JP5028973B2 - COMMUNICATION SYSTEM CONTROL METHOD, COMMUNICATION DEVICE, AND COMMUNICATION SYSTEM - Google Patents

Description

  The present invention provides a control method for controlling activation / stop of at least one communication node in a communication system including three or more communication nodes that communicate with each other via multiple communication paths, and implements this control method. The present invention relates to a communication apparatus suitable for the above, and a communication system.

  In order to reduce the number (weight) of wire harnesses connecting various electrical components such as sensors, actuators, control devices,... To automobiles, these parts are connected by multiple communication paths.

  In addition, in a car, for example, when a control system that needs to operate in an engine stopped state, such as a keyless entry system, is configured using multiple communication paths, it is connected to the multiple communication paths even when the vehicle is stopped. If the communication nodes (sensors, actuators, control devices, etc.) are operated, the battery is consumed, so-called battery exhaustion occurs, and the engine may not be started.

  For this reason, in a communication system, particularly a communication system driven by a battery such as an automobile, the start / stop (wake-up / sleep) of each communication node is controlled so that the communication node operates only when necessary. Therefore, it is general to reduce the power consumption of the communication system.

  By the way, in the control of the wakeup / sleep of such a communication node, the communication node activated by an external operation or the like activates another communication node by transmitting a wakeup signal to the multiplex communication path. After startup, it is performed by a procedure of detecting that the communication node itself or all communication nodes have completed communication and shifting to a sleep state.

  In this case, each communication node needs to monitor a wake-up signal from all other communication nodes and control wake-up / sleep. Therefore, depending on the communication system, each communication node may have its communication node Must be equipped with a circuit that detects wake-up signals from other communication nodes that are not directly related to each other, which complicates the configuration of each communication node and increases the number of development days and costs. Occurs.

  On the other hand, in order to prevent this problem, a dedicated line for directly inputting / outputting a wakeup signal between communication nodes is provided, and it is also proposed that each communication node controls wakeup / sleep in the state of this dedicated line. Has been.

  However, in this method, when the dedicated line is disconnected or short-circuited to the power supply line or the ground line, there is a problem in that each communication node cannot stop operation (sleep), resulting in battery exhaustion.

Therefore, in order to prevent such problems, the wake-up signal transmission path is duplicated by using the dedicated line and the multiplex communication path, so that even if an abnormality occurs in the dedicated line, each communication node wakes up / sleeps. It has also been proposed to be able to normally control (see, for example, Patent Document 1).
JP-A-6-122350

  However, in the proposed control method, since the transmission path of the wakeup signal is simply duplicated, the wakeup / sleep of each communication node is controlled using the multiple communication path when an abnormality occurs in the dedicated line. In order to be able to do so, each communication node must monitor wake-up signals from all other communication nodes, simplify the configuration of each communication node, reduce development days, and manufacture The intended purpose of reducing the cost cannot be achieved.

  The present invention has been made in view of these problems, and in a communication system comprising a large number of communication nodes that communicate with each other via multiple communication paths, the activation / deactivation of a specific communication node can be controlled more easily and at low cost. The purpose is to be able to.

  In order to achieve this object, the invention according to claim 1 is a communication system composed of three or more communication nodes that communicate with each other via multiple communication paths, and activate / stop at least one communication node. The present invention relates to a control method for controlling.

  In this control method, one of the communication nodes is used as a monitoring node, and the monitoring node is directly connected to the control target node whose start / stop is to be controlled by the first signal line. A communication request from another communication node is monitored via the multiplex communication path, and when a communication request is generated in any of the communication nodes including itself, the first signal is thereafter transmitted until the communication of all the communication nodes is completed. By outputting the operation signal to the control target node via the line, the control target node is activated, and the operation of the control target node is continued during the operation signal output period.

  Therefore, according to the method of the present invention, one communication node set as a monitoring node needs to monitor a communication request from another communication node, and is connected to this monitoring node via the first signal line. The activated communication node (control target node) is switched from start / stop (that is, wake-up / sleep) in accordance with an operation signal input from the monitoring node via the first signal line. / Stop can be controlled with a very simple configuration.

  In other words, the monitoring node may be provided with a circuit for outputting an operation signal to the first signal line, and the control target node may be provided with a circuit for receiving the operation signal and starting the control target node. Therefore, the start / stop control of the control target node can be realized very easily and at low cost.

  In addition, for example, each communication node monitors an wake-up signal transmitted from another communication node to the multiplex communication path, and controls the start / stop of the communication node to another communication system. When adding a communication node having a function, one of the existing communication nodes and the communication node to be added are directly connected via the first signal line, and the connected existing communication node is monitored. If one of the existing communication nodes is improved to output an operation signal to the added communication node (control target node) via the first signal line when the monitoring node is operating as a node Good. That is, in this way, in an existing communication system, the activation / stop of the added communication node (control target node) can be controlled very easily according to the method of the present invention.

  Therefore, according to the method of the present invention, it becomes possible to add a communication node to an existing communication system very easily, and the design change and improvement of the communication system can be realized in a short period of time.

  By the way, in the present invention, since the operation signal is output from the monitoring node to the control target node using the first signal line, if an abnormality such as disconnection / short circuit occurs in the first signal line, the control target node is normal. Cannot be started / stopped.

  When the control target node cannot stop the operation, the power consumption by the control target node increases, and in a battery-driven communication system such as an automobile communication system, battery power is consumed wastefully. May run out of battery.

Therefore, in the present invention, when the operation signal is input via the first signal line and the operation is continued in the control target node, the communication operation of the monitoring node is monitored via the multiple communication path. When the communication operation of the monitoring node is stopped, it is determined that an abnormality has occurred in the first signal line, and its own operation is stopped .

  In other words, if the operation signal is not normally input from the monitoring node to the control target node due to disconnection / short circuit of the first signal line, the control target node side detects that fact. Thus, the operation can be stopped and the power consumption by the control target node can be suppressed to prevent the battery from running out.

  In this case, in the control target node, it is necessary to monitor the communication operation of the monitoring node and determine whether to stop the communication operation of the monitoring node. For this determination, for example, the output from the monitoring node is monitored. When the output stop period continues for the operation stop determination time or longer, it is only necessary to determine that the monitoring node has stopped the communication operation, and it is not necessary to check the transmission data from the monitoring node. This determination can be easily realized.

  Further, as described above, a communication node is added to the existing communication system, and one of the existing communication nodes is set as a monitoring node, and the monitoring node and the added communication node (control target node) are connected by the first signal line. When connected, the start / stop of the control target node can be easily controlled, but in order to enable the monitoring node to detect a communication request from the added control target node, the control target node can receive multiple communication paths. Therefore, it is necessary to be able to decode the communication request data output to the monitoring node side, and it is necessary to add a circuit for that purpose.

Therefore, in order to enable the monitoring node to easily detect a communication request from the added control target node, as described in claim 2 , the monitoring node and the control target node are connected to the second signal line. When the communication request is generated, the control target node may notify the monitoring node of the communication request via the second signal line.

  That is, in this way, the monitoring node can detect a communication request from the control target node based on the notification signal input via the second signal line, and the control target node can switch to the multiple communication path. Since it is not necessary to decode the output communication request data, the monitoring node can be easily configured using the existing communication node.

When the monitoring node and the control target node are connected via the second signal line as described above, the monitoring node is controlled via the second signal line as described in claim 3. When the notification signal is input from the node, the communication operation of the control target node is monitored via the multiplex communication path. When the communication data of the control target node has not changed for a certain time, the communication from the control target node It may be determined that there is no request.

  In this way, when an abnormality such as disconnection / short circuit occurs in the second signal line, it is erroneously determined that the notification signal is input from the control target node on the monitoring node side. Can be prevented.

Next, the invention described in claims 4 and 5 relates to a communication apparatus suitable for realizing a control target node in the control method of the present invention described above (claims 1 to 3 ).

The communication device according to claim 4 is configured to be able to input an operation signal from another communication node constituting the communication system via the first signal line, and the first operation is performed while the operation is stopped. When the operation signal is input through the signal line, the operation is started, and then the operation is continued until the input of the operation signal is stopped.

According to a fourth aspect of the present invention, when an operation signal is input through the first signal line, the communication device of the communication node connected through the first signal line via the multiple communication path is provided. The communication operation is monitored, and when the communication operation of this communication node is stopped, it is determined that an abnormality has occurred in the first signal line, and its own operation is stopped.
Therefore, if the communication device according to claim 4 is used as a control target node, the control method according to claim 1 can be realized.

In addition, when the communication device according to claim 5 generates its own communication request, the communication device notifies the other communication node connected via the first signal line via the second signal line. To do. Therefore, if this communication apparatus is used as a control target node, the control method according to claim 2 or claim 3 can be realized.

Next, the invention described in claims 6 to 8 relates to a communication system suitable for controlling activation / stop of at least one communication node according to the control method of the present invention ( claims 1 to 3 ) described above. Is.

The communication system according to claim 6 is provided with a monitoring node and a control target node connected via a first signal line as one of the communication nodes.
Then, the monitoring node monitors communication requests from other communication nodes via the multiplex communication path, and when a communication request occurs in any of the communication nodes including itself, the communication of all the communication nodes is completed thereafter. Until then, the operation signal is output to the control target node via the first signal line.
Further, the control target node starts when an operation signal is input through the first signal line while the operation is stopped, and then continues to operate until the input of the operation signal is stopped.
In addition, when the operation signal is input via the first signal line, the control target node monitors the communication operation of the monitoring node via the multiple communication path, and the communication operation of the monitoring node is stopped. Sometimes, it is determined that an abnormality has occurred in the first signal line, and its own operation is stopped.
Therefore, according to this communication system, the start / stop of at least one communication node can be controlled according to the control method described in claim 1 .

  Further, in the communication system according to claim 7, the monitoring node can acquire a notification signal indicating that a communication request has occurred in the control target node from the control target node via the second signal line. When the notification signal is acquired from the control target node via the second signal line, it is detected that the control target node is outputting a communication request.
  Further, when the communication target node generates a communication request, the control target node notifies the monitoring node connected via the first signal line of the communication request via the second signal line.
  Therefore, according to this communication system, the start / stop of at least one communication node can be controlled according to the control method described in claim 2.
  In the communication system according to claim 8, when the notification signal is input via the second signal line, the monitoring node monitors the communication operation of the control target node via the multiple communication path. When the communication data of the control target node has not changed for a certain period of time, it is determined that no communication request has been output from the control target node.
  Therefore, according to this communication system, the activation / stop of at least one communication node can be controlled according to the control method described in claim 3.

An embodiment of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a communication system according to a first embodiment to which the present invention is applied.

  In the communication system of the present embodiment, a plurality of body-type control devices (door ECU, meter ECU, etc.) mounted on an automobile are used as communication nodes, and these nodes A, B,. It is configured by adding a node X composed of a smart ECU to an existing vehicle communication system that enables data communication between the nodes A, B,.

  When nodes A, B,... Constituting the existing vehicle communication system generate a communication request in their own node (for example, when there is a door unlock request in the door ECU), the nodes A, B,. By shifting to the wake-up state and transmitting a wake-up signal to the multiplex communication path 2, the other node is shifted from the sleep state to the wake-up state, and communication with the other node is started. When there is no communication request from the other node, the communication is stopped and the state shifts to the sleep state.

Further, when each node A, B,... Is in a sleep state, it is determined whether or not there is a communication request from another node by monitoring a wake-up signal transmitted from the other node via the multiplex communication path 2. When a wakeup signal is transmitted from another node (that is, when there is a communication request from another node), a wakeup signal monitoring circuit is provided that activates the own node.

  Of the body control devices constituting the nodes A, B,..., The door ECU is for locking / unlocking the door, opening / closing the power window, etc. in accordance with a command from the vehicle occupant. The meter ECU 14 is for displaying various vehicle states such as a vehicle speed, an engine speed, a door open / close state, and a shift range of a transmission on a display device (not shown).

  On the other hand, the smart ECU constituting the newly added node X performs wireless communication with the electronic key 20 possessed by the user, and locks / unlocks the door to the door ECU according to the communication result. As shown in FIG. 1, the wireless communication device 10 for performing wireless communication with the electronic key 20 and communication with other nodes A, B,... The communication circuit 14 for performing, the microcomputer (microcomputer) 12 etc. which are connected to these each part and implement | achieve the function as smart ECU are comprised.

  By the way, when adding a node X composed of such smart ECUs to an existing vehicle communication system, the node X is monitored for wake-up signals from other nodes in the same manner as the other nodes A, B,. In order to configure the system so that it can be started up, the development period becomes longer and the cost increases.

  Therefore, in this embodiment, the node A is set as a monitoring node, and a direct line 4 different from the multiplex communication path 2 is provided between the node A and the node X that is the control target node. When activated in accordance with a communication request from a node or another node and in a wake-up state, an operation signal is output from the operation signal output circuit 18 to the node X via the direct line 4, and on the node X side, The activation circuit 16 activates the microcomputer 12 in accordance with an operation signal input via the direct line 4.

  As a result, the node X can be activated (shifted from the sleep state to the wake-up state) without monitoring the wake-up signal transmitted from the other nodes A, B,. The circuit configuration for starting up the node X can be greatly simplified.

  The direct line 4 corresponds to the first signal line of the present invention. In this embodiment, as shown in FIG. 2, at least one node including the node X has a communication request. Thus, when the node A is in the wake-up state, the operation signal output circuit 18 of the node A outputs an operation signal by setting the potential of the direct line 4 to the high level, and all nodes including the node X are output. When there is no communication request and no communication continuation request and the transition to the sleep state is possible, the operation signal output circuit 18 of the node A stops the output of the operation signal by setting the potential of the direct line 4 to the low level. Have been to.

  Further, when the node X is in the sleep state and a communication request is generated by the signal from the electronic key 20 or the like, the node X is activated even if the direct line 4 is at the low level, and the multiple communication path 2 wakeup signals representing communication requests are sent to activate the other nodes A, B,. When the node A receives the wake-up signal from the node X and starts up, the node A switches the direct line 4 to the high level.

  After that, even if there is no communication request from the node X, if there is a communication request from another node, the node A keeps the direct line 4 at the high level and no wakeup signal is transmitted from all nodes. Then, the direct line 4 is set to a low level to shift to the sleep state.

  As described above, in order to activate the other nodes A, B,... By the wakeup signal from the node X, each node A, B,... Can be monitored for the wakeup signal from the node X. Although each node A, B,... Originally has a wakeup signal monitoring function, it is only necessary to add the wakeup signal from the node X as the monitoring target signal.

  Therefore, when adding the node X to the existing communication system composed of the nodes A, B,..., One of the communication nodes (node A) and the node X constituting the existing communication system as in the present embodiment. If the node A is connected via the direct line 4 and an operation signal is output from the node A via the direct line 4, a new communication system with the addition of the node X can be opened at low cost and in a short period of time. Can be realized.

  By the way, when the node X is activated by the operation signal output from the node A through the direct line 4 as described above, the direct line 4 is disconnected, or the power line or the ground line. It is conceivable that the node X cannot shift to the sleep state when it is short-circuited.

  Therefore, in order to ensure that the node X can be shifted to the sleep state even if an abnormality such as disconnection / short circuit occurs in the direct wire 4, the sleep determination shown in FIG. What is necessary is just to perform a process.

That is, this sleep determination process is a process repeatedly executed by the microcomputer 12 when the node X is in the wake-up state.
In this sleep determination process, first, in S110 (S represents a step), it is determined whether or not the node X is communicating with another node, and if it is communicating with another node, S110 is executed. By doing so, it waits for the communication with other nodes to end.

  If it is determined in S110 that communication is not being performed with another node, the process proceeds to S120, and it is determined whether or not the direct line 4 is at a low level. It is determined whether or not A has entered the sleep state. In S120, if it is determined that the direct line 4 is at the low level and the node A has shifted to the sleep state, the process shifts to S150 to shift the own node to the sleep state.

  On the other hand, if it is determined in S120 that the direct line 4 is not at the low level, the process proceeds to S130, and the transmission output from the node A is monitored via the multiplex communication path 2. In subsequent S140, the node A stops operating by determining whether or not the period during which transmission output from the node A is stopped (output stop period) exceeds a preset sleep determination time. Judge whether or not.

  If it is determined that the output stop period of the node A is equal to or shorter than the sleep determination time and the node A is operating in S140, the process proceeds to S110 again. Conversely, the output stop period of the node A is the sleep determination time. If it is determined that the time has passed and it is determined in S140 that the node A has stopped operating, the process proceeds to S150, and the own node is shifted to the sleep state.

As a result, the node X confirms that the node A has stopped data transmission (in other words, is in the sleep state) even if the direct line 4 is in a state where communication is continued (high level). Thus, it becomes possible to shift to the sleep state. Therefore, according to the present embodiment, it is possible to prevent the battery from being consumed due to an unnecessary operation of the node X and the engine from being unable to be started.

  In order to prevent the node X from shifting to the sleep state due to the disconnection / short circuit of the direct line 4 as described above, it is not always necessary to monitor the transmission output from the node A, as shown in FIG. As described above, when the operation signal output circuit 18 of the node A outputs a pulse signal whose signal level periodically changes as the operation signal, and when the activation circuit 16 detects the pulse signal (waveform) on the node X side, When a signal for starting and continuation of operation is generated and the direct line 4 is fixed at a high or low level, the output of the signal may be stopped.

In other words, in this way, when an abnormality occurs in the direct line 4, the node X can be surely shifted to the sleep state, and battery consumption can be prevented.
[Second Embodiment]
Next, FIG. 5 is a block diagram illustrating a configuration of a communication system according to the second embodiment.

  The communication system according to the present embodiment basically has the same configuration as that of the communication system according to the first embodiment. The difference from the first embodiment is a direct line directly connecting the node X and the node A. This is the point that two (signal lines) are provided.

  Of these two direct lines, one direct line 4 is used to output an operation signal from the node A to the node X as the first signal line, as in the first embodiment. The other direct line is used as a second signal line to notify the communication request from the node X to the node A.

  That is, as shown in FIG. 6, when the node X has a communication request in its own node, the direct line 6 is set to the high level, and when the node X has neither a communication request nor a communication continuation request, the direct line The notification signal output circuit 28 for notifying the node A of the communication request is provided by setting 6 to the low level, and the node A detects the communication request from the node X from the signal level of the direct line 6. A communication request detection circuit 26 that activates (wakes up) the own node if the own node is in a sleep state is provided.

  Therefore, according to the present embodiment, the node A monitors the wakeup signal output from the node X to the multiplex communication path 2 when monitoring the communication requests of all the nodes connected to the multiplex communication path 2. There is no need, and the communication request of the node X can be detected from the signal level of the direct line 6.

  Therefore, according to the present embodiment, when adding the node X, it is not necessary to improve the node A so that the wakeup signal output from the node X to the multiplex communication path 2 can be monitored. The system can be realized more easily and at a lower cost.

  When abnormality such as disconnection / short circuit occurs in the direct wire 6, it is considered that the communication request detection circuit 26 of the node A erroneously detects the communication request from the node X and cannot enter the sleep state. However, in order to prevent this problem, the communication request detection circuit 26 of the node A may determine the communication request from the node X according to the procedure shown in FIG.

  That is, the flowchart shown in FIG. 7 represents the communication request determination process in the case where the communication request detection circuit 26 is realized by the operation of the microcomputer constituting the node A.

In this communication request determination process, first, in S210, it is determined whether or not a notification signal indicating a communication request is input from the node X by determining whether or not the direct line 6 is at a high level. If the direct line 6 is not at the high level, it is determined in S250 that there is no communication request from the node X, and the process is terminated.

  On the other hand, when the direct line 6 is at the high level, the transmission output from the node X is monitored via the multiple communication path 2 in S220. In subsequent S230, the node X stops operating by determining whether or not the period during which the transmission output from the node X does not change (output unchanged period) exceeds a preset sleep determination time. Judge whether or not.

  If it is determined that the output unchanged period of the node X is equal to or shorter than the sleep determination time and the node X is operating in S230, it is determined that there is a communication request from the node X in S240. On the contrary, when the output unchanged period of the node X exceeds the sleep determination time and it is determined in S230 that the node X has stopped operating, in S250, the node X is terminated. It is determined that there is no communication request from, and the process ends.

  As a result, even if the direct line 6 is at the high level, the node A can check the operation state of the node X and determine that the node X has no communication request. It is possible to prevent the battery from being exhausted unnecessarily without being able to shift to the sleep state when an abnormality occurs.

  Further, according to the present embodiment, since the node A detects the communication request of the node X via the direct line 6, the node A communicates with the node X after the communication request is generated in the node X. As compared with the first embodiment, the communication establishment delay time until the communication can be started can be shortened.

  That is, each node A, X starts an oscillator that generates an operation clock at the time of wakeup from the sleep state, and starts communication after the output of the oscillator becomes stable. Therefore, communication can be started after startup. A certain delay time is required until this time.

  In the communication system according to the first embodiment configured such that when the node A is in the sleep state and is activated according to the communication request from the node X, the node A detects the communication request based on the wakeup signal from the node X. As shown in FIG. 8A, the communication establishment delay time from when the communication request is generated at the node X until the communication between the nodes A and X becomes possible is the delay time generated at each of the nodes A and X. It is time to add.

  On the other hand, if the communication request is output from the node X to the node A via the direct line 6 as in the present embodiment, the communication request of the node X is transmitted as shown in FIG. Since transmission to the node A is possible in a short time, the communication establishment delay time from when the communication request is generated at the node X to when communication between the nodes A and X becomes possible can be shortened.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, a various aspect can be taken.
For example, in the embodiment described above, the node A is the monitoring node, the node X is the control target node, and the direct line 4 as the first signal line is provided between the node A and the node X. As illustrated in FIGS. 9A and 9B, the control target nodes connected to the node A as the monitoring node via the direct line 4 are two nodes X and B, or It may be the above.

  In the above embodiment, the node X has been described as being added to the existing communication system. However, from the beginning of the communication system design, a part of the plurality of communication nodes is set as a control target node, and the system You may make it build.

  In addition, as the states of the direct lines 4 and 6, high is waked up and low is sleep, but there is no problem if they are defined in reverse.

It is a block diagram showing the structure of the communication system of 1st Embodiment. 3 is a time chart showing operations of a node A and a node X in the communication system of FIG. It is a flowchart showing the sleep determination process performed in the node X of FIG. FIG. 6 is a time chart showing a modified example of operations of node A and node X in the communication system of FIG. 1. FIG. It is a block diagram showing the structure of the communication system of 2nd Embodiment. 6 is a time chart showing the operations of node A and node X in the communication system of FIG. 5. It is a flowchart showing the communication request determination process performed in the node A of FIG. It is explanatory drawing explaining the difference of the communication establishment delay time produced by the presence or absence of the direct line 6. FIG. It is a block diagram explaining the modification of a communication system.

Explanation of symbols

  2 ... Multiple communication paths, A, B, X ... Node (communication node), 4 ... Direct line (first signal line), 6 ... Direct line (second signal line), 10 ... Wireless communication device, DESCRIPTION OF SYMBOLS 12 ... Microcomputer, 14 ... Communication circuit, 16 ... Start-up circuit, 18 ... Operation signal output circuit, 20 ... Electronic key, 26 ... Communication request detection circuit, 28 ... Notification signal output circuit

Claims (8)

In a communication system comprising three or more communication nodes that communicate with each other via multiple communication paths, a control method for controlling activation / stop of at least one communication node,
One of the communication nodes is set as a monitoring node, and the monitoring node and the control target node whose start / stop is to be controlled are directly connected by a first signal line,
On the monitoring node side, communication requests from other communication nodes are monitored via the multiplex communication path. When a communication request occurs in any of the communication nodes including itself, communication of all the communication nodes is completed thereafter. Until the operation target signal is output to the control target node via the first signal line until the control target node is activated and the operation of the control target node is continued during the operation signal output period. Let
The control target node monitors a communication operation of the monitoring node via the multiple communication path when an operation signal is input via the first signal line and continues to operate, and the monitoring node When the communication operation is stopped, it is determined that an abnormality has occurred in the first signal line, and the operation of the communication system is stopped . When the control target node generates its own communication request, it notifies the monitoring node of the communication request via the second signal line,
The method according to claim 1 , wherein the monitoring node detects a communication request from the control target node based on a notification signal input via the second signal line . The monitoring node monitors a communication operation of the control target node via the multiple communication path when a notification signal is input from the control target node via the second signal line, and the control target node 3. The communication system control method according to claim 2 , wherein when there is no change in the communication data for a certain period of time, it is determined that there is no communication request from the control target node . In a communication system comprising three or more communication nodes that communicate with each other via multiple communication paths, a communication device used as one of the communication nodes,
  An operation signal can be input from the other communication node constituting the communication system via the first signal line.
  When an operation signal is input through the first signal line while the operation is stopped, the operation is started, and then the operation is continued until the input of the operation signal is stopped.
  When the operation signal is input via the first signal line, the communication operation of the communication node connected via the first signal line is monitored via the multiple communication path, and the communication is performed. When the communication operation of the node is stopped, it is determined that an abnormality has occurred in the first signal line, and the communication device stops its own operation.   5. The communication request is notified via a second signal line to another communication node connected via the first signal line when the communication request is generated. Communication equipment. In a communication system comprising three or more communication nodes that communicate with each other via multiple communication paths,
  As one of the communication nodes, comprising a monitoring node and a control target node connected via a first signal line,
  The monitoring node is
  A communication request from another communication node is monitored via the multiplex communication path, and when a communication request is generated in any of the communication nodes including itself, the first communication is completed until communication of all the communication nodes is completed. Configured to output an operation signal to the control target node via a signal line of
  The controlled node is
  When the operation signal is input through the first signal line while the operation is stopped, the operation is started, and then the operation is continued until the input of the operation signal is stopped, and the operation is continued through the first signal line. When the operation signal is input, the communication operation of the monitoring node is monitored via the multiplex communication path, and when the communication operation of the monitoring node is stopped, the first signal line is abnormal. To determine that has occurred and stop working
  A communication system characterized by the above.   The monitoring node is
  The control target node is configured to be able to acquire a notification signal indicating that a communication request has occurred to the control target node via the second signal line, and the control target node via the second signal line. When the notification signal is acquired from, it is detected that the control target node is outputting a communication request,
  The controlled node is
  The communication request is notified via the second signal line to a monitoring node connected via the first signal line when the communication request is generated. Communications system.   The monitoring node is
  When the notification signal is input via the second signal line, the communication operation of the control target node is monitored via the multiplex communication path, and the communication data of the control target node exceeds a certain time. The communication system according to claim 7, wherein when there is no change, it is determined that a communication request is not output from the control target node.

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