JP2008022078A - Communication network system and startup method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To start an ordinary communication operation by surely executing startup processing while effectively suppressing the generation of branches by making the number of startup nodes to a necessary minimum. <P>SOLUTION: At least one of non-startup nodes not subscribing to a startup process is set as a synchronous backup node 100. When the synchronous backup node 100 detects that synchronous frames transmitted from the startup nodes are deficient due to the occurrence of a failure or the like in one of the startup nodes subscribing to the startup process, the synchronous backup node 100 subscribes to the startup process and transmits a pseudo synchronous frame simulating the synchronous frame to a communication bus 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a time division multiplexing communication network system and a time-division multiplexing communication network system startup method.

  A communication protocol called FlexRay (registered trademark of Daimler Chrysler AG) is known as one type of protocol for a communication network system mounted on a vehicle. This FlexRay realizes a maximum communication speed of about 10 Mbps while ensuring high reliability, and is important in putting electronic control (X-by-wire) directly related to vehicle running into practical use. It is attracting attention as a technology.

  In a communication network system that employs FlexRay as a communication protocol, in order to synchronize each node on the network, a process called startup is performed as a process in a preparation stage after the system is started and before normal communication operation is started. Done.

The startup process in FlexRay is executed by a plurality of nodes predetermined as startup nodes among the nodes on the network. After the power is turned on, the startup node performs communication start preparation processing (wakeup) such as activation of its own node and setting of a communication function. Then, the start-up node that completed the communication start preparation process first continues to send out a synchronization frame on the communication bus at each communication cycle at its own timing. After that, the start-up node that has completed the communication start preparation process next receives the synchronization frame on the communication bus a predetermined number of times, and then transmits the synchronization frame following the synchronization frame. Then, these two startup nodes synchronize while correcting a time recognition shift based on the transmission / reception timings of the mutual synchronization frames, thereby establishing communication synchronization. After that, other startup nodes and other nodes other than the startup node receive the synchronization frame transmitted from the two startup nodes a predetermined number of times, and then participate in communication in accordance with the timing of these two startup nodes. Normal communication operation is started. The details of such a startup process in FlexRay are described in Non-Patent Document 1 below.
“FlexRay Communication System Protocol Specification Version 2.1 Revision A”, December 2005, p. 156

  By the way, in a communication network system that employs FlexRay as a communication protocol, when the size of the network increases and the number of nodes and the length of the communication bus increase, a phenomenon called branching occurs and a plurality of synchronization groups are created on the network. Has been found to occur. This is because when a plurality of startup nodes connected to physically distant locations complete the communication start preparation process at the same time and each of them starts sending a synchronous frame independently, the remaining startup nodes This is considered to be caused by following and synchronizing with the startup node closer to the own node. Therefore, in order to effectively suppress this phenomenon called division, it is desired to limit the number of startup nodes so that startup processing is performed with the minimum number of startup nodes.

  However, when the number of startup nodes is minimized, if a failure occurs in one of the startup nodes and the synchronization frame cannot be transmitted, normal communication operation is started without establishing communication synchronization. The problem of being unable to do so arises.

  The present invention was devised in view of the conventional situation as described above, and normally performs startup processing reliably while effectively suppressing the occurrence of branching by minimizing the number of startup nodes. It is an object of the present invention to provide a communication network system and a communication network system start-up method capable of starting the communication operation.

  In the present invention, at least two startup nodes establish synchronization of communication by sending a synchronization frame on a communication bus at the time of system startup, and other nodes participate in communication in accordance with the timing of the startup node. A time division multiplexing communication network system in which communication operation is started is targeted. In such a time division multiplex communication type communication network system, in the present invention, when there is a shortage in the synchronization frame transmitted from the startup node in at least one of the nodes other than the startup node, the synchronization frame The above-described problem is solved by providing a function of sending a pseudo-synchronous frame that simulates the above to the communication bus.

  According to the present invention, when a failure occurs in any of the startup nodes and the synchronization frame cannot be transmitted, a pseudo synchronization frame is transmitted on the communication bus from a node other than the startup node. The normal communication operation can be started by reliably performing the start-up process while effectively suppressing the occurrence of the shard by minimizing the number of scramblers.

  As an embodiment of the present invention, an example in which the present invention is applied to a communication network system in which five nodes A to E are connected to the communication bus 10 as nodes on the network as shown in FIG. Explained. The communication network system shown in FIG. 1 employs FlexRay as a communication protocol, and two nodes, node A and node E, are startup nodes having a function of transmitting a synchronization frame in a startup process, and the remaining nodes B, C, and D are non-startup nodes that participate in communication after communication synchronization is established by node A and node E.

  When the power is turned on at the time of system startup, the node A and the node E, which are startup nodes, perform communication start preparation processing such as startup of the own node and setting of communication functions. Then, a state called “cold start listen” is entered in order from the node where the communication start preparation processing is completed, and the signal on the communication bus 10 is monitored for a predetermined time. Here, for example, if the node A completes the communication start preparation process before the node E, the node A ends monitoring for a predetermined time without detecting a signal on the communication bus 10. When monitoring for a predetermined time is completed, a signal called CAS (collision avoidance symbol) is transmitted on the communication bus 10 to become a leading node that leads the startup process. On the other hand, the node E that has completed the communication start preparation process after the node A detects the CAS sent from the node A onto the communication bus 10 while monitoring for a predetermined time, and therefore follows the node A. Become a following node for the startup process.

  Node A, which has become the leading node, sends CAS onto the communication bus 10 and then continues to send a synchronization frame onto the communication bus 10 at each communication cycle at the timing of its own node. On the other hand, the node E that has become the following node waits until the node A receives the synchronization frame sent out on the communication bus 10 four times. When the node E receives the synchronization frame four times, the next communication cycle starts. Then, following the synchronization frame from the node A, the synchronization frame of the own node is continuously sent out on the communication bus 10. Then, the nodes A and E synchronize while correcting the time recognition shift based on the transmission / reception timings of the mutual synchronization frames, thereby establishing communication synchronization.

  The nodes B, C, and D that are non-startup nodes wait until the synchronization frames from the node A and the node E that are the startup nodes are received four times after the communication start preparation process is completed. When the synchronization frame from E is received four times, the frame of the own node is transmitted in accordance with the timings of these nodes A and E to participate in communication. As a result, a normal communication operation is started.

  The FlexRay frame format is schematically shown in FIG. As shown in FIG. 2, the FlexRay frame is composed of three segments: a header segment (5 bytes), a payload segment (0 to 254 bytes), and a trailer segment (3 bytes). Header information related to data to be transmitted is stored in the header segment, and data itself is stored in the payload segment. In addition, the trailer segment has a function of checking whether there is an error in the entire frame, and stores a result of subjecting the header segment and the payload segment to CRC (Cyclic Redundancy Check).

  The header information stored in the header segment includes a 1-bit synchronization frame indicator and a 1-bit startup frame indicator. The synchronization frame indicator is a flag indicating whether or not the frame is a synchronization frame, and the startup frame indicator is a flag indicating whether or not the frame is a frame transmitted in the startup process. In the communication network system according to the present embodiment, the synchronization frames transmitted from the startup nodes Node A and Node E onto the communication bus 10 during the startup process include the values of the synchronization frame indicator and the startup frame indicator. Are both “1”, that is, a value indicating flag on.

  The communication network system of the present embodiment is basically shifted to the normal communication operation through the above-described startup process, but the startup node is limited to two nodes, node A and node E. However, if a synchronization frame is not transmitted due to a failure in either node A or node E, the startup process may not be completed and the normal communication operation may not be performed. is there. Therefore, in the communication network system according to the present embodiment, the synchronization frame is simulated when there is a shortage in the synchronization frame transmitted from the startup node in at least one of the nodes B, C, and D that are non-startup nodes. A function to send out the pseudo-synchronous frame on the communication bus 10, and even if a failure occurs in either node A or node E and the synchronous frame is not sent out, the startup process is completed and It is possible to shift to communication operation.

  More specifically, when both the start-up nodes A and E are normal, the node A becomes a leading node, and the node E becomes a following node, as shown in FIG. Node A sends out a synchronization frame onto the communication bus 10 every communication cycle. When the node E normally receives the synchronization frame transmitted from the node A over four communication cycles (T1 to T5), the transmission timing assigned to the own node within the communication cycle with reference to the synchronization frame from the node A And the synchronization frame is transmitted onto the communication bus 10 at the transmission timing assigned to the own node from the next communication cycle. Thereafter, the node A and the node E synchronize while correcting the time recognition shift based on the transmission / reception timings of the mutual synchronization frames, thereby establishing communication synchronization. Further, when nodes B, C, and D, which are non-startup nodes, normally receive both the synchronization frame from node A and the synchronization frame from node E over four communication cycles (T5 to T9), the startup process is performed. It is determined that the transmission is normally completed, and the transmission timings assigned to the own node in the communication cycle are recognized based on the synchronization frames from these nodes A and E, respectively. Then, the nodes B, C, and D participate in the communication by transmitting frames at the transmission timing assigned to the node from the next communication cycle, and the normal communication operation is started.

  Here, for example, it is assumed that a failure occurs in the frame transmission function of the node E, and the frame E is in a state where the synchronization frame cannot be transmitted. In this case, as shown in FIG. 3B, the synchronization frame from the node A is originally transmitted onto the communication bus 10 in the four communication cycles (T5 to T9) after being transmitted onto the communication bus 10 four times. The synchronization frame from the node E to be transmitted is not sent on the communication bus 10. For this reason, if it is normal, the startup process is completed when eight communication cycles have elapsed after node A sends out the synchronization frame (T9), and the non-startup nodes B, C, and D communicate from the next communication cycle. The normal communication operation should be performed by participating in the network, but since the synchronization frame is not transmitted from the node E, the startup process is not completed and the non-startup nodes B, C, and D cannot participate in the communication. . Therefore, in the communication network system according to the present embodiment, when at least one of the non-startup nodes B, C, and D has a shortage in the synchronization frame transmitted from the startup node, pseudo synchronization that simulates the synchronization frame A function of sending a frame onto the communication bus 10 is provided.

  For example, when the node B has a function of transmitting a pseudo synchronization frame, the node B transmits a synchronization frame from the node E when eight communication cycles have elapsed after the node A transmits the synchronization frame (T9). It is detected that the start-up process is not completed due to the shortage of the node, and the transmission timing assigned to the own node within the communication cycle is recognized based on the synchronization frame from the node A, and from the next communication cycle to the own node A pseudo synchronization frame is transmitted onto the communication bus 10 at the assigned transmission timing. Node A and Node B synchronize with each other to establish communication synchronization. Nodes C and D, which are non-startup nodes other than Node B, cannot transmit a synchronization frame. When both of the pseudo synchronization frames from Node B are normally received over four communication periods (T9 to T12), it is determined that the startup process has been completed normally, and the synchronization frames from Node A and Node B Recognize each transmission timing assigned to its own node within the communication cycle based on the pseudo-synchronous frame, and participate in communication by sending each frame at the transmission timing assigned to this node from the next communication cycle. Normal communication operation is started.

  Note that the pseudo-synchronous frame that node B, which is a non-startup node, detects a lack of synchronization frames and sends it out on the communication bus 10 includes the value of the synchronization frame indicator stored in the header segment of the frame format described above. This is a frame in which the value of the start-up frame indicator is both “1”. That is, the node B that is a non-startup node sets the value of the synchronization frame indicator and the value of the startup frame indicator to “1” only when the node A or node E that is the startup node cannot output a synchronization frame due to some trouble. Is output.

[Example]
Next, in the communication network system of the present embodiment, specific examples (first and second examples) of a non-startup node having a function of detecting a lack of synchronization frames in a startup process and transmitting a pseudo synchronization frame This will be described in detail. In the following embodiments, a non-startup node having such a function will be described as “synchronous backup node”. In the communication network system having the configuration shown in FIG. 1, any one or all of the non-startup nodes B, C, D are synchronous backup nodes. In addition, the following embodiments show specific examples of the synchronous backup node, and the configuration and operation of the synchronous backup node are not limited to those described in these embodiments. Needless to say, various modifications are possible as long as the function of detecting the shortage and transmitting the pseudo synchronization frame can be realized.

<First embodiment>
FIG. 4 is a diagram illustrating an internal configuration of the synchronous backup node 100 according to the first embodiment. The synchronous backup node 100 according to the present embodiment counts the elapsed time since the condition for participation in communication is established, and determines that the synchronization frame is deficient when communication synchronization is not established within a predetermined time. In this example, a pseudo-synchronous frame is transmitted, and includes a transmission processing unit 110, a reception processing unit 120, a synchronization control unit 130, a backup control unit 140, and a bus driver 150 as main components. .

  The transmission processing unit 110 is a part that performs transmission processing of a frame, and includes a transmission buffer 111 that prepares transmission data, a selector 112 that selects a transmission frame, and a transmission frame that encodes the transmission frame into a frame conforming to the FlexRay protocol. Encoder 113, selector 114 for selecting whether to send a transmission frame on communication bus 10, transmission control unit 115 for controlling the operation of selector 112 and selector 114 to send the desired transmission frame onto communication bus 10. It is composed of

  In the synchronous backup node 100 of the present embodiment, a transmission frame A, a transmission frame B, and a transmission frame C are stored in the transmission buffer 111 of the transmission processing unit 110, and these three transmission frames A, B, and C are stored. The data can be selectively transmitted onto the communication bus 10. Of these three transmission frames A, B, and C, the transmission frame B is a pseudo synchronization frame in which the values of the synchronization frame indicator and the startup frame indicator in the header information are set to “1”. This transmission frame B is selected by the selector 112 and transmitted onto the communication bus 10 only when it is detected in the startup process that the synchronization frame from the startup node is insufficient.

  The reception processing unit 120 is a part that performs frame reception processing. Among the transmission frames transmitted on the communication bus 10, a selector 121 that takes only a target frame as a reception frame, and control of reception timing by the selector 121. It is comprised from the reception control part 122 which performs.

  The synchronization control unit 130 is a part that recognizes a global time, which is a common time on the network, by clock synchronization and controls the timing of processing by the transmission processing unit 110 and the reception processing unit 120.

  The backup control unit 140 is a characteristic part of the synchronous backup node 100 according to the present embodiment, and after power-on reset or the like, communication start preparation processing such as activation of its own node or setting of a communication function is completed and communication is performed. The system is composed of a start-up timer 141 that starts when a condition for participation (network start-up condition) is satisfied, and outputs a start-up start-up signal when time-out occurs, and a switch 142 that turns on / off the start-up start-up signal output from the start-up timer 141. .

  The bus driver 150 is a physical layer driver that converts between a voltage level and a logic level in order to transmit / receive data handled by the transmission processing unit 110 and the reception processing unit 120 on the communication bus 10.

  Next, the operation at the time of system startup of the synchronous backup node 100 of the present embodiment configured as described above will be described.

  If the startup nodes (node A and node E in the example shown in FIG. 1) are operating normally at the time of system startup, the synchronous backup node 100 is a non-startup node, so even if the network startup conditions are met, the startup process The synchronization control unit 130 monitors that the start-up node establishes communication synchronization. At the same time, the backup control unit 140 starts the startup timer 141 when the network start condition is satisfied.

  When a time-out occurs, the start-up timer 141 outputs a start-up start signal for entering a mode for joining a start-up process and transmitting a pseudo synchronization frame. The timeout output of the startup timer 141 is connected to the synchronization control unit 130 via the switch 142. Further, the switch 142 is released when a startup completion signal indicating completion of the startup process is output from the synchronization control unit 130, and disconnects the timeout output of the startup timer 141 from the synchronization control unit 130.

  Here, the start-up timer 141 is set to a time slightly longer than the time for normally completing the start-up process (which differs depending on the scale of the system and the like and is obtained at the time of system design). For this reason, when the startup node is operating normally, the startup completion signal is output from the synchronization control unit 130 before the startup timer 141 times out, and the switch 142 is opened, so the startup activation signal is synchronized. It is not input to the unit 130, and the pseudo synchronization frame (transmission frame B) is not transmitted.

  On the other hand, if a synchronization frame is not transmitted because of a failure in one of the startup nodes at the time of system startup, the startup process is not completed before the startup timer 141 times out, so the startup timer remains switched on. 141 times out and a start-up activation signal is input to the synchronization control unit 130. In this case, the synchronization control unit 130 notifies the transmission control unit 115 of the transmission processing unit 110 of a command indicating participation in the startup process. Then, the transmission control unit 115 of the transmission processing unit 110 controls the operation of the selector 112 and the selector 114 according to the command from the synchronization control unit 130, and transmits the transmission frame B that is a pseudo synchronization frame onto the communication bus 10. .

  FIG. 5 is a flowchart schematically showing a flow of processing in the synchronous backup node 100 according to the present embodiment from when the network activation condition is established to when normal communication operation is started.

  When the network activation condition is satisfied, the synchronous backup node 100 of the present embodiment first activates the startup timer 141 of the backup control unit 140 in step S1. Then, in a state in which the startup timer 141 is activated, in step S2, the synchronization control unit 130 monitors whether the startup process is completed. If the startup process is completed, in step S3, a normal communication subscription operation, that is, startup An operation of sending the transmission frame A or the transmission frame B onto the communication bus 10 is performed in accordance with the timing of the node, and then the normal communication operation is performed. On the other hand, if the start-up timer 141 times out before the start-up process is completed (Yes in step S4), an operation for joining the start-up process, that is, a transmission frame B that is a pseudo-synchronous frame is sent on the communication bus 10 in step S5. Then, when communication synchronization is established and another non-startup node joins the communication, a normal communication operation is performed. By operating the synchronous backup node 100 of the present embodiment as described above, it is possible to effectively avoid a situation in which a normal communication operation is not started due to a failure of the startup node.

<Second embodiment>
FIG. 6 is a diagram illustrating an internal configuration of the synchronous backup node 200 according to the second embodiment. The synchronous backup node 200 according to the present embodiment monitors the transmission state of the synchronization frame on the communication bus 10, and when the synchronization frame is not transmitted from at least one of the startup nodes, the synchronization frame is insufficient. In this example, a pseudo-synchronous frame is transmitted and a backup control unit 210 is provided instead of the backup control unit 140 in the backup node 100 of the first embodiment described above. Since the other configurations of the synchronous backup node 200 of this embodiment are the same as those of the backup node 100 of the first embodiment, the same reference numerals are used for the configurations common to the backup node 100 of the first embodiment. A description thereof will be omitted.

  The backup control unit 210 in the synchronous backup node 200 of this embodiment directly monitors the frame input from the communication bus 10 during the startup process, and all the synchronous frames from the startup node are normally transmitted. A start-up synchronization frame shortage detection unit 211 that determines whether or not When the startup synchronization frame shortage detecting unit 211 detects that a synchronization frame from any startup node is not transmitted on the communication bus 10 during the startup process, the startup synchronization frame shortage detecting unit 211 detects the synchronization control unit 130. A startup activation signal for entering a mode for joining the startup process and transmitting a pseudo-synchronous frame is output.

  Next, the operation at the time of system startup of the synchronous backup node 200 of the present embodiment configured as described above will be described.

  If the startup nodes (node A and node E in the example shown in FIG. 1) are operating normally when the system is started up, the synchronous backup node 200 is a non-startup node. The synchronization control unit 130 monitors that the start-up node establishes communication synchronization. At the same time, the start-up synchronization frame shortage detection unit 211 of the backup control unit 210 monitors the frames input from the communication bus 10 and whether all the synchronization frames from the start-up nodes Node A and Node E are transmitted normally. Whether it is determined.

  Here, if the start-up nodes A and E are operating normally, all the synchronization frames that should be sent out on the communication bus 10 have been sent out on the communication bus 10, so that the startup synchronization frame The startup activation signal from the shortage detection unit 211 is not input to the synchronization control unit 130, and the pseudo synchronization frame (transmission frame B) is not transmitted.

  On the other hand, if a synchronization frame has not been sent due to a failure in either node A or node E when the system is started, the startup synchronization frame shortage detection unit 211 detects the lack of a synchronization frame, and the startup synchronization frame is insufficient. A startup activation signal output from the detection unit 211 is input to the synchronization control unit 130. In this case, the synchronization control unit 130 notifies the transmission control unit 115 of the transmission processing unit 110 of a command indicating participation in the startup process. Then, the transmission control unit 115 of the transmission processing unit 110 controls the operation of the selector 112 and the selector 114 according to the command from the synchronization control unit 130, and transmits the transmission frame B that is a pseudo synchronization frame onto the communication bus 10. .

  FIG. 7 is a flowchart schematically showing a flow of processing in the synchronous backup node 200 according to the present embodiment from when the network activation condition is established to when normal communication operation is started. FIG. 7 shows a case where, among the nodes A and E, which are startup nodes, the node A is a leading node that leads the startup process, and the node E is a following node that follows the node A and performs the startup process. It is an example.

  In the synchronous backup node 200 of this embodiment, when the network activation condition is satisfied, first, in step S11, the startup synchronization frame detection unit 211 of the backup control unit 210 causes the synchronization frame from the node A to be transmitted a predetermined number of times on the communication bus 10. It is determined whether or not (for example, 4 times) has been transmitted, and if the synchronization frame from node A has been transmitted a prescribed number of times, both the synchronization frame from node A and the synchronization frame from node E are both sent in the next step S12. Is transmitted on the communication bus 10 a predetermined number of times (for example, four times). If both the synchronization frame from node A and the synchronization frame from node E can be detected a predetermined number of times in the determination in step S12, in step S13, the transmission frame is synchronized with the normal communication joining operation, that is, the startup node timing. The operation of sending A or the transmission frame B onto the communication bus 10 is performed, and then the normal communication operation is performed. On the other hand, if the synchronization frame from node A cannot be detected a predetermined number of times in the determination in step S11, or if the synchronization frame from node A and node E cannot be detected a predetermined number of times in the determination in step S12, step S14 , The operation of joining the startup process, that is, the operation of sending the transmission frame B, which is a pseudo-synchronous frame, to the communication bus 10 is performed, and then communication synchronization is established and other non-startup nodes join the communication. Transition to normal communication operation at the stage. By operating the synchronous backup node 200 of this embodiment as described above, it is possible to effectively avoid a situation in which a normal communication operation is not started due to a failure of the startup node.

  As described above in detail with specific examples, in the communication network system of this embodiment, at least one of the nodes B, C, and D that are non-startup nodes is a synchronous backup node and is a startup node. Since there is a function to send a pseudo-synchronous frame onto the communication bus 10 when there is a shortage in the synchronous frames sent from the node A and the node E, the startup nodes are the nodes A and E. The start-up process is ensured by the backup of the synchronous backup node even if a failure occurs in either node A or node E and the synchronous frame is not sent out, while effectively suppressing the occurrence of splitting And normal communication operation can be started.

  Note that the communication network system described above exemplifies an application example of the present invention, and the technical scope of the present invention is not limited to the contents disclosed in the above description, and is easy from these disclosures. Of course, various alternative technologies that can lead to the above are also included.

1 is a diagram illustrating an overall configuration of a communication network system to which the present invention is applied. It is a figure which shows the frame format in a FlexRay protocol. It is a figure explaining the startup process performed at the time of system starting, (a) is a figure which shows the mode at the time of normality, (b) is a figure which shows the mode at the time of abnormality when the synchronous frame is not sent out from the node E which is a startup node. is there. It is a figure which shows the internal structure of the synchronous backup node of 1st Example. 6 is a flowchart schematically showing a flow of processing from when a network activation condition is established until a normal communication operation is started in the synchronous backup node of the first embodiment. It is a figure which shows the internal structure of the synchronous backup node of 2nd Example. 6 is a flowchart schematically showing a flow of processing from when a network activation condition is satisfied until a normal communication operation is started in the synchronous backup node of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Communication bus 100 Synchronous backup node 110 Transmission processing part 120 Reception processing part 130 Synchronization control part 140 Backup control part 141 Startup timer 142 Switch 150 Bus driver 200 Synchronous backup node 210 Backup control part 211 Startup synchronous frame shortage detection part

Claims (4)

At the time of system startup, at least two startup nodes establish a synchronization of communication by sending a synchronization frame on the communication bus, and other nodes participate in the communication in accordance with the timing of the startup node, thereby performing a normal communication operation. In the time-division multiplex communication network system to be started,
Pseudo-synchronization in which at least one of the other nodes other than the startup node sends out a pseudo-synchronization frame imitating the synchronization frame on the communication bus when there is a shortage in the synchronization frame transmitted from the startup node A communication network system comprising frame transmission means.   The pseudo-synchronous frame transmission means counts the elapsed time since the condition for participation in communication is established, and determines that the synchronization frame is deficient when communication synchronization is not established within a predetermined time. The communication network system according to claim 1, wherein the pseudo synchronization frame is transmitted.   The pseudo synchronization frame transmission means monitors the transmission state of the synchronization frame on the communication bus, and when the synchronization frame is not transmitted from at least one of the startup nodes, the synchronization frame is insufficient. The communication network system according to claim 1, wherein the pseudo-synchronization frame is transmitted after being determined to be present. When at least two startup nodes establish synchronization of communication by transmitting a synchronization frame at the time of system startup, and normal communication operation is started when another node participates in communication in accordance with the timing of the startup node A startup method for a division multiplexing communication network system,
When at least one of the nodes other than the startup node has a shortage in the synchronization frame transmitted from the startup node, the pseudo synchronization frame imitating the synchronization frame is transmitted on the communication bus. A start-up method for a communication network system.

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