JP2017103644A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable transmission by avoiding interference even for a frame of low priority order while restricting an increase in the number of frame IDs in a communication system.SOLUTION: A communication system comprises: a counting part in which a monitor node 1 among nodes 1 to 4 measures, for each frame ID and within a specified time, the frequency of transmissions, which is the number of frames transmitted to a bus 13 from the nodes 2 to 4 to be monitored; a determination part that determines whether there is a frame that is equal to or smaller than a predetermined value in the frequency of transmissions within the specified time (hereinafter, referred to as a fewer transmission frame); and a notification part that, if it is determined that there is a fewer transmission frame, transmits a bus 13 a transmission control frame of high priority order including the node ID of the fewer transmission node, which is the transmission source of the fewer transmission frame. If the nodes 2 to 4 determine on the basis of the node ID in the transmission control frame that the node is a node other than the fewer transmission node, they stop transmission from the node for only a predetermined period.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication system in which a plurality of nodes are connected to a bus.

  For example, CAN is known as a protocol for a communication system mounted on an automobile. CAN is an abbreviation for “Controller Area Network”. CAN is a registered trademark.

  The CAN protocol is a multi-master communication protocol that allows transmission from any node when the bus is free. For this reason, in the CAN protocol, frames may be transmitted simultaneously from a plurality of nodes, and frame collision may occur on the bus.

  In order to perform communication arbitration to prevent such a collision, in the CAN protocol, an ID indicating the priority order of the frame is included in the head portion of the frame. ID is an abbreviation of “Identifier”, that is, an identifier. This ID is an identifier for identifying the content of data set in the subsequent area and the source node, and is set for each frame. Therefore, this ID is also a frame identifier. This ID is also called CANID.

  In the CAN protocol, when a plurality of nodes start transmitting a frame at the same time, a frame with an ID having a low priority is lost in arbitration, and the transmission source node of the frame that has lost the arbitration stops transmission. Therefore, among the nodes that have started transmission at the same time, one node that is a transmission source of a frame having a higher priority than frames from other nodes obtains the transmission right and continuously transmits the frame. It becomes. For this reason, when the bus load is high, the residence time of frames with low priority is long. The staying time is a time during which a frame continues to stay without being arbitrated and transmitted. Note that a frame having a high priority is a frame including an ID having a high priority, and a frame having a low priority is a frame including an ID having a low priority.

  In the CAN protocol, since there is no upper limit to the number of nodes, the residence time is likely to increase as the number of nodes increases. In the CAN protocol, the data length is 8 bytes at the maximum, but a CAN protocol corresponding to a variable data rate that can extend the data length to 64 bytes has also appeared. In the CAN protocol corresponding to the variable data rate, there is a possibility that the bus load further increases and the residence time becomes longer.

  On the other hand, for example, Patent Document 1 describes a technique for shortening the residence time of a frame that has lost arbitration. In the technology, when it is determined that each node has waited for transmission of the transmission target frame longer than a predetermined time, the ID assigned to the transmission target frame has the highest priority among all the frames. It is to change to ID.

Japanese Patent Laying-Open No. 2015-154185

  In the technique disclosed in Patent Document 1, since it is necessary to change the ID, it is necessary to allocate two IDs per frame in each node constituting the communication system. One of the two IDs is an ID that is used in a normal case, and the other is an ID that is used when the arbitration is continuously lost.

  For this reason, the number of IDs required to configure the communication system increases, which may cause a problem of ID depletion. For example, in an automobile, the number of control devices as nodes tends to increase due to an increase in functions to be mounted. For this reason, in the future, it is considered that there is a desire to reduce the number of IDs used in one control device.

  In view of the above, an object of the present invention is to enable transmission by avoiding collision even in a frame having a low priority while suppressing an increase in the number of frame IDs in a communication system.

The communication system (11) of the present invention includes a plurality of nodes (1 to 4) connected to a bus (13).
A frame transmitted from each node to the bus includes a frame ID indicating the priority of the frame as well as an identifier of the frame.

  Each node starts frame transmission when no frame is transmitted from another node to the bus. In this communication system, when two or more nodes start transmission at the same time, transmission of a frame including a frame ID having a lower priority than frames from other nodes among the nodes that have started transmission at the same time. The node that started the transmission stops transmitting the frame. The frame in which transmission is stopped in this way is a frame that has lost arbitration. Conversely, a node that has started transmitting a frame including a frame ID having a higher priority than frames from other nodes will continue to transmit that frame. Communication arbitration is performed by such an operation.

In the communication system of the present invention, one of the plurality of nodes is the monitoring node (1), and at least the nodes (2 to 4) other than the monitoring node are the plurality of nodes to be monitored.
The monitoring node includes a counting unit (S110, S120), a determination unit (S130), and a notification unit (S140 to S170).

  The counting unit counts the number of transmissions, which is the number of frames transmitted from the monitored node to the bus, for each frame ID and within a specified time. The frame transmitted to the bus is a frame that has been transmitted without stopping on the way.

  When the counting unit finishes counting the number of transmissions, based on the counting result of the counting unit, the number of transmissions within a specified time is less than or equal to a predetermined determination value among frames transmitted from the monitored node. It is determined whether there is a small transmission frame that is a received frame.

  The notification unit transmits the transmission control frame to the bus when the determination unit makes an affirmative determination, that is, when it is determined that there are few transmission frames. The transmission control frame includes identification information that can identify a small transmission node that is a transmission source node of the small transmission frame, and includes a frame ID indicating the highest priority in the communication system as a frame ID. is there.

The monitoring target node includes a determination unit (S220, S225) and a transmission prohibition unit (S240 to S260).
When the determination unit receives the transmission control frame, based on the identification information included in the transmission control frame, the determination unit determines that the node is a small transmission node and a restriction target node that is a node other than the small transmission node. It is discriminate | determined which is.

The transmission prohibition unit prohibits transmission of a frame from the node for a predetermined period when the determination unit determines that the node is a restriction target node.
In such a communication system, for example, it is assumed that the frame FA with the frame ID “A” continues to lose arbitration, and the number of transmissions of the frame FA within a specified time becomes equal to or less than the determination value. That is, it is assumed that the frame FA is a small transmission frame.

  In this case, in the monitoring node, an affirmative determination is made by the determination unit, and the notification unit transmits a transmission control frame including identification information that can identify the node NA that is the transmission source of the frame FA to the bus. The transmission control frame is received by all the nodes because the priority of the frame ID included in the transmission control frame is highest in the communication system.

  Among the nodes to be monitored, in the nodes other than the node NA, the determination unit determines that the node is a restriction target node, and the transmission prohibition unit prohibits frame transmission from the node for a predetermined period. To do. On the other hand, in the node NA, since the determination unit determines that the node is a small transmission node, frame transmission is not prohibited. For this reason, the node NA that is a small transmission node can freely transmit the frame FA that is a small transmission frame without being deprived of the transmission right by other nodes.

  Therefore, according to this communication system, it is possible to avoid collision and transmit even frames with low priority and easy to lose arbitration. Furthermore, since the monitoring node only needs to have one frame ID with the highest priority as the transmission control frame ID, an increase in the number of frame IDs can be suppressed. Therefore, it is possible to avoid a collision even in a frame having a low priority and to enable transmission while suppressing an increase in the number of frame IDs.

  In addition, the code | symbol in the parenthesis described in this column and a claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is shown. It is not limited.

It is a block diagram which shows the structure of the communication system of embodiment. It is explanatory drawing of a flame | frame. It is explanatory drawing of the table memorize | stored in the monitoring node. It is a flowchart showing the monitoring process of 1st Embodiment. It is a flowchart showing the transmission restriction | limiting process of 1st Embodiment. It is a flowchart showing the transmission restriction | limiting process of 2nd Embodiment. It is a flowchart showing the monitoring process of 3rd Embodiment. It is a flowchart showing the transmission restriction | limiting process of 3rd Embodiment.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings.
[First Embodiment]
<Configuration>
A communication system 11 shown in FIG. 1 is a communication system mounted on a vehicle, and is a system for communicating necessary information between nodes mounted on the vehicle.

As shown in FIG. 1, the communication system 11 includes a plurality of nodes 1 to 4 connected to a bus 13. In this example, the number of nodes is four, but the number of nodes may be other than four.
The nodes 1 to 4 are ECUs that control each part of the vehicle, and are configured around a known microcomputer (hereinafter referred to as a microcomputer) including a CPU, a ROM, a RAM, and the like. The ECU is an abbreviation of “Electronic Control Unit”, that is, an electronic control unit. Various functions of the microcomputer are realized by the CPU executing a program stored in a non-transitional tangible recording medium. In this example, the ROM corresponds to a non-transitional tangible recording medium that stores a program. By executing this program, a method corresponding to the program is executed. Further, the number of microcomputers constituting the nodes 1 to 4 may be one or plural. Moreover, you may implement | achieve part or all of the function which the nodes 1-4 perform using the hardware which combined the logic circuit, the analog circuit, etc.

<Communication protocol>
In the communication system 11, the CAN protocol is used as a communication protocol.
In the CAN protocol, the nodes 1 to 4 transmit frames by confirming that the state of the bus 13 is bus idle. The bus idle is a state in which no frame is transmitted to the bus 13 (that is, an empty state).

  For this reason, two or more of the nodes 1 to 4 may start transmitting frames at the same time. In that case, a plurality of frames collide on the bus 13. In the CAN protocol, when a frame collides, a known communication arbitration is performed such that transmission of a frame having a high priority is given priority and transmission of a frame having a low priority is stopped.

  Here, as shown in FIG. 2, a frame in the CAN protocol includes a header area and a data area following the header area. The header area includes a frame identifier and an ID indicating the priority of the frame (hereinafter also referred to as a frame ID). This frame ID is called CANID, and is binary data having a data size of a prescribed data length (for example, 11 bits).

  The bus 13 is configured such that the signal level on the bus 13 becomes low level when a high level signal and a low level signal are simultaneously output from two or more of the nodes 1 to 4. Yes. That is, the signal level on the bus 13 is dominant (ie, dominant) at a low level corresponding to logic 0, and inferior (ie, recessive) at a high level corresponding to logic 1.

  Since a frame is transmitted bit by bit from the beginning, the smaller the logical value of the frame ID, the higher the priority of the frame. In other words, the smaller the logical value of the frame ID, the easier it is to survive when there is a collision with another frame on the bus 13.

  Each of the nodes 1 to 4 monitors the signal level of the bus 13, and if the signal level of the logical value transmitted by the node does not match the signal level of the bus 13, it is determined that the node has lost communication arbitration. Then, frame transmission is stopped.

  For this reason, when two or more of the nodes 1 to 4 start transmission at the same time, transmission of a frame including a frame ID having a lower priority than frames from other nodes among the nodes that have started transmission at the same time. The starting node stops transmission of the frame. Then, the node that has started transmission of a frame including a frame ID having a higher priority than frames from other nodes continues to transmit the frame. By such an operation, communication arbitration at the time of frame collision is performed.

<Role of node>
One of the nodes 1 to 4 is a monitoring node that counts the number of frame transmissions for each frame ID, and the other node is a monitoring target node (hereinafter, referred to as a monitoring target node) that counts the number of frame transmissions by the monitoring node. A monitoring target node). In the present embodiment, for example, the node 1 is a monitoring node, and the nodes 2 to 4 are monitoring target nodes. Therefore, in the following, the node 1 is also referred to as a monitoring node 1. Nodes 2 to 4 are also referred to as monitoring target nodes 2 to 4.

  The number of frame transmissions refers to the number of frames transmitted to the bus 13. More specifically, the number of frames transmitted without stopping during transmission to the bus 13, that is, the bus 13 without losing arbitration. The number of frames transmitted to.

<Information stored in advance in the node>
Among the nodes 1 to 4, at least the memory (for example, ROM) provided in the monitoring node 1 stores an ID correspondence table 15 indicating the correspondence between frame IDs and node IDs as shown in FIG. . The ID correspondence table 15 is a data table in which the frame ID of each frame transmitted from the nodes 2 to 4 and the node ID that is the identifier of the transmission source node that transmits the frame of the frame ID are recorded in association with each other. is there.

  Note that “0x020”, “0x02F”, and the like shown in FIG. 3 represent frame IDs in hexadecimal. Similarly, “0x04”, “0x02”, and the like shown in FIG. 3 represent node IDs in hexadecimal numbers.

Then, the monitoring node 1 uses the ID correspondence table 15 to create a monitoring table 17 for monitoring the number of frame transmissions from the nodes 2 to 4.
As shown in FIG. 3, in addition to the contents recorded in the ID correspondence table 15, the monitoring table 17 counts the number of transmissions for each frame ID recorded in the ID correspondence table 15 for the frame ID. Is a data table having a storage area in which is stored. In the monitoring table 17, at least the storage area for the number of transmissions is provided in a rewritable memory (for example, RAM) provided in the monitoring node 1.

<Description of processing>
<Monitoring process>
The monitoring node 1 performs the monitoring process shown in FIG. 4 at regular time intervals, for example.

  As shown in FIG. 4, when the monitoring node 1 starts the monitoring process, in S110, the monitoring node 1 performs a process of counting (that is, counting) the number of transmissions of each frame to the bus 13 for each frame ID. Specifically, the monitoring node 1 monitors the bus 13 and detects the frame ID of the frame transmitted to the bus 13. Each time a frame ID is detected, the value of the number of transmissions stored in the storage area corresponding to the detected frame ID in the monitoring table 17 is increased by one. That is, the number of transmissions corresponding to the detected frame ID is incremented (that is, counted up).

  In step S120, the monitoring node 1 determines whether or not the specified time has elapsed. If the specified time has not elapsed, the monitoring node 1 returns to S110 and continues the process of counting the number of transmissions of each frame. .

  If the monitoring node 1 determines in S120 that the specified time has elapsed, the monitoring node 1 proceeds to S130. At this time, the monitoring table 17 stores the count result of the number of transmissions within the specified time for each frame ID of each frame. That is, the monitoring node 1 counts the number of transmissions of each frame from the nodes 2 to 4 to the bus 13 by the processing of S110 and S120 for each frame ID and within a specified time.

  In S130, the monitoring node 1 refers to the monitoring table 17, and among the frames transmitted from the monitoring target nodes 2 to 4, the number of transmissions within a specified time is less than or equal to a predetermined determination value ( Hereinafter, it is determined whether there is a small transmission frame). If it is determined that there are few transmission frames, the process proceeds to S140.

  In S <b> 140, the monitoring node 1 identifies the small transmission node that is the transmission source node of the small transmission frame from the monitoring table 17. Specifically, in the monitoring table 17, the node indicated by the node ID recorded corresponding to the frame ID of the small transmission frame is specified as the small transmission node.

In step S150, the monitoring node 1 transmits a transmission control frame corresponding to the small transmission node specified in step S140 to the bus 13.
The transmission control frame includes identification information that can identify a small number of transmission nodes, and includes a frame ID indicating the highest priority in the communication system 11 as a frame ID. In the present embodiment, the identification information is a node ID of a small transmission node. The node ID serving as identification information is arranged at a predetermined position in the data area of the transmission control frame.

  In addition, priorities are determined in advance for the monitoring target nodes 2 to 4, and the monitoring node 1 stores the priorities. If there are a plurality of small transmission nodes, the monitoring node 1 selects one of the plurality of small transmission nodes in descending order of priority, and transmits corresponding to the selected small transmission node in S150. Send a control frame.

  In the next S160, the monitoring node 1 determines whether or not the transmission of the transmission control frame has been completed for all the small transmission nodes specified in S140, and if it determines that the transmission has not been completed, The process proceeds to S170 and waits for a predetermined transmission interval time. Note that this transmission interval time is set to a time longer than a predetermined time in which it is determined whether or not it has passed in S250 of FIG. Then, after waiting for the transmission interval time in S170, the monitoring node 1 returns to S150, and transmits a transmission control frame corresponding to the small transmission node having the next highest priority among the plurality of small transmission nodes.

  Further, if the monitoring node 1 makes an affirmative determination in S160, that is, if transmission of the transmission control frame is completed for all of the small transmission nodes, or if it is determined in S130 that there are no small transmission frames, it remains as it is. The monitoring process ends.

  Note that the monitoring node 1 deletes the number of transmissions stored in the monitoring table 17 when the monitoring process ends. This is because the number of transmissions within the next specified time is counted by the next processing of S110 and S120.

  Further, if the monitoring node 1 makes an affirmative determination in S160 or makes a negative determination in S130, it immediately returns to S110 after deleting the number of transmissions stored in the monitoring table 17. May be.

<Transmission restriction processing>
When the monitoring target nodes 2 to 4 receive the frame from the bus 13, the monitoring target nodes 2 to 4 perform the transmission restriction process illustrated in FIG. 5.

  The nodes 2 to 4 transmit a frame to be transmitted at a predetermined transmission timing every time a predetermined transmission timing arrives by a transmission process different from the process of FIG. The transmission timing may be regular or irregular due to occurrence of a predetermined event. In the communication system 11, each of the nodes 1 to 4 performs reception even during transmission of the node. Therefore, the nodes 2 to 4 perform the transmission restriction process of FIG. 5 not only when receiving a frame from another node but also when receiving a frame transmitted by the node.

  As illustrated in FIG. 5, when starting the transmission restriction process, the nodes 2 to 4 determine whether or not the received frame is a transmission control frame from the monitoring node 1 in S210. Specifically, if the frame ID of the received frame is the frame ID of the transmission control frame, it is determined that the received frame is a transmission control frame.

  If the nodes 2 to 4 determine in S210 that the received frame is not a transmission control frame, the transmission restriction process is terminated as it is. In this case, the nodes 2 to 4 perform processing according to the contents of the received frame.

If the nodes 2 to 4 determine in S210 that the received frame is a transmission control frame, that is, if the transmission control frame is received, the process proceeds to S220.
In S220, the nodes 2 to 4 determine whether or not the received transmission control frame is a frame addressed to the node.

  Specifically, it is determined whether the node ID included in the data area of the received transmission control frame is the node ID of the node. If the node ID is the node ID of the node, the received transmission control frame is determined. Is a frame addressed to the node. Conversely, if the node ID included in the data area of the received transmission control frame is not the node ID of the node, it is determined that the received transmission control frame is not a frame addressed to the node.

  When the nodes 2 to 4 determine that the received transmission control frame is a frame addressed to the node, the nodes 2 to 4 determine that the node is a small transmission node. Further, when the nodes 2 to 4 determine that the received transmission control frame is not a frame addressed to the node, the node is a node other than the small transmission node (hereinafter referred to as a restriction target node) among the monitoring target nodes. ). That is, when the node ID included in the data area of the transmission control frame is the node ID of the node, the nodes 2 to 4 determine that the node is a small transmission node. The nodes 2 to 4 determine that the node is a restriction target node if the node ID included in the data area of the transmission control frame is not the node ID of the node.

  If the nodes 2 to 4 determine in S220 that the received transmission control frame is a frame addressed to the node, that is, if it is determined that the node is a small transmission node, the process proceeds to S230. Allow frame transmission by processing. That is, the frame transmission is continued. Then, the transmission restriction process ends.

  If the nodes 2 to 4 determine in S220 that the received transmission control frame is not a frame addressed to the node, that is, if it is determined that the node is a restriction target node, the process proceeds to S240.

  In S240, the nodes 2 to 4 prohibit frame transmission by the transmission process, and in the next S250, determine whether or not a certain time has elapsed since prohibiting frame transmission. If it is determined that the predetermined time has elapsed, the process proceeds to S260, and the frame transmission prohibition is canceled. That is, frame transmission is resumed. Then, the transmission restriction process ends.

  Therefore, the nodes 2 to 4 continue to transmit frames when it is determined in S220 that the node is a small transmission node, but in S220, the node is determined to be a restriction target node. In this case, transmission of all frames is stopped for a certain time.

<Example of action>
In the communication system 11, when the nodes 2 to 4 are freely communicating, the monitoring node 1 counts the number of frame transmissions from the nodes 2 to 4 within a specified time for each frame ID.

  The monitoring node 1 has the highest priority when there is a frame (that is, a small number of transmission frames) in which the number of transmissions within a specified time is less than or equal to a determination value among frames transmitted from the nodes 2 to 4 A transmission control frame is transmitted to the bus 13. The transmission control frame includes the node ID of the small transmission node as identification information of the small transmission node that is the transmission source of the small transmission frame.

  For example, if the count result of the number of transmissions within a specified time is the value described in the column “Number of transmissions” in FIG. 3, the determination value for determining whether the frame is a small transmission frame is “5”. Then, the frame with the frame ID “0x7FF” is a small transmission frame. For this reason, the monitoring node 1 identifies the node 3 as a small transmission node in S140 of FIG. In this case, the monitoring node 1 transmits a transmission control frame including the node ID of the node 3 to the bus 13.

  Then, among the nodes 2 to 4, the node 3 determines in S220 of FIG. 5 that the transmission control frame from the monitoring node 1 is a frame addressed to the node, and that the node is a small transmission node. For this reason, the node 3 continues to transmit the frame.

  On the other hand, the other nodes 2 and 4 determine in S220 of FIG. 5 that the transmission control frame from the monitoring node 1 is not a frame addressed to the node but that the node is a restriction target node. For this reason, the nodes 2 and 4 stop transmitting frames for a fixed time. For this reason, the node 3 can preferentially transmit a frame without the transmission right being deprived by the other nodes 2 and 4 during the predetermined time. Therefore, the node 3 can transmit a small transmission frame in which the number of transmissions within the specified time is equal to or less than the determination value without losing arbitration.

<Effect>
According to the first embodiment described in detail above, it is possible to avoid collision and transmit even frames with low priority and easy to lose arbitration. Furthermore, since the monitoring node 1 only needs to have one frame ID with the highest priority as the transmission control frame ID, an increase in the number of frame IDs can be minimized.

  Further, the identification information included in the transmission control frame is the node ID of the small transmission node. Then, if the node ID in the transmission control frame is the node ID of the node, the monitoring target nodes 2 to 4 determine that the node is a small transmission node, and the node ID in the transmission control frame is If it is not the node ID of the node, it is determined that the node is a restriction target node. For this reason, the monitoring target nodes 2 to 4 can easily determine whether the node is a small transmission node for which transmission is prioritized or a restriction target node for which transmission is restricted.

  In addition, when there are a plurality of small transmission nodes, the monitoring node 1 is a plurality of transmission control frames respectively corresponding to the small transmission nodes, each including a node ID of each of the small transmission nodes. Are transmitted in order from the one corresponding to the small transmission node having the higher priority. This is realized by the processing of S150 to S170 in FIG. For this reason, even when there are a plurality of small transmission nodes, transmission of frames from the small transmission nodes can be performed without causing a collision (that is, with priority). As a result, among the frames to be transmitted by each small transmission node, a frame that has been a small transmission frame can be transmitted without losing arbitration.

  In addition, when the monitoring target nodes 2 to 4 become the restriction target nodes, the monitoring target nodes 2 to 4 stop transmission for a predetermined period, and the predetermined period is a period until a certain time elapses. This is realized by the processing of S240 to S260 in FIG. For this reason, for example, it is not necessary to instruct to cancel the frame transmission stop from the outside of the monitoring target nodes 2 to 4.

  In the first embodiment, among the processes of FIG. 4 performed by the monitoring node 1, the processes of S110 and S120 correspond to the process as the counting unit, and the process of S130 corresponds to the process as the determination unit. The processing of S140 to S170 corresponds to processing as a notification unit. In addition, among the processes of FIG. 5 performed by the monitoring target nodes 2 to 4, the process of S220 corresponds to the process as the determination unit, and the processes of S240 to S260 correspond to the process as the transmission prohibition unit.

[Second Embodiment]
A second embodiment will be described below with reference to the drawings. In the second embodiment, parts different from the first embodiment will be described. The same reference numerals as those in the first embodiment indicate the same configuration, and the preceding description is referred to. The same applies to other embodiments described later.

The communication system 11 according to the second embodiment differs from the first embodiment in the following points (A) and (B).
(A) The monitoring node 1 uses, in the data area of the transmission control frame transmitted in S150 of the monitoring process, a small transmission frame whose source is the small transmission node as identification information that can identify the small transmission node. Frame ID.

  If there is one small transmission frame, the frame ID of the small transmission frame is used as identification information. When there are a plurality of small transmission frames for the same small transmission node, the frame ID of the lowest priority among the plurality of small transmission frames is used as identification information.

(B) The monitoring target nodes 2 to 4 perform the transmission restriction process in FIG. 6 instead of the transmission restriction process in FIG. 5.
The transmission restriction process of FIG. 6 is provided with S225 instead of S220 and S245 instead of S240 as compared with the transmission restriction process of FIG.

  In S225 in the transmission restriction process in FIG. 6, the nodes 2 to 4 determine whether the frame ID as identification information included in the data area of the received transmission control frame is the frame ID of the frame transmitted by the node. Determine whether or not.

  If the frame ID as identification information is the frame ID of the frame transmitted by the node, it is determined that the received transmission control frame is a frame addressed to the node, that is, the node is a small transmission node. And proceed to S230.

  If the frame ID as identification information is not the frame ID of the frame transmitted by the node, it is determined that the received transmission control frame is not a frame addressed to the node. And proceed to S245.

  In S245, the nodes 2 to 4 do not prohibit transmission of all frames transmitted by the node, but rather have a frame ID having a higher priority than the frame ID as identification information included in the transmission control frame. Transmission is prohibited only for the frames.

<Effect>
According to the second embodiment, in addition to the same effects as those of the first embodiment, the following effects can be obtained.
In other words, it is possible to minimize the frames that are prohibited from being transmitted. This is because the restriction target node can transmit any frame that has a lower priority than the frame ID as identification information included in the transmission control frame.

  In the second embodiment, among the processes of FIG. 6 performed by the monitoring target nodes 2 to 4, the process of S225 corresponds to the process as a determination unit, and the processes of S245 to S260 are the process as a transmission prohibition unit. It corresponds to.

On the other hand, as a modification of the second embodiment, in S245 of FIG. 6, transmission of all frames may be prohibited as in S240 of FIG.
[Third Embodiment]
The communication system 11 according to the third embodiment differs from the first embodiment in the following points (a) and (b).

(A) The monitoring node 1 performs the monitoring process of FIG. 7 instead of the monitoring process of FIG.
In the monitoring process of FIG. 7, S153 and S155 are added between S150 and S160 as compared with the monitoring process of FIG. Further, S170 is deleted, and if NO is determined in S160, the process returns to S150 as it is.

  In the monitoring process of FIG. 7, when the monitoring node 1 transmits a transmission control frame in S150, the monitoring node 1 waits for a predetermined set time in S153. In step S155, the monitoring node 1 transmits a restart control frame to the bus 13, and then proceeds to step S160.

  The resume control frame is a frame for instructing the restriction target node in the transmission prohibited state to resume transmission. For this reason, the set time waiting in S153 corresponds to a transmission stop time during which the restriction target node stops frame transmission. Therefore, this set time can be set in advance, for example, at a time equivalent to a certain time for determining whether or not the time has passed in S250 of FIG. 5 in the first embodiment. Moreover, this setting time can also be variably set according to the traffic in the said communication system 11, for example. For example, the longer the traffic is, the longer the set time (that is, transmission stop time) can be set.

  Further, the frame ID of the resume control frame can be set to the same highest priority frame ID as the transmission control frame, for example. In this case, frame type data indicating that the frame is a restart control frame may be arranged in the data area of the frame, for example, instead of the identification information described above. As another example, for example, if a frame ID indicating a restart control frame is provided, the frame ID can be identified by the frame ID, so that the frame type data is not arranged in the data area. May be.

(B) The monitoring target nodes 2 to 4 perform the transmission restriction process of FIG. 8 instead of the transmission restriction process of FIG.
The transmission restriction process of FIG. 8 is provided with S255 instead of S250 as compared with the transmission restriction process of FIG.

  In the transmission restriction process of FIG. 8, when the transmission of the frame is prohibited in S <b> 240, the nodes 2 to 4 proceed to S <b> 255 and wait until receiving the restart control frame from the monitoring node 1. If a restart control frame is received, the process proceeds to S260 and the frame transmission prohibition is canceled. The nodes 2 to 4 can determine that the frame is a restart control frame if the above-described frame identification data is arranged in the data area of the received frame. If a dedicated frame ID is assigned to the restart control frame, the nodes 2 to 4 can determine whether the frame is the restart control frame from the frame ID of the received frame.

  That is, the nodes 2 to 4 stop transmitting after determining that the node is a restriction target node based on the identification information in the transmission control frame until receiving the restart control frame. ing.

<Effect>
According to the third embodiment, in addition to the same effects as in the first embodiment, the monitoring node 1 can control the transmission restart timing of the node that has stopped transmission among the monitoring target nodes 2 to 4. The effect is obtained.

  In the third embodiment, among the processes of FIG. 7 performed by the monitoring node 1, the processes of S140 to S160 correspond to the process as a notification unit. Further, among the processes of FIG. 8 performed by the monitoring target nodes 2 to 4, the processes of S 240 to S 260 correspond to the process as the transmission prohibition unit.

On the other hand, the contents of the third embodiment can be similarly applied to the second embodiment.
[Other Embodiments]
As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the above-mentioned embodiment, It can implement in various deformation | transformation.

  For example, in each of the above embodiments, the node 1 is a node that functions only as a monitoring node that monitors frames transmitted from the other nodes 2 to 4, but the node 1 also transmits a frame to be monitored. At the same time, the transmission restriction process of FIGS. 5, 6, and 8 may be further performed. That is, the node 1 may be a node that functions as both a monitoring node and a monitoring target node.

  In addition, a plurality of functions of one constituent element in the above-described embodiment may be realized by a plurality of constituent elements, or one function of one constituent element may be realized by a plurality of constituent elements. Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or a single function realized by a plurality of constituent elements may be realized by one constituent element. Moreover, you may abbreviate | omit a part of structure of the said embodiment. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claims are embodiments of the present invention. Further, in addition to the communication system described above, a node constituting the communication system, a program for causing a computer to function as the node, a non-transitory actual recording medium such as a semiconductor memory storing the program, a communication system The present invention can also be realized in various forms such as the control method.

  1 to 4 nodes, 11 communication systems, 13 buses.

Claims (6)

Comprising a plurality of nodes (1-4) connected to a bus (13);
The frame transmitted by each node to the bus includes a frame ID indicating the priority of the frame as well as an identifier of the frame.
Each of the nodes starts transmission of the frame when the frame is not transmitted from the other nodes to the bus;
When two or more of the nodes start transmission at the same time, among the nodes that have started transmission at the same time, the node that has started transmission of a frame including the frame ID having a lower priority than frames from other nodes However, in the communication system (11) in which communication arbitration is performed by stopping transmission of the frame,
One of the plurality of nodes is a monitoring node (1), and at least nodes (2 to 4) other than the monitoring node are nodes to be monitored,
The monitoring node is
A counting unit (S110, S120) for counting the number of transmissions, which is the number of frames transmitted from the monitored node to the bus, for each frame ID and within a specified time;
When the counting of the number of transmissions by the counting unit ends, based on the counting result of the counting unit, the number of transmissions within the specified time is less than or equal to a predetermined determination value among frames transmitted from the monitoring target node. A determination unit (S130) for determining whether or not there is a small transmission frame that is a frame that has existed;
When affirmative determination is made by the determination unit, it includes identification information that can identify a small transmission node that is a transmission source node of the small transmission frame, and the frame ID represents the highest priority in the communication system. A notification unit (S140 to S170) that transmits a transmission control frame, which is a frame including a frame ID, to the bus,
The monitored node is:
When the transmission control frame is received, based on the identification information included in the transmission control frame, the node is either the small transmission node or a restriction target node that is a node other than the small transmission node A determination unit (S220, S225) for determining
A transmission prohibition unit (S240 to S260) that prohibits transmission of the frame from the node for a predetermined period when the determination unit determines that the node is the restriction target node;
Communications system. The communication system according to claim 1,
The identification information included in the transmission control frame is a node ID of the small transmission node among node IDs that are identifiers of the nodes,
The determination unit (S220)
If the node ID as the identification information included in the transmission control frame is the node ID of the node, it is determined that the node is the small transmission node, and the node ID is the identification information, If the node ID is not the node ID, the node is configured to determine that the node is the restriction target node.
Communications system. The communication system according to claim 1,
The identification information included in the transmission control frame is a frame ID of the small transmission frame,
The determination unit (S225)
If the frame ID as the identification information included in the transmission control frame is a frame ID of a frame transmitted by the node, it is determined that the node is the small transmission node, and the identification information is If the frame ID is not the frame ID of the frame transmitted by the node, the node is configured to determine that the node is the restriction target node.
The transmission prohibition unit (S245 to S260)
When the determination unit determines that the node is the restriction target node, transmission of a frame with a frame ID having a higher priority than the frame ID as the identification information among frames transmitted by the node Is prohibited only during the predetermined period,
Communications system. The communication system according to any one of claims 1 to 3,
Priorities are defined for the monitored nodes,
The notification unit
When there are a plurality of the small transmission nodes, the transmission control frame includes a plurality of transmission control frames respectively corresponding to the small transmission nodes, each including the identification information capable of identifying the small transmission nodes. The frame is configured to be transmitted in order from the one corresponding to the small transmission node having a high priority,
Communications system. In the communication system according to any one of claims 1 to 4,
The predetermined period is a period until a predetermined time elapses.
Communications system. In the communication system according to any one of claims 1 to 4,
The predetermined period is
It is a period until receiving a restart control frame transmitted from the monitoring node in order to command transmission restart.
Communications system.

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