JP2017050717A - CAN communication unit and CAN communication program - Google Patents

Abstract

[PROBLEMS] To suppress traffic on a CAN bus. A node 10Z includes a message ID for uniquely identifying a message, a received message ID of a received message from another node via the CAN bus 2, a processing content corresponding to the received message ID, and a CAN bus 2. A message ID table 11Z that stores a transmission message ID of a transmission message to another node via the URL and a processing content corresponding to the transmission message ID in association with each other. When the received message is stored in the message ID table 11Z when the received message is received, the node 10Z executes the processing content corresponding to the received message ID of the received message, and then the transmitted message ID corresponding to the received message ID. The processing contents corresponding to the above are executed, and the transmission message assigned with the transmission message ID is sent to another node via the CAN bus 2. [Selection] Figure 1

Description

  The present invention relates to a CAN communication unit and a CAN communication program.

  CAN (Control Area Network) is a network that can be constructed at low cost because of its simple network configuration. Furthermore, CAN communication is known as a highly reliable communication method that has an excellent failure detection function.

  For example, there is a CAN in which a plurality of ECUs (Electronic Control Units) mounted on a vehicle are connected to a CAN bus for each group, and two CAN buses are connected by a relay device. In this CAN, there is a technique for transferring information received from one CAN bus to a specified relay device according to identification information included in the information.

JP 2013-135430 A

  However, in CAN, a node that determines whether data is necessary, a node that has data, and a node that uses data for processing may be different. In this case, in the above technique, first, a node that determines whether data is necessary acquires data from a node that has data according to the determination result. Thereafter, there is a problem in that the CAN bus traffic increases due to data exchange in which a node that determines whether data is necessary transmits the acquired data to a node that uses the data for processing.

  In view of the above-described problems, an example of an embodiment aims to suppress CAN bus traffic.

  The CAN communication unit and the CAN communication program according to an example of the embodiment include, for example, a received message of a received message from another CAN (Control Area Network) communication unit via a CAN bus among message IDs that uniquely identify the message. It has a message table for storing the processing contents corresponding to the ID and the received message ID, the transmission message ID of the transmission message to other CAN units via the CAN bus, and the processing contents corresponding to the transmission message ID in association with each other. And when the received message is stored in the message table when the received message is received, the processing content corresponding to the received message ID of the received message is executed, and then the processing corresponding to the received message ID and the corresponding transmitted message ID The contents are executed, and the transmission message assigned with the transmission message ID is sent to another CAN communication unit via the CAN bus. If the reception message is not stored in the message table, the reception message is discarded.

  According to an example of the embodiment, traffic on the CAN bus can be suppressed.

FIG. 1 is a block diagram illustrating an example of a CAN according to the embodiment. FIG. 2 is a diagram illustrating an example of a message ID in the CAN according to the embodiment. FIG. 3 is a diagram illustrating an example of a reception message ID table and a transmission message ID table included in the node A according to the embodiment. FIG. 4 is a diagram illustrating an example of a message ID table included in the node Z according to the embodiment. FIG. 5 is a diagram illustrating an example of a reception message ID table and a transmission message ID table included in the node B according to the embodiment. FIG. 6 is a sequence diagram illustrating communication processing in the CAN according to the embodiment. FIG. 7 is an explanatory diagram showing the effect of the embodiment. FIG. 8 is a sequence diagram illustrating communication processing in the CAN according to another embodiment.

  Hereinafter, a CAN communication unit and a CAN communication program according to an example embodiment will be described with reference to the drawings. The following embodiments are merely examples, and do not limit the disclosed technology. The following embodiments can be appropriately combined within a consistent range.

[Embodiment]
(CAN according to the embodiment)
FIG. 1 is a block diagram illustrating an example of a CAN according to the embodiment. A CAN (Control Area Network) 1 according to the embodiment includes a node A_10A, a node Z_10Z, and a node B_10B. In CAN1, the node A_10A, the node Z_10Z, and the node B_10B are connected via the CAN bus 2. The CAN bus 2 may be a 2-wire bus such as I2C (Inter-Integrated Circuit, registered trademark) or a 3-wire bus such as SPI (Serial Peripheral Interface, registered trademark).

  For example, the node A_10A is a node that determines whether data held by the node Z_10Z is necessary. The node Z_10Z is a node that holds data. Further, the node B_10B is a node that receives data held by the node Z_10Z, which is determined to be necessary by the determination of the node A_10A, and executes data processing.

  Each node has a processing unit such as a CPU (Central Processing Unit) and an MPU (Micro-Processing Unit), and a CAN controller that executes processing related to basic functions such as communication arbitration and error detection defined in the CAN protocol. . Each node executes processing by each processing unit, and CAN communication is controlled by a CAN controller. Although not shown, the node includes various modules such as a sensor that performs various sensings such as a temperature sensor and a pulse sensor, and an actuator that performs actuation such as display, various operations, and various controls. Note that the number of nodes shown in FIG. 1 is merely an example.

(Example of message ID in CAN according to the embodiment)
FIG. 2 is a diagram illustrating an example of a message ID in the CAN according to the embodiment. “Message ID” shown in the list of FIG. 2 is a unique identifier in CAN1, and the association of “message ID”, “processing content”, and “receiving node” is unique in CAN1. For example, in CAN 1, the messages “message ID” “# 1” and “# 2” are messages for “processing content” and “data request” for “receiving node” “node Z”. Further, for example, in CAN 1, the message with “message ID” “# 3” is a message for performing “processing contents” and “data transmission” with respect to “receiving node” “node B”. "Node B" is a message for "Processing content" and "Data reception". Further, for example, in CAN 1, the message “message ID” “# 4” is a message for performing “processing contents” and “data transmission” for “receiving node” “node A”, and the “receiving node” that received this message. "Node A" is a message for "Processing content" and "Data reception".

(Node A according to the embodiment)
The node A_10A includes a message ID table 11A, a processing unit 12A, and a CAN controller 13A. The message ID table 11A includes a reception message ID table 11A-1 and a transmission message ID table 11A-2. The reception message ID table 11A-1 and the transmission message ID table 11A-2 are stored in a nonvolatile storage device (not shown) such as an EPROM (Erasable Programmable Read Only Memory) or a FLASH ROM (Read Only Memory). The reception message ID table 11A-1 and the transmission message ID table 11A-2 are stored in a volatile storage area such as a RAM (Random Access Memory) (not shown) that can be accessed by the processing unit 12A when the node A_10A is powered on. Be expanded.

  FIG. 3 is a diagram illustrating an example of a reception message ID table and a transmission message ID table included in the node A according to the embodiment. For example, as shown in FIG. 3A, the reception message ID table 11A-1 stores “reception message ID”, “processing content”, and “reception node” in association with each other. “Reception message ID” is an identifier unique within CAN1. For example, when the message of “reception message ID” “# 4” is received from the CAN bus 2 via the CAN controller 13A, the processing unit 12A executes the processing of “processing content” and “data reception”.

  For example, when the processing unit 12A receives a data frame having a message “reception message ID” “# 4” from the CAN bus 2 via the CAN controller 13A, according to “processing content” and “data reception”, Data is extracted from the received data frame. Then, the processing unit 12A performs a predetermined process on the extracted data.

  The CAN communication frame is a remote frame for transmitting a request to another node when “1” is stored in the “RTR (Remote Transmission Request) field”. The CAN communication frame is a data frame that transmits data in response to a request from another node when “0” is stored in the “RTR field”.

  For example, as illustrated in FIG. 3B, the transmission message ID table 11A-2 stores “transmission message ID”, “processing content”, and “reception node” in association with each other. “Transmission message ID” is an identifier unique within CAN1. For example, when “transmission message ID” “# 1” is input, the processing unit 12A transmits a remote frame of “processing content” and “data request” embedded with “transmission message ID” “# 1” to “ The data is sent to the CAN bus 2 via the CAN controller 13A with the receiving node “node Z” as the destination.

  Further, for example, when “transmission message ID” “# 2” is input, the processing unit 12A transmits a remote frame of “processing content” “data request” in which “transmission message ID” “# 2” is embedded. , "Receiving node" and "Node Z" are sent to the CAN bus 2 via the CAN controller 13A.

  Further, for example, when “transmission message ID” “# 3” is input, the processing unit 12A transmits a data frame of “processing content” and “data transmission” in which “transmission message ID” “# 3” is embedded. , "Receiving node" and "Node B" are sent to the CAN bus 2 via the CAN controller 13A. Note that the data frame of “processing content” and “data transmission” in which “transmission message ID” “# 3” is embedded is data acquired from the node Z_10Z or data acquired in the node A_10A.

(Node Z according to the embodiment)
The node Z_10Z includes a message ID table 11Z, a processing unit 12Z, a CAN controller 13Z, and a storage unit 14Z that stores data transmitted and received between the nodes. The message ID table 11Z is stored in a nonvolatile storage device (not shown) such as EPROM or FLASH ROM. The message ID table Z11 is expanded to a volatile storage area such as a RAM (not shown) that can be accessed by the processing unit 12Z when the node Z_10Z is powered on.

  As shown in FIG. 4, the message ID table 11Z associates “row No.”, “reception message ID”, “processing content”, “reception node” with “transmission message ID”, “processing content”, and “reception node”. Store. “Row No.” is a number for identifying each row in the message ID table 11Z.

  “Reception message ID” is an identifier unique within CAN1. For example, when the processing unit 12Z receives a remote frame of “reception message ID” “# 1” from the CAN bus 2 via the CAN controller 13Z, the “processing content” in which “transmission message ID” “# 4” is embedded. "Data transmission" data frame is sent to the CAN bus 2 via the CAN controller 13Z with the "receiving node" "node A" as the destination. Note that the data frame in which the “transmission message ID” “# 4” is embedded is the data read from the storage unit 14Z according to the “processing content” “data request” of the remote frame of the “reception message ID” “# 1”. Including.

  Further, for example, when the processing unit 12Z receives a remote frame of “reception message ID” “# 2” from the CAN bus 2 via the CAN controller 13Z, the processing unit 12Z embeds “transmission message ID” “# 3”. A data frame “processing content” “data transmission” is sent to the CAN bus 2 via the CAN controller 13Z with “receiving node” “node B” as a destination. Note that the data frame in which the “transmission message ID” “# 3” is embedded is the data read from the storage unit 14Z according to the “processing content” “data request” of the remote frame of the “reception message ID” “# 2”. Including.

  By converting the “reception message ID” to the corresponding “transmission message ID” in this way, for example, in response to a request from the node A_10A, the node Z_10Z reads data from the storage unit 14Z and transmits the data to the node A_10A. In response to a request from the node A_10A, the node Z_10Z can read the data from the storage unit 14Z and directly transmit the data to the node B_10B in a transmission / reception process in which A_10A transmits data to the node B_10B. For example, in response to a request from the node B_10B, the node Z_10Z reads out data from the storage unit 14Z and transmits the data to the node B_10B, and the node B_10B transmits data to the node A_10A. In response, the node Z_10Z can read the data from the storage unit 14Z and transmit it directly to the node A_10A.

(Node B according to the embodiment)
The node B_10B includes a message ID table 11B, a processing unit 12B, and a CAN controller 13B. The message ID table 11B includes a reception message ID table 11B-1 and a transmission message ID table 11B-2. The reception message ID table 11B-1 and the transmission message ID table 11B-2 are stored in a nonvolatile storage device (not shown) such as an EPROM or a FLASH ROM. The reception message ID table 11B-1 and the transmission message ID table 11B-2 are expanded in a volatile storage area such as a RAM (not shown) that can be accessed by the processing unit 12B when the node B_10B is powered on.

  FIG. 5 is a diagram illustrating an example of a reception message ID table and a transmission message ID table included in the node B according to the embodiment. For example, as shown in FIG. 5A, the reception message ID table 11B-1 stores “reception message ID”, “processing content”, and “reception node” in association with each other. “Reception message ID” is an identifier unique within CAN1. For example, when the message of “reception message ID” “# 3” is received from the CAN bus 2 via the CAN controller 13A, the processing unit 12B executes the processing of “processing content” and “data reception”.

  For example, when the processing unit 12B receives a data frame having a message “reception message ID” “# 3” from the CAN bus 2 via the CAN controller 13B, according to “processing content” and “data reception”, Data is extracted from the received data frame. Then, the processing unit 12B performs a predetermined process on the extracted data.

  For example, as illustrated in FIG. 5B, the transmission message ID table 11B-2 stores “transmission message ID”, “processing content”, and “reception node” in association with each other. “Transmission message ID” is an identifier unique within CAN1. For example, when “transmission message ID” “# 1” is input, the processing unit 12B transmits a remote frame of “processing content” and “data request” embedded with “transmission message ID” “# 1” to “ The data is sent to the CAN bus 2 via the CAN controller 13A with the receiving node “node Z” as the destination.

  Further, for example, when “transmission message ID” “# 2” is input, the processing unit 12B transmits a remote frame of “processing content” “data request” in which “transmission message ID” “# 2” is embedded. , "Receiving node" and "Node Z" are sent to the CAN bus 2 via the CAN controller 13B.

  Further, for example, when “transmission message ID” “# 4” is input, the processing unit 12B transmits a data frame of “processing content” and “data transmission” in which “transmission message ID” “# 4” is embedded. , "Receiving node" and "Node A" are sent to the CAN bus 2 via the CAN controller 13A. Note that the data frame of “processing content” and “data transmission” in which “transmission message ID” “# 4” is embedded is data acquired from the node Z_10Z or data acquired in the node B_10B.

(Communication processing in CAN according to the embodiment)
FIG. 6 is a sequence diagram illustrating communication processing in the CAN according to the embodiment. In FIG. 6, the “reception message ID” is the same as that shown in FIGS.

  First, in step S11, the node A_10A sends a data request message to the CAN bus 2 via the CAN controller 13A. Here, it is assumed that the “message ID” of the data request message is “# 1” or “# 2”. Due to the CAN communication standard, the data request message sent in step S11 is delivered to the node Z_10Z and the node B_10B. However, since the node B_10B is not the target of the data request message sent in step S11, the data request message is discarded in the node B_10B.

  Next, in step S12, the processing unit 12Z of the node Z_10Z extracts “message ID” from the received data request message, and determines whether or not the extracted “message ID” exists in the message ID table 11Z. When the “message ID” extracted in step S12 exists in the message ID table 11Z (step S12: Yes), the processing unit 12Z moves the process to step S13. On the other hand, when the “reception message ID” extracted in step S12 does not exist in the message table 11Z (step S12: No), the processing unit 12Z moves the process to step S18. In step S18, the processing unit 12Z discards the data request message received in step S12.

  In step S13, the processing unit 12Z determines whether or not the “message ID” extracted in step S12 corresponds to “row No.” “1” in the message ID table 11Z. When the “message ID” extracted in step S12 corresponds to “row No.” “1” in the message ID table 11Z (step S13: Yes), the processing unit 12Z moves the process to step S14. On the other hand, when the “message ID” extracted in step S12 does not correspond to “line No.” or “1” in the message ID table 11Z (step S13: No), the processing unit 12Z moves the process to step S16.

  In step S14, the processing unit 12Z executes “processing content” corresponding to “reception message ID” “# 1” extracted in step S12 in the message ID table 11Z, and corresponding “transmission message ID” “# 4”. A message (data frame) with "" set is generated. Subsequently, in step S15, the processing unit 12Z sends the message (data frame) generated in step S14 to the CAN bus 2 via the CAN controller 13Z. Note that the message (data frame) transmitted in step S15 is delivered to the node A_10A and the node B_10B according to the CAN communication standard. However, since the node B_10B is not subject to the message (data frame) sent in step S15, the message (data frame) is discarded in the node B_10B.

  It should be noted that the flow of processing from step S11 → step S12: Yes → step S13: Yes → step S14 → step S15 is, for example, that a message “message ID” “# 1” is sent from the node A_10A in step S11. This is the case. That is, the node A_10A receives the data requested to the node Z_10Z by itself.

  On the other hand, in step S16, the processing unit 12Z executes “processing content” corresponding to “reception message ID” “# 2” extracted in step S12 in the message ID table 11Z, and corresponding “transmission message ID” “ A message (data frame) in which # 3 ″ is set is generated. Subsequently, in step S17, the processing unit 12Z sends the message (data frame) generated in step S16 to the CAN bus 2 via the CAN controller 13Z. Note that in accordance with the CAN communication standard, the message (data frame) sent in step S17 is delivered to the node A_10A and the node B_10B. However, since node A_10A is not subject to the message (data frame) sent in step S17, the message (data frame) is discarded at node A_10A.

  Note that the flow of processing from step S11 → step S12: Yes → step S13: No → step S16 → step S17 is, for example, that a message “message ID” “# 2” is transmitted from the node A_10A in step S11. This is the case. That is, the node A_10A directly transmits the data requested to the node Z_10Z to the node B_10B.

(Effect by embodiment)
FIG. 7 is an explanatory diagram showing the effect of the embodiment. In the prior art shown in FIG. 7A, the node A_10A executes the following process in order to transfer the data stored in the node Z_10Z-1 to the node B_10B. That is, first, the node A_10A sends a data request message to the node Z_10Z-1 via the CAN bus 2 (step S1a). Next, the node Z_10Z-1 that has received the data request message from the node A_10A sends response data corresponding to the data request to the node A_10A via the CAN bus 2 (step S2a). Then, the node A_10A that has received the response data from the node Z_10Z-1 transmits the response data to the node B_10B via the CAN bus 2 (step S3a). That is, in the prior art, the node A_10A uses the CAN bus 2 over three steps from step S1a to step S3a in order to transfer the data stored in the node Z_10Z-1 to the node B_10B.

  On the other hand, in the example of the embodiment illustrated in FIG. 7B, the node A_10A performs the following process in order to transfer the data stored in the node Z_10Z to the node B_10B. That is, first, the node A_10A sends a data request message to the node Z_10Z (step S1b). Then, the node Z_10Z that has received the data request message converts the “message ID” of the data request message into a “message ID” that can be processed by the node B_10B in response data for the data request message. Then, the node Z_10Z sends response data to the node B_10B (step S2b). That is, in the example of the embodiment, the node A_10A uses the CAN bus 2 over two steps S1b to S2b in order to pass the data stored in the node Z_10Z to the node B_10B. For this reason, in an example of the embodiment, the time for using the CAN bus 2 can be shortened, the traffic of the CAN bus 2 can be reduced, and the utilization efficiency of the CAN bus 2 can be improved. And an example of embodiment can reduce the load of a CAN system.

[Other forms of embodiment]
(1) About Communication Processing in CAN FIG. 8 is a sequence diagram showing communication processing in CAN according to another embodiment of the embodiment. The communication process in the CAN according to another embodiment of the embodiment is different in that step S13a is executed between step S13: No and step S16 in the communication process in the CAN according to the embodiment. Step S13: In the case of No, in step S13a, the processing unit 12Z of the node Z_10Z determines whether or not to send data addressed to the node A_10A. When the processing unit 12Z sends data addressed to the node A_10A (step S13a: Yes), the processing unit 12Z moves the process to step S14. On the other hand, when the processing unit 12Z sends data addressed to the node B_10B (step S13a: No), the processing unit 12Z moves the process to step S16.

  Here, in step S13: No, in response to a request from the node A_10A, the node Z_10Z reads the data from the storage unit 14Z and transmits the data to the node A_10A, and the node A_10A does not transmit the data to the node B_10B. This is a case where the node Z_10Z reads data from the storage unit 14Z and directly transmits it to the node B_10B in response to a request from A_10A. However, for example, when the priority of a message that can be determined from the “message ID” is high and there are other messages that should be transmitted with higher priority, the processing unit 12Z responds to a request from the node A_10A. Regardless of the determination result that the data is read from the storage unit 14Z and transmitted directly to the node B_10B, a message to be transmitted with priority may be transmitted, and the data may be transmitted to the node A_10A. That is, there may be a plurality of messages to be sent to the node B_10B during the determination process in step S13a, and there may be a message having a higher priority than the data sent in response to the data request message in step S11. At this time, a message with a high priority is sent first. For this reason, since the data sent in response to the data request message in step S11 has a low priority, the data is sent as addressed to node A_10A through the process of step S13a: Yes → step S14 → step S15, and passes through node A_10A. And sent to the node B_10B.

  Further, for example, during the determination process in step S13a, traffic from the node Z_10Z to the node B_10B may be in a congested state, and traffic from the node Z_10Z to the node A_10A may be free. At this time, the data sent in response to the data request message in step S11 is sent to the node A_10A through the process of step S13a: Yes → step S14 → step S15, avoiding traffic congestion, and is sent to the node A_10A. To the node B_10B.

  For example, by setting “# 4” instead of setting “# 3” in the “message ID” of the message to be sent, the message addressed to the node B_10B can be addressed to the node A_10A (see FIG. 4). ). As described above, in response to the request from the node A_10A in step S13, the node Z_10Z reads the data from the storage unit 14Z and directly transmits it to the node B_10B, and transmits it to the node A_10A in step S13a. As a result, depending on the priority of the message and traffic on the CAN bus 2, the data may reach the target destination Node B_10B more quickly.

(2) About Remote Frame and Data Frame In the above embodiment, a frame that requests data is a remote frame, and a frame that transmits data in response to the remote frame is a data frame. However, the disclosed technology is not limited to this, and data may be requested in a data frame and data may be transmitted in response to the data request in the data frame. For example, a data frame in which no data is stored in the data field of the data frame may be used as a frame for requesting data, and a data frame in which data is stored in the data field may be used as a frame for transmitting data.

(3) Regarding the point of setting the transmission message ID based on the message ID table 14Z In the above embodiment, when the data stored in the node Z_10Z is transferred to the node B_10B under the instruction of the node A_10A, The transmission message ID is set so that the data is transmitted to the node B_10B without going through the node A_10A. However, the setting of the transmission message ID is not limited to the one relating to the change from the indirect delivery of data to the direct delivery, and can be applied to the processing in each node in general. For example, under the instruction of the node A_10A, the node Z_10Z and the node B_10B perform processing in cooperation with each other, return the processing results from the node Z_10Z and the node B_10B to the node A_10A, and the node A_10A Depending on each processing result, the next processing may be instructed to the node Z_10Z and the node B_10B. In such a case, the node Z_10Z and the node B_10B can complete the processing by not passing back the processing results to the node A_10A but by passing the processing results between the nodes Z_10Z and B_10B. .

  In other words, there may be an intermediate node responsible for intermediate processing between the start point node that is the start point of the process and the end point node that is the end point of the process. In this case, the embodiment changes the setting of the message ID transmitted from the start point node to the intermediate node according to the description content of the message ID table held by the intermediate node. Thus, the embodiment can be widely applied when message exchange between the start node and the intermediate node or between the intermediate node and the end node can be omitted.

  Each unit of the node A_10A, the node Z_10Z, and the node B_10B according to the above embodiment is executed by a CPU or MPU cooperating with a storage device such as a memory or a processing device such as an FPGA or an ASIC executing a CAN communication program. Realized. FPGA is a Field-Programmable Gate Array. ASIC is an Application Specific Integrated Circuit. And each part of node A_10A, node Z_10Z, and node B_10B which concerns on said embodiment may be integrated or disperse | distributed suitably according to a processing load or circuit design. In addition, a CAN communication unit configured by appropriately combining, substituting, or omitting each part of the node A_10A, the node Z_10Z, and the node B_10B according to the above embodiment is also included in the CAN communication unit according to the disclosed technology.

1 CAN
2 CAN bus 10A Node A
10Z Node Z
10B Node B
11A-1, 11B-1 Reception message ID table 11B-2, 11B-2 Transmission message ID table 11Z Message ID table 12A, 12Z, 12B Processing unit 13A, 13Z, 13B CAN controller 14Z Storage unit

Claims (4)

Among the message IDs that uniquely identify the message, the received message ID of the received message from another CAN (Control Area Network) communication unit via the CAN bus, the processing content corresponding to the received message ID, and the CAN bus A message table for storing a transmission message ID of a transmission message to another CAN unit via the storage unit and a processing content corresponding to the transmission message ID in association with each other;
When the received message is stored in the message table when the received message is received, the processing content corresponding to the received message ID of the received message is executed, and then the transmitted message ID corresponding to the received message ID is set. If the received message is not stored in the message table, the received message is sent to another CAN communication unit via the CAN bus. A CAN communication unit comprising: a processing unit that discards a message. A storage unit for storing data;
When the received message is stored in the message table when the received message is received from the first other CAN communication unit, the processing unit stores the storage unit according to the received message ID of the received message. After the data is acquired, the data is embedded in the transmission message assigned with the transmission message ID corresponding to the reception message ID, and is transmitted to the second other CAN communication unit via the CAN bus. The CAN communication unit according to claim 1. When the transmission unit sends the transmission message to another CAN communication unit via the CAN bus, the processing unit changes the transmission message ID of the transmission message according to the communication status of the CAN bus and transmits the transmission message. The CAN communication unit according to claim 1 or 2, characterized by the above-mentioned. On the computer,
Receive messages from other CAN (Control Area Network) communication units via the CAN bus,
When the received message is received, among the message IDs that uniquely identify the message, the received message ID of the received message, the processing content corresponding to the received message ID, and other CAN units via the CAN bus If the received message is stored in the message table with reference to the message table that stores the transmission message ID of the transmission message and the processing content corresponding to the transmission message ID in association with each other, the received message of the received message After executing the processing content according to the ID, execute the processing content according to the transmission message ID corresponding to the reception message ID, and send the transmission message with the transmission message ID to the other CAN communication unit via the CAN bus. Send out through
A CAN communication program for executing a process of discarding the received message when the received message is not stored in the message table when the received message is received.

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