JP5958335B2 - Communication node and communication system - Google Patents

Description

  The present invention relates to a communication system.

  One or a plurality of communication systems are mounted on the vehicle. 2. Description of the Related Art A local interconnect network (LIN) is known as a communication protocol for an in-vehicle LAN mainly used for a body system of a vehicle.

  In LIN, there is one communication node as a master and one or more communication nodes as slaves. In other words, the single master multi-master method is applied to LIN.

  The master communication node controls communication timing and the like. In LIN, one communication node becomes the master.

  64 message IDs from 000000 to 111111 are assigned to messages transmitted and received by LIN.

  After verifying the error between the second pulse width and the third pulse width based on the ratio between the first pulse width and the second pulse width of the received binary level signal, the communication node to be the slave A technique for determining a pulse having the second pulse width as a Synch Field is known (see, for example, Patent Document 1).

JP 2009-303178 A

  It is necessary to assign different message IDs to messages transmitted and received on the LIN. This message ID is given by the Frame identifier of the Protected identifier field (PID) of the LIN frame. According to the LIN specification, the PID is 8 bits. These 8 bits include a 6-bit frame identifier and a 2-bit parity. Therefore, in the LIN frame rule, information represented by 6 bits, in other words, 64 message IDs can be assigned. In other words, LIN can send and receive 64 types of messages.

  Even when 64 types of messages can be transmitted and received, when 16 communication nodes are included in the LIN, the number of messages is limited to 4 types on average for one communication node.

  If 64 or more messages are transmitted / received, it is necessary to divide the network into a plurality of networks or use a communication method that can specify more message IDs than LIN. Dividing a network into a plurality of parts is not preferable because the scale of the network increases and the network communication schedule needs to be redesigned.

  An object of the present invention is to extend a message ID without increasing the number of bits in the ID field.

The communication node of one embodiment of the disclosure is
A communication node that communicates with a slave node connected via a communication bus,
Specifying a message identifier of a message to be transmitted to the slave node, and creating a message including the message identifier;
A frame transmission control unit that executes control for transmitting the message created by the message creation unit, and
The message identifier is represented by a combination of information represented by the length of the break field and information of the ID field.

The communication node of one embodiment of the disclosure is
A communication node that receives a message from a master node connected via a communication bus,
A message analysis unit that analyzes the content of the message corresponding to the message identifier based on the message identifier included in the message transmitted by the master node;
A response creation unit that creates a response to the message analyzed by the message analysis unit;
A response transmission control unit that executes control to transmit the response created by the response creation unit, and
The message identifier is represented by a combination of information represented by the length of the break field and information of the ID field,
The message analysis unit analyzes the content of the message based on a combination of information represented by the length of the break field of the message transmitted by the master node and information of the ID field.

A communication system according to an embodiment of the disclosure includes:
A communication system having a slave node and a master node connected to the slave node via a communication bus,
The master node
Specifying a message identifier of a message to be transmitted to the slave node, and creating a message including the message identifier;
A frame transmission control unit that executes control for transmitting the message created by the message creation unit, and
The message identifier is represented by a combination of information represented by the length of the break field and information of the ID field,
The slave node is
Based on a message identifier included in the message transmitted by the master node, a message analysis unit for analyzing the content of the message corresponding to the message identifier;
A response creation unit that creates a response to the message analyzed by the message analysis unit;
A response transmission control unit that executes control to transmit the response created by the response creation unit, and
The message analysis unit analyzes the content of the message based on a combination of information represented by the length of the break field of the message transmitted by the master node and information of the ID field.

  According to the disclosed embodiment, the message ID can be expanded without increasing the number of bits in the ID field.

It is a figure which shows one Example of a communication system. It is a figure which shows one Example of a frame format. It is a figure which shows one Example of a break field. It is a figure which shows one Example of ID field. It is a figure which shows one Example of message ID. It is a figure which shows one Example of a master node. It is a functional block diagram which shows one Example of a master node. It is a figure which shows one Example of message ID. It is a flowchart which shows one Example of operation | movement of a master node. It is a figure which shows one Example of a slave node. It is a functional block diagram which shows one Example of a slave node. It is a flowchart which shows one Example of operation | movement of a slave node. It is a figure which shows the modification of a communication system. It is a figure which shows one modification of message ID. It is a figure which shows the modification of a break field.

Next, the form for implementing this invention is demonstrated, referring drawings based on the following Examples.
In all the drawings for explaining the embodiments, the same reference numerals are used for those having the same function, and repeated explanation is omitted.

<Example>
<Communication system>
FIG. 1 shows an embodiment of a communication system.

  The communication system has a plurality of communication nodes. The communication system may be a single line network. A cluster may be configured by a plurality of communication nodes.

The plurality of communication nodes include master nodes 100 ₁ to 100 _k (k is an integer of k> 1) and slave nodes 200 ₁ to 200 _n (n is an integer of n> 1). It is.

Master node 100 ₁ -Master node 100 _k controls when to send a message. Specifically, the master node 100 ₁ -master node 100 _k schedules the timing for transmitting the header included in the message. At the time of scheduling, it is preferable to set an ID (identifier) of a message to be transmitted, a transmission order, a transmission time interval, and the like.

The master node 100 ₁ -master node 100 _k and the slave node 200 ₁ -slave node 200 _n are connected by wire via the communication bus 300. Communication is performed between the master node 100 ₁ -master node 100 _k and the slave node 200 ₁ -slave node 200 _n via the communication bus 300 according to a predetermined communication protocol. Specifically, communication is performed according to LIN.

  A signal flowing through the communication bus 300 has one of two logic levels. The two logic level states are called "dominant" and "recessive". Dominant is a logic level 0 state that is close to ground potential. Recessive is a logic level 1 state that is close to the potential of the + (plus) terminal of the battery.

The master node 100 ₁ -master node 100 _k transmits a message according to a predetermined frame format.

<Frame format>
FIG. 2 shows an embodiment of a frame format transmitted / received between the master node 100 ₁ -master node 100 _k and the slave node 200 ₁ -slave node 200 _n .

  The frame includes a header and a response. The header is transmitted from the master node, and the response is transmitted from the slave node.

  The header includes a break field (Break field), a sync field (Sync field), and a protected identifier field (Protected identifier field).

  The break field is a field for notifying all slave nodes of the cluster of the start of the frame. The dominant duration of the break field is preferably 13 bits or longer. In one embodiment of the communication system, the break field dominant duration is varied.

  The sync field is used to correct a clock error between communication nodes included in the cluster.

  The protected identifier field is preferably composed of a total of 8 bits including a frame ID of 6 bits (0 to 5 bits) representing a frame identification number and a parity of 2 bits (6 and 7 bits).

  The response preferably includes a data field (Data Field) and a checksum (Checksum). The data field and checksum are preferably transmitted in a UART (Universal Asynchronous Receiver / Transmitter) frame. There may be one or more data fields. Each data field can store a maximum of 8 bytes of data. The checksum is used in determining whether data has been received correctly. Specifically, the checksum stores a value obtained by inverting the sum of the values of each data.

  The header is preferably 47 bits or less and the response is 126 bits or less.

  An inter-frame space (not shown) is set between adjacent frames.

<Breakfield>
FIG. 3 shows an example of a break field. FIG. 3 shows four types of break fields. Each break field has a different break field length. In other words, the time during which the dominant state of the break field continues is different.

  For example, “00” is associated with the break field having the longest break field length (FIG. 3 (1)). The break field having the longest break field length has the longest time during which the dominant state of the break field continues.

  “01” is made to correspond to a break field having a long break field length (FIG. 3B). A break field having a long break field length has the second longest duration in which the dominant state of the break field continues.

  “10” is made to correspond to a break field having a short break field length (FIG. 3 (3)). A break field having a short break field length has the third longest duration in which the dominant state of the break field continues.

  “11” is made to correspond to the break field having the shortest break field length (FIG. 3 (4)). The break field having the shortest break field length has the shortest time during which the dominant state of the break field continues.

  According to (1)-(4) of FIG. 3, information for 2 bits is represented by the break field length.

<Protected identifier field>
FIG. 4 shows an example of a protected identifier field.

  In FIG. 4, a 6-bit frame ID representing a frame identification number is represented by “ID0”, “ID1”, “ID2”, “ID3”, “ID4”, and “ID5”. In FIG. 4, 2-bit parity is represented by “P0” and “P1”.

  The protected identifier field can represent 2 to the 6th power, that is, 64 message IDs from 0 to 63.

  FIG. 5 shows an embodiment of the message ID (identifier). In one embodiment of the communication system, 2 bits of information represented by a break field and 6 bits of information represented by a protected identifier field are combined.

  In FIG. 5, information of 2 bits represented by the break field is represented by “IDB0” and “IDB1”, and information of 6 bits represented by the protected identifier field is represented by “ID0”, “ID1”, “ID1”. It is represented by “ID2”, “ID3”, “ID4”, “ID5”. By combining 2-bit information represented by the break field and 6-bit information represented by the protected identifier field, 8-bit information, that is, 256 types of information can be represented. That is, the message ID can be expanded from 64 to 256.

<Master node>
Figure 6 illustrates a master node 100 _1. Since master node 100 ₁ -master node 100 _k have substantially the same configuration, master node 100 ₁ will be described as a representative.

The master node 100 _1, the micro controller unit: includes a (MCU Micro-Control Unit) 102 , and a transceiver 106.

  The microcontroller unit 102 includes one or more microcomputers. A CPU may be included instead of the microcomputer, or the microcomputer and the CPU may be mixed. Further, the microcontroller unit 102 includes a communication device 104. The communication device 104 performs serial communication with the transceiver 106. Specifically, the communication device 104 may be a UART.

  The transceiver 106 is connected to the microcontroller unit 102 and the communication bus 300. The transceiver 106 transmits data input from the microcontroller unit 102 to the communication bus 300 and inputs data from the communication bus 300 to the microcontroller unit 102.

Master node 100 ₁ may have a plurality of micro-controller unit. The master node 100 ₁ may have a plurality of transceivers.

<Master node function>
The master node 100 ₁ sends a message (header) containing the message ID corresponding to the message to be transmitted. In identifying message ID, the master node 100 ₁ identifies those falling from a plurality of message ID is set in advance, selects.

Figure 7 is a functional block diagram illustrating the master node 100 _1. FIG. 7 mainly shows a part for transmitting a message and omits the other parts.

  The functions represented by the functional block diagram of FIG. 7 are mainly executed by the microcontroller 102. That is, the microcontroller 102 functions as the master function unit 110.

  The function as the master function unit 110 is preferably executed by the microcontroller 102 in accordance with an application (firmware) stored in the microcontroller 102. Further, the function as the master function unit 110 may be executed by the microcontroller 102 in accordance with the application stored in the storage unit (not shown).

The master node 100 ₁ functions as a master function unit 110. The master function unit 110 includes a message ID storage unit 112, a message creation unit 114, and a frame transmission control unit 116.

  The message ID storage unit 112 stores a message and a message ID corresponding to the message in association with each other. The message is preferably the content of data requested from the slave node.

  FIG. 8 shows an example of information stored in the message ID storage unit 112. In FIG. 8, break field length information, protected identifier field information, message ID, and message content are associated with each other.

  In one embodiment of the communication system, the message ID is represented by 8 bits, which is a sum of 2 bits of information indicated by the break field length information and 6 bits of information indicated by the protected identifier field information.

  In the example shown in FIG. 8, when the break field length information is “00” and the protected identifier field information is “001100”, the message ID is indicated by “00001100”, and the message content is “A”. Is associated with.

  Also, when the break field length information is “01” and the protected identifier field information is “001100”, the message ID is indicated by “01100100”, and the message content is associated with “B”.

  When the break field length information is “10” and the protected identifier field information is “001100”, the message ID is indicated by “100001100”, and the content of the message is associated with “C”.

  When the break field length information is “11” and the protected identifier field information is “001100”, the message ID is indicated by “11001100”, and the message content is associated with “D”.

  When the break field length information is “00” and the protected identifier field information is “001110”, the message ID is indicated by “00001110”, and the content of the message is associated with “E”.

  When the break field length information is “01” and the protected identifier field information is “001110”, the message ID is indicated by “01001110”, and the message content is associated with “F”.

  When the break field length information is “10” and the protected identifier field information is “001110”, the message ID is indicated by “100001110”, and the content of the message is associated with “G”.

  When the break field length information is “11” and the protected identifier field information is “001110”, the message ID is indicated by “11001110”, and the content of the message is associated with “H”.

  The message creation unit 114 is connected to the message ID storage unit 112. The message creation unit 114 creates a message including the message ID corresponding to the message to be transmitted with reference to the correspondence between the message stored in the message ID storage unit 112 and the message ID. The message creation unit 114 inputs a message to the frame transmission control unit 116. That is, the message creation unit 114 inputs a break field, a sync field, and a protected identifier field to the frame transmission control unit 116 based on the message ID.

  The frame transmission control unit 116 is connected to the message creation unit 114. The frame transmission control unit 116 executes control for transmitting a message from the message creation unit 114. The frame transmission control unit 116 performs break field transmission control based on the break field length information included in the message ID. Subsequently, the frame transmission control unit 116 performs sync field transmission control. After transmission of the sync field, the frame transmission control unit 116 performs transmission control of the protected identifier field based on the information of the protected identifier field.

  The message is transmitted from the transceiver 106 by transmission control by the frame transmission control unit 116.

<Operation of master node>
Figure 9 shows an example of the operation of the master node 100 _1. 9 shows, the master node 100 _1, operation when the message to be transmitted is generated is shown. The same applies to the operations of the master nodes 100 _{2 to} 100 _k .

At step S902, the master node 100 ₁ sets a break field length. That is, the message creation unit 114 refers to the correspondence between the message content stored in the message ID storage unit 112 and the message ID, and acquires information on the break field length of the message ID corresponding to the message to be transmitted. The message creation unit 114 sets the break field length in the frame transmission control unit 116.

At step S904, the master node 100 ₁ starts transmission of the brake field. The frame transmission control unit 116 starts transmitting the break field according to the break field length set by the message creating unit 114.

In step S906, the master node 100 ₁ ends the transmission of the brake field. The frame transmission control unit 116 terminates after transmitting the break field according to the break field length set by the message creation unit 114.

In step S908, the master node 100 ₁ starts transmission of the sync field. That is, the message creation unit 114 creates a sync field and inputs it to the frame transmission control unit 116. The frame transmission control unit 116 starts transmission of the sync field from the message creation unit 114.

In step S910, the master node 100 ₁ ends the transmission of the sync field. The frame transmission control unit 116 ends the transmission of the sync field input by the message creation unit 114.

In step S912, the master node 100 ₁ starts transmission of protected Identifier field. That is, the message creation unit 114 refers to the correspondence between the message stored in the message ID storage unit 112 and the message ID, and acquires information on the protected identifier field corresponding to the message to be transmitted. The message creation unit 114 inputs information about the protected identifier field to the frame transmission control unit 116. The frame transmission control unit 116 starts transmission of the protected identifier field according to the information of the protected identifier field input by the message creation unit 114.

In step S914, the master node 100 ₁ ends the transmission of the protected Identifier field. The frame transmission control unit 116 ends the transmission of the protected identifier field input by the message creation unit 114.

<Slave node>
Figure 10 shows an example of the slave node 200 _1. Configuration of the slave node 200 ₂ to the slave node 200 _n are the configuration and substantially the same configuration the slave _node 2001, representatively described slave node 200 _1.

Slave _node 2001 includes a microcontroller unit 202, and a transceiver 206.

  The microcontroller unit 202 includes one or more microcomputers. A CPU may be included instead of the microcomputer, or the microcomputer and the CPU may be mixed. Further, the microcontroller unit 202 includes a communication device 204. The communication device 204 performs serial communication with the transceiver 206. Specifically, the communication device 204 may be a UART.

  The transceiver 206 is connected to the microcontroller unit 202 and the communication bus 300. The transceiver 206 transmits data input from the microcontroller unit 202 to the communication bus 300, and inputs data from the communication bus 300 to the microcontroller unit 202.

Slave _node 2001 may have a plurality of micro-controller unit. The slave _node 2001 may have a plurality of transceivers.

<Function of slave node>
Slave _node 2001 analyzes the message from the master node transmits the response corresponding to the message. When analyzing the message, the slave _node 2001 identifies the content of the message corresponding to the message ID which is set in advance.

Figure 11 is a functional block diagram illustrating a slave node 200 _1. FIG. 11 mainly shows a part for transmitting a response based on a message from the master node, and omits other parts.

  The functions represented by the functional block diagram of FIG. 11 are mainly executed by the microcontroller 202. That is, the microcontroller 202 functions as the slave function unit 210.

  The function as the slave function unit 210 is preferably executed by the microcontroller 202 according to the application (firmware) stored in the microcontroller 202. Further, the function as the slave function unit 210 may be executed by the microcontroller 202 in accordance with the application stored in the storage unit (not shown).

Slave _node 2001 serves as a slave function unit 210. The slave function unit 210 includes a message ID storage unit 212, a message reception control unit 214, a message analysis unit 216, a response creation unit 218, and a response transmission control unit 220.

  The message ID storage unit 212 stores the message content and the message ID corresponding to the message in association with each other. The content of the message preferably includes the content of data requested from the master node to the slave node.

  An example of information stored in the message ID storage unit 212 is substantially the same as that in FIG.

  The message reception control unit 214 performs control when receiving a message from the master node. The message reception control unit 214 detects a dominant signal. The message reception control unit 214 sequentially executes control for receiving the break field, the sync field, and the protected identifier field when the length of time during which the dominant state continues is equal to or longer than the time corresponding to 13 bits.

  The message analysis unit 216 is connected to the message ID storage unit 212 and the message reception control unit 214. The message analysis unit 216 specifies the content of the message corresponding to the message ID included in the message from the master node based on the correspondence between the message content stored in the message ID storage unit 212 and the message ID. The message analysis unit 216 inputs the content of the identified message to the response creation unit 218.

  The response creation unit 218 is connected to the message analysis unit 216. The response creation unit 218 creates a response based on the message input from the message analysis unit 216. The response creation unit 218 preferably acquires the corresponding data based on the content of the message from the message analysis unit 216. The response creation unit 218 creates a response including the acquired data and inputs the response to the response transmission control unit 220.

  The response transmission control unit 220 is connected to the response creation unit 218. The response transmission control unit 220 executes control for transmitting a response from the response creation unit 218. A response whose transmission is controlled by the response transmission control unit 220 is transmitted from the transceiver 206 to the communication bus 300.

<Operation of slave node>
Figure 12 shows an embodiment of the operation of the slave _node 2001. The operations of the slave nodes 200 ₂ to 200 _n are substantially the same as the operation of the slave node 200 ₁ . FIG 12, the slave _node 2001, operation when the message is received is shown.

In step S1202, the slave _node 2001 detects a dominant signal. That is, the message reception control unit 214 detects a dominant signal based on the signal from the transceiver 206 received by the communication device 204.

In step S1204, the slave _node 2001 measures the dominant lengths. That is, the message reception control unit 214 measures the length of time that the dominant state of the detected dominant signal continues.

In step S1206, the slave _node 2001 determines whether a dominant length is 13 bits or more. That is, the message reception control unit 214 measures whether or not the length of time that the dominant state continues is equal to or longer than the time corresponding to 13 bits. This is because the dominant length is set to be 13 bits or more.

In step S1208, if the dominant length is determined to be 13 or more bits in step S1206, the slave _node 2001 detects a break field. That is, the message reception control unit 214 detects a break field.

In step S1210, the slave _node 2001 determines whether it is detected that the received dominant signals are completed. That is, the message reception control unit 214 determines whether or not the reception of the dominant signal has been detected.

In step S1212, when it is determined that the received dominant signals is completed in step S1210, the slave _node 2001 detects a break field length. That is, the message reception control unit 214 detects the length of time that the dominant state of the break field continues.

In step S1214, the slave node 200 ₁ receives the synch field. That is, the sync field is received by the communication device 204 and input to the message reception control unit 214.

In step S1216, the slave node 200 ₁ receives the protected Identifier field. That is, the protected identifier field is received by the communication device 204 and input to the message reception control unit 214.

In step S1218, the slave _node 2001 identifies the message ID. That is, the message analysis unit 216 identifies the message ID based on the break field and the protected identifier field included in the message whose reception is controlled by the message reception control unit 214.

In step S1220, if the dominant length is determined to be less than 13 bits in step S1206, the slave _node 2001 determines whether it is detected that the received dominant signals are completed. That is, the message reception control unit 214 determines whether or not the reception of the dominant signal has been detected. If it is determined that reception of the dominant signal is completed, the process returns to step S1202. If it is not determined that reception of the dominant signal has been completed, the process returns to step S1204.

  After identifying the message ID in step S1208, the message analysis unit 216 identifies the content of the message corresponding to the message ID based on the correspondence between the message content stored in the message ID storage unit 212 and the message ID.

  The response creation unit 218 creates a response based on the content of the message. The response creation unit 218 acquires corresponding data based on the content of the message.

  The response transmission control unit 220 executes control for transmitting a response including the corresponding data. A response whose transmission is controlled by the response transmission control unit 220 is transmitted from the transceiver 206 to the communication bus 300.

  In one embodiment of the communication system, the length of time that the dominant state of the break field continues is associated with the information. A message ID of the message is a combination of information indicated by the length of time that the dominant state of the break field continues and information indicated by the frame identifier of the protected identifier field. In this way, the number of message IDs that can be assigned to a message can be increased without increasing the number of bits in the protected identifier field.

  Since the number of message IDs can be increased, the number of messages that can be transmitted / received on the network can be increased, so that more information can be exchanged. Even when many communication nodes are connected to the network, there is no shortage of message IDs assigned to messages. Increasing the number of messages sent and received by increasing the number of PID bits is not preferable because it does not match the LIN standard. In addition, when increasing the number of messages sent and received by increasing the number of PID bits, there must be a communication node that has increased the number of PID bits and a previous communication node that has not increased the number of PID bits. However, these communication nodes cannot coexist in the same LIN. In other words, all communication nodes need to have an increased number of PID bits, which increases development costs. According to an embodiment of the communication system, this is not the case, and the types of messages to be transmitted and received can be increased.

  In addition, when there are not enough message IDs to be assigned to messages, it may be possible to use a communication method that can specify more message IDs than LIN. Also, using a communication method that can specify more message IDs than LIN is not preferable because it may be expensive.

<Modification (Part 1)>
<Communication system>
FIG. 13 shows a modification of the communication system.

  In a modification of the communication system, a conventional slave node in which the length of time during which the dominant state of the break field continues and information are not associated with each other, that is, the message ID is not expanded, is connected to the communication system described above. Is.

  The communication system has a plurality of communication nodes. The communication system may be a single line network. A cluster may be configured by a plurality of communication nodes.

The plurality of communication nodes, the master node 100 _1, and the slave nodes 200 ₁ to the slave node 200 _n, the slave node ₄₀₀ 1 to 400 _m (m is, m> 1 integer) is included. As in the embodiment described above, there may be a plurality of master nodes. FIG. 13 shows an example where n = 2 and m = 2.

The slave nodes 200 ₁ to 200 _n are the same as in the above-described embodiment. The slave nodes 400 _{1 to} 400 _m are the same as the conventional slave nodes in which the length of the break field and the information are not associated with each other.

In one embodiment of the communication system, the number of message IDs is increased (extended) according to the frame rule of the LIN standard. The signal transmitted on the bus 300 is completely compliant with the LIN standard. Therefore, even when the slave nodes 400 _{1 to} 400 _m detect signals transmitted from the slave nodes 200 ₁ to 200 _m , it is possible to identify that the signals are LIN messages.

  As described above, the slave node in which the length of time in which the dominant state of the break field continues and the information are associated with each other and the slave node in which the length of time in which the dominant state of the break field continues and the information are not associated with each other Can coexist on the same network.

The configurations of the slave nodes 400 _{1 to} 400 _m are substantially the same as those in FIGS.

Figure 14 is a message ID storage unit 112 of the master node 100 _1, and the message ID corresponding to the message and the message stored slave nodes ₂₀₀ 1 to 200 DEG _n, the message ID storage unit 212 of the slave node ₄₀₀ 1 to 400 _m A corresponding modification is shown.

In order for the slave nodes 200 ₁ to 200 _n and the slave nodes 400 _{1 to} 400 _m to coexist in the same network, the message used by the slave nodes 400 _{1 to} 400 _m includes a frame identifier in the protected identifier field. Is one type. In this way, it is possible to prevent the message transmitted from the master node 100 ₁ is erroneously recognized on the receiving side.

  In a variation of the communication system, the length of time that the dominant state of the break field continues is associated with information, that is, the slave node whose message ID is extended, and the time that the dominant state of the break field continues Can be coexisted in the same network with conventional slave nodes whose message IDs are not associated with each other, that is, whose message ID is not expanded.

<Modification (Part 2)>
In a second modification of the communication system (part 2), the information associated with the length of time that the dominant state of the break field continues may be 1 bit or 3 bits or more. According to the LIN standard, the length of time that the dominant state of the break field continues is 13 bits or more and 26 bits or less, and is preferably less than or equal to the information represented by 14 bits. For example, 14 steps can be set in units of time corresponding to 1 bit from the time corresponding to 13 bits to the time corresponding to 26 bits for the duration of the dominant state of the break field.

  FIG. 15 shows an example of a break field. FIG. 15 shows four types of break fields. Each break field has a different length of time that the dominant state of the break field lasts.

  For example, “00” is made to correspond to a break field that lasts for a time corresponding to 19 bits in the length of time that the dominant state of the break field lasts (FIG. 15 (1)).

  “01” is made to correspond to a break field that lasts for a time corresponding to a 17-bit length of time during which the dominant state of the break field continues (FIG. 15 (2)).

  “10” is made to correspond to a break field that lasts for a length of time that the dominant state of the break field lasts for 15 bits (FIG. 15 (3)).

  “11” is made to correspond to the break field that lasts for a time corresponding to 13 bits in the length of time that the dominant state of the break field lasts (FIG. 15 (4)).

  According to (1)-(4) of FIG. 15, information of 2 bits is represented by the length of time during which the dominant state of the break field continues.

  In a variation of the communication system, the length of time during which the dominant state of the break field continues is associated with the information. A message ID of the message is a combination of information indicated by the length of time that the dominant state of the break field continues and information indicated by the frame identifier of the protected identifier field. In this way, the number of message IDs that can be assigned to a message can be increased without increasing the number of bits in the protected identifier field.

  Although the present invention has been described above with reference to specific embodiments and modifications, each embodiment and modification is merely illustrative, and those skilled in the art will recognize various modifications, modifications, alternatives, and substitutions. You will understand examples. For convenience of explanation, an apparatus according to an embodiment of the present invention has been described using a functional block diagram, but such an apparatus may be implemented in hardware, software, or a combination thereof. The present invention is not limited to the above-described embodiments, and various variations, modifications, alternatives, substitutions, and the like are included without departing from the spirit of the present invention.

100 _{1 to} 100 _k (k is an integer of k> 0) Master node 102 Microcontroller unit 104 Communication device 106 Transceiver 112 Message ID storage unit 114 Message creation unit 116 Frame transmission control unit 200 ₁ to 200 _n (n is n > 0) Slave node 202 Microcontroller unit 204 Communication device 206 Transceiver 212 Message ID storage unit 214 Message reception control unit 216 Message analysis unit 218 Response creation unit 220 Response transmission control unit 300 Communication bus 400 _{1 to} 400 _m (m is , M> 0) Slave node

Claims (7)

A communication node that communicates with a slave node connected via a communication bus,
Specifying a message identifier of a message to be transmitted to the slave node, and creating a message including the message identifier;
A frame transmission control unit that executes control for transmitting the message created by the message creation unit, and
The message identifier is a communication node represented by a combination of information represented by a length of a break field and information of an ID field.   The communication node according to claim 1, wherein the frame transmission control unit sets a length of time during which a dominant state of a break field continues based on the message identifier. A storage unit for storing a message transmitted to and received from a slave node and an identifier of the message in association with each other;
The message creation unit identifies a message identifier corresponding to a message to be transmitted to the slave node based on a correspondence between a message stored in the storage unit and an identifier of the message. Communication node. A communication node that receives a message from a master node connected via a communication bus,
A message analysis unit that analyzes the content of the message corresponding to the message identifier based on the message identifier included in the message transmitted by the master node;
A response creation unit that creates a response to the message analyzed by the message analysis unit;
A response transmission control unit that executes control to transmit the response created by the response creation unit, and
The message identifier is represented by a combination of information represented by the length of the break field and information of the ID field,
The message analysis unit is a communication node that analyzes the content of a message based on a combination of information represented by a length of a break field of the message transmitted by the master node and information of an ID field. 5. The communication node according to claim 4, further comprising: a message reception control unit configured to execute control for detecting the break field when a dominant state of a message transmitted by the master node continues for a time corresponding to a predetermined number of bits. . A storage unit for storing a message transmitted to and received from a slave node and an identifier of the message in association with each other;
The communication node according to claim 4 or 5, wherein the message analysis unit analyzes the content of the message transmitted by the master node based on the association between the message stored in the storage unit and the identifier of the message. . A communication system having a slave node and a master node connected to the slave node via a communication bus,
The master node
Specifying a message identifier of a message to be transmitted to the slave node, and creating a message including the message identifier;
A frame transmission control unit that executes control for transmitting the message created by the message creation unit, and
The message identifier is represented by a combination of information represented by the length of the break field and information of the ID field,
The slave node is
Based on a message identifier included in the message transmitted by the master node, a message analysis unit for analyzing the content of the message corresponding to the message identifier;
A response creation unit that creates a response to the message analyzed by the message analysis unit;
A response transmission control unit that executes control to transmit the response created by the response creation unit, and
The said message analysis part is a communication system which analyzes the content of a message based on the combination of the information represented by the length of the break field of the message transmitted by the said master node, and the information of ID field.