection failure, or short-circuit failure. When the first detection unit 223 executes the failure diagnosis, the result is recorded in the first recording unit 224.

The second communication unit 230 includes a second communication control unit 231, a second communication execution unit 232, a second detection unit 233, and a second recording unit 234. The second communication control unit 231 is a functional block that controls the entire second communication unit 230 and controls the communication by the second communication unit 230. The second communication execution unit 232 is a functional block that executes communication packet exchange with another device 21d through the communication cable 30d based on the instruction of the second communication control unit 231.

The second detection unit 233 is a functional block that executes a failure diagnosis of the communication cable 30d based on the instruction of the second communication control unit 231. The second recording unit 234 is a register that records the result of the failure diagnosis acquired by the second detection unit 233. In the failure diagnosis, at least the distance information that correlates with the length from the second communication unit 230 to the failure point in the communication cable 30d is detected.

When executing the failure diagnosis, the second detection unit 233 sends out a specific signal waveform to the connected communication cable 30d and detects the reflected signal. As a result, the second detection unit 233 detects the distance information that correlates with the length of the communication cable 30d to the failure point. Further, a failure determination may be performed to determine the state of the communication cable 30d, that is, whether it is normal, disconnection failure, or short-circuit failure. When the second detection unit 233 executes the failure diagnosis, the second detection unit 233 records the result in the second recording unit 234.

§3 Operation example FIG. 4 is a flowchart for explaining the processing procedure of the PC 50. Although the case where this process is performed by the PC 50 will be described, the process may be performed by any of the server 10, the HMI (terminal device) 11 or the PC 51.

First, the PC 50 sets a port number for executing automatic diagnosis in each of the slave devices 21a to 21d, 22a to 22c, and 23a to 23c connected to the network system 1 (S1). For example, in the slave device 21c, the slave device 21b is connected to the upstream side (master device 20 side), and the slave device 21d is connected to the downstream side (opposite side to the master device 20). If the respective communication ports are "1" and "2", the PC 50 sets the port number 1 and the port number 2 for the slave device 21c. For example, the PC 50 transmits the port number 1 and the port number 2 for executing the automatic diagnosis to the slave device 21c, and the slave device 21c stores the port number for executing the diagnosis. Similarly, the port number for executing the automatic diagnosis is set for the other slave devices.

Finally, the PC 50 sets a predetermined time for each slave device after the power of the slave device is turned on until the automatic diagnosis is executed (S2). This predetermined time is, for example, the time from when the power of the slave device is turned on until the initialization is performed and communication becomes possible. The PC 50 transmits to each of the slave devices 21a to 21d, 22a to 22c, and 23a to 23c a predetermined time until the automatic diagnosis is executed. Each of the slave devices 21a to 21d, 22a to 22c, and 23a to 23c stores a predetermined time until the received automatic diagnosis is executed.

FIG. 5 is a flowchart for explaining the processing procedure of the slave device 21c. First, when the power of the slave device 21c is turned on (S11), communication with the master device 20 is performed (S12). Then, the control unit 210 determines whether or not a predetermined time has elapsed after the power is turned on (S13). This predetermined time is a time preset by the PC 50 as described above.

If the predetermined time has not elapsed since the power was turned on (S13, No), the process of step S12 is repeated. Further, if a predetermined time has elapsed after the power is turned on (S13, Yes), the control unit 210 determines whether or not the port 1 or the port 2 is linked down (S14). The control unit 210 determines the link down of the port number set as the port for executing the automatic diagnosis by the PC 50.

If neither port 1 nor port 2 is linked down (S14, No), the process ends. If port 1 or port 2 is linked down (S14, Yes), the communication cable of the linked port is diagnosed (S15).

Then, the control unit 210 notifies the user (network administrator) of the diagnosis result of the communication cable (S16), and ends the process. The control unit 210 transmits the diagnosis result of the communication cable to the server 10, the HMI 11, the master device 20, the PC 50 or 51 via the first communication unit 220 or the second communication unit 230, and these devices display the diagnosis result. It may be presented to the user by doing so. Further, the control unit 210 may notify the user by causing the LED or the like provided in the slave device 21c to emit light. Further, the control unit 210 may store the diagnosis result of the cable in the first recording unit 224 and the second recording unit 234, and the master device 20 may read out the information.

If both port 1 and port 2 of the slave device 21c are linked down, communication with the master device 20 cannot be performed.

§4 Action, Effect According to the first embodiment of the present invention, when the port 1 or the port 2 is linked down after a predetermined time has elapsed from the power-on, the slave device 21c automatically connects the communication cable to the port. Diagnosis is performed and the automatic diagnosis result is notified to the user. Therefore, the network administrator can easily recognize the abnormality of the communication cable connected to each slave device.

Further, since the faulty part of the communication cable in which the abnormality has occurred is shown as the distance from the slave device 21c, the faulty part of the cable abnormality can be easily known. In an industrial network, the length of a communication cable connecting devices is sometimes as long as 100 m, but in such a case, it is uneconomical to replace the entire communication cable in which a failure occurs. Therefore, for example, a 20 m communication cable is connected with a connector and used as a longer communication cable. In such a case, according to the slave device according to the first embodiment, since the location where the abnormality occurs is specified, it is only necessary to replace the communication cable for, for example, 20 m including the faulty portion, and the maintenance of the network system 1 is economical. Can be done.

Furthermore, since the location of the failure is uniquely identified, the administrator can easily know where in the factory the communication cable has failed. There are various situations in the factory where there is a risk of damaging the communication cable, for example, as follows. Communication cables are provided along moving parts such as robot arms and moving stages, and exercise causes stress. It should be installed in a place subject to vibration or pressure. It should be installed in a place exposed to temperature changes. Exposure to sparks and high or low temperatures. Exposure to chemicals such as chemicals and gases.

If it is found that a failure has occurred at a specific position on the communication cable, the administrator can easily find out which of these factors causing the cable abnormality in the factory actually caused the failure. can. Therefore, it becomes easy to take measures so as not to cause the same failure next time.

Therefore, the administrator of the network system can efficiently carry out maintenance work such as removal and replacement of the location where the cable abnormality occurs in the field network, identification of the location where the cable abnormality is likely to occur, and countermeasures.

Further, according to the first embodiment, the slave device 21c automatically performs the cable diagnosis after a predetermined time has elapsed from the power-on, and notifies the result. Therefore, since it is possible to immediately know where in the network system 1 the failure has occurred, it is possible to carry out prompt repair measures.

[Embodiment 2]
The network system according to the second embodiment of the present invention will be described below. For convenience of explanation, the same reference numerals are added to the components having the same functions as the components described in the first embodiment, and the description thereof will not be repeated.

FIG. 6 is a flowchart for explaining a processing procedure of the network system according to the second embodiment of the present invention. First, when the power of the master device 20 and the slave device 21c is turned on (S21), the master device 20 determines whether or not a communication abnormality has occurred in the network system 1 (S22). For example, the master device 20 sequentially communicates with the slave devices 21a to 21d, 22a to 22c, and 23a to 23c, and if there is a slave device that does not respond, it is determined that a communication abnormality has occurred.

If no communication error has occurred (S22, No), the process of step S22 is repeated. If a communication error has occurred (S22, Yes), the master device 20 instructs each slave device to execute the diagnosis of the communication cable (S23).

Each of the slave devices 21a to 21d, 22a to 22c, and 23a to 23c executes the diagnosis of the communication cable when receiving the instruction of executing the diagnosis of the communication cable from the master device 20 (S24).

Then, the control unit 210 notifies the user (network administrator) of the diagnosis result of the communication cable (S25), and ends the process. The control unit 210 transmits the diagnosis result of the communication cable to the server 10, the HMI 11, the master device 20, the PC 50 or 51 via the first communication unit 220 or the second communication unit 230, and these devices display the diagnosis result. It may be presented to the user by doing so. Further, the control unit 210 may notify the user by causing the LED or the like provided in the slave device 21c to emit light. Further, the control unit 210 may store the diagnosis result of the cable in the first recording unit 224 and the second recording unit 234, and the master device 20 may read out the information.

As described above, according to the network system according to the second embodiment of the present invention, when the PC 50 detects a communication abnormality, the slave devices 21a to 21d, 22a to 22c, and 23a to 23c are connected to each of the communication cables. Instruct to execute the diagnosis. Then, each of the slave devices 21a to 21d, 22a to 22c, and 23a to 23c notifies the network administrator of the diagnosis result of the communication cable. Therefore, the network administrator can easily recognize the abnormality of the communication cable connected to each slave device.

[Example of implementation by software]
The functional block (particularly, the control unit 210) of the slave device 21c may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

In the latter case, the control device includes a computer that executes instructions of a program that is software that realizes each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. Then, in the computer, the processor reads the program from the recording medium and executes the program, thereby achieving the object of the present invention.

As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, a "non-temporary tangible medium", for example, a ROM (Read Only Memory) or the like, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. Further, a RAM (Random Access Memory) for expanding the above program may be further provided. Further, the program may be supplied to the computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. It should be noted that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

The present invention is not limited to the above-described embodiments and examples, and various modifications can be made within the scope of the claims, and the technical means disclosed in the different embodiments and examples can be appropriately used. The embodiments obtained in combination are also included in the technical scope of the present invention.

1 network system 10 server 11 HMI
20 Master device 21a to 21d, 22a to 22c, 23a to 23c Slave device 30a, 30b, 30c, 30d, 30e Communication cable 32a, 32b, 33 Hub device 210 Control unit 220 1st communication unit 221 1st communication control unit 222 1 Communication execution unit 223 1st detection unit 224 1st recording unit 230 2nd communication unit 231 2nd communication control unit 232 2nd communication execution unit 233 2nd detection unit 234 2nd recording unit

Claims (12)

When the first other device is connected to the first communication cable and a link down occurs between the first communication cable, the first communication unit that diagnoses the failure of the first communication cable and the first communication unit.
A slave device including a control unit that controls external notification of the failure diagnosis result of the first communication cable. The slave device is further connected to the second other device by a second communication cable, and when a link down occurs between the second other device, a failure diagnosis of the second communication cable is performed. Equipped with 2 communication units
The slave device according to claim 1, wherein the control unit controls the notification of the failure diagnosis result of the first communication cable or the failure diagnosis result of the second communication cable to the outside. According to claim 2, the first communication unit determines whether or not a link down has occurred with the first other device after a predetermined time has elapsed from the power-on of the slave device. The slave device described. The slave device according to claim 2 or 3, wherein the first communication unit calculates the length of the first communication cable from the slave device to the failure point from the failure diagnosis result of the first communication cable. .. 2. 4. The slave device according to any one of 4. The second communication unit calculates the length of the second communication cable from the slave device to the failure point from the failure diagnosis result of the second communication cable, according to any one of claims 2 to 5. The slave device described in. The control unit notifies the master device or an external device of the failure diagnosis result of the first communication cable or the failure diagnosis result of the second communication cable via the first communication unit or the second communication unit. , The slave device according to any one of claims 2 to 6. The first other machine is arranged on the master device side.
The slave device according to any one of claims 2 to 7, wherein the second other machine is arranged on the opposite side of the master device. A network system in which a master device and multiple slave devices are connected.
Each of the plurality of slave devices is connected to the first other device on the master device side by a first communication cable, and when a link down occurs between the first other device, the first device is used. The first communication unit that diagnoses the failure of the communication cable and
A network system including a control unit that controls transmission of a failure diagnosis result of the first communication cable to the master device. A network system in which a master device and multiple slave devices are connected.
When the master device detects a communication abnormality, it sends a cable diagnosis execution instruction to the plurality of slave devices.
Each of the plurality of slave devices is connected to the first other device on the master device side by the first communication cable, and when the execution instruction of the cable diagnosis is received, the failure diagnosis of the first communication cable is performed. With the first communication unit that performs
A network system including a control unit that controls notification of a failure diagnosis result of the first communication cable to the master device. The step of determining whether or not the slave device has a link down with the first other device connected by the first communication cable, and
When a link down occurs with the first other device, the step of performing a failure diagnosis of the first communication cable and the step of performing the failure diagnosis,
A method for controlling a slave device, which comprises a step of notifying the outside of a failure diagnosis result of the first communication cable. A computer program that causes a computer to execute a control method for a slave device.
A step of determining whether or not a link down has occurred with the first other device connected by the first communication cable, and
When a link down occurs with the first other device, the step of performing a failure diagnosis of the first communication cable and the step of performing the failure diagnosis,
A computer program including a step of notifying the outside of the failure diagnosis result of the first communication cable.

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