JP2014086812A - Can system and node - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system capable of increasing failure resistance while suppressing bus usage efficiency degradation.SOLUTION: A CAN system 900 includes: a first node 91; and a second node 92. The first node transmits a re-transmission request frame for requesting frame re-transmission, if own node is in an error passive state when frame reception through a CAN bus 90 fails. The second node stores a frame transmitted to CAN bus in a storage part, obtains a frame whose re-transmission is requested by a re-transmission frame transmitted by the first node, and re-transmits the frame to the first node.

Description

  The present invention relates to a CAN system and a node, and can be suitably used for a technique for mutually transmitting and receiving frames between a plurality of nodes via a CAN (Controller Area Network) bus, for example.

  In recent years, functional safety has attracted attention, and fault tolerant functions are mainly required for in-vehicle applications. CAN, which is a main in-vehicle network, has an automatic retransmission transmission specification due to an error. However, there is a state in which a reception error notification is impossible (error passive state) as a state of a node that is a communication subject by CAN. For this reason, when a node has an error passive state and a message reception error occurs due to a communication failure in the node, the message remains missed.

  With respect to such a problem, Patent Document 1 discloses a technique for reducing a missed received message in a CAN system. In the CAN system disclosed in Patent Document 1, a message set as a retransmission target is always retransmitted. As a result, even when a message transmitted to the node in the error passive state is not normally received, it is possible to reduce the missed message.

JP 2010-147590 A

  However, in the technique disclosed in Patent Document 1, since the message is always retransmitted, there arises a problem that the use efficiency of the bus is lowered. Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

  According to one embodiment, the CAN system comprises a first node and a second node. If the first node is in an error passive state when reception of a frame via the CAN bus fails, the first node transmits a retransmission request frame requesting retransmission of the frame. The second node stores the frame transmitted to the CAN bus in the storage unit, acquires the frame requested to be retransmitted from the retransmission request frame transmitted from the first node, from the storage unit, Resend to node.

  According to the one embodiment, it is possible to improve fault tolerance while suppressing a decrease in bus use efficiency.

1 is a configuration diagram of a CAN system according to a first embodiment. 3 is a configuration diagram for explaining an outline of operation of a CAN system according to Embodiment 1. FIG. 3 is a configuration diagram of a node according to Embodiment 1. FIG. 4 is a flowchart illustrating an operation when a reception error is detected by a node according to the first embodiment. 4 is a flowchart showing an operation when a retransmission request frame is received by a node according to the first embodiment. FIG. 5 is a conceptual diagram showing an operation when a retransmission request frame conflicts in the CAN system according to the first embodiment. 6 is a time chart illustrating an operation when a retransmission request frame conflicts in the CAN system according to the first embodiment. 6 is a time chart showing an operation at the time of simultaneous transmission of a retransmission frame and another transmission frame of the CAN system according to the first embodiment. 6 is a time chart illustrating a frame processing operation when a retransmission request is generated in the CAN system according to the first embodiment. 3 is a configuration diagram of a CAN system according to a second embodiment. FIG. FIG. 10 is a configuration diagram for explaining an operation outline of a CAN system according to a second embodiment. 6 is a configuration diagram of a general node according to Embodiment 2. FIG. 6 is a configuration diagram of a past frame server node according to Embodiment 2. FIG. 14 is a time chart showing an operation at the time of simultaneous transmission of a retransmission frame and another transmission frame of the CAN system according to the third embodiment. 10 is a time chart illustrating a frame processing operation when a retransmission request is generated in the CAN system according to the third embodiment. It is a lineblock diagram of a CAN system used as an outline composition of an embodiment.

  For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Each element described in the drawings as a functional block for performing various processes can be configured by a CPU, a memory, and other circuits in terms of hardware, and a program loaded in the memory in terms of software. Etc. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof, and is not limited to any one. Note that, in each drawing, the same element is denoted by the same reference numeral, and redundant description is omitted as necessary.

<Embodiment 1>
Embodiment 1 will be described. First, the configuration of a CAN system 1000 according to the first embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram of a CAN system 1000 according to the first embodiment.

  The CAN system 1000 includes, for example, a body system node 101, a safety system node 102, an information system node 103, an engine system node 104, a chassis system node 105, and the like. Each of the nodes 101 to 105 is connected to each other by a CAN bus 90, and an arbitrary frame can be transmitted / received to / from the CAN bus 90. The CAN system 1000 is built in an automobile.

  The body node 101 controls body devices such as a headlamp, a mirror, an air conditioner, and a door based on a frame received from another node. The safety node 102 controls safety devices such as sensors and airbags based on frames received from other nodes. The information node 103 controls information devices such as car audio, car radio, and car TV based on frames received from other nodes. The engine node 104 controls the engine and engine-related devices such as AT (Automatic Transmission) based on frames received from other nodes. The chassis node 105 controls chassis devices such as steering and brakes based on frames received from other nodes. In addition, each of the nodes 101 to 105 transmits an arbitrary frame to another node as necessary. Hereinafter, each of the nodes 101 to 105 is also collectively referred to as “node 100”. In addition, the types of nodes in the CAN system 1000 are not limited to the above-described body system, safety system, information system, engine system, and chassis system, and may have different types of nodes.

  In addition, at least one of the nodes 101 to 105 may be a gateway (bus bridge) node that connects a plurality of nodes of the same type and the CAN bus 90. For example, a body gateway node is connected to a plurality of body nodes, each of which controls a body device, by a LIN (Local Interconnect Network) bus. That is, the gateway node transmits and receives frames between the same type of node and other nodes on the CAN bus 90.

  Subsequently, an outline of operation of the CAN system 1000 according to the first embodiment will be described with reference to FIG. FIG. 2 is a configuration diagram for explaining an operation outline of the CAN system 1000 according to the first embodiment.

  Each of the nodes 100 includes a frame counter 110 and a transmission record FIFO 120. The frame counter 110 is a free running counter that counts the frames that appear on the CAN bus 90. The transmission record FIFO 120 is a storage for storing the transmitted frames of the own node.

  Each of the nodes 100 counts up the frame counter 110 when transmission or reception of a frame appearing on the CAN bus 90 is completed regardless of whether the node 100 or another node has transmitted. Each of the nodes 100 stores the transmitted frame together with the frame counter value of the frame counter 110 in the transmission record FIFO 120 at the timing when the node 100 finishes transmitting the frame and finishes counting up the frame counter 110 accordingly.

  Each node 100 transmits a retransmission request frame for requesting retransmission of a frame when a reception error of the frame occurs when the node 100 is in an error passive state. The retransmission request frame includes information that can specify the frame counter value of the frame counter 110 at the time of transmission of the frame that requests retransmission based on the frame counter value of the frame counter 110 at that time.

  When each of the nodes 100 receives a retransmission request frame, the node 100 selects a frame requested for retransmission from the frames stored in the transmission record FIFO 120 based on the frame counter value specified by the information of the retransmission request frame. Identify. Each of the nodes 100 retransmits the frame (retransmission frame) when a frame requested to be retransmitted in the retransmission request frame exists in the transmission record FIFO 120. Further, each of the nodes 100 suppresses transmission of a frame from its own frame for a predetermined time when a frame requested to be retransmitted in the retransmission request frame does not exist in the transmission record FIFO 120, and transmits a retransmission frame. The right to use the bus is given to the retransmitting node.

  Next, the configuration of the node 100 according to Embodiment 1 will be described with reference to FIG. FIG. 3 is a configuration diagram of the node 100 according to the first embodiment.

  The node 100 includes a CAN controller LSI (Large Scale Integration) 10 and a bus transceiver 20. The CAN controller LSI 10 includes a CAN controller module 1, a CPU (Central Processing Unit) 21, and other peripheral modules 22. Each of the CAN controller module 1, the CPU 21, and the other peripheral module 22 is connected to each other via a local bus 23.

  The CAN controller module 1 includes a bit stream control unit 2, a message handler 3, a message buffer memory 4, a frame counter 5, a transmission record control unit 6, a transmission record FIFO (First In First Out) 7, an error management unit 8, and a retransmission. A request transmission control unit 9 is included.

  The CAN controller module 1 is accessed from the CPU 21 via the local bus 23. The CAN controller module 1 is connected to the CAN bus 90 via the bus transceiver 20. The CAN controller module 1 transmits / receives a frame to / from another node 100.

  The bit stream control unit 2 receives the transmission frame 40 output from the message handler 3. The bit stream control unit 2 calculates a CRC (Cyclic Redundancy Check) based on the received transmission frame 40. The bit stream control unit 2 adds the calculated CRC to the transmission frame 40 in accordance with the CAN protocol frame format. The bit stream control unit 2 inserts stuff bits into the transmission frame to which the CRC is added based on bit stuffing defined by the CAN protocol. That is, a stuff bit having a logical value inverted from the logical value is inserted after five consecutive bits having the same logical value. The bit stream control unit 2 outputs the transmission frame in which the stuff bit is inserted in the bit stream format to the bus transceiver 20 via the transmission signal line (TxD) 30.

  The bit stream control unit 2 receives a reception frame output from the bus transceiver 20 via the reception signal line (RxD) 31 in a bit stream format. The bit stream control unit 2 removes stuff bits defined by the CAN protocol from the received reception frame. The bit stream control unit 2 performs a CRC check based on the received frame from which the stuff bits are removed. The bit stream control unit 2 removes the CRC from the received frame after the CRC check. The bit stream control unit 2 outputs the reception frame 41 from which the CRC is removed to the message handler 3.

  Further, when the bit stream control unit 2 detects a reception error (reception failure) of the received frame, the bit stream control unit 2 outputs an error occurrence signal 45 to the error management unit 8. The error occurrence signal 45 is a signal for notifying the occurrence of a reception error. The reception error corresponds to, for example, a CRC error, a stuff error, and a form error detected in the CRC check described above.

  Also, the bit stream control unit 2 sends the end-of-frame signal 42 to the frame counter 5 when the output of the transmission frame (transmission of the transmission frame) is completed or when reception of the reception frame (reception of the reception frame) is completed. Output to. The end-of-frame signal 42 is a signal for notifying completion of frame transmission or reception. Specifically, when the received frame is a data frame or a remote frame, the bit stream control unit 2 observes the EOF (end-of-frame) of the received frame and outputs the end-of-frame signal when the final bit is observed. Output to the frame counter 5. When the received frame is an active error frame, the bit stream control unit 2 observes the error delimiter of the received frame, and outputs the end-of-frame signal 42 to the frame counter 5 when the final bit is observed. As described above, the bit stream control unit 2 transmits the frame to the CAN bus 90 regardless of whether the frame is transmitted on the CAN bus 90 by the own node or the frame transmitted on the CAN bus 90 by another node. In response to the completion of transmission, an end-of-frame signal 42 is output to the frame counter 5.

  Further, when the transmission of the transmission frame is completed, the bit stream control unit 2 outputs a transmission completion signal 44 for notifying the transmission completion of the transmission frame to the transmission record control unit 6 immediately after outputting the end-of-frame signal 42. To do.

  The message handler 3 acquires the transmission frame 40 stored in the transmission buffer of the message buffer memory 4 and outputs it to the bitstream control unit 2. At this time, the message handler 3 also outputs the transmission frame 40 to the transmission record control unit 6. Further, the message handler 3 stores the reception frame 41 output from the bit stream control unit 2 in the reception buffer of the message buffer memory 4.

  The message buffer memory 4 has a reception buffer and a transmission buffer. The transmission buffer stores transmission frames to be transmitted to other nodes 100. The reception buffer stores reception frames received from other nodes 100. The message buffer memory 4 includes an arbitrary storage device for configuring a reception buffer and a transmission buffer. The storage device is, for example, a register and a memory. Each of the transmission frame and the reception frame has an arbitration field including an ID, a control field including a data length code (DLC), a data field including arbitrary data, and the like based on the CAN specification.

  The frame counter 5 counts the number of frames transmitted to the CAN bus 90. The frame counter 5 corresponds to the frame counter 110. The frame counter 5 increments the frame counter value 43 held therein according to the output of the end-of-frame signal 42 from the bit stream control unit 2. The frame counter 5 includes an arbitrary storage device for holding the frame counter value 43. The frame counter 5 outputs the frame counter value 43 to the transmission record control unit 6 and the retransmission request transmission control unit 9.

  In response to the transmission completion signal 44 output from the bit stream control unit 2, the transmission record control unit 6 transmits the frame counter value 43 output from the frame counter 5, the transmission frame 40 output from the message handler 3, and the transmission Each enable bit is associated and stored in the transmission record FIFO 7. As a result, the transmission frame transmitted on the CAN bus 90 is uniquely associated with the frame counter value 43 after being incremented according to the transmission. Further, by holding the transmission frame 40 in the transmission record FIFO 7 in this way, it is possible to identify and retransmit the transmission frame 40 requested to be retransmitted, as will be described later.

  At this time, the value of the transmission enable bit is set to “1”. The transmission enable bit is information indicating validity / invalidity of retransmission. When the transmission enable bit is “1”, the transmission frame associated therewith is retransmitted, and when the transmission enable bit is “0”, retransmission of the transmission frame associated therewith is suppressed. When a transmission frame is retransmitted, the value of the transmission enable bit associated therewith is updated to “0”. Also, when the transmission frame is an active error frame, it is not always necessary to retransmit, since device control according to frame reception is unnecessary at the receiving node. Therefore, when the transmission frame is an active error frame, “0” is set from the beginning as the value of the transmission enable bit stored in association with it.

  As described above, the transmission record FIFO 7 stores the frame counter value, the transmission enable bit, and the transmission frame by the transmission record control unit 6. The transmission record FIFO 7 corresponds to the transmission record FIFO 120. The transmission record FIFO 7 stores a frame counter value, a transmission enable bit, and a transmission frame in a FIFO format for each unit with which each is associated. The transmission record FIFO 7 includes a frame counter value, a transmission enable bit, and an optional storage device for holding a transmission frame.

  The error management unit 8 includes an error counter 11 that counts the number of frame transmission / reception errors with respect to the CAN bus 90 of the own node, and manages the state of the own node 100. The error management unit 8 counts up the counter value of the error counter 11 when an error occurs in the own node 100 according to the CAN specification. When the counter value of the error counter 11 exceeds a predetermined threshold, the error management unit 8 changes the state of the own node 100 to the “error passive state”. In the error passive state, as described above, retransmission of a frame in response to a retransmission request from another node 100 is suppressed according to the CAN specification.

  Further, the error management unit 8 determines whether or not the state of the own node 100 is “error passive state” in accordance with the output of the error occurrence signal 45 from the bit stream control unit 2. Specifically, when the counter value of the error counter 11 exceeds a predetermined threshold, the error management unit 8 determines that the state of the own node 100 is “error passive state”. When the error management unit 8 determines that the state of the node 100 is “error passive state”, the error management unit 8 outputs a retransmission request trigger signal 46 instructing a retransmission request of the received frame to the retransmission request transmission control unit 9.

  Specifically, the error management unit 8 includes, as the error counter 11, a transmission error counter and a reception error counter that count transmission errors and reception errors, respectively. That is, in FIG. 3, only one error counter 11 is shown, but strictly speaking, the error management unit 8 has two error counters 11, that is, a transmission error counter and a reception error counter. Refer to the CAN protocol standard for the timing and number of counts up and down of the transmission error counter and the reception error counter. In general, the transmission error counter counts up when a transmission error is detected, and transmission can be performed normally. Sometimes it counts down. Similarly, the reception error counter counts up when a reception error is detected, and counts down when normal reception is possible.

  The error management unit 8 sets the status of the node 100 according to the count value (REC) of the reception error counter and the count value (TEC) of the transmission error counter to the error active state, the error passive state, and the bus off state. Transition between two error states. The error active state is a state in which communication on the bus can be normally joined, and the error passive state is a state in which an error is more likely to occur than the error active state. Compared with the node 100 in the error active state, the node 100 in the error passive state is provided with restrictions on continuous transmission and error notification. The bus off state is a state in which an error is more likely to occur than in the error passive state, and the node 100 in this state is prohibited from performing all transmission and reception operations and cannot participate in communication on the CAN bus 90.

  The above three error state transitions are made based on the count values of the transmission error counter and the reception error counter. When the count value TEC of the transmission error counter and the count value REC of the reception error counter are both 0 to 127, the node 100 is in an error active state, and when either TEC or REC is 128 to 255, The node 100 enters an error passive state. Regardless of the REC, when the TEC becomes 256 or more, the node 100 is in a bus-off state and is disconnected from the communication on the CAN bus 90.

  In this way, the CAN specifies the error state according to the degree to which an error is likely to occur, and adds a restriction according to the error state to the transmission / reception operation of the node 90, thereby enabling communication of the node 90 that is likely to cause an error. Avoid interference.

  The retransmission request transmission control unit 9 transmits retransmission request frame transmission data 47 serving as data of a retransmission request frame to the bit stream control unit 2 in response to the output of the retransmission request trigger signal 46 from the error management unit 8. As a result, the retransmission request frame is transmitted to the other nodes 100 by the bit stream control unit 2 as will be described later.

  The CPU 21 controls the devices included in the node 100 by outputting control instruction data that instructs the other peripheral modules 22 to control the devices included in the node 100 via the local bus 23. Specifically, the CPU 21 acquires a reception frame received from another node 100 from the reception buffer of the message buffer memory 4 via the local bus 23. The CPU 21 controls devices included in the node 100 based on the content of the received frame received from the other node 100. Further, the CPU 21 generates a transmission frame to be transmitted to another node 100 and stores it in the transmission buffer of the message buffer memory 4 via the local bus 23.

  The other peripheral module 22 controls the devices included in the node 100 based on the control instruction data output from the CPU 11. For example, when the node 100 is a body node 101 that controls a mirror as a device, the other peripheral module 22 corresponds to an actuator that drives the mirror.

  The bus transceiver 20 transmits the transmission frame output from the bit stream control unit 2 via the transmission signal line 30 to another node 100 via the CAN bus 90. The bus transceiver 20 outputs a reception frame received from another node 100 via the CAN bus 90 to the bit stream control unit 2 via the reception signal line 31.

  Next, with reference to FIG. 4, an operation at the time of reception error detection of the node 100 according to Embodiment 1 will be described. FIG. 4 is a flowchart showing an operation when the node 100 according to the first embodiment detects a reception error.

  When receiving the received frame via the bus transceiver 20 (S1), the bit stream control unit 2 determines whether the reception of the received frame has failed (S2). That is, as described above, the bit stream control unit 2 determines whether a reception error such as a CRC error, a stuff error, and a form error has occurred based on the received frame.

  If it is determined that reception of the received frame has failed (S2: Yes), the bit stream control unit 2 outputs an error occurrence signal 45 to the error management unit 8. In response to the output of the error occurrence signal 45 from the bitstream control unit 2, the error management unit 8 determines whether or not the state of the own node 100 is the “error passive state” (S3). When determining that the state of the own node 100 is the “error passive state” (S3: Yes), the error management unit 8 outputs a retransmission request trigger signal 46 to the retransmission request transmission control unit 9.

  The retransmission request transmission control unit 9 captures the frame counter value 43 output from the frame counter 5 in response to the output of the retransmission request trigger signal 46 from the error management unit 8 (S4), and stores the retransmission request frame transmission data 47. Transmit to the bitstream control unit 2. The retransmission request frame transmission data 47 includes a retransmission request frame ID. Note that the capture of the frame counter value 43 is performed at the timing when the frame counter 110 has finished counting up due to reception of a received frame that has failed to be received. For example, the bit stream control unit 2 may output the error occurrence signal 45 after outputting the end-of-frame signal 42.

  The bit stream control unit 2 generates a retransmission request frame according to the output of the retransmission request frame transmission data 47 from the retransmission request transmission control unit 9. In this retransmission request frame ID, the ID of the retransmission request included in the retransmission request frame transmission data 47 is set. The bit stream control unit 2 starts transmission via the bus transceiver 20 using the generated retransmission request frame as a transmission frame (S5).

  If the retransmission request frame can be transmitted without losing the contention (S6: Yes), the bit stream control unit 2 outputs a retransmission request frame transmission start signal 48 to the retransmission request transmission control unit 9. In this case, the “arbitration loss” in the so-called CAN protocol does not occur, the transmission of the arbitration field in which the ID of the retransmission request frame is set is completed, and the transmission of the retransmission request frame is continued. The retransmission request frame transmission start signal 48 is a signal notifying that transmission of the retransmission request frame is started without losing the competition.

  If the retransmission request frame loses the contention and the ID portion is not transmitted (S6: No), the retransmission request is again made after the reception of the received frame from the other node 100 that won the contention is completed. Frame transmission is started (S5).

  In response to the output of the retransmission request frame transmission start signal 48 from the bit stream control unit 2, the retransmission request transmission control unit 9 calculates a difference value between the current frame counter value 18 and the frame counter value 18 captured in step S4. Is calculated. This difference value is a value obtained by subtracting the captured frame counter value 18 from the current frame counter value 18. The retransmission request transmission control unit 9 additionally outputs the calculated difference value to the bit stream control unit 2 as retransmission request frame transmission data 47. The bit stream control unit 2 transmits the difference value of the retransmission request frame transmission data 47 output from the retransmission request transmission control unit 9 as data of the retransmission request frame via the bus transceiver 20 (S7). That is, the difference value is set, for example, in the data field of the retransmission request frame. As described above, the bit stream control unit 2 generates the bit stream of the retransmission request frame from the ID and the difference value sequentially transmitted from the retransmission request transmission control unit 9 and transmits them.

  Next, with reference to FIG. 5, the operation of node 100 according to Embodiment 1 when receiving a retransmission request frame will be described. FIG. 5 is a flowchart showing an operation when the node 100 according to Embodiment 1 receives a retransmission request frame.

  When the bit stream control unit 2 receives a reception frame via the bus transceiver 20 (S11), the bit stream control unit 2 outputs the reception frame 41 to the message handler 3. The message handler 3 determines whether or not the received frame 41 output from the bitstream control unit 2 is a retransmission request frame (S12). Specifically, the message handler 3 determines that the received frame 41 is a retransmission request frame when the ID of the received frame 41 is the ID of a retransmission request frame.

  When the reception frame 41 is a retransmission request frame (S12: Yes), the retransmission request reception signal 49 and the retransmission request frame difference value 50 are output to the transmission record control unit 6. The retransmission request reception signal 49 is a signal notifying that a retransmission request frame has been received. The retransmission request frame difference value 50 is a difference value included in the retransmission request frame.

  In response to the output of the retransmission request reception signal 49 from the message handler 3, the transmission record control unit 6 determines the retransmission request frame difference output from the message handler 3 from the frame counter value 43 before counting up due to reception of the retransmission request frame. A value obtained by subtracting the value 50 is calculated (S13). The transmission record control unit 6 searches for a value obtained by subtracting the retransmission request frame difference value 50 from the frame counter value 43 from the frame counter value stored in the transmission record FIFO 7 (S14).

  When the retrieved value is stored as a frame counter value in the transmission record FIFO 7 (S14: Yes), the transmission record control unit 6 determines whether or not the transmission enable bit associated with the frame counter value is “1”. Is determined (S15). When the transmission enable bit is “1” (S15: Yes), the transmission record control unit 6 reads the transmission frame associated with the frame counter value and the transmission enable bit from the transmission record FIFO 7 (S16). The transmission record control unit 6 outputs the read transmission frame as a retransmission frame 51 to the message handler 3. At the same time, the transmission record control unit 6 outputs a command meaning “transmission of retransmission frame” to the message handler 3 as the retransmission frame search result signal 52.

  The message handler 3 outputs the retransmission frame 51 output from the transmission recording control unit 6 to the bit stream control unit 2 as the transmission frame 40 in response to the output of those data from the transmission recording control unit 6. In this case, the message handler 3 delays transmission of transmission data stored in the transmission buffer of the message buffer memory 4. Then, the bit stream control unit 2 transmits the retransmission frame output from the message handler 3 as the transmission frame 40 via the bus transceiver 20 (S17).

  On the other hand, when the value searched in step S14 is not stored as the frame counter value in the transmission record FIFO 7 (S14: No), or when the transmission enable bit is “0” (S15: No), the transmission record control unit 6 outputs a command meaning “retransmission frame transmission unnecessary” to the message handler 3 as the retransmission frame search result signal 52.

  In response to the output of the retransmission frame search result signal 52 indicating that “retransmission frame transmission is not required” from the transmission record control unit 6, the message handler 3 maintains an idle state for a predetermined fixed period (fixed time). Transmission is suppressed (S18). This enables another node 100 to transmit a retransmission frame. Further, when the message handler 3 receives a received frame during this fixed period, the received frame is a retransmission frame unnecessary for the node 100 itself, and is therefore excluded from being stored in the message buffer memory 4. And avoiding duplicate reception. That is, as this fixed time, for example, a time until transmission of a retransmission frame is completed may be determined.

  If the retransmission request frame is a frame requesting retransmission, it is an active error frame, and if it is a frame that has already been retransmitted triggered by an active error flag or the like of another node 100, it is stored in the transmission record FIFO 7. Since the transmission enable bit of the corresponding frame is set to “0”, retransmission is not performed.

  Next, with reference to FIGS. 6 to 8, an operation at the time of a retransmission request frame contention in the CAN system 1000 according to Embodiment 1 will be described. FIG. 6 is a conceptual diagram showing an operation when the retransmission request frame conflicts in the CAN system 1000 according to the first embodiment. FIG. 7 is a time chart showing an operation at the time of a retransmission request frame contention of the CAN system 1000 according to the first embodiment. FIG. 8 is a time chart showing an operation at the time of simultaneous transmission of a retransmission frame and another transmission frame of the CAN system 1000 according to the first embodiment.

  Hereinafter, a case where nodes A, B, and Z that operate as the node 100 described above exist in the CAN system 1000 will be described. A case will be described in which the node A transmits a transmission frame, but the error passive node Z fails to receive the transmission frame as a reception frame.

  In this case, the node Z starts transmission of a retransmission request frame that requests retransmission of the transmission frame. Here, it is assumed that transmission of a transmission frame having higher importance than the retransmission request frame is started from another Node B at the same timing as the retransmission request frame (T0 in FIG. 7). Here, the transmission frame having a high importance is, for example, an immediacy such as a frame that instructs the chassis node 105 to control the brake or a frame that instructs the safety node 102 to operate the airbag. This corresponds to a frame that requires. An ID (high priority ID) having a higher priority than an ID (low priority ID) of another frame having a lower importance is assigned to the frame having a higher importance. For example, an ID having a higher priority than an ID of a retransmission request frame is assigned to a frame having a high importance.

  According to this, as shown in FIG. 6 and FIG. 7, when a retransmission request frame and a transmission frame having a higher priority compete with each other, the retransmission request frame is arbitrated lost (arbitration loss) based on the CAN specification. Thus, the transmission of the retransmission request frame by the node Z is interrupted, and the transmission frame of the high priority ID is transmitted by the node B. Thus, if a low priority ID is assigned to a retransmission request frame, transmission of a highly important transmission frame assigned a high priority ID is not hindered. Note that if the transmission start timing of the transmission frame by the node B is earlier than the transmission start timing of the retransmission request frame by the node Z, naturally, the transmission of the transmission frame by the node B is performed based on the CAN specification. Is called.

  Then, after the transmission of the transmission frame by the node B, if there is no other contention with a transmission frame having a higher priority, the retransmission request frame is transmitted by the node Z (T1 in FIG. 7). At this time, since the second previous frame is requested to be retransmitted, “1” is set as the difference value set in the retransmission request frame (as described above, the frame recorded in the transmission record FIFO). Is associated with the frame counter value after the count-up by the transmission of the frame, and therefore when the retransmission of the frame transmitted N times before is requested, the difference value is (N−1)). In response to receiving this retransmission request frame, node A retransmits the transmission frame that node Z has failed to receive (T2 in FIG. 7).

  Here, it is assumed that a transmission frame having a higher priority ID is queued in the node B during transmission of the retransmission request frame by the node Z (T1 ′ in FIG. 8). Here, “T1” in FIG. 7 indicates the same time as “T1” in FIG. 8, and “T2” in FIG. 7 indicates the same time as “T2” in FIG. However, in this case, since the node B also receives the retransmission request frame and there is no frame requested by the retransmission request frame in the transmission record FIFO of the node B, the node B responds to the retransmission request frame. It is determined that the retransmission frame is not the subject of transmission. In this case, as described above, the Node B suppresses transmission of a transmission frame for a certain period. Thereby, when the transmission of the retransmission request frame by the node Z is completed, even if the transmission frame having a high priority is held in the node B, the retransmission frame is transmitted from only the node A among the node B and the node A. Therefore, the retransmission of the retransmission frame is performed by the node A (T2 in FIG. 8). Then, after transmission of the retransmission frame by node A is completed, transmission of the transmission frame by node B is performed (T3 in FIG. 8).

  As described above, according to the first embodiment, a retransmission frame is always transmitted after a retransmission request frame regardless of the contention state. That is, according to this, the node Z has failed to receive, and can grasp when the frame requested to be retransmitted is transmitted. Therefore, even when a frame reception error occurs, the node Z can control the apparatus according to the contents of the frame in the original transmission order of the frame.

  Next, the operation will be described with reference to FIG. FIG. 9 is a time chart showing a frame processing operation when a retransmission request occurs in the CAN system 1000 according to the first embodiment. Here, in FIG. 9, the node Z is the body system node 101, and the nodes A and B are nodes that transmit a transmission frame instructing the body system control to the node Z that is the body system node 101. Will be described.

  It is assumed that the node A has transmitted the transmission frame A instructing control of the body device (T10), but the error passive node Z has failed to receive the transmission frame as a reception frame. In this case, the node Z starts transmission of a retransmission request frame requesting retransmission of the transmission frame (T11). Here, it is assumed that transmission of a transmission frame B instructing control of the body apparatus is started from another Node B at the same timing as the retransmission request frame. Here, it is assumed that the ID of the transmission frame whose transmission is started from the node B has a higher priority than the ID of the retransmission request frame whose transmission is started from the node Z.

  In this case, since the retransmission request frame loses arbitration, the node Z interrupts transmission of the retransmission request frame. Then, the transmission frame B is transmitted by the node B. The node Z receives the transmission frame B transmitted from the node B, and stores it in the reception buffer of the message buffer memory 4 as the reception frame B. At this time, the transmission frame B from the node B is received by the node Z, overtaking the transmission frame A from the node A. For this reason, if the transmission frame B from the node B is processed before the transmission frame A from the node A, there is a risk that inconsistency occurs in device control. Therefore, the CPU 21 of the node Z suppresses the processing of the reception frame B stored in the reception buffer of the message buffer memory 4.

  The node Z starts transmission of the retransmission request frame again after the transmission of the transmission frame B by the node B is completed (T12). If there is no other contention with a transmission frame having a higher priority, a retransmission request frame is transmitted. In response to the reception of this retransmission request frame, the node A retransmits the transmission frame A that has failed to be received by the node Z as a retransmission frame (T13). The node Z receives the transmission frame A transmitted from the node A, and stores it in the reception buffer of the message buffer memory 4 as the reception frame A. At this time, even if the transmission frame C having a higher priority than the transmission frame A transmitted from the node A is stored in the transmission buffer of the message buffer memory 4 in the node B, the transmission of the transmission frame C is suppressed. Is done. Therefore, the node Z can determine that the retransmission frame received from the node A after transmission of the retransmission request frame is the transmission frame A that has failed to be received at T10 to T11. That is, the node Z can determine that the retransmission frame received from the node A is the transmission frame A transmitted immediately before the transmission frame B transmitted from the node B.

  Therefore, the CPU 21 of the node Z first processes the received frame A received from the node A among the received frames stored in the message buffer memory 4 (T14), and then processes the received frame B received from the node B. By doing this (T15), it becomes possible to maintain the consistency of device control. For example, the CPU 21 of the node Z controls the apparatus based on the received frame B after controlling the apparatus based on the received frame A. When the node Z is a gateway node, the node Z transfers the received frame A to the target node, and then transfers the received frame B to the target node.

  As described above, in the first embodiment, when the node 100 fails to receive a frame, the error counter 11 exceeds the predetermined threshold, and the node 100 determines that the node 100 is in the error passive state. In such a case, a retransmission request frame for requesting retransmission of the frame is transmitted. Further, the node 100 stores the frame transmitted to the CAN bus 90 in the transmission record FIFO 7, acquires the frame requested to be retransmitted from the retransmission request frame from the transmission record FIFO 7, and retransmits the frame.

  According to this, since the frame 100 is requested to be retransmitted only when the node 100 fails to receive the frame, it is possible to suppress a decrease in bus use efficiency. Also, even in the error passive state where reception error notification is not possible due to the use of CAN, the frame resending is requested when frame reception fails, thus improving fault tolerance. be able to.

  Further, in the first embodiment, in consideration of a case where a retransmission request frame cannot be transmitted immediately after a frame that has failed to be received, the number of frames before the retransmission request frame is indicated in the retransmission request frame. Information (difference value) is embedded. The node 100 that has received the retransmission request frame can identify the frame that has failed to be received based on the information indicating “how many frames ago”. Thus, even when a retransmission request frame cannot be transmitted immediately after a frame that has failed to be received, it is possible to identify and retransmit the frame that has failed to be received.

<Embodiment 2>
Next, the second embodiment will be described. First, the configuration of the CAN system 1000 according to the second embodiment will be described with reference to FIG. FIG. 10 is a configuration diagram of a CAN system 1000 according to the second embodiment. Hereinafter, the description of the same contents as those in Embodiment 1 will be omitted as appropriate.

  The CAN system 1000 further includes a past frame server node 109 as compared with the first embodiment. The past frame server node 109 stores the frame appearing on the CAN bus 90, and retransmits the frame requested for retransmission among the frames stored in response to the retransmission request from each of the nodes 101 to 105. Further, unlike the first embodiment, each of the nodes 101 to 105 does not have a function of retransmitting a frame in response to a retransmission request from a node in an error passive state. Hereinafter, such nodes 101 to 105 are also referred to as “general nodes 108”. That is, in the second embodiment, the past frame server node 109 collects the frame retransmission function according to the retransmission request from the node that failed to receive the frame in the error passive state. However, the general nodes 101 to 105 may naturally have a normal frame retransmission function according to the CAN specification (retransmission request from a node that is not in the error passive state).

  Next, an outline of operation of the CAN system 1000 according to the second embodiment will be described with reference to FIG. FIG. 11 is a configuration diagram for explaining an operation outline of the CAN system 1000 according to the second embodiment.

  Each general node 108 has a frame counter 110. On the other hand, the past frame server node 109 has a frame counter 110 and a past frame recording FIFO 130. In the second embodiment, the past frame recording FIFO 130 is used as a storage for storing the frame appearing on the CAN bus 90 in the past frame server node 109 regardless of the frame transmitted by either the own node 109 or the other node 108. Function.

  The general node 108 and the past frame server node 109 count up the frame counter 110 when transmission or reception of a frame appearing on the CAN bus 90 is completed regardless of which of the own node / other nodes has transmitted. . The past frame server node 109 transmits the received or received frame together with the frame counter value of the frame counter 110 together with the frame counter value of the frame counter 110 at the timing when the transmission of the frame of the general node 108 has been completed and the frame counter 110 has finished counting up. To store.

  Each of the general nodes 108 transmits a retransmission request frame requesting retransmission of the frame when a reception error of the frame occurs when the own node is in the error passive state. The retransmission request frame includes information that can specify the frame counter value of the frame counter 110 at the time of transmission of the retransmission request target frame based on the frame counter value of the frame counter 110 at that time.

  When the past frame server node 109 receives a retransmission request frame, a retransmission is requested from the frames stored in the past frame recording FIFO 130 based on the frame counter value specified by the information of the retransmission request frame. Identify the frame and retransmit the frame. Each general node 108, when receiving a retransmission request frame from another node 108, suppresses transmission of the frame from its own frame for a predetermined time and retransmits the frame. The right to use the bus is transferred to 109.

  Next, the configuration of the general node 108 according to the second embodiment will be described with reference to FIG. FIG. 12 is a configuration diagram of the general node 108 according to the second embodiment.

  The general node 108 according to the second embodiment does not include the transmission record control unit 6 and the transmission record FIFO 7 as compared with the node 100 according to the first embodiment.

  Since the second embodiment does not include the transmission record control unit 6 and the transmission record FIFO 7, in the first embodiment, the message handler 3 determines whether or not to suppress transmission of a transmission frame for a certain period. The determined retransmission frame search result signal 52 does not exist. Therefore, in the second embodiment, the message handler 3 maintains an idle state for a certain period according to the output of the retransmission request frame from the bitstream control unit 2 due to the reception of the retransmission request frame, and transmits Transmission of the frame 40 is suppressed.

  The operation at the time of detection of a reception error is the same as the operation at the time of detection of a reception error according to Embodiment 1 described with reference to FIG.

  Next, the configuration of the past frame server node 109 according to the second embodiment will be described with reference to FIG. FIG. 13 is a configuration diagram of the past frame server node 109 according to the second embodiment.

  The past frame server node 109 has a past frame recording control unit 12 instead of the transmission recording control unit 6 and a past frame recording FIFO 13 instead of the transmission recording FIFO 7 as compared with the node 100 according to the first embodiment. . Further, the past frame server node 109 abolishes the transmission completion signal 44 that was the operation trigger of the transmission record control unit 6 as compared with the node 100 according to the first embodiment, and instead of the end of frame signal 42, It is also output to the past frame recording control unit 12 as an operation trigger. The bit stream control unit 2 also outputs the received frame 41 received via the bus transceiver 20 to the past frame recording control unit 12.

  Then, the past frame recording control unit 12 executes the operation performed by the transmission recording control unit 6 according to the output of the transmission completion signal 44 according to the output of the end-of-frame signal 42. However, the frame to be stored in the past frame recording FIFO by the past frame recording control unit 12 is not only the transmission frame 40 but also the reception frame 41. As a result, not only the transmission frame 40 transmitted by the own node 109 but also the reception frame 41 received from the other node 108 is recorded in the past frame recording FIFO 13.

  Here, in order to store the frame counter value 43 after being incremented according to the transmission or reception of the frame and the frame in association with each other, the past frame recording control unit 12 stores the frame counter value 43 in the past frame recording FIFO 13. The output end-of-frame signal 42 is delayed from the end-of-frame signal 42 output to the frame counter 5 by the first order. In addition, among the transmission frame 40 and the reception frame 41, the last frame output to the past frame recording control unit 12 is stored in the past frame recording FIFO 13, so that the frame transmitted or received at that time is stored. To be.

  As described above, the past frame recording FIFO 13 stores not only the transmission frame 40 transmitted by the own node 109 but also the reception frame 41 transmitted by the other node 108 as compared with the transmission recording FIFO 7 according to the first embodiment. . The past frame recording FIFO 13 corresponds to the past frame recording FIFO 130.

  Note that the operation when the retransmission request frame is received by the past frame server node 109 according to the second embodiment is basically the operation when the retransmission request frame is received by the node 100 according to the first embodiment described with reference to FIG. Since this is the same, the description thereof is omitted. However, in the second embodiment, only the past frame server node 109 retransmits the retransmission frame in response to the retransmission request frame. Therefore, in order to prevent contention during retransmission frame transmission in the first embodiment, it is not necessary for the past frame server node 109 to execute the suppression of transmission frames for a certain period of time performed in step S18.

  As described above, in the second embodiment, when the general node 108 fails to receive a frame, the error counter 11 exceeds a predetermined threshold, and the own node 108 is in the error passive state. If it is determined, a retransmission request frame requesting retransmission of the frame is transmitted. Further, the past frame server node 109 stores the frame transmitted to the CAN bus 90 in the past frame recording FIFO 13 and acquires the frame requested to be retransmitted by the retransmission request frame from the past frame recording FIFO 13 and retransmits it. I am doing so.

  According to this, since the retransmission of the frame is requested only when the general node 108 fails to receive the frame, it is possible to suppress a decrease in bus use efficiency. Also, even in the error passive state where reception error notification is not possible due to the use of CAN, the frame resending is requested when frame reception fails, thus improving fault tolerance. be able to.

  In the second embodiment, since the general node 108 does not need to include the transmission record FIFO 7, the cost can be reduced accordingly.

<Embodiment 3>
Subsequently, Embodiment 3 will be described. First, contents to be solved in the third embodiment will be described with reference to FIG.

  In Embodiment 1 described above, as described with reference to FIG. 8, when each of the nodes 100 receives a retransmission request frame, if the own node 100 is not a transmission subject of the retransmission frame, the transmission is performed for a certain period of time. Frame transmission is suppressed. Also, this allows the node 100 that has transmitted the retransmission request frame to identify the frame transmitted next to the retransmission request frame as a retransmission frame, and can process the frame according to the transmission order.

  However, in this case, as shown in FIG. 8, when transmission of a retransmission frame and another transmission frame is started at the same time, even if the ID of the other transmission frame is a high priority ID, the transmission is not performed. Will be deterred. Therefore, there is a problem that processing of a transmission frame that requires immediacy is delayed.

  In the following, the third embodiment describes a technique that can specify a retransmission frame while guaranteeing immediacy of processing of a high priority frame in order to solve such a problem.

  The configuration of CAN system 1000 according to Embodiment 3 is the same as that of CAN system 1000 according to Embodiment 1 described with reference to FIG. The operation overview of the CAN system 1000 according to the third embodiment is the same as the operation overview of the CAN system 1000 according to the first embodiment described with reference to FIG.

  Here, the configuration of the node 100 according to the third embodiment is the same as the configuration of the node 100 according to the first embodiment described with reference to FIG. 3, but the operation is different in the following points. Other explanations of the same contents as those in Embodiment 1 are omitted as appropriate.

  In the third embodiment, the message handler 3 does not perform transmission frame transmission suppression for a certain period of time even when the own node is not the node that retransmits the retransmission frame. That is, when the retransmission record search result signal 52 indicating that “retransmission frame transmission is not required” is output from the transmission record control unit 6, the message handler 3 does not transmit the retransmission frame, but does not suppress transmission for a certain period.

  In Embodiment 3, when the transmission frame 40 is a retransmission frame, the bit stream control unit 2 delays the time for one bit and starts transmission of the transmission frame (retransmission frame). According to this, when transmission of a retransmission frame and another transmission frame is started, transmission of another transmission frame is always started earlier than the retransmission frame. For this reason, other transmission frames are preferentially transmitted on the CAN bus 90 over the retransmission frame, and therefore transmission of a transmission frame with a high priority ID is suppressed when the retransmission frame is transmitted. Disappears. In addition, since the node that has transmitted the retransmission request frame can identify the transmission frame transmitted with a delay of one bit as the retransmission frame, it is possible to process the frame according to the transmission order.

  Next, with reference to FIG. 14, it is a time chart showing an operation at the time of simultaneous transmission of a retransmission frame and another transmission frame of the CAN system 1000 according to the third embodiment. FIG. 14 is a time chart showing an operation at the time of simultaneous transmission of a retransmission frame and another transmission frame of the CAN system 1000 according to the third embodiment.

  Hereinafter, as in FIG. 8, a case where nodes A, B, and Z that operate as the above-described node 100 exist in the CAN system 1000 will be described. A case will be described in which the node A transmits a transmission frame, but the error passive node Z fails to receive the transmission frame as a reception frame.

  As in FIG. 8, it is assumed that a transmission frame with a higher priority ID is queued in the node B during transmission of the retransmission request frame by the node Z (T1 ′ in FIG. 14). In this case, the node B also receives the retransmission request frame, but in the third embodiment, the transmission of the transmission frame by the node B is not suppressed. In addition, the node A starts transmission of a retransmission frame corresponding to the retransmission request frame from the node Z from a timing delayed by one bit from the timing (T2) when the transmission frame can be transmitted next (T2) ( T2 ′).

  Therefore, a transmission frame from Node B that has started transmission is transmitted, and a retransmission frame from Node A is not transmitted. Then, after the transmission of the transmission frame from the node B is completed, if there is no transmission of a transmission frame from another node at the timing (T3) when the transmission frame can be transmitted next, a time delay of 1 bit from that timing At this timing, a retransmission frame is transmitted by the node A (T3 ′).

  As described above, in the third embodiment, transmission of transmission frames is not suppressed even when the node 100 is not a retransmission frame transmission subject. In addition, the node 100 that has received the retransmission request is configured to start transmitting the retransmission frame at a timing delayed by one bit. Therefore, when a transmission frame is queued by a node that is not a retransmission frame transmission subject until the retransmission frame is transmitted, the transmission frame can be preferentially transmitted.

  Therefore, processing of a transmission frame that requires immediacy, such as a frame to which a high priority ID is assigned, is not delayed. The retransmission frame is transmitted at a timing delayed by 1 bit from the timing at which the transmission frame can be transmitted. According to this, the node Z fails to receive and can grasp when the frame for which retransmission is requested is transmitted. That is, it is possible to specify a transmission frame whose transmission is started at a timing delayed by 1 bit from the timing at which the transmission frame can be transmitted as a retransmission frame. Therefore, even when a frame reception error occurs, the node Z can control the apparatus according to the contents of the frame in the original transmission order of the frame.

  Next, the operation will be described with reference to FIG. FIG. 15 is a time chart showing a frame processing operation when a retransmission request occurs in the CAN system 1000 according to the third embodiment. Here, in FIG. 15, node Z is body system node 101, and nodes A and B are nodes that transmit a transmission frame instructing body system control to node Z that is body system node 101. Will be described. Node B also transmits a transmission frame to nodes other than body node 101 (node Z).

  The node A transmits the transmission frame A instructing the control of the body device, but the description starts from the point in time when the node Z in the error passive state fails to receive the transmission frame A. In this case, the node Z starts transmission of a retransmission request frame requesting retransmission of the transmission frame A (T20). Here, it is assumed that transmission of a transmission frame B instructing control of the body apparatus is started from another Node B at the same timing as the retransmission request frame. Here, it is assumed that the ID of the transmission frame transmitted from the node B has a higher priority than the ID of the retransmission request frame transmitted from the node Z.

  In this case, since the retransmission request frame loses arbitration, the node Z interrupts transmission of the retransmission request frame. Then, the transmission frame is transmitted by the node B. The node Z receives the transmission frame B transmitted from the node B, and stores it in the reception buffer of the message buffer memory 4 as the reception frame B. At this time, the transmission frame B from the node B is received by the node Z, overtaking the transmission frame A from the node A. For this reason, if the transmission frame B from the node B is processed before the transmission frame A from the node A, there is a risk that inconsistency occurs in device control. Therefore, the CPU 21 of the node Z suppresses the processing of the reception frame B stored in the reception buffer of the message buffer memory 4.

  Here, it is assumed that a high-priority transmission frame C intended for transmission to a node other than the body system is stored in the transmission buffer of the message buffer memory 4 in the node B during transmission of the retransmission request frame. In this case, the Node B transmits the transmission frame C after completing the transmission of the retransmission request frame (T22). Further, in response to reception of the retransmission request frame, the node A tries to start transmission of the retransmission frame at a timing delayed by one bit from the timing (T22). However, since transmission of the transmission frame C from the node B has been started first, the retransmission frame is not transmitted (T22 ′). The node Z receives the transmission frame C transmitted from the node B, and stores it in the reception buffer of the message buffer memory 4 as the reception frame C. However, the CPU 21 of the node Z determines that the ID of the reception frame C is not a body transmission frame, discards the reception frame C, and does not execute the process.

  Then, the node A transmits a retransmission frame (T23 ′) if there is no transmission from another frame at the timing (T23) after the transmission of the transmission frame C is completed. The node Z receives a transmission frame A that is a retransmission frame transmitted from the node A, and stores it as a reception frame A in the reception buffer of the message buffer memory 4. At this time, the node Z transmits that the retransmission frame transmitted at the timing (T23 ′) delayed by one bit from the timing at which the transmission frame can be transmitted (T23) failed to be received before T20. It can be determined that it is frame A. That is, the node Z can determine that the transmission frame A received from T23 ′ delayed by 1 bit is the transmission frame A that failed to be received before T20.

  Therefore, the CPU 21 of the node Z first processes the reception frame A received from the node A among the transmission frames stored in the message buffer memory 4 (T24), and then processes the reception frame B received from the node B. By doing so (T25), it becomes possible to maintain consistency of device control.

  In the third embodiment, the case where the technology is applied to the node 100 according to the first embodiment has been described. However, the technique may be applied to the past frame server node 109 according to the second embodiment. That is, as the third embodiment, the embodiment in which the operations of the bitstream control unit 2 and the message handler 3 of the node 100 according to the first embodiment are changed is illustrated, but the past frame server node 109 according to the second embodiment is illustrated. This can also be implemented by changing the operations of the bit stream control unit 2 and the message handler 3 in the same manner.

  As described above, in the third embodiment, the node 100 transmits a frame requested to be retransmitted by a retransmission request frame after a predetermined delay time has elapsed since the frame can be transmitted after the retransmission request frame is received. To resend. According to this, the node 100 that has requested retransmission can identify the retransmission frame and maintain the consistency of device control.

<Other embodiments>
In Embodiments 1 to 3 described above, the difference value of the frame counter value of the frame counter 5 is included in the data field of the retransmission request frame so that the retransmission target frame can be identified at the node that has received the retransmission request frame. However, it is not limited to this. The difference value of the frame counter value may be indicated by the ID of the retransmission request frame. The ID of the retransmission request frame may be arbitrarily determined in advance according to each value that can be taken by the difference value of the frame counter value. For example, when the difference value of the frame counter value is “1”, the ID may be “1F”, and when the difference value of the frame counter value is “2”, the ID may be “2F”. .

  According to this, the length of the retransmission request frame can be shortened as much as possible by omitting the data field of the retransmission request frame. Therefore, the amount of data that can be transmitted and received on the CAN bus 90 can be reduced, and the communication efficiency on the CAN bus 90 can be improved.

<Outline configuration of the embodiment>
The above embodiment can be understood as a schematic configuration described below. A schematic configuration of the embodiment will be described with reference to FIG. FIG. 16 is a configuration diagram of a CAN system 900 that is a schematic configuration of the CAN system 1000 according to the embodiment.

  The CAN system 900 includes a first node 91 and a second node 92. The first node 91 and the second node 92 exchange frames with each other via the CAN bus.

  The first node 91 includes an error counter 911, an error management unit 912, and a retransmission request unit 913 based on the CAN specification. The error counter 911 corresponds to the error counter 11.

  When the error management unit 912 fails to receive a frame via the CAN bus 90, the error management unit 912 determines whether or not the error counter 11 exceeds a predetermined threshold and the own node is in an error passive state. The error management unit 912 corresponds to the error management unit 8.

  If the error management unit 912 determines that the node is in the error passive state when the error management unit 912 fails to receive a frame, the retransmission request unit 913 transmits a retransmission request frame requesting retransmission of the frame. The retransmission request unit 913 corresponds to the retransmission request transmission control unit 9.

  The second node 92 includes a storage unit 921, a recording control unit 922, and a retransmission control unit 923.

  The storage unit 921 stores frames. The storage unit 921 corresponds to the transmission recording FIFO 7 and the past frame recording FIFO 13.

  The recording control unit 922 stores the frame transmitted to the CAN bus 90 in the storage unit 921. The recording control unit 922 corresponds to the transmission recording control unit 6 and the past frame recording control unit 12.

  The retransmission control unit 923 acquires from the storage unit 921 a frame requested to be retransmitted by the retransmission request frame transmitted from the first node 91 and retransmits the frame to the first node 91. The retransmission control unit 923 corresponds to the message handler 3.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the embodiments already described, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

  In the present embodiment, the case where the difference value of the frame counter value of the frame counter 5 is used as the information that can identify the frame to be retransmitted in the retransmission request frame has been illustrated, but based on the frame counter value of the frame counter 5 Thus, the information is not limited to this as long as it can identify the frame to be retransmitted. For example, the frame counter value 43 of the frame counter 5 when a reception error occurs may be included as it is in the retransmission request frame as information that makes it possible to specify the frame to be retransmitted. In this case, the calculation in step S13 is not necessary. Further, the transmission recording control unit 6 or the past frame recording control unit 12 acquires the frame counter value included in the retransmission request frame from the message handler 3 in step S14, and obtains the frame counter value from the transmission recording FIFO 7 or the past frame recording FIFO 13. Search should be done.

  In this embodiment, it is possible to identify a transmission frame to be retransmitted by managing a transmission frame and a frame counter value of the frame counter 5 after counting up by completion of transmission of the transmission frame. It is not limited to this. For example, the transmission frame and the frame counter value of the frame counter 5 before counting up due to the completion of transmission of the transmission frame may be associated and managed. In this case, in step S4, it is necessary to capture the frame counter value 43 before the frame counter 110 counts up due to reception of a received frame that has failed to be received.

  In the third embodiment, the delay time for starting transmission of the retransmission frame is set to one bit, but is not limited to this time. An arbitrary time may be determined in advance as a delay time for starting transmission of the retransmission frame. For example, the bit stream control unit 2 may transmit the retransmission frame with a time delay of 2 bits.

  The nodes 100, 108, and 109 according to the embodiment of the present invention can be executed by a node (computer) or a CPU (Central Processing Unit) included in the node executing a program that realizes the functions of the above-described embodiments. It is possible to configure.

  Further, the above-described program can be stored using various types of non-transitory computer readable media and supplied to a computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  A part or all of the above embodiments can be described as in the following supplementary notes.

(Supplementary note 1) A CAN communication method for transmitting and receiving frames to and from each other via a CAN (Controller Area Network) bus between a plurality of nodes including a first node and a second node,
The second node stores a frame transmitted to the CAN bus in a storage unit;
When the first node fails to receive a frame via the CAN bus, the count value of an error counter that counts the number of frame transmission / reception errors for the CAN bus exceeds a predetermined threshold. , Determine whether the node is in an error passive state,
When the first node determines that its own node is in an error passive state when it fails to receive the frame, it transmits a retransmission request frame requesting retransmission of the frame,
The second node acquires a frame requested to be retransmitted by the retransmission request frame transmitted from the first node from the storage unit and retransmits the frame to the first node;
CAN communication method.

(Supplementary Note 2) A control program for controlling a node that transmits and receives a frame to and from a plurality of nodes via a CAN (Controller Area Network) bus,
A process of storing a frame transmitted to the CAN bus in a storage unit;
In response to reception of a retransmission request frame to be transmitted when another node fails to receive a frame via the CAN bus and is in an error passive state, a frame requested to be retransmitted in the retransmission request frame is stored in the memory A process of acquiring from the network and resending to the other node;
A control program that causes nodes to execute.

(Supplementary Note 3) A control program for controlling a node that mutually transmits and receives frames to and from a plurality of nodes via a CAN (Controller Area Network) bus,
When reception of a frame through the CAN bus fails, the count value of an error counter that counts the number of frame transmission / reception errors with respect to the CAN bus exceeds a predetermined threshold value, and the own node is in an error passive state. Processing to determine whether or not,
When it is determined that the current node is in an error passive state when reception of the frame fails, retransmission for requesting retransmission of the frame to another node holding the frame transmitted to the CAN bus Processing to send a request frame;
A control program that causes nodes to execute.

DESCRIPTION OF SYMBOLS 1 CAN controller module 2 Bit stream control part 3 Error management part 4 Retransmission request transmission control part 5 Message handler 6 Message buffer memory 7, 110 Frame counter 8 Transmission recording control part 9, 120 Transmission recording FIFO
10 CAN controller LSI
11 Error counter 12 Past frame recording control unit 13, 130 Past frame recording FIFO
20 Bus transceiver 21 CPU
22 Other peripheral module 23 Local bus 30 Transmission signal line 31 Reception signal line 40 Transmission frame 41 Reception frame 42 End-of-frame signal 43 Frame counter value 44 Transmission completion signal 45 Error occurrence signal 46 Retransmission request trigger signal 47 Retransmission request frame transmission data 48 Retransmission Request frame transmission start signal 49 Retransmission request reception signal 50 Retransmission request frame difference value 51 Retransmission frame 52 Retransmission frame search result signal 90 CAN bus 91 First node 92 Second node 100 Node 101 Body node 102 Safety node 103 Information System node 104 Engine system node 105 Chassis system node 108 General node 109 Past frame server node 911 Error counter 912 Error management unit 913 Retransmission request unit 921 Storage unit 922 Recording control unit 923 Retransmission control unit 1000 CAN system

Claims (12)

A CAN system comprising a plurality of nodes including a first node and a second node that transmit and receive frames to and from each other via a CAN (Controller Area Network) bus,
The first node is:
An error counter for counting the number of frame transmission / reception errors for the CAN bus of the own node;
An error management unit that determines whether or not the count value of the error counter exceeds a predetermined threshold and the own node is in an error passive state when frame reception via the CAN bus fails;
When the error management unit determines that the current node is in an error passive state when reception of the frame fails, it has a retransmission request unit that transmits a retransmission request frame requesting retransmission of the frame,
The second node is
A storage unit for storing the frame;
A recording control unit for storing a frame transmitted to the CAN bus in the storage unit;
A retransmission control unit that obtains, from the storage unit, a frame requested to be retransmitted by the retransmission request frame transmitted from the first node, and retransmits the frame to the first node.
CAN system. Each of the plurality of nodes includes the error counter, the error management unit, the retransmission request unit, the storage unit, the recording control unit, and the retransmission control unit, and the first node and the second control unit Acts as a node,
The recording control unit stores, in the storage unit, a frame transmitted from the node to the CAN bus,
The retransmission control unit, when a frame requested to be retransmitted in the retransmission request frame is stored in the storage unit, retransmits the frame to the first node;
The CAN system according to claim 1. The retransmission control unit suppresses frame transmission for a predetermined transmission suppression time when a frame requested to be retransmitted in the retransmission request frame is not stored in the storage unit.
The CAN system according to claim 2. The retransmission control unit retransmits a frame for which retransmission is requested in the retransmission request frame after a predetermined delay time has elapsed since the frame can be transmitted after receiving the retransmission request frame.
The CAN system according to claim 2. The plurality of nodes include a plurality of the first nodes;
The recording control unit stores the frame transmitted from the first node to the CAN bus in the storage unit;
The retransmission control unit retransmits the frame requested to be retransmitted in the retransmission request frame to the first node that transmitted the retransmission request frame, instead of the first node that transmitted the frame.
The CAN system according to claim 1. The first node further includes a transmission control unit that transmits the frame;
The transmission control unit suppresses transmission of a frame for a predetermined transmission suppression time when the retransmission request frame is transmitted from another first node.
The CAN system according to claim 5. The retransmission control unit retransmits a frame for which retransmission is requested in the retransmission request frame after a predetermined delay time has elapsed since the frame can be transmitted after receiving the retransmission request frame.
The CAN system according to claim 5. Each of the first node and the second node further includes a frame counter that counts the number of frames transmitted or received by the own node;
The recording control unit stores the frame transmitted to the CAN bus in the storage unit in association with the counter value of the frame counter;
The retransmission request unit generates specific information for specifying a frame for which retransmission is requested based on a counter value of the frame counter, includes the generated specific information in the retransmission request frame, and transmits the specific information.
The retransmission control unit specifies a frame requested to be retransmitted in the retransmission request frame from the frames stored in the storage unit, based on identification information included in the retransmission request frame.
The CAN system according to claim 1. The specific information is a difference value between a counter value of the frame counter when the retransmission request frame is transmitted and a counter value of the frame counter when the frame that has failed to be received is transmitted,
The retransmission control unit calculates a counter value of the frame counter when a frame that has failed to be received is transmitted based on a counter value of the frame counter and a difference value included in the retransmission request frame. Identify the frame associated with the counter value as the frame requested for retransmission in the retransmission request frame,
The CAN system according to claim 8. The specific information is included in the retransmission request frame as an ID of the retransmission request frame.
The CAN system according to claim 8. A node that transmits and receives frames to and from a plurality of nodes via a CAN (Controller Area Network) bus.
A storage unit for storing the frame;
A recording control unit for storing a frame transmitted to the CAN bus in the storage unit;
In response to reception of a retransmission request frame to be transmitted when another node fails to receive a frame via the CAN bus and is in an error passive state, a frame requested to be retransmitted in the retransmission request frame is stored in the memory A retransmission control unit that obtains from the unit and retransmits to the other node;
A node with A node that transmits and receives frames to and from a plurality of nodes via a CAN (Controller Area Network) bus.
An error counter for counting the number of frame transmission / reception errors for the CAN bus of the own node;
An error management unit that determines whether or not the count value of the error counter exceeds a predetermined threshold and the own node is in an error passive state when frame reception via the CAN bus fails;
If the error management unit determines that the node is in an error passive state when reception of the frame fails, the frame is transmitted to another node that holds the frame transmitted to the CAN bus. A retransmission request unit that transmits a retransmission request frame for requesting retransmission of
A node with

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