JP2009010630A - Network system, relaying device, program, and hardware description code - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for synchronizing a transmitting timing of a frame transmitted by each of all nodes in a plurality of networks connected through relay nodes. <P>SOLUTION: At first, a main transmission/reception portion 10a of a relay node 3 becomes in a communication condition ("YES" at s120). After synchronizing with a transmitting timing of a frame transmitted by each node connected to a main network 2, a receiving route is changed so that a frame distributed within the main network may be received by each slave transmission/reception portion, during a period required for each node connected to a slave network 2 being in a communication condition (s150 to s200). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a network system including a plurality of networks each connected with one or more nodes, and a relay node that relays transmission / reception of frames interposed between the networks.

Such a network system is generally configured such that each node in each network transmits a frame at any time when an event occurs (so-called CSMA / CD (Carrier Sense Multiple Access / Collision Detection) method). Yes (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 03-283842

  In the network system as described above, since each node of each network is configured to transmit a frame when an event occurs, it is not necessary to synchronize the frame transmission timing by each node in each network.

  However, considering that the network system is applied to a configuration in which each node of each network transmits a frame in a specific time slot in a predetermined repetition period (so-called time division multiplexing), the system as a whole In order to synchronize the operation, it is necessary to synchronize the transmission timing of frames by the nodes of all the networks.

  However, in a time division multiplexing network, the transmission timing of frames by each node is synchronized independently of other networks, and it is difficult to synchronize the transmission timing of frames by all nodes in a plurality of networks. It was.

  Specifically, in each network, the node that is activated first starts transmission of a frame at a certain period, and other nodes activated after that synchronize with the transmission period of the frame, It is common for each node to be in a communication state in which transmission and reception of frames are repeated by time division multiplexing. In this case, it is difficult to synchronize the transmission timing of frames by the nodes of all networks.

  Further, since each network transmission timing changes every time the power is turned on, it is impossible to predict in advance the time required for frame transfer between networks via the relay device. Therefore, there is a problem in that the delay time of the frame passing through the relay device varies and the response characteristic of the vehicle control realized by the electrical device (engine control device or the like) of the control system is deteriorated.

  The present invention has been made to solve such a problem, and an object of the present invention is to synchronize frame transmission timings by all nodes in a plurality of networks connected via relay nodes. Is to provide.

  In order to solve the above problems, a network system comprising a plurality of networks each connected with one or more nodes and a relay node that relays frame transmission / reception between the networks interposed between the networks, The first configuration (Claim 1) described below is preferable.

  In this configuration, the main network, which is one of the plurality of networks, starts transmission of a frame at a fixed period from the node (including the relay node) that has been started earliest, and has started after that When other nodes synchronize with the transmission cycle of the frame, each node enters a communication state in which transmission and reception of frames are repeated by time division multiplexing. In the slave network that is a network other than the main network among the plurality of networks, the relay node starts transmission of a frame at a constant period, and other nodes synchronize with the transmission period of the frame. Thus, each node enters a communication state in which frame transmission / reception is repeated in time division multiplexing.

  The relay node controls transmission / reception of frames with the main network while being connected to the main network, and is different from a main transmission / reception unit functioning as a node connected to the main network. While being connected to the slave network, control of frame transmission / reception with the slave network and one or more slave transceiver units functioning as nodes connected to the slave network; and the transceiver unit (the master unit) Frame relay means for relaying frames between the transmission / reception unit and the slave transmission / reception unit).

  Further, in this relay node, after the relay node is activated, the first command means starts frame transmission at a constant cycle to the main transmitter / receiver, or is synchronized with the frame transmission cycle. To indicate that the communication state should be established. After the command from the first command means is received and the main transmission / reception unit is in a communication state, the second command means starts transmission of frames at a constant period to each of the slave transmission / reception units, or It is instructed that the communication state should be established by synchronizing with the frame transmission cycle.

  A reception path through which the slave transmission / reception unit receives a frame after a predetermined period elapses after the path switching unit receives a command from the first command unit and the main transmission / reception unit enters a communication state. Each is switched from the slave network to which the slave transceiver unit is connected to the master network.

  According to the network system configured as described above, first, after the main transmission / reception unit of the relay node is in a communication state and the frame transmission timings of the nodes connected to the main network are synchronized, a predetermined period elapses. In the meantime, the reception path is switched so that the frame flowing through the main network is received by each of the slave transmitting / receiving units.

  Each of the slave transmission / reception units becomes in a communication state in synchronization with the transmission cycle of the frame received in this manner, thereby repeating frame transmission / reception with respect to the slave network to which the slave transmission / reception unit itself is connected. At this time, the slave transmission / reception unit is in communication with the transmission cycle of the frames flowing through the main network, and thus is naturally synchronized with the transmission timing of the frame by each node of the main network.

  Thereafter, the frame repeatedly transmitted by the slave transceiver unit is received by each of the other nodes in the slave network to which the slave transceiver unit is connected. The communication state is established in synchronization with the transmission cycle of the frame transmitted by the unit. At this time, since the transmission timing of the frame by the slave transmission / reception unit is synchronized with the transmission timing of the frame by each node of the main network, the communication state is synchronized with the transmission cycle of the frame by the slave transmission / reception unit. Similarly, each node is synchronized with the transmission timing of a frame by each node of the main network.

  In this way, each of the nodes connected to the slave transmission / reception unit and the slave network transmits a frame in synchronization with the transmission timing of each node of the master network, so that a plurality of nodes connected via the relay node Frame transmission timings of all the nodes in the network can be synchronized.

  In the above configuration, synchronization with the transmission timing of each node of the main network can be achieved in the order of the main transmission / reception unit, the sub transmission / reception unit, and each node of the sub network in the relay node regardless of the activation timing. Therefore, even in an environment where the startup timing of each node accompanying startup as a system is not constant, the transmission timing of frames by all the nodes of all the networks connected via the relay node is definitely synchronized. Can do.

  In the above configuration, the period during which the relay node path switching unit switches the reception path only needs to ensure a period required for each node (including the slave transceiver unit) connected to the slave network to be in a communication state. The specific period is not particularly limited.

In order to ensure such a period, for example, it is conceivable that the path switching means has a second configuration (claim 2) as described below.
In this configuration, after the path switching unit switches each of the reception paths, each of the slave transmission / reception units enters the communication state in synchronization with a transmission cycle of a frame received via the reception path. The first synchronization period required for the transmission and the other nodes in the slave network to which the slave transmission / reception unit is connected are synchronized with the transmission cycle of the frame repeatedly transmitted by the slave transmission / reception unit in the communication state. When the second synchronization period required for entering the communication state elapses, each of the reception paths is re-switched from the main network to the slave network.

  With this configuration, as a period during which the relay node path switching unit switches the reception path, at least a period required for each node (including the slave transceiver unit) connected to the slave network to be in a communication state is secured. can do.

Further, in this configuration, it may be determined how the first synchronization period and the second synchronization period described above have elapsed.
For example, it may be determined that the period has elapsed when a predetermined time has elapsed as the time corresponding to the total period of the first synchronization period and the second synchronization period. It is also conceivable that the repetition period in which the frame is transmitted in the main network is repeated by the number corresponding to the total period of the first synchronization period and the second synchronization period, and it is determined that the period has elapsed.

For this latter case, it can be considered that the second configuration is a third configuration (claim 3) as described below.
The relay node having this configuration is provided with period counting means for counting the number of repetitions of transmission of frames in the main network after each reception path is switched by the path switching means. When the count value counted by the cycle counting unit is equal to or greater than the value corresponding to the total period of the first synchronization period and the second synchronization period, the path switching unit is The transmission / reception unit is configured to switch the reception path through which the frame is received from the main network to the sub network again.

  With this configuration, the first synchronization period and the second synchronization period elapse according to the count value by counting the number of times the frame is transmitted in the main network (that is, the cycle in which the frame is transmitted). Can be determined.

Moreover, as a configuration for solving the above-described problem, a relay device including all the means included in the relay node in any one of the first to third configurations may be used.
This is because this relay device can constitute a part of the network system in any one of the first to third configurations.

  In addition, as a configuration for solving the above problems, a program for causing a computer system to execute various processing procedures for causing all the means included in the relay node in any of the first to third configurations to be included, Alternatively, it may be hardware description code (claim 5) to be executed by dedicated hardware.

This is because a computer system controlled by this program can constitute a part of any of the first to third configurations.
The above-described program is composed of an ordered sequence of instructions suitable for processing by a computer system, and is a network system, a relay device, and a user who uses this via various recording media and communication lines. Is provided.

Embodiments of the present invention will be described below with reference to the drawings.
(1) Overall Configuration As shown in FIG. 1, the network system 1 relays transmission / reception of frames between a plurality of networks 2 to which one or more nodes 100 are connected, and between the networks 2. Relay node 3 to be used.

  Each of the nodes 100 is configured as a well-known ECU (Electronic Control Unit) that controls a predetermined actuator, and a predetermined protocol is transmitted via the transceiver 102 and the transceiver 102 that connect the node 100 to the network 2 at the physical layer level. (In the present embodiment, a communication unit 104 that performs communication according to FlexRay (the same applies hereinafter), a control unit 106 configured as a known microcomputer that controls the operation of the entire node 100, and the like are provided.

  The relay node 3 is a relay device used in a state of being interposed between a plurality of networks 2, and controls the operation of the transmission / reception unit 10 that controls transmission / reception of frames through each network 2 and the entire relay node 3. The control part 20 etc. to perform are provided.

  Among these, each of the transmission / reception units 10 includes a transceiver 12 that connects the relay node 3 to the network 2 at the physical layer level, a communication unit 14 that performs communication according to a predetermined protocol via the transceiver 12, and the like. By operating in response to this command, the single unit itself is configured to function in the same manner as the node 100 described above.

  Of these transmission / reception units 10, each of the transmission / reception units (hereinafter referred to as “sub transmission / reception units”) 10 b excluding a specific transmission / reception unit (hereinafter referred to as “main transmission / reception unit”) 10 a is received by the transceiver 12. A changeover switch 16 is provided in the reception path for transmitting the frame to the communication unit 14.

  This change-over switch 16 forms a reception path so that a frame received by the transceiver 12 of the slave transmission / reception unit 10b itself is transmitted to the communication unit 14 in the initial state. When the command is received, the reception path is switched so that the frame received by the transceiver 12 of the main transmission / reception unit 10 a is transmitted to the communication unit 14.

  The control unit 20 is composed of a well-known microcomputer or dedicated hardware, and transfers the frame transferred from each transmission / reception unit 10 to the reception buffer 22 for temporarily storing the frame and each transmission / reception unit 10. A transmission buffer 24 that temporarily stores frames, a relay control unit 26 that controls relaying of frames between the transmission and reception unit 10, and the like are provided.

  Each node including the relay node 3 (the transmission / reception unit 10) configured as described above is sequentially activated in accordance with the power supply to the entire system, and then connected between the nodes for each network 2 according to the protocol implemented in each node. So that communication is possible (hereinafter referred to as “communication state”), and thereafter, frames are repeatedly transmitted in a specific order in a specific order by time division multiplexing (TDM). Become.

  The synchronization between the nodes is as follows. Among nodes connected to the same network 2, a specific node (hereinafter referred to as “leading node”) starts transmission of a frame at a constant period, and other nodes ( Hereinafter, the procedure is performed in which the “synchronization node”) specifies the frame transmission timing by itself based on the transmission period of the frame.

  Here, in the network 2 to which the transmission / reception unit 10 of the relay node 3 is connected, the network (hereinafter referred to as “main network”) 2 to which the main transmission / reception unit 10a is connected is one of the earliest startup timings. Is configured so that it can function as a “leading node”, whereas in the network 2 to which the slave transmitting / receiving unit 10b is connected (hereinafter referred to as “secondary network”), only the slave transmitting / receiving unit 10b is provided. It is set so that it can function as a “leading node”.

  In the present embodiment, each node (including the transmission / reception unit 10) is set to transmit a frame in a predetermined time slot in a period (communication cycle) in which the lead node transmits a frame. The synchronization node receives the frames transmitted by the lead node for a certain period (four in this embodiment), so that the transmission period of the frame and the time at which the frame should transmit the frame in that period Slots can be specified.

Each node (including the transmission / reception unit 10) has a built-in cycle counter that counts the number of times the above-described cycle has been repeated with an initial value “0” as a predetermined value as an upper limit. The frame header information is configured to store the count value of the cycle counter.
(2) Processing by Relay Control Unit 26 Hereinafter, processing executed by the relay control unit 26 of the control unit 20 will be described.
(2-1) Communication Start Process First, the process procedure of the communication start process started when the relay node 3 is started will be described with reference to FIG.

  When this communication start process is activated, first, the main transmission / reception unit 10a is instructed to start communication (s110). The main transmission / reception unit 10a that has received this command starts processing for synchronization between nodes.

  Specifically, if the main transmission / reception unit 10a starts processing for synchronization in the main network 2 for the first time, the main transmission unit 10a starts transmitting frames at a fixed period as a leading node, and thereby enters a communication state. And transition. After that, the other node 100 specifies the frame transmission period and the time slot in which the node 100 itself should transmit the frame based on the transmission period of the frame, and transitions to the communication state.

  On the other hand, unless this main transmission / reception unit 10a starts processing for the first time, as a synchronization node, based on the frame transmitted from the lead node at a constant cycle, the frame 100 itself transmits the frame. A time slot to be specified is specified, and a transition is made to a communication state.

  Thus, in the main network 2, each of the main transmission / reception unit 10a and the node 100 transmits and receives frames at a fixed period in a specific time slot (see FIG. 3).

  After the instruction by s110, the main transmission / reception unit 10a is in a standby state until it changes to the communication state (s120: NO). In the present embodiment, since the value indicating the state of the main transmission / reception unit 10a is configured to be set in the register in the communication unit 14 as needed, whether or not the state of the main transmission / reception unit 10a has transitioned to the communication state. Is checked based on the value set in that register.

  After that, when the main transmission / reception unit 10a transitions to the communication state (s120: YES), the slave transmission / reception unit 10b is instructed to start communication (s130). The slave transmission / reception unit 10b that has received this command starts processing for synchronization between nodes in the same manner as the main transmission / reception unit 10a described above.

  Next, based on the count value of the cycle counter built in the communication unit 14 of the main transmission / reception unit 10a, the number of repetitions of the frame transmission cycle by the main node of the main network 2 is checked (s140). As described above, since the cycle counter returns to the initial value after the count value is counted up to the upper limit, the cycle counter repeatedly counts a series of cycles counted up to the upper limit. If this count value is an initial value, it means that the timing of the beginning of the series of cycles has arrived.

  In this s140, it will be in a standby state until it reaches the initial value “0” when the predetermined value is the upper limit (s140: NO). On the other hand, if the number of repetitions is the initial value “0” (s140: YES), The changeover switch 16 of each transmission / reception unit 10b is instructed to switch the reception path for transmitting a frame to the communication unit 14 from the transceiver 12 of the slave transmission / reception unit 10b to the transceiver 12 of the main transmission / reception unit 10a (s150). ).

  When the changeover switch 16 that has received this switching instruction switches the reception path, a frame distributed in the main network 2 is input to the communication unit 14 of the slave transmission / reception unit 10b via the transceiver 12 of the main transmission / reception unit 10a. It becomes like this.

  Thus, when a frame that circulates through the main network 2 is input, the slave transmitting / receiving unit 10b regards this frame as a frame that is transmitted from the lead node at a constant cycle, and the frame transmission cycle, the node 100 itself is the frame. Is specified, and the state transitions to the communication state (see “cycles 2n to 2n + 3” in FIG. 3).

  Thereafter, the other node 100 in the slave network 2 determines the frame transmission cycle and the time slot in which the node 100 itself should transmit the frame based on the frame transmission cycle by the slave transmitting / receiving unit 10b thus changed to the communication state. As a result, a transition to the communication state is made (see “cycle 2n + 4 to sn + 7” in FIG. 3).

Next, a variable CTR for counting the number of repetitions of a cycle in which the lead node transmits a frame is initialized (0 → CTR) (s160).
Next, until the counting by the cycle counter is performed, that is, until the frame transmission cycle is repeated (s170: NO), when the frame transmission cycle is repeated (s170: YES), the variable CTR is incremented ( CTR + 1 → CTR) (s180).

Next, it is checked whether or not the value of the variable CTR has reached a predetermined determination value D (CTR = D) (s190).
Here, the number of repetitions of the period required for each of the slave transmitting / receiving units 10b to be in communication with the transmission period of the frame received via the reception path (in the present embodiment, “4”; (Hereinafter referred to as “first cycle period”) and the transmission cycle of a frame in which other nodes in the slave network 2 to which the slave transceiver unit 10b is connected are repeatedly transmitted by the slave transceiver unit 10b in the communication state. The total value of the number of repetitions of the period required to establish the communication state in synchronization (in this embodiment, “4”; hereinafter referred to as “second period period”) and the total value are determined as the determination value D. This determination value D is the sum of the first period period and the second period period, and means a period required for each node (including the slave transmitting / receiving unit 10b) connected to the slave network 2 to enter the communication state. ing.

  When it is determined in s190 that the value of the variable CTR has not reached the predetermined determination value D (s190: NO), the process returns to s170, and thereafter, the value of the variable CTR is determined to be the predetermined determination value. The count of the variable CTR by s170 to s190 is repeated until D is reached and each of the nodes connected to the slave network 2 is in a communication state.

  If it is determined in s190 that the value of the variable CTR has reached the predetermined determination value D (s190: YES), the changeover switch 16 of each slave transmitting / receiving unit 10b is transferred to the communication unit 14. And a command to switch the reception path for transmitting the frame from the transceiver 12 of the main transceiver 10a to the transceiver 12 of the slave transceiver 10b (s200).

  When the changeover switch 16 that has received this switching instruction switches the reception path again, a frame that circulates in the slave network 2 is input to the communication unit 14 of the slave transmission / reception unit 10b via the transceiver 12 of the slave transmission / reception unit 10b. It becomes like this.

In this way, after s200 is performed, this communication start process is completed.
Thus, in this communication start process, the master network 2 is connected to the slave network 2 until the slave transceiver 10b and the node 100 of the slave network 2 are in a communication state after the slave transceiver 10b is activated. (S150), after entering the communication state (s190 “YES”), the main network 2 is disconnected from the slave network 2 (s200).
(2-2) Frame Relay Process Next, the process procedure of the frame relay process that is repeatedly executed after the communication start process is completed will be described with reference to FIG.

  When this frame relay process is activated, it is first checked whether or not a frame has been received via any of the transmission / reception units 10 (s210). In the present embodiment, the frames received by any of the transmission / reception units 10 are stored in the reception buffer 22 and then sequentially transferred. Thus, when the frames are thus transferred from the reception buffer 22, It is determined that a frame has been received.

  If it is determined that the frame is received in s210 (s210: YES), it is checked based on the relay table whether the frame is a frame to be relayed (s220). As shown in FIG. 5, this relay table indicates whether or not each frame should be relayed with respect to each identification unit (identification information stored in the frame) that can be received via each transmission / reception unit 10 (requirement for relay). ), A data table registered in association with the network 2 (relay destination) to be relayed. In s220, when the transfer destination corresponding to the identification unit in the frame received in s210 is registered in the relay table, it is determined that the frame is a frame to be relayed.

If it is determined in s220 that the frame is not to be relayed (s220: NO), the process immediately returns to s210.
If it is determined in s220 that the frame is to be relayed (s220: YES), the frame is transferred to the transmission buffer 24 so as to be transferred to the transmission / reception unit 10 reaching the network 2 to be relayed. After being made (s230), the process returns to s210. If necessary at the time of frame transfer, the frame identification unit may be changed.

The frame thus transferred to the transmission buffer 24 is transferred to the transmission / reception unit 10 that reaches the network 2 to be relayed, and the transmission / reception unit 10 that receives the frame transmits the frame to the network 2.
(3) Operation and Effect According to the network system 1 configured as described above, first, the main transmission / reception unit 10a of the relay node 3 enters the communication state (s120 “YES” in FIG. 2) and is connected to the main network 2. After the transmission timings of the frames by the respective nodes are synchronized, until the predetermined period elapses, the reception path is switched so that the sub-transmission / reception units receive the frames circulating through the main network (s150 to s150 in the figure). s200).

  Each of the slave transmitting / receiving units 10b enters the communication state in synchronization with the transmission cycle of the frame thus received (see “cycles 2n to 2n + 3” in FIG. 3), so that the slave transmitting / receiving unit 10b itself is connected. 2 repeats frame transmission / reception (refer to “cycle 2n + 4” and thereafter in the figure). At this time, since the slave transmitting / receiving unit 10b enters the communication state in synchronization with the transmission cycle of the frame that circulates through the main network 2, it is naturally synchronized with the transmission timing of the frame by each node of the main network 2. Yes.

  Thereafter, the frame repeatedly transmitted by the slave transceiver unit 10b is received by each of the other nodes in the slave network 2 to which the slave transceiver unit 10b is connected. The communication state is established in synchronization with the transmission cycle of the frame transmitted by the slave transmission / reception unit 10b (refer to “cycle 2n + 8” and thereafter in the figure). At this time, since the slave transmission / reception unit 10b is synchronized with the transmission timing of the frame by each node of the main network 2, each node that is in communication with the transmission cycle of the frame by the slave transmission / reception unit 10b. Similarly, is synchronized with the frame transmission timing by each node of the main network 2.

  In this way, each of the nodes connected to the slave transmission / reception unit 10b and the slave network 2 are all synchronized with the transmission timings of the nodes of the master network 2, so that a plurality of nodes connected via the relay node 3 can be obtained. It is possible to synchronize the transmission timing of frames by all the nodes in the network.

  In the above-described embodiment, the transmission timings of the nodes of the main network 2 in the order of the main transmission / reception unit 10a, the sub transmission / reception unit 10b, and the nodes 100 of the sub-network 2 in the relay node 3 regardless of the activation timing. Can be synchronized. Therefore, even in an environment where the start timing of each node associated with the start-up as a system is not constant, the transmission timing of the frames by the nodes of all the networks 2 connected via the relay node 3 is definitely synchronized. Can be made. Therefore, it is possible to predict in advance the delay time of the frame passing through the relay device, and there is no variation in the delay of the frame due to passing through the relay device.

  Further, in the above-described embodiment, the nodes (including the slave transmission / reception unit 10b) connected to the slave network 2 are in the slave transmission / reception until the period (determination value D) required to enter the communication state (variable CTR = D) is reached. The reception path in the unit 10b is switched from the transceiver 12 of the slave transmission / reception unit 10b to the transceiver 12 of the main transmission / reception unit 10a (s150 to s200 in FIG. 2). Thereby, as a period for switching the reception path of the slave transmission / reception unit 10b, a period required for each node connected to the slave network 2 to be in a communication state can be secured.

In the above embodiment, each of the nodes connected to the slave network 2 enters the communication state when the value of the variable CTR reaches the determination value D indicating the sum of the first period period and the second period period. Therefore, it is possible to determine that the period required for elapses, and thereby the reception path in the slave transceiver unit 10b can be returned to the initial state (s200 in FIG. 2).
(4) Modifications The embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and can take various forms as long as they belong to the technical scope of the present invention. Needless to say.

  For example, in the above embodiment, the configuration in which only two transmission / reception units 10 are provided in the relay node 3 is illustrated in FIG. 1, but a configuration in which three or more transmission / reception units 10 are provided can be employed. Needless to say.

  Moreover, in the said embodiment, whether the period (a 1st period period and a 2nd period period) required for each node (including the slave transmission / reception part 10b) connected to the slave network 2 to be in a communication state passed. Is determined based on the count value of the variable CTR, that is, the value obtained by counting the number of repetitions of the cycle in which the initiative node transmits a frame (170 to s190 in FIG. 2).

  However, it may be determined how the first synchronization period and the second synchronization period have elapsed, for example, as a time corresponding to the total period of the first synchronization period and the second synchronization period. It can be determined that the period has elapsed when the given time has elapsed.

  In this case, in s160 to s190 in FIG. 2, the process waits until the elapsed time after the reception path is switched in s150 in FIG. 2 reaches a time corresponding to the total period of the first synchronization period and the second synchronization period. When the time is reached, the process may be shifted to s200 in FIG. When the above-described determination method is used, it is necessary to acquire a reference time from the communication unit 104 and grasp the elapsed time.

Further, the communication start process in the above embodiment is configured such that the process after s140 in FIG. 2 is performed after the slave transmission / reception unit 10b is instructed to start communication by s130 in FIG. However, the command to the slave transmission / reception unit 10b by s130 may be made after any of s140 to s160 in FIG.
(5) Correspondence with the Present Invention In the embodiment described above, s210 to s230 in FIG. 4 are relay means in the present invention, s110 in FIG. 2 is first command means in the present invention, and s130 in FIG. The second command means in the present invention, s150 and s200 in the figure are the path switching means in the invention, and s170 and s180 in the figure are the period counting means in the invention.

Block diagram showing the overall configuration of the network system Flow chart showing communication start processing Timing chart showing how frames are transmitted in each network Flow chart showing frame relay processing Diagram showing data structure of relay table

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Network system, 2 ... Master network, 2 ... Slave network, 3 ... Relay node, 10 ... Transmission / reception part, 10a ... Master transmission / reception part, 10b ... Slave transmission / reception part, 12 ... Transceiver, 14 ... Communication part, 16 ... Changeover switch , 20 ... control section, 22 ... reception buffer, 24 ... transmission buffer, 26 ... relay control section, 100 ... node, 102 ... transceiver, 104 ... communication section, 106 ... control section.

Claims (5)

A network system comprising a plurality of networks each connected with one or more nodes, and a relay node that relays frame transmission / reception between the networks via the networks,
Of the plurality of networks, the main network, which is one of the networks, has the node (including the relay node) that is activated earliest start frame transmission at a certain period, and other nodes that are activated thereafter By synchronizing with the transmission cycle of the frame, each node will be in a communication state that repeats transmission and reception of frames in time division multiplexing,
Of the plurality of networks, the slave network that is a network other than the main network is configured such that the relay node starts transmitting a frame at a constant period, and the other nodes are synchronized with the transmission period of the frame. Each node is in a communication state in which transmission and reception of frames are repeated by time division multiplexing.
The relay node is
A main transmission / reception unit that controls transmission / reception of frames to / from the main network while connected to the main network, and functions as a node connected to the main network;
One or more slave transmission / reception units that control transmission / reception of frames to / from the slave networks while functioning as nodes connected to the slave networks in a state of being connected to different slave networks;
Frame relay means for relaying frames between the transmission / reception units (the main transmission / reception unit, the sub transmission / reception unit);
After the relay node is activated, the main transmission / reception unit is instructed to start transmission of a frame at a constant cycle or to be in the communication state by synchronizing with a frame transmission cycle. First command means;
After the main transmission / reception unit enters the communication state in response to the command from the first command means, the slave transmission / reception unit starts transmission of a frame at a constant cycle, or the frame transmission cycle Second command means for commanding that the communication state should be established by synchronizing;
Each of the slave transmission / reception units receives a frame from which the slave transmission / reception unit receives a frame until the predetermined period elapses after the master transmission / reception unit is in a communication state upon receiving a command from the first command unit. A path switching means for switching from the slave network connected to the master network to the main network. In the relay node,
After switching each of the reception paths, the path switching unit requires each of the slave transmission / reception units to be in the communication state in synchronization with a transmission cycle of a frame received via the reception path. One synchronization period and other nodes in the slave network to which the slave transmission / reception unit is connected are synchronized with the transmission cycle of the frame repeatedly transmitted by the slave transmission / reception unit in the communication state. 2. The network according to claim 1, wherein when the second synchronization period required for the elapse of time elapses, each of the reception paths is re-switched from the main network to the sub-network. system. In the relay node,
A period counting unit that counts the number of times the frame is transmitted in the main network after each of the reception paths is switched by the path switching unit;
When the count value counted by the period counting unit is equal to or greater than a value corresponding to a total period of the first synchronization period and the second synchronization period, the path switching unit is configured to transmit the slave transmission / reception unit. 3. The network system according to claim 2, wherein each of the reception paths for receiving a frame is switched from the primary network to the secondary network. 4. All the means with which the relay node in any one of Claim 1 to 3 is provided. The relay apparatus characterized by the above-mentioned.   A program for causing a computer system to execute various processing procedures for causing the relay node according to any one of claims 1 to 3 to function as all means, or a hardware description code for causing a dedicated hardware to execute.

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