JP2013012915A - Communication node, communication system, and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a communication system employing a master-slave system as a communication system employing a multi-master system.SOLUTION: A communication node for performing communication with a slave node connected via a communication bus includes: a priority level field setting unit for setting a priority level field including a priority level regarding transmission and reception of a message field to the message field to be transmitted or received to/from the slave node; a priority level field transmission unit for transmitting the priority level field; a communication bus state detection unit for detecting the state of the communication bus; a bus arbitration determination unit for determining whether the state of the communication bus corresponds with the state of the communication bus which should be detected by the priority level field having been transmitted; and a message frame transmission control unit for stopping transmission of the message field if it has been determined that the state of the communication bus is different from the state of the communication bus which should be detected by the priority level field having been transmitted.

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 vehicle system of a vehicle.

  The LIN includes a communication node serving as a master and a communication node serving as a slave. The master communication node controls network communication timing and the like. In LIN, one communication node becomes a master.

  Regarding LIN, a technique is known in which a plurality of communication nodes can be master candidates while maintaining a master-slave method (see, for example, Patent Document 1).

JP 2010-28793 A

  A new communication node for autonomous communication cannot be added to an existing LIN cluster. In order to newly add a communication node, a communication schedule for controlling the added communication node is designed, or a communication schedule for controlling a communication node included in an existing LIN cluster is redesigned. There is a need to.

  Further, when there are a plurality of independent LIN clusters whose operations are guaranteed, these LIN clusters cannot be combined as one LIN cluster.

  In addition, there is a restriction in design when trying to make the master-slave relationship between communication nodes in communication control coincide with the master-slave relationship in actual communication control.

  Since LIN employs a master-slave method, a plurality of master nodes cannot be arranged in one network.

  A case where a plurality of master nodes are arranged in one network will be described.

  FIG. 1 shows an example where scheduling is executed independently by each master node when a plurality of master nodes are arranged in one LIN. FIG. 1 shows a case where N (N is an integer of N> 1) master nodes are arranged in one LIN. N master nodes are connected to the same communication bus. Further, the N master nodes operate independently.

  The master node 1 performs scheduling for transmitting the message 1 (M1) on the communication bus. The message includes a plurality of frames, and each frame is represented by ID1, ID2, ID3, and ID4. The master node 2 performs scheduling for transmitting the message 2 (M2) on the communication bus. The message includes a plurality of frames, and each frame is represented by ID1, ID2, ID3, and ID4. The master node N performs scheduling for transmitting the message N (MN) on the communication bus. The message includes a plurality of frames, and each frame is represented by ID1, ID2, ID3, and ID4.

  During the time when ID1 of message 2 is transmitted by scheduling by master node 2, ID1 of message 1 is transmitted on the communication bus by scheduling by master node 1. Since ID1 of message 1 is transmitted on the communication bus, a plurality of messages are scheduled in duplicate on the communication bus. In this state, when ID1 of message 2 is transmitted according to the scheduling by master node 2, ID1 of message 2 collides with ID1 of message 1.

  Also, during the time when ID2 of message 2 is transmitted by scheduling by master node 2, ID3 of message 1 is transmitted on the communication bus by scheduling by master node 1. Since ID3 of message 1 is transmitted on the communication bus, a plurality of messages are scheduled redundantly on the communication bus. In this state, when ID2 of message 2 is transmitted according to the scheduling by master node 2, ID2 of message 2 collides with ID3 of message 1.

  In addition, due to the scheduling by the master node 2, the time for transmitting ID3 of the message 2 is not scheduled as the time for transmitting the message. Since no message is transmitted on the communication bus, ID3 of message 2 is transmitted according to the scheduling by the master node 2.

  The ID4 of the message 2 is transmitted on the communication bus by the scheduling by the master node N during the time when the ID4 of the message 2 is transmitted by the scheduling by the master node 2. Since ID4 of message N is transmitted on the communication bus, a plurality of messages are scheduled redundantly on the communication bus. In this state, when ID4 of message 2 is transmitted according to the scheduling by master node 2, ID4 of message 2 collides with ID4 of message N.

  Also, during the time when ID1 of message N is transmitted by scheduling by master node N, ID2 of message 1 is transmitted on the communication bus by scheduling by master node 1. Since ID2 of message 1 is transmitted on the communication bus, a plurality of messages are scheduled redundantly on the communication bus. In this state, when ID1 of message N is transmitted according to the scheduling by master node N, ID1 of message N collides with ID2 of message 1.

  Also, during the time when ID2 of message N is transmitted by scheduling by master node N, ID3 of message 1 is transmitted on the communication bus by scheduling by master node 1. Since ID3 of message 1 is transmitted on the communication bus, a plurality of messages are scheduled redundantly on the communication bus. In this state, when ID2 of message N is transmitted according to the scheduling by master node N, ID2 of message N collides with ID3 of message 1.

  The ID3 of the message N is transmitted by the scheduling by the master node N. The ID3 of the message 2 is transmitted on the communication bus by the scheduling by the master node 2. Since ID3 of message 2 is transmitted on the communication bus, a plurality of messages are scheduled redundantly on the communication bus. In this state, when ID3 of message N is transmitted according to the scheduling by master node N, ID3 of message N collides with ID3 of message 2.

  In addition, due to the scheduling by the master node N, the time when ID4 of the message N is transmitted is not scheduled as the time when the message is transmitted. Since no message is transmitted on the communication bus, ID4 of the message N is transmitted according to the scheduling by the master node N.

  As described above, when a plurality of master nodes are arranged in a communication system adopting the master-slave method, message collision may occur.

  The present invention has been made in view of the above points, and an object of the present invention is to operate a master-slave communication system as a multi-master communication system.

The communication node of one embodiment of the disclosure is
A communication node that communicates with a slave node connected via a communication bus,
A priority field setting unit for setting a priority field including a priority for transmission / reception of the message field in a message field to be transmitted / received to / from a slave node;
A priority field transmitting unit for transmitting a priority field to be set by the priority field setting unit;
A communication bus state detection unit for detecting the state of the communication bus;
A bus for determining whether the state of the communication bus to be detected by the communication bus state detection unit is the same as the state of the communication bus to be detected by transmitting the priority field by the priority field transmission unit An arbitration determination unit;
The state of the communication bus to be detected by the communication bus state detection unit by the bus arbitration determination unit is different from the state of the communication bus to be detected by transmitting the priority field by the priority field transmission unit. And a message frame transmission control unit for stopping transmission of the message field.

A communication system according to an embodiment of the disclosure includes:
A communication system having a slave node and a communication node connected to the slave node via a communication bus,
The communication node is
A priority field setting unit for setting a priority field including a priority for transmission / reception of the message field in a message field to be transmitted / received to / from a slave node;
A priority field transmitting unit for transmitting a priority field to be set by the priority field setting unit;
A communication bus state detection unit for detecting the state of the communication bus;
A bus for determining whether the state of the communication bus to be detected by the communication bus state detection unit is the same as the state of the communication bus to be detected by transmitting the priority field by the priority field transmission unit An arbitration determination unit;
The state of the communication bus to be detected by the communication bus state detection unit by the bus arbitration determination unit is different from the state of the communication bus to be detected by transmitting the priority field by the priority field transmission unit. And a message frame transmission control unit for stopping transmission of the message field.

A communication method according to an embodiment of the disclosure is as follows.
A communication method in a communication node that performs communication with a slave node connected via a communication bus,
A priority field setting step for setting a priority field including a priority related to transmission / reception of the message field in a message field to be transmitted / received to / from the slave node;
A priority field transmission step of transmitting a priority field to be set by the priority field setting step;
A communication bus state detection step for detecting the state of the communication bus;
A bus for determining whether the state of the communication bus to be detected by the communication bus state detection step is the same as the state of the communication bus to be detected by transmitting the priority field in the priority field transmission step. An arbitration determination step;
The state of the communication bus to be detected by the communication bus state detection step by the bus arbitration determination step is different from the state of the communication bus to be detected by transmitting the priority field by the priority field transmission step. A message frame transmission control step for stopping the transmission of the message field.

  According to the disclosed embodiments, a master-slave communication system can be operated as a multi-master communication system.

It is a figure which shows an example of the scheduling by the some master node connected on the same bus | bath. It is a figure which shows one Example of a communication system. It is a figure which shows an example of a frame format. It is a figure which shows one Example of a master node. It is a figure which shows one Example of bus arbitration. It is a functional block diagram which shows one Example of a master node. It is a figure which shows one Example of an arbitration process. It is a flowchart which shows one Example of operation | movement of a master node. It is a figure which shows the method of synchronizing a priority field between master nodes.

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. 2 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 the plurality of communication nodes.

The plurality of communication nodes include a master node 100 _l (l is an integer of l> 1) and a slave node 200 _m (m is an integer of m> 1).

Master node 100 ₁ -Master node 100 _l controls when to send a message. Specifically, the master node 100 _{1 to the} master node 100 _l schedule the timing for transmitting the header included in the message. During the scheduling, an ID of a message to be transmitted, a transmission order, a transmission time interval, and the like are set.

The master node 100 ₁ -master node 100 _l and the slave node 200 ₁ -slave node 200 _m are connected by wire via the communication bus 300. The master node 100 ₁ -master node 100 _l and the slave node 200 ₁ -slave node 200 _m communicate 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 _l transmits a message according to a predetermined frame format.

<Frame format>
FIG. 3 shows an example of a frame format transmitted / received between master node 100 ₁ -master node 100 _l and slave node 200 ₁ -slave node 200 _m .

  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), a priority field (Priority 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 represented by “t _Break ”. For example, the dominant duration of the break field is 13 bits or longer. The dominant duration of the break field is called “break field length”. In this embodiment, the dominant duration of the break field of each master node has a fixed length and is substantially the same.

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

  The priority field is used when the bus arbitration is performed between the plurality of master nodes when the frame transmission timings match between the plurality of master nodes. When the frame transmission timings match among a plurality of master nodes, transmission data collide. For this reason, the priority field is used to determine whether or not the master node can occupy the bus.

  The protected identifier field is 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 includes a data field (Data Field) and a checksum (Checksum). The data field and checksum are 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 total of the sync field length, the priority field length, the protected identifier field length, and the data field length is represented by “t _{Frame_Slot} ”. Specifically, “t _{Frame_Slot} ” is based on the rising edge of the break field. Hereinafter, the _total of the sync field length, priority field length, protected identifier field length, and data field length represented by “t _{Frame_Slot} ” is referred to as “frame slot length”.

  In addition, an inter-frame space (not shown) is set between adjacent frames.

  Further, in the example shown in FIG. 3, jitter is shown. Jitter represents fluctuations in the signal waveform in the time axis direction. The time set as the jitter is called “jitter time”.

<Master node>
FIG. 4 shows a master node. Since the master node 100 ₁ -master node 100 _l have substantially the same configuration, the master node 100 _l will be described as a representative.

The master node 100 _l has a micro-control unit (MCU) 102 _l and a transceiver 106 _l .

The MCU 102 _l includes one or a plurality of microcomputers. A CPU may be included instead of the microcomputer, and MCU and CPU may be mixed. Further, the MCU 102 _l, include communication devices 104 _l is. The communication device 104 _l performs serial communication with the transceiver 106 _l . Specifically, the communication device 104 _l may be a UART.

The transceiver 106 _l is connected to the MCU 102 _l and the communication bus 300. The transceiver 106 _l transmits data input from the MCU 102 _l to the communication bus 300, and inputs data from the communication bus 300 to the MCU 102 _l .

<Master node function>
If another master node is sending a message, the master node 100 _l waits until the next frame. Specifically, a timer for measuring jitter time (hereinafter referred to as “jitter”) based on the elapse of the frame slot length based on the rising edge of the break field included in the message to be transmitted by another master node. "Time measurement timer"). The jitter time may be set in advance as a fixed value. When the jitter time elapses due to the expiration of the jitter time measurement timer, the master node 100 _l starts a break field and a timer for measuring the break field length (hereinafter referred to as “break field length measurement timer”). to start.

When the break field length elapses due to the expiration of the break field length measurement timer, the master node 100 _l starts sending out the sync field and also measures a timer for measuring the sync field length (hereinafter referred to as “sync field length measurement timer”). ").

The master node 100 _l transmits the priority field when the sync field length elapses due to the expiration of the sync field length measurement timer.

If the master node trying to send messages to other the master node 100 _l is present in the state of the communication bus 300 contemplated by priority field by the master node 100 _l is sent, actual communication bus When it is detected that the status of 300 is different, transmission of the priority field is stopped. The master node 100 _l waits until the next frame.

On the other hand, if it is not detected that the state of the communication bus 300 assumed when the priority field is transmitted by the master node 100 _l and the actual state of the communication bus 300 are not detected, the master node 100 ₁ The communication bus 300 can be occupied. If you can occupy a communication bus 300, the master node 100 _1, following the priority field, and transmits the protected Identifier field.

  FIG. 5 shows an example of bus arbitration.

The example shown in FIG. 5 shows an example of bus arbitration in _two master nodes (master nodes 100 ₁ and 100 ₂ ). The same applies to the case of three or more master nodes.

In the example shown in FIG. 5, data to be transmitted is generated in the master node 100 ₁ and the master node 100 ₂ . Data to be transmitted may be generated when a message is being transmitted by another master node.

The master node 100 ₁ and the master node 100 ₂ wait until the next frame when data is transmitted by another master node.

The master node 100 ₁ and the master node 100 ₂ wait until the frame slot length from the start of the break field of the other master node 100 ₁ elapses. The master node 100 ₁ and the master node 100 ₂ start the jitter time measurement timer based on the elapse of the frame slot length based on the rising edge of the break field.

When the master node 100 ₁ and the master node 100 ₂ detect that the jitter time has elapsed due to the expiration of the jitter time measurement timer, the master node 100 ₁ and the master node 100 ₂ start transmitting the break field and start the break field length measurement timer (1). .

When the master node 100 ₁ and the master node 100 ₂ detect that the break field length has elapsed due to the expiration of the break field length measurement timer, the master node 100 ₁ and the master node 100 ₂ start transmission of the sync field and start the sync field length measurement timer ( 2).

When the master node 100 ₁ and the master node 100 ₂ detect that the sync field length has elapsed due to the expiration of the sync field length measurement timer, the master node 100 ₁ and the master node 100 ₂ start transmitting the priority field (3).

In the example shown in FIG. 5, the communication bus 300 by the master node 100 ₁ is shown for the case to be occupied. That is, in the master node 100 _l , the state of the communication bus 300 assumed when the priority field is transmitted from the master node 100 _l matches the actual state of the communication bus 300.

On the other hand, _second master node 100, in the course of transmission of the priority field, the state of communication bus 300 contemplated by the priority field from the master node 100 ₂ is sent, and the actual communication bus 300 different states Detect that. When it is detected that the state of the communication bus 300 assumed by the transmission of the priority field is different from the actual state of the communication bus 300, transmission of the priority field is stopped.

Master node 100 ₁ that occupies the communication bus 300, following the priority field, and transmits the protected Identifier field. The master node 100 _{l that} has transmitted the protected identifier field receives data from the slave node (5).

FIG. 6 is a functional block diagram showing the master node 100 _l . FIG. 6 mainly describes the part related to the present embodiment. Therefore, the function as a slave node, the diagnostic function, etc. are omitted.

The master node 100 _l has a master function unit 110. The master function unit 110 includes a priority field setting unit 112, a priority field transmission control unit 114, a bus arbitration determination unit 116, and a frame transmission control unit 118. The MCU 102 _l may function as the master function unit 110 by functioning according to a predetermined program. The predetermined program may be stored in the MCU 102 _l .

  The priority field setting unit 112 functions when a message to be transmitted occurs. The priority field setting unit 112 sets information to be included in the priority field according to the message to be transmitted. Specifically, different values may be set according to the priority regarding message transmission / reception. A table in which a message is associated with a priority to be set may be prepared. The table may be different for each master node. This is because the message to be transmitted may be different. The priority field setting unit 112 inputs information to be included in the set priority field to the priority field transmission control unit 114.

The priority field transmission control unit 114 is connected to the priority field transmission control unit 114 and the transceiver 106 _l . The priority field transmission control unit 114 performs priority field transmission control based on information to be included in the priority field to be input by the priority field setting unit 112. Specifically, the priority field transmission control unit 114 sends the priority field to the transceiver 106 _l . The priority field transmission control unit 114 inputs information representing the priority field to be transmitted to the transceiver 106 _l to the bus arbitration determination unit 116. When transmission of the priority field is completed, the priority field transmission control unit 114 notifies the bus arbitration determination unit 116 that transmission of the priority field has ended.

The bus arbitration determination unit 116 is connected to the priority field transmission control unit 114 and the transceiver 106 _l . Based on the priority field to be input by the priority field transmission control unit 114, the bus arbitration determination unit 116 determines the state of the communication bus 300 that is assumed when the priority field is transmitted, and the actual state of the communication bus 300. Whether or not matches. The state of the communication bus 300 includes a recessive state and a dominant state.

When it is determined that they do not match, the bus arbitration determination unit 116 determines that the master node 100 _l cannot occupy the communication bus 300. When it is determined that the communication bus 300 cannot be occupied, the bus arbitration determination unit 116 notifies the priority field transmission control unit 114 that they do not match. The priority field transmission control unit 114 stops transmission of the priority field when notified by the bus arbitration determination unit 116 that they do not match.

On the other hand, the state of the communication bus 300 assumed by the transmission of the priority field to be input by the priority field transmission control unit 114 until the priority field transmission control unit 114 notifies the transmission of the priority field. And the actual state of the communication bus 300 match, the bus arbitration determination unit 116 determines that the master node 100 _l can occupy the communication bus 300. When it is determined that the master node 100 _l can occupy the communication bus 300, the bus arbitration determination unit 116 notifies the frame transmission control unit 118 that the communication bus 300 can be occupied.

<Bus arbitration processing>
FIG. 7 shows a bus arbitration determination process to be executed by the bus arbitration determination unit 116.

  In the example shown in FIG. 7, the priority field is represented by 8 bits. The priority field may be represented by 7 bits or less, or may be represented by 9 bits or more.

The master node 100 _1, as the information contained in the priority field, a "01010100", to the order of "01010100". The master node 100 _2, as the information contained in the priority field, a "01011111", to the order of "01011111".

If the master node is a master node 100 _1, arbitration determination unit 116, the status of the communication bus 300 contemplated by the sent priority field, it can detect that the actual communication bus 300 states coincide.

If the master node is a master node 100 _2, arbitration determination unit 116, the status of the communication bus 300 contemplated by the sent priority field, it and the actual communication bus 300 states up to 4 bits match Can be detected. However, as indicated by (A), for the fifth bit, the transmitted bit is “1”, whereas the actual state of the communication bus 300 is “0”. On the other hand, "0" is sent from the master node 100 _1.

  When different information is transmitted from a plurality of master nodes, “0” is reflected in the communication node. That is, dominant is given priority in the communication bus 300. Therefore, when transmission / reception priority is set as information included in the priority field, “0” becomes a continuous value as the priority increases. For this reason, as the priority increases, the state of the communication bus 300 assumed by the transmitted priority field and the actual state of the communication bus 300 continue to match. For this reason, the communication bus 300 can be occupied as the priority increases. That is, the master node that has continued to transmit “0” for a long time can occupy the communication bus.

The frame transmission control unit 118 is connected to the bus arbitration determination unit 116 and the transceiver 106 _l . When notified from the bus arbitration determination unit 116 that the communication bus 300 can be occupied, the frame transmission control unit 118 performs control to transmit a protected identifier field following the priority field.

<Operation of master node>
FIG. 8 shows an embodiment of the operation of the master node 100 _l . FIG. 8 shows an example when a message to be transmitted to the master node 100 _l is generated.

The master node 100 _l measures the jitter time (step S802). The master node 100 _l starts a jitter time measurement timer when the frame slot slot length time has elapsed.

The master node 100 _l determines whether or not the jitter time measurement timer has expired (step S804).

  If it is determined that the jitter time measurement timer has not expired (step S804: NO), the process returns to step S804. Continue until the jitter time timer expires.

When it is determined that the jitter time measurement timer has expired (step S804: YES), the master node ₁₀₀₁ transmits a break field (step S806). The master node 100 _l starts a break field length measurement timer and measures the break field length.

The master node 100 _l determines whether or not the break field length measurement timer has expired (step S808).

If it is not determined that the break field length measurement timer has expired (step S808: NO), the master node ₁₀₀₁ returns to step S808. It continues until the break field length measurement timer expires.

When it is determined that the break field length measurement timer has expired (step S808: YES), the master node ₁₀₀₁ transmits a sync field (step S810). The master node 100 _l starts a sync field length measurement timer and measures the sync field length.

The master node 100 _l determines whether or not the sync field length measurement timer has expired (step S812).

If it is not determined that the sync field length measurement timer has expired (step S812: NO), the master node ₁₀₀₁ returns to step S812. It continues until the sync field length measurement timer expires.

When it is determined that the sync field length measurement timer has expired (step S812: YES), the master node ₁₀₀₁ sets a priority field (step S814). That is, the priority field setting unit 112 sets the priority field according to the priority related to transmission / reception of the message to be transmitted.

The master node 100 _l transmits the priority field (step S816). That is, the priority field is transmitted according to control by the priority field transmission control unit 114.

The master node 100 _l determines whether or not the state of the communication bus 300 that should be assumed by the transmitted priority field matches the actual state of the communication bus 300 (step S818). In other words, the bus arbitration determination unit 116 determines a state of the communication bus 300 contemplated by the sent priority field, whether the state of the communication bus 300 to be detected through the transceiver 106 _l coincide.

When it is determined that they match (step S818: YES), the master node ₁₀₀₁ determines whether or not the transmission of the priority field is finished (step S820). That is, if the bus arbitration determination unit 116 determines that the state of the communication bus 300 assumed by the transmitted priority field matches the state of the communication bus 300 to be detected via the transceiver 106, the bus arbitration determination unit 116 Determine whether all bits have been sent.

  If it is not determined that all bits have been transmitted (step S820: NO), the process returns to step S816. For the bits that have not been transmitted, the processing of step S816 to step S820 is performed.

If all the bits transmitted is determined to have been performed (step S820: YES), the master node 100 _l transmits a protection gated Identifier field (step S822). That is, for all bits, the frame transmission control unit 118 determines that the state of the communication bus 300 assumed by the transmitted priority field matches the state of the communication bus 300 to be detected through the transceiver 106 _l. If it is determined that the communication bus 300 can be occupied by the master node 100 _l . When it is determined that the communication bus 300 can be occupied, the frame transmission control unit 118 transmits a protected identifier field following the priority field.

If it is not determined to match in step S818 (step S818: NO), the master node ₁₀₀₁ stops transmission of the priority field (step S824). That is, if the bus arbitration determination unit 116 determines that the state of the communication bus 300 assumed by the transmitted priority field does not match the state of the communication bus 300 to be detected via the transceiver 106 _l , The master node 100 _l determines that the communication bus cannot be occupied. In this case, transmission of the priority field is stopped, and the process returns to step S802. This is because it is necessary to wait until the next frame in order to transmit the message.

In this embodiment, between the master node ₁₀₀ 1 -100 _l, preferably priority field are synchronized. This is because it is determined whether the state of the communication bus 300 assumed by the transmitted priority field matches the state of the communication bus 300 to be detected via the transceiver 106 _l .

  FIG. 9 illustrates a method for synchronizing priority fields between master nodes.

  In order to perform synchronization, the break field gap represented by the time to the sync field and the sync field gap represented by the time to the priority field using the rise edge of the sync field as the base point And the same value between master nodes.

  According to this embodiment, a plurality of master nodes can be connected to the same communication bus. That is, a new master node can be added to an existing communication cluster. Further, since there is no need to change the gap between frames or the break field length for each message, the frame length can be made the same. For this reason, time management of the whole frame can be simplified. Also, variations in message transmission speed can be reduced.

  In addition, it is possible to detect a collision between a plurality of master nodes and perform transmission or hold transmission. Therefore, even in a single task communication network, a plurality of nodes can be used as master nodes. That is, multitasking can be performed.

  Specifically, a bus arbitration function can be realized by defining a field used when a communication bus is occupied between master nodes in a frame to be transmitted. Since arbitration can be realized, a master-slave communication system can be operated as a multi-master communication system.

  In the above case, it is not necessary to change the hardware of the master node. For this reason, the freedom degree of the design of a communication schedule can be improved, without increasing cost.

  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 _l (l is an integer of l> 1) Master node 102 _l (l is an integer of l> 1) MCU
104 _l (l is an integer of l> 1) Communication device 106 _l (l is an integer of l> 1) transceiver 112 priority field setting unit 114 priority field transmission control unit 116 bus arbitration determination unit 118 frame transmission control unit 200 _m (M is an integer of l> 1) Slave node 300 Communication bus

Claims (6)

A communication node that communicates with a slave node connected via a communication bus,
A priority field setting unit for setting a priority field including a priority for transmission / reception of the message field in a message field to be transmitted / received to / from a slave node;
A priority field transmitting unit for transmitting a priority field to be set by the priority field setting unit;
A communication bus state detection unit for detecting the state of the communication bus;
A bus for determining whether the state of the communication bus to be detected by the communication bus state detection unit is the same as the state of the communication bus to be detected by transmitting the priority field by the priority field transmission unit An arbitration determination unit;
The state of the communication bus to be detected by the communication bus state detection unit by the bus arbitration determination unit is different from the state of the communication bus to be detected by transmitting the priority field by the priority field transmission unit. And a message frame transmission control unit that stops transmission of the message field when it is determined that the communication node. The communication node according to claim 1,
The priority field transmission unit is a communication node that transmits a priority field following a sync field. In the communication node according to claim 1 or 2,
The message frame transmission control unit is detected by the state of the communication bus to be detected by the communication bus state detection unit by the bus arbitration determination unit and the priority field transmitted by the priority field transmission unit. A communication node that continues transmission of a message field when transmission with a priority field is finished without determining that the state of the communication bus to be different is different. In the communication node according to any one of claims 1 and 3,
The bus arbitration determination unit has a communication bus state to be detected by the communication bus state detection unit and a communication bus state to be detected by transmitting a priority field by the priority field transmission unit. A communication node that determines whether each bit is the same. A communication system having a slave node and a communication node connected to the slave node via a communication bus,
The communication node is
A priority field setting unit for setting a priority field including a priority for transmission / reception of the message field in a message field to be transmitted / received to / from a slave node;
A priority field transmitting unit for transmitting a priority field to be set by the priority field setting unit;
A communication bus state detection unit for detecting the state of the communication bus;
A bus for determining whether the state of the communication bus to be detected by the communication bus state detection unit is the same as the state of the communication bus to be detected by transmitting the priority field by the priority field transmission unit An arbitration determination unit;
The state of the communication bus to be detected by the communication bus state detection unit by the bus arbitration determination unit is different from the state of the communication bus to be detected by transmitting the priority field by the priority field transmission unit. A message frame transmission control unit that stops transmission of the message field when it is determined that A communication method in a communication node that performs communication with a slave node connected via a communication bus,
A priority field setting step for setting a priority field including a priority related to transmission / reception of the message field in a message field to be transmitted / received to / from the slave node;
A priority field transmission step of transmitting a priority field to be set by the priority field setting step;
A communication bus state detection step for detecting the state of the communication bus;
A bus for determining whether the state of the communication bus to be detected by the communication bus state detection step is the same as the state of the communication bus to be detected by transmitting the priority field in the priority field transmission step. An arbitration determination step;
The state of the communication bus to be detected by the communication bus state detection step by the bus arbitration determination step is different from the state of the communication bus to be detected by transmitting the priority field by the priority field transmission step. A message frame transmission control step of stopping transmission of the message field when it is determined that

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