Communication device and communication system

Abstract

A communication device transmits data via a communication bus. The communication device has a processing section that performs processing. The processing section is configured to, in a case where a beacon signal is transmitted, determine whether an object communication device has transmitted data, for one of data transmitted via the communication bus in a predetermined order for the communication device itself and a plurality of second communication devices, by the object communication device transmitting the one data; change the order in a case where it is determined that the object communication device has not transmitted data; and the data transmitted via the communication bus includes pseudo data whose transmission destination is different from the communication device other than the transmission source among the communication device itself and the plurality of second communication devices.

Description

Technical Field

[0001] This disclosure relates to a communication device and a communication system.

[0002] This application claims priority based on Japanese Application No. 2021-078008, filed on April 30, 2021, and invokes all the contents of that Japanese application. Background Technology

[0003] Patent document 1 discloses a communication system in which multiple communication devices are connected to a communication bus. This communication system is mounted on a vehicle. Each communication device transmits data to other communication devices via the communication bus.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent document 1: Japanese Patent Application Publication No. 2016-213653. Summary of the Invention

[0007] One aspect of this disclosure relates to a communication device that transmits data via a communication bus. The communication device includes a processing unit that performs processing. The processing unit is configured to, when a beacon signal is transmitted, determine, at a predetermined time when a target communication device included in the plurality of second communication devices transmits the data via the communication bus, whether the target communication device has transmitted data. If it is determined that the target communication device has not transmitted data, the order is changed. The data transmitted via the communication bus includes pseudo-data whose destination is different from that of the communication device itself and the plurality of second communication devices except for the sending source.

[0008] One aspect of the communication system disclosed herein includes multiple communication devices connected to a communication bus. When a beacon signal is transmitted, the multiple communication devices transmit data via the communication bus in a predetermined order. If a target communication device among the multiple communication devices does not have data to be transmitted to any of the other communication devices, it transmits pseudo-data with a destination different from the other communication devices. The communication device different from the target communication device has a processing unit that performs processing. The processing unit determines whether the target communication device has transmitted data at a specific time interval when the target communication device transmits data, and changes the order if it determines that the target communication device has not transmitted data.

[0009] Furthermore, this disclosure can be implemented not only as a communication device having such a characteristic processing unit, but also as a communication method that sets the aforementioned characteristic processing as steps, or as a computer program for causing a computer to execute the aforementioned steps. Additionally, this disclosure can be implemented as a semiconductor integrated circuit that implements part or all of the communication device, or as a communication system that includes the communication device. Attached Figure Description

[0010] Figure 1 This is a block diagram showing the main structural components of the communication system in Embodiment 1.

[0011] Figure 2 This is an illustration of the data frame transmission method.

[0012] Figure 3 It is a diagram showing the ID, function, and transmission order of the first ECU and (N-1) second ECUs.

[0013] Figure 4 This is a waveform diagram of the beacon signal.

[0014] Figure 5 This is an illustration of the contents of a data frame.

[0015] Figure 6 This is a block diagram showing the main structural components of the first ECU.

[0016] Figure 7 This is a circuit diagram of a bit-based communicator.

[0017] Figure 8 This is a flowchart illustrating the steps involved in preparing to send a frame.

[0018] Figure 9 This is a flowchart illustrating the steps of the transmission process performed by the IC control unit of the first ECU.

[0019] Figure 10 This is a flowchart illustrating the steps of the transmission process performed by the IC control unit of the second ECU.

[0020] Figure 11 This is a flowchart illustrating the steps involved in fault detection and processing.

[0021] Figure 12 This is a flowchart illustrating the steps of the update process.

[0022] Figure 13 This is an explanatory diagram of the update of the order table.

[0023] Figure 14 This is an illustration of the effects of the communication system.

[0024] Figure 15This is a block diagram showing the main structural components of the first ECU in Embodiment 2.

[0025] Figure 16 It is a chart showing the contents of the table during standby.

[0026] Figure 17 This is a flowchart illustrating the steps of the update process.

[0027] Figure 18 This is an illustration of the effects of the communication system.

[0028] Figure 19 This is an explanatory diagram of the features of the communication system in embodiments 1 and 2.

[0029] Figure 20 These are explanatory diagrams illustrating other features of the communication system in embodiments 1 and 2.

[0030] Figure 21 This is an explanatory diagram of the data frame transmission method in Implementation Method 3.

[0031] Figure 22 It is a chart showing the contents of the table during standby.

[0032] Figure 23 This is an explanatory diagram of the data frame transmission method in Implementation Method 4.

[0033] Figure 24 This is a flowchart illustrating the steps involved in fault detection and processing.

[0034] Figure 25 This is a flowchart illustrating the steps of the update process for the second ECU that does not send pseudo-frames. Detailed Implementation

[0035] [The problem this disclosure aims to solve]

[0036] The communication system described in Patent Document 1 does not take into account the detection of communication device malfunctions.

[0037] Therefore, the objective is to provide a communication device and a communication system capable of detecting faults in devices connected to a communication bus.

[0038] [The Effects of This Disclosure]

[0039] According to this disclosure, it is possible to detect faults in the object's communication device.

[0040] [Description of embodiments of this disclosure]

[0041] First, embodiments of this disclosure will be described by way of example. At least some of the embodiments described below may be combined arbitrarily.

[0042] (1) In one aspect of this disclosure, a communication device transmits data via a communication bus. The communication device includes a processing unit that performs processing. The processing unit is configured to, when a beacon signal is transmitted, determine, at a time when a target communication device included in the plurality of second communication devices transmits the data via the communication bus in a predetermined order, whether the target communication device has transmitted the data. If it is determined that the target communication device has not transmitted the data, the order is changed. The data transmitted via the communication bus includes pseudo-data whose destination is different from that of the communication device itself and the plurality of second communication devices except for the sending source.

[0043] In the above method, data transmitted via the communication bus is received by all devices connected to the communication bus. For example, the target communication device must transmit either data to one of the devices connected to the communication bus or pseudo data. Faults are detected by determining whether the target communication device has transmitted data. If it is determined that the target communication device has not transmitted data, the transmission order is changed to the order in which the faulty device has been removed.

[0044] (2) In a communication device according to one aspect of the present disclosure, the processing unit changes the order when it determines that the target communication device has not sent data multiple times in a row.

[0045] In the above method, a fault in the target communication device is detected if it is determined multiple times consecutively that the target communication device has not transmitted data. Therefore, the possibility of erroneously detecting a fault in the target communication device is low.

[0046] (3) One aspect of the communication device disclosed herein includes a signal transmitting unit that repeatedly transmits the beacon signal.

[0047] In the above method, beacon signals are repeatedly transmitted and faults are detected.

[0048] (4) The communication device according to one aspect of the present disclosure includes a data transmission unit that transmits data. The data transmission unit transmits data after a first predetermined period has elapsed since the transmission of the beacon signal ended, or after a second predetermined period has elapsed since the transmission of data by the preceding second communication device ended. The processing unit extends the first predetermined period or the second predetermined period if it determines that the target communication device has not transmitted data.

[0049] In the above method, for example, if a fault is detected in the target communication device, the transmission order is changed to the order in which the faulty device has been removed. If the last device in the sequence finishes transmitting data, a beacon signal is transmitted. If a fault is detected in the target communication device, the first predetermined period or the second predetermined period is extended, thus preventing a decrease in the beacon signal transmission interval.

[0050] (5) A communication system according to one aspect of the present disclosure includes multiple communication devices connected to a communication bus. When a beacon signal is sent, the multiple communication devices send data via the communication bus in a predetermined order. When a target communication device included in the multiple communication devices does not send data to any of the other communication devices, it sends pseudo data whose destination is different from the other communication devices. The communication device different from the target communication device in the multiple communication devices has a processing unit that performs processing. The processing unit determines whether the target communication device has sent data at the time when the target communication device sends data, and changes the order if it determines that the target communication device has not sent data.

[0051] In the above method, data transmitted via the communication bus is received by all devices connected to the communication bus. The target communication device must transmit either data or pseudo-data. Faults are detected by determining whether the target communication device has transmitted data. If a faulty device determines that the target communication device has not transmitted data, it changes the transmission order to the order in which the faulty device's order has been removed.

[0052] (6) In a communication system according to one aspect of the present disclosure, among the plurality of communication devices therein is a non-transmitting device that does not transmit the pseudo data, and the processing unit, when determining that the target communication device has not transmitted data, causes the non-transmitting device to start transmitting the pseudo data.

[0053] In the above method, if a fault is detected in the target communication device, the non-transmitting device begins transmitting pseudo-data. Therefore, it is possible to prevent a decrease in the transmission interval of the beacon signal.

[0054] [Details of the embodiments disclosed herein]

[0055] Hereinafter, specific examples of communication systems according to embodiments of the present disclosure will be described with reference to the accompanying drawings. Furthermore, the present invention is not limited to these examples, but is intended to include all modifications within the meaning and scope of the claims, as indicated by the claims themselves.

[0056] (Implementation Method 1)

[0057] <Structure of Communication Systems>

[0058] Figure 1 This is a block diagram showing the main structural components of the communication system 1 in Embodiment 1. The communication system 1 is mounted on a vehicle M. The communication system 1 includes a first ECU 11 and (N-1) second ECUs 12. ECU is an abbreviation for Electronic Control Unit. N is an integer greater than or equal to 3, representing the number of ECUs in the communication system 1. The first ECU 11 and (N-1) second ECUs 12 are connected to the communication bus B.

[0059] Each of the first ECU 11 and (N-1) second ECUs 12 is connected to electrical equipment and sensors. Illustrations of the electrical equipment and sensors are omitted. The sensors detect vehicle-related values ​​and output these values ​​to either the first ECU 11 or the second ECU 12 connected to them. For example, when the sensor detection values ​​are input, the first ECU 11 and (N-1) second ECUs 12 respectively transmit data frames containing the sensor detection values ​​as main data via communication bus B. The data frames indicate the transmission destination. Furthermore, the main data is not limited to the sensor detection values.

[0060] ECU 11 detects a fault in ECU 12. The fault in ECU 12 is that it stops sending data frames. Upon detecting the fault in ECU 12, ECU 11 sends a data frame containing the main data indicating that ECU 12 has malfunctioned via the communication bus. Hereinafter, the main data indicating that ECU 12 has malfunctioned will be referred to as fault data. The destination of the data frame containing the fault data is the remaining, functioning ECU 12.

[0061] If one of the first ECU 11 and (N-1) second ECUs 12 sends a data frame, both the first ECU 11 and (N-1) second ECUs 12 will receive the data frame. If the destination of the data frame is not this device, the first ECU 11 and (N-1) second ECUs 12 will discard the received data frame.

[0062] When the first ECU 11 receives a data frame, and the destination of the data frame is this device, the first ECU 11 determines the action to be performed by the electrical equipment connected to this device based on the master data contained in the received data frame. When the second ECU 12 receives a data frame whose master data differs from fault data, and the destination of the data frame is this device, the second ECU 12 determines the action to be performed by the electrical equipment connected to this device based on the master data contained in the received data frame.

[0063] Each of the first ECU 11 and (N-1)th second ECUs 12, upon determining the action to be performed by the electrical equipment, outputs an action signal indicating the determined action to the electrical equipment. Once the action signal has been input to the electrical equipment, the electrical equipment performs the action indicated by the input action signal.

[0064] The first ECU 11 notifies the normal second ECU 12 of the malfunction by sending a data frame containing fault data. Upon detecting a fault in the second ECU 12, both the first ECU 11 and the normal second ECU 12 execute predetermined fault-related procedures.

[0065] <Data Frame Transmission Method>

[0066] Figure 2 This is an illustration of the data frame transmission method. Figure 3 This is a diagram showing the IDs, functions, and transmission order of the first ECU11 and (N-1)th second ECU12. ID is an abbreviation for Identification Data. Figure 2 and Figure 3 The example shown is where N is 5.

[0067] The first ECU11 and (N-1) second ECUs12 each send data frames, for example, according to PLCA (Physical Layer Collision Avoidance). Figure 2 As shown, beacon signals are repeatedly transmitted via communication bus B. Upon receiving a beacon signal, five data frames are transmitted via communication bus B. The beacon signal indicates the start of data frame transmission. The beacon signal is transmitted by the ECU acting as the master unit. ECU 11 acts as the master unit, repeatedly transmitting beacon signals via communication bus B. (N-1) ECUs 12 act as slave units.

[0068] When the first ECU 11 sends a beacon signal, the first ECU 11 and (N-1) second ECUs 12 send data frames in a predetermined order. For example... Figure 3 As shown, IDs are pre-assigned to the first ECU11 and (N-1) second ECUs12. Figure 3 In this example, the ID of ECU11 is 001. Each of the four ECUs12 is assigned one of IDs from 002 to 005. Figure 3 In this configuration, the transmission order of 001 to 005 is set from 1 to 5. The host's transmission order is 1.

[0069] When ECU11 sends a beacon signal, ECU11 with ID 001 first sends a data frame. Next, ECU12 with ID 002 sends a data frame. Then, the three ECU12 units corresponding to IDs 003 to 005 send data frames sequentially. When ECU12 with ID 005 finishes sending a data frame, ECU11 sends the beacon signal again.

[0070] ECU 11 remains in standby mode until the standby period elapses from the transmission of the end beacon signal. The standby period is a constant and preset value. After the standby period has elapsed, ECU 11 transmits a data frame. Each ECU 12 remains in standby mode until the standby period elapses from the end of the data frame transmission. After the standby period elapses, each ECU 12 transmits a data frame. The standby period corresponds to both the first predetermined period and the second predetermined period.

[0071] As described above, for example, in PLCA mode, the first ECU11, which acts as the master, and the (N-1) second ECUs12, which act as slave devices, synchronize using beacon signals to avoid data conflicts.

[0072] When N is different from 5, the first ECU11 and (N-1) second ECU12 send data frames in a predetermined order, just as when N is 5.

[0073] <Beacon Signal>

[0074] Figure 4 This is a waveform diagram of the beacon signal. (The diagram is shown in...) Figure 4 The voltage difference and time are shown on the vertical and horizontal axes. Figure 4 The waveform of the beacon signal shown is an example. Communication bus B includes wire 1 W1 and wire 2 W2 (see reference). Figure 7 The first wire W1 and the second wire W2 are twisted together. This creates a twisted pair. The beacon signal consists of multiple bits. The first ECU11 and (N-1)th second ECU12 adjust the voltage difference between the first wire W1 and the second wire W2 on the communication bus B to a high or low level each time a 1-bit period elapses, thereby transmitting the beacon signal. Figure 4 In this context, H and L represent high-level voltage and low-level voltage, respectively.

[0075] The first ECU11 and (N-1) second ECUs12 adjust the voltage difference between the first wire W1 and the second wire W2 of the communication bus B to a high level or a low level each time a 1-bit period elapses, thereby sending a data frame.

[0076] Each bit represents a high-level voltage or a low-level voltage. Figure 4 In the example, the beacon signal consists of 7 bits. It is output alternately with high and low voltage levels. Furthermore, the number of bits constituting the beacon signal is not limited to 7.

[0077] The waveform of the beacon signal is predetermined. When the first ECU 11 transmits the beacon signal via communication bus B, all second ECUs 12 receive the beacon signal. Each second ECU 12 outputs a clock signal consisting of high and low voltage levels. The clock signal periodically rises or falls in voltage. A voltage rise is a switch from low to high voltage, and a voltage fall is a switch from high to low voltage. Upon receiving the beacon signal, each second ECU 12 adjusts the timing of the clock signal's rise or fall. Each second ECU 12, for example, adjusts the rise or fall timing to, for example, the end time of the beacon signal.

[0078] Here, in the structure that performs processing at the rising point of the clock signal, the rising point of the clock signal is adjusted. In the structure that performs processing at the falling point of the clock signal, the falling point of the clock signal is adjusted.

[0079] Synchronization between the first ECU 11 and (N-1) second ECUs 12 is achieved by adjusting the rise or fall times of the clock signal in each second ECU 12. Therefore, the timing of processing performed by the first ECU 11 and (N-1) second ECUs 12 is substantially consistent. Furthermore, the waveform of the beacon signal is not limited to... Figure 4 The waveform shown.

[0080] <Content of the data frame>

[0081] Figure 5 This is an illustration of the contents of a data frame. A data frame contains a destination field, a data length field, and a data field. A data frame is data, consisting of multiple bits. Each bit outputs a high-level voltage or a low-level voltage. For example, a bit value of 1 and zero correspond to a high-level voltage and a low-level voltage, respectively.

[0082] The destination field of the data frame indicates the destination of the data frame. For example, an ID may be shown in the destination field. The data field of the data frame contains the master data. As mentioned above, the master data is, for example, the sensor's detection value. The data length field of the data frame indicates the length of the master data. The length of the master data is in bits.

[0083] Regarding data frames, the number of bits constituting the portion outside the data fields is fixed. If the length of the main data is determined, then the length of the data frame is also determined. The number of bits constituting the main data varies. However, the upper limit of the number of bits constituting the main data is predetermined.

[0084] ECU11 (first ECU) and (N-1) ECUs (second ECUs) each transmit data frames destined for ECUs connected to communication bus B that exist in ECUs other than the source ECU. Hereinafter, this data frame will be referred to as a transmission frame. A transmission frame is equivalent to transmitting data. A data frame containing fault data is a transmission frame.

[0085] like Figure 3 As shown, when five IDs are assigned, the destination of the transmission frame sent by the first ECU11 with ID 001 is at least one of the four second ECUs12 corresponding to IDs 002 to 005. Similarly, the destination of the transmission frame sent by the second ECU12 with ID 002 is at least one of the first ECU11 corresponding to ID 001 and the three second ECUs12 corresponding to IDs 003 to 005.

[0086] The first ECU11 and (N-1)th second ECU12 each further transmit data frames whose destinations are different from those of the first ECU11 and (N-1)th second ECU12. These data frames will be referred to as pseudo-frames. A pseudo-frame is equivalent to pseudo-data.

[0087] like Figure 3 As shown, with 5 IDs assigned, the destination of the pseudo-frame is different from any of the 1st ECU11 corresponding to 001 and any of the four 2nd ECUs12 corresponding to 002 to 005. The destination of the pseudo-frame is, for example, the ECU with ID 999.

[0088] As described above, when the first ECU 11 and (N-1) second ECUs 12 receive a data frame, they discard the received data frame if the destination of the data frame is different from that of this device. Therefore, in the case of a spurious frame being transmitted, the first ECU 11 and (N-1) second ECUs 12 each discard the received spurious frame.

[0089] As mentioned above, the destination of the pseudo-frame does not exist in the ECU connected to communication bus B. Therefore, the destination of the pseudo-frame in the ECU connected to communication bus B is different from any other ECU except the sending source.

[0090] <Structure of ECU11>

[0091] Figure 6This is a block diagram showing the main structural components of the first ECU 11. The first ECU 11 includes a communication IC 21, an input unit 22, an output unit 23, a device storage unit 24, and a device control unit 25. IC is an abbreviation for Integrated Circuit. The communication IC 21, input unit 22, output unit 23, device storage unit 24, and device control unit 25 are connected to the device bus 26. The communication IC 21 is further connected to the communication bus B. The input unit 22 is further connected to a sensor. The output unit 23 is further connected to electrical equipment. Illustrations of the sensors and electrical equipment are omitted.

[0092] The sensor outputs its detected value to the input unit 22. For example, when the sensor's detected value has been input to the input unit 22, the device control unit 25 generates a transmission frame containing the sensor's detected value as master data. The device control unit 25 provides the generated transmission frame to the communication IC 21. Upon receiving the transmission frame, the communication IC 21 transmits the provided transmission frame via the communication bus B.

[0093] Communication IC21 receives data frames transmitted via communication bus B. If the destination of the received data frame is different from that of the first ECU11, communication IC21 discards the received data frame. Therefore, if communication IC21 receives a spurious frame, it discards the spurious frame.

[0094] When communication IC 21 receives a data frame, if the destination of the received data frame is the first ECU 11, it provides the received data frame to the device control unit 25. A data frame whose destination is the first ECU 11 is a transmission frame. As described above, the transmission destination of a data frame containing fault data is the second ECU 12. Therefore, a transmission frame whose destination is the first ECU 11 does not contain fault data.

[0095] When the device control unit 25 receives a received transmission frame, it determines the operation to be performed by the electrical equipment based on the master data of the transmitted frame. Once the device control unit 25 has determined the operation to be performed by the electrical equipment, it instructs the output unit 23 to output an operation signal representing the determined operation to the electrical equipment. As described above, when an operation signal is input, the electrical equipment performs the operation represented by the input operation signal.

[0096] Communication IC21 detects a fault in ECU12. Upon detecting a fault in ECU12, communication IC21 sends a transmission frame containing fault data. The destination of this transmission frame is the functioning ECU12.

[0097] The device storage unit 24 is, for example, a non-volatile memory. A computer program P is stored in the device storage unit 24. The device control unit 25 has a processing element for performing processing, such as a CPU (Central Processing Unit). The processing element of the device control unit 25 executes the transmission frame generation process and the signal output process in parallel by executing the computer program P. In the transmission frame generation process, the device control unit 25 generates a transmission frame as described above and provides the generated transmission frame to the communication IC 21. In the signal output process, the device control unit 25 instructs the output unit 23 to output an operation signal as described above.

[0098] Furthermore, the computer program P can also be provided to the first ECU 11 using a non-temporary storage medium A on which the computer program P is recorded in a readable manner. Storage medium A is, for example, a portable memory. Examples of portable memory include CD-ROMs, USB (Universal Serial Bus) memory, SD cards, microSD cards, or CF flash memory cards (registered trademarks). When storage medium A is a portable memory, the processing element of the device control unit 25 can also use a reading device (not shown) to read the computer program P from storage medium A. The read computer program P is then stored in the device storage unit 24. Further, the computer program P can also be provided to the first ECU 11 by communicating with an external device via a communication unit (not shown) of the first ECU 11. In this case, the processing element of the device control unit 25 obtains the computer program P via the communication unit. The obtained computer program P is then stored in the device storage unit 24.

[0099] <Structure of Communication IC21>

[0100] The communication IC 21 includes an IC control unit 31, an interface 32, an IC storage unit 33, a clock unit 34, and a bit communicator 35. These are connected to an IC bus 36. The interface 32 is further connected to the device bus 26. The clock unit 34 is further connected to the bit communicator 35. The bit communicator 35 is further connected to the communication bus B.

[0101] The device control unit 25 provides a transmission frame to the IC control unit 31 via the interface 32. The IC control unit 31 has a processing element, such as a CPU, that performs processing and functions as a processing unit. When a transmission frame is provided, the IC control unit 31 writes the provided transmission frame to the IC storage unit 33. The IC storage unit 33 is, for example, a non-volatile memory. Pseudo-frames are pre-stored in the IC storage unit 33.

[0102] The IC control unit 31 detects a fault in the second ECU 12. Upon detecting a fault in the second ECU 12, the IC control unit 31 generates a transmission frame containing fault data indicating that a fault has occurred in the second ECU 12. The IC control unit 31 writes the generated transmission frame to the IC storage unit 33.

[0103] The clock unit 34 outputs a clock signal to the bit communicator 35. The IC control unit 31 provides the bit communicator 35 bit by bit with the transmission frames or pseudo frames stored in the IC storage unit 33. The IC control unit 31 provides the bit communicator 35 bit by bit with the beacon signal.

[0104] Bit communicator 35 transmits 1 bit of signal or data provided by IC control unit 31 each time the clock signal rises. Bit communicator 35 transmits 1 bit of signal or data by adjusting the voltage difference between the first wire W1 and the second wire W2 included in the communication bus B to a high level or a low level. The voltage difference is maintained at a high level or a low level within one cycle of the clock signal. The cycle of the clock signal corresponds to the period of 1 bit.

[0105] Each time the clock signal rises, the bit communicator 35 detects the voltage difference between the first wire W1 and the second wire W2 included in the communication bus B, thereby receiving 1 bit of signal or data. The bit communicator 35 then notifies the IC control unit 31 of the received 1 bit of signal or data.

[0106] Furthermore, the bit communicator 35 can also transmit 1 bit of data provided by the IC control unit 31 whenever the clock signal falls. Additionally, the bit communicator 35 can also detect the voltage difference on the communication bus B whenever the clock signal falls, thereby receiving 1 bit of signal or data.

[0107] When the bit communicator 35 receives a data frame, the IC control unit 31 discards the received data frame if its destination is not the first ECU 11. Therefore, when the bit communicator 35 receives a spurious frame, the IC control unit 31 discards the received spurious frame. When the bit communicator 35 receives a data frame, and the destination of the received data frame is the first ECU 11, the IC control unit 31 provides the received data frame to the device control unit 25 via the interface 32. As described above, the data frame provided by the IC control unit 31 to the device control unit 25 is a transmission frame.

[0108] The IC storage unit 33 stores a computer program (not shown). The IC control unit 31 executes the computer program to perform write processing, transmit processing, receive processing, fault detection processing, and update processing in parallel. In the write processing, the IC control unit 31 writes a transmit frame to the IC storage unit 33 as described above. In the transmit processing, the IC control unit 31 causes the bit communicator 35 to transmit a beacon signal. After causing the bit communicator 35 to transmit the beacon signal, the IC control unit 31 causes the bit communicator 35 to transmit a transmit frame or a pseudo frame. In the receive processing, the IC control unit 31 performs processing related to the data frame received by the bit communicator 35 as described above. In the fault detection processing, the IC control unit 31 detects a fault in the second ECU 12. In the update processing, the IC control unit 31 updates the sequence table.

[0109] The IC storage unit 33 stores a sequence table indicating the transmission order of the first ECU 11 and (N-1) second ECUs 12. During transmission processing, the IC control unit 31 causes the bit communicator 35 to transmit transmission frames or pseudo-frames according to the order shown in the sequence table. In the sequence table, as shown... Figure 3 As shown, the order of transmission is illustrated by corresponding to each of the N IDs.

[0110] <Structure of Bit Communicator 35>

[0111] Figure 7 This is a circuit diagram of a bit communicator 35. The bit communicator 35 has three resistors 41a, 41b, and 42, three capacitors 43, 44a, and 44b, a common-mode choke coil 45, and a switching section 46. The common-mode choke coil 45 has a first inductor 45a, a second inductor 45b, and a ring-shaped magnetic body. The first inductor 45a and the second inductor 45b are wound around the magnetic body.

[0112] The conversion unit 46 of the bit communicator 35 is connected to the first wire W1 of the communication bus B via device wire Wa. The conversion unit 46 of the bit communicator 35 is connected to the second wire W2 of the communication bus B via device wire Wb. The conversion unit 46 is further connected to the clock unit 34 and the IC bus 36.

[0113] A capacitor 44a and a first inductor 45a are disposed midway along the device conductor Wa. The capacitor 44a is disposed on the first conductor W1 side of the first inductor 45a. Similarly, a capacitor 44b and a second inductor 45b are disposed midway along the device conductor Wb. The capacitor 44b is disposed on the second conductor W2 side of the second inductor 45b.

[0114] On the first lead W1 side of capacitor 44a, one end of resistor 41a is connected to device lead Wa. Similarly, on the second lead W2 side of capacitor 44b, one end of resistor 41b is connected to device lead Wb. The other end of resistor 41a is connected to the other end of resistor 41b. The connection point between resistors 41a and 41b is connected to one end of resistor 42 and capacitor 43. The other ends of resistor 42 and capacitor 43 are connected to the first conductor G1. The first conductor G1 is located within the first ECU11.

[0115] Resistors 41a, 41b, 42 and capacitor 43 function as a terminating circuit to suppress the reflection of signals or data represented by the voltage difference between the first conductor W1 and the second conductor W2.

[0116] Two capacitors 44a and 44b remove the DC component from the two voltages input from the two device wires Wa and Wb, respectively. The capacitors 44a and 44b output the two voltages with the DC component removed to the common-mode choke coil 45.

[0117] The common-mode choke coil 45 removes common-mode noise from the two voltages output from capacitors 44a and 44b, and outputs the two voltages with removed common-mode noise to the conversion unit 46.

[0118] The conversion unit 46 detects the voltage difference between two voltages input from the common-mode choke coil 45 whenever the clock signal input from the clock unit 34 rises or falls. Upon detecting a voltage difference, the conversion unit 46 outputs a bit value corresponding to the detected voltage difference to the IC control unit 31. The bit value is either zero or 1. For example, if the voltage difference is a low-level voltage, zero is output as the bit value. If the voltage difference is a high-level voltage, 1 is output as the bit value. The bit value is represented by the voltage of the reference potential, which is the potential of the second conductor G2. For example, the bit values ​​1 and zero correspond to a high-level voltage and a low-level voltage of the reference potential, which is the second conductor G2, respectively. The second conductor G2 is located within the first ECU 11 and is different from the first conductor G1.

[0119] As described above, the bit communicator 35 transmits a 1-bit signal or data. The IC control unit 31 provides the 1-bit signal or data to the conversion unit 46. Whenever the clock signal input from the clock unit 34 rises or falls, the conversion unit 46 adjusts the voltage difference between the two device wires Wa and Wb to the voltage corresponding to the 1-bit signal or data provided by the IC control unit 31.

[0120] The two voltages output from the converter 46 are input to the common-mode choke coil 45. The common-mode choke coil 45 removes common-mode noise from the two voltages output from the converter 46 and outputs the two voltages with removed common-mode noise to two capacitors 44a and 44b. The two capacitors 44a and 44b remove the DC component from the two voltages input from the common-mode choke coil 45. The capacitors 44a and 44b apply the two voltages with removed DC components to the first conductor W1 and the second conductor W2 of the communication bus B. As a result, the voltage difference between the first conductor W1 and the second conductor W2 is adjusted to a high-level voltage or a low-level voltage.

[0121] The bit communicator 35 conforms to the 10BASE-T1S standard of IEEE 802.3cg (IEEE is a registered trademark). Therefore, the bit communicator 35 is configured to transmit a baseband signal at a data transmission rate of 10 Mbps. Here, the baseband signal is transmitted via a twisted pair consisting of a first conductor W1 and a second conductor W2. IEEE is an abbreviation for the Institute of Electrical and Electronics Engineers.

[0122] <Structure of ECU12>

[0123] In the structure of the second ECU 12, except for the structures related to receiving data frames and transmitting beacon signals, the other structures are configured the same as those of the first ECU 11. In the description of the structure of the first ECU 11, the first ECU 11 is replaced by the second ECU 12. Thus, the structure of the second ECU 12 can be described.

[0124] When the bit communicator 35 receives a data frame, the IC control unit 31 discards the received data frame if the destination of the received data frame is not the second ECU 12. Therefore, when the bit communicator 35 receives a spurious frame, the IC control unit 31 discards the received spurious frame. When the bit communicator 35 receives a data frame, and the destination of the received data frame is the second ECU 12 (this device), the IC control unit 31 determines whether the main data of the data frame is fault data.

[0125] Fault data is stored in the IC storage unit 33. If the second ECU 12 is not faulty, the fault data indicates no fault. If the IC control unit 31 determines that the main data is fault data, it updates the fault data stored in the IC storage unit 33 with the fault data contained in the received data frame. If the IC control unit 31 determines that the main data is not fault data, it provides the received data frame to the device control unit 25 via the interface 32.

[0126] In the second ECU12, the IC control unit 31 does not provide a beacon signal to the bit communicator 35. The bit communicator 35 receives the beacon signal. When the beacon signal is received, the IC control unit 31 adjusts the rising or falling point of the clock signal based on the received beacon signal, as described in the description of the beacon signal. In a structure where processing is performed at the rising point of the clock signal, the rising point of the clock signal is adjusted. In a structure where processing is performed at the falling point of the clock signal, the falling point of the clock signal is adjusted.

[0127] The IC control unit 31 of the second ECU 12 performs write, transmit, and update processes similarly to the IC control unit 31 of the first ECU 11. However, in the transmit process of the second ECU 12, the IC control unit 31 adjusts the clock signal based on the beacon signal received by the bit communicator 35 before causing the bit communicator 35 to transmit a transmit frame or a pseudo-frame. In the receive process of the second ECU 12, the IC control unit 31 performs processing related to the data frames received by the bit communicator 35 as described above. The IC control unit 31 of the second ECU 12 does not detect faults.

[0128] <Steps for sending a data frame>

[0129] Figure 8 This is a flowchart illustrating the steps involved in preparing for the transmission of a frame. The preparation for transmitting the frame is performed similarly in each of the first ECU 11 and (N-1) second ECUs 12. Figure 8 The diagram shows the transmission frame generation process of the device control unit 25 and the writing process of the IC control unit 31.

[0130] In the transmission frame generation process, the device control unit 25 first determines whether to generate a transmission frame (step S1). In step S1, the device control unit 25 determines whether to generate a transmission frame, for example, when a sensor detection value is input to the input unit 22. In this case, the main data of the transmission frame is the sensor detection value that has been input to the input unit 22. If the device control unit 25 determines that no transmission frame has been generated (S1: "No"), it executes step S1 again and waits until the timing for generating a transmission frame arrives.

[0131] When the device control unit 25 determines that a transmission frame needs to be generated (S1: "Yes"), it generates the transmission frame (step S2). For example, whenever step S2 is executed, the device control unit 25 may always generate a transmission frame with a predetermined data length. The predetermined length is, for example, an upper limit on the number of bits in the data field constituting the data frame. When the data length is fixed, the number of bits constituting the transmission frame generated by the device control unit 25 is always constant. In the structure where a transmission frame with a predetermined data length is generated, the data length of the pseudo-frame may also be a predetermined length. In this case, the number of bits constituting the pseudo-frame is the same as the number of bits constituting the transmission frame.

[0132] Next, the device control unit 25 provides the transmission frame generated in step S2 to the IC control unit 31 via interface 32 (step S3). After executing step S3, the device control unit 25 ends the transmission frame generation process. After ending the transmission frame generation process, the device control unit 25 executes the transmission frame generation process again.

[0133] During the write process, the IC control unit 31 first determines whether a transmission frame has been provided by the slave device control unit 25 (step S11). If the IC control unit 31 determines that no transmission frame has been provided (S11: "No"), it executes step S11 again and waits until a transmission frame is provided by the slave device control unit 25.

[0134] If the IC control unit 31 determines that a transmission frame has been provided by the slave device control unit 25 (S11: "Yes"), it writes the provided transmission frame into the IC storage unit 33 (step S12). After executing step S12, the IC control unit 31 ends the writing process. After ending the writing process, the IC control unit 31 executes the writing process again.

[0135] As described above, when the device control unit 25 generates a transmission frame, the generated transmission frame is written to the IC storage unit 33. The transmission frame stored in the IC storage unit 33 is transmitted via the communication bus B.

[0136] Figure 9This is a flowchart illustrating the transmission process performed by the IC control unit 31 of the first ECU 11. In the transmission process, the IC control unit 31 of the first ECU 11 first determines whether to transmit a beacon signal (step S21). If, after a standby period has elapsed, the second ECU 12 (the last in sequence) begins transmitting a data frame, the time when the second ECU 12 finishes transmitting the data frame is the timing for transmitting the beacon signal. If, after a standby period has elapsed, the second ECU 12 (the last in sequence) has not begun transmitting a data frame, the time when the beacon signal is transmitted is the timing for elapsed. As described above, the data length field of the data frame shows the data length of the main data. Based on the data length shown in the data length field of the data frame transmitted by the last ECU 12, the IC control unit 31 can determine the timing for the end of data frame transmission.

[0137] If the IC control unit 31 determines that no beacon signal has been transmitted (S21: "No"), it executes step S21 again and waits until the timing for transmitting the beacon signal arrives. If the IC control unit 31 determines that a beacon signal should be transmitted (S21: "Yes"), it instructs the bit communicator 35 to transmit the beacon signal via the communication bus B (step S22). As described above, in the second ECU 12, when the bit communicator 35 receives the beacon signal, the IC control unit 31 adjusts the clock signal.

[0138] After executing step S22, the IC control unit 31 determines whether it is the timing for starting the transmission of the data frame (step S23). Since the first ECU 11 acts as the master, its transmission order is first. In this case, in step S23, the IC control unit 31 determines whether a standby period has elapsed since the end of the beacon signal transmission. The elapsed standby period is the timing for starting transmission. If the IC control unit 31 determines that it is not the timing for starting transmission (S23: "No"), it executes step S23 again and remains in standby mode until the timing for starting transmission arrives.

[0139] If the IC control unit 31 determines that it is time to start transmission (S23: "Yes"), it determines whether a transmission frame is stored in the IC storage unit 33 (step S24). If the IC control unit 31 determines that a transmission frame is stored in the IC storage unit 33 (S24: "Yes"), it instructs the bit communicator 35 to transmit the transmission frame stored in the IC storage unit 33 bit by bit via the communication bus B (step S25). The bit communicator 35 functions as a data transmission unit. After executing step S25, the IC control unit 31 deletes the transmitted frame from the IC storage unit 33 (step S26).

[0140] If the IC control unit 31 determines that no transmission frame is stored in the IC storage unit 33 (S24: "No"), it instructs the bit communicator 35 to transmit the pseudo-frame stored in the IC storage unit 33 bit by bit (step S27). After executing one of steps S26 or S27, the IC control unit 31 ends the transmission process. After ending the transmission process, the IC control unit 31 executes the transmission process again. Because the transmission process is repeatedly executed, the bit communicator 35 repeatedly transmits the beacon signal. The bit communicator 35 also functions as a signal transmission unit.

[0141] Figure 10 This is a flowchart illustrating the transmission processing steps performed by the IC control unit 31 of the second ECU 12. Steps S34 to S37 of the transmission processing performed by the IC control unit 31 of the second ECU 12 are the same as steps S24 to S27 of the transmission processing performed by the IC control unit 31 of the first ECU 11. Therefore, the explanation of steps S34 to S37 is omitted.

[0142] In the transmission process, the IC control unit 31 of the second ECU12 first determines whether the bit communicator 35 has received the beacon signal (step S31). If the IC control unit 31 determines that the bit communicator 35 has not received the beacon signal (S31: "No"), it executes step S31 again and waits until the bit communicator 35 receives the beacon signal.

[0143] When the IC control unit 31 determines that the bit communicator 35 has received a beacon signal (S31: "Yes"), it adjusts the clock signal output by the clock unit 34 (step S32). In step S32, the IC control unit 31 adjusts the rise or fall time of the clock signal as described above. After executing step S32, the IC control unit 31 determines whether it is the timing to start transmitting a data frame (step S33).

[0144] like Figure 3 As shown, when the transmission order is assigned, in step S33, the IC control unit 31 assumes that, after the standby period has elapsed, the first ECU 11 or the second ECU 12, which is the previous one in the sequence table, has started transmitting a data frame. In this case, the time point from when the first ECU 11 or the second ECU 12, which is the previous one, finishes transmitting a data frame, after the standby period, is the time point for starting transmission. If, after the standby period has elapsed, the first ECU 11 or the second ECU 12, which is the previous one, has not started transmitting a data frame, the time point from that time point, after the standby period has further elapsed, is the time point for starting transmission of a data frame.

[0145] Regarding ECU12 with ID 002, the preceding ECU is ECU11 with ID 001. Regarding ECU12 with ID 003, the preceding ECU is ECU12 with ID 002.

[0146] Based on the data length shown in the data length field of the data frame sent by the preceding first ECU 11 or second ECU 12, the IC control unit 31 can determine the timing of when the first ECU 11 or second ECU 12 ends the transmission of the data frame.

[0147] If the IC control unit 31 determines that the timing is not for the transmission of the start data frame (S33: "No"), it executes step S33 and waits until the timing for the transmission of the start data frame arrives. If the IC control unit 31 determines that the timing is for the transmission of the start data frame (S33: "Yes"), it executes step S34. After ending the transmission process, the IC control unit 31 executes the transmission process again.

[0148] As described above, if there are no transmission frames in the IC storage unit 33 for transmission to any other ECU besides this device, the bit communicator 35 of the first ECU 11 and (N-1) second ECUs 12 will transmit a pseudo frame. Therefore, when it is the transmission order, the bit communicator 35 of the first ECU 11 and (N-1) second ECUs 12 will definitely transmit either a transmission frame or a pseudo frame.

[0149] Additionally, regarding the first ECU11 and (N-1)th second ECU12, the order in which the data frames are sent is as follows: Figure 3 The sequence is predetermined. Therefore, when the beacon signal is transmitted, the bit communicators 35 of the first ECU 11 and (N-1) second ECUs 12 transmit data frames via the communication bus B in a predetermined order. The beacon signal indicates the start of data frame transmission by the bit communicators 35 of the first ECU 11 and (N-1) second ECUs 12. The first ECU 11 and the second ECU 12 function as communication devices for transmitting data. The second ECU 12 also functions as a second communication device.

[0150] <Fault Detection and Handling>

[0151] Figure 11 This is a flowchart illustrating the steps of the fault detection process. As described above, the fault detection process is performed by the IC control unit 31 of the first ECU 11. The IC control unit 31 performs the fault detection process again after it has ended.

[0152] The value of an integer K is stored in the IC storage unit 33. The value of the integer K is changed by the IC control unit 31. Fault data is stored in the IC storage unit 33 of the first ECU 11. The fault data representing the second ECU 12 is updated by the IC control unit 31. As described above, if the second ECU 12 does not have a fault, the fault data indicates no fault.

[0153] In fault detection processing, the IC control unit 31 of the first ECU 11 determines whether each of the (N-1) second ECUs 12 has sent a data frame. The second ECU 12 functions as a target communication device. For each of the second to Nth second ECUs 12, the IC storage unit 33 stores the number of consecutive determinations that no data frame has been sent. The (N-1) determination counts are changed by the IC control unit 31. At the time when the first ECU 11 is started, the (N-1) determination counts are zero.

[0154] In the fault detection process, the IC control unit 31 of the first ECU 11 first changes the value of the integer K to 2 (step S41). Next, the IC control unit 31 determines whether it is the transmission timing of the Kth second ECU 12 (step S42). K is the order of transmitting data frames, as shown in the order table. The transmission timing is the timing of transmitting data frames.

[0155] If the IC control unit 31 determines that it is not the transmission timing of the Kth second ECU 12 (S42: "No"), it executes step S42 again and waits until the transmission timing of the Kth second ECU 12 arrives. If the IC control unit 31 determines that it is the transmission timing of the Kth second ECU 12 (S42: "Yes"), it determines whether the Kth second ECU 12 has transmitted a data frame (step S43).

[0156] As described above, a data frame sent by one ECU connected to communication bus B is received by all ECUs connected to communication bus B. Therefore, if the bit communicator 35 does not receive a data frame, the IC control unit 31 determines that the Kth second ECU 12 has not sent a data frame. If the bit communicator 35 receives a data frame, the IC control unit 31 determines that the Kth second ECU 12 has sent a data frame.

[0157] If the IC control unit 31 determines that the Kth second ECU 12 has not sent a data frame (S43: "No"), it increments the determination count of the Kth second ECU 12 by 1 (step S44). Next, the IC control unit 31 determines whether the determination count of the Kth second ECU 12 is a predetermined number (step S45). The predetermined number is a constant value, which is 2 or more. If the IC control unit 31 determines that the determination count of the Kth second ECU 12 is more than the predetermined number (S45: "Yes"), it considers a fault to have occurred in the Kth second ECU 12 and updates the fault data (step S46). In step S46, the IC control unit 31 appends the Kth second ECU 12 to the second ECU 12 represented by the fault data. In the fault data, the Kth second ECU 12 is represented by ID.

[0158] If the IC control unit 31 determines that the Kth second ECU 12 has sent a data frame (S43: "Yes"), it changes the determination count of the Kth second ECU 12 to zero (step S47). If the IC control unit 31 determines that the determination count of the Kth second ECU 12 is lower than a predetermined count (S45: "No"), or after executing one of steps S46 and S47, it increments the integer K by 1 (step S48). Next, the IC control unit 31 determines whether the value of the integer K is N (step S49). If the IC control unit 31 determines that the value of the integer K is not N (S49: "No"), it executes step S42. The IC control unit 31 determines whether each of the (N-1)th second ECUs 12 (from the 2nd to the Nth) has sent a data frame.

[0159] If the IC control unit 31 determines that the value of integer K is N (S49: "Yes"), it determines whether the fault data has been updated during the current fault detection process (step S50). If the IC control unit 31 determines that the fault data has been updated (S50: "Yes"), it writes a transmission frame containing the fault data into the IC storage unit 33 (step S51). As a result, the bit communicator 35 transmits the transmission frame containing the fault data via the communication bus B. The fault data is stored in the IC storage unit 33 of the second ECU 12. In the second ECU 12, when the bit communicator 35 receives a transmission frame containing fault data, the IC control unit 31 updates the fault data stored in the IC storage unit 33 to the fault data contained in the transmission frame received by the bit communicator 35.

[0160] If the IC control unit 31 determines that the fault data has not been updated (S50: "No"), or after executing step S51, it ends the fault detection process. As described above, the IC control unit 31 executes the fault detection process again after ending the fault detection process.

[0161] <Update the order table>

[0162] Figure 12 This is a flowchart illustrating the steps of the update process. The update process is performed by the IC control unit 31 of the first ECU 11 and (N-1)th second ECU 12. During the update process, the IC control unit 31 determines whether the fault data stored in the IC storage unit 33 has been updated (step S61). If the IC control unit 31 determines that the fault data has not been updated (S61: "No"), it executes step S61 again and waits until the fault data is updated in the IC storage unit 33.

[0163] If the IC control unit 31 determines that fault data has been updated (S61: "Yes"), it determines whether it is the timing for updating the sequence table (step S62). If the IC control unit 31 determines that it is not the timing for updating the sequence table (S62: "No"), it executes step S62 again and waits until the timing for updating the sequence table arrives. The update timing is, for example, the timing for starting the communication IC 21 or the timing for starting the transmission of the next beacon signal. If the IC control unit 31 determines that it is the timing for updating the sequence table (S62: "Yes"), it updates the sequence table based on the fault data stored in the IC storage unit 33 (step S63).

[0164] Figure 13 This is an illustration of the update of the order table. For example... Figure 13 As shown, the order table establishes a correspondence between the order in which data frames are sent and their respective IDs. Figure 13 In the example, 001 to 005 correspond to numbers 1 to 5, respectively. When the fault data is displayed as ID 003, the IC control unit 31 deletes the 003 column from the sequence table. Therefore, since number 3 is deleted, numbers 4 and 5 are changed to 3 and 4, respectively. Consequently, the first ECU 11 and the three normal second ECUs 12, recognizing that number 003 does not exist, send data frames.

[0165] like Figure 12 As shown, after executing step S63, the IC control unit 31 ends the update process. After ending the update process, the IC control unit 31 executes the update process again.

[0166] As described above, the IC control unit 31 of the first ECU 11 detects a fault in the target communication device if it determines that the target communication device included in (N-1) second ECUs 12 has failed to send data a predetermined number of consecutive times. Therefore, the possibility of erroneously detecting a fault in the target communication device is low.

[0167] When the IC control unit 31 of the first ECU 11 detects a fault in the target communication device, it updates the fault data and instructs the bit communicator 35 to send the updated fault data to the remaining second ECUs 12, excluding the target communication device. As a result, the fault data of the remaining second ECUs 12 is updated to match the fault data of the first ECU 11. Subsequently, based on the updated fault data, the first ECU 11 and the normal second ECUs 12 update the transmission order shown in the sequence table to the order excluding the target communication device. Consequently, if the IC control unit 31 of the first ECU 11 determines that the target communication device has not transmitted data frames a predetermined number of times consecutively, it changes the transmission order of data frames to the order excluding the target communication device. The first ECU 11 also functions as a communication device for changing the transmission order.

[0168] Figure 14 This is an explanatory diagram illustrating the effect of communication system 1. In Figure 14 The example shown is where N is 5. Under the condition that the first ECU11 and (N-1) second ECUs12 are operating normally, as follows... Figure 14 As shown in the upper part, when the first ECU 11 sends a beacon signal, the first ECU 11 and (N-1) second ECUs 12 send data frames in the order shown in the sequence table. When the last second ECU 12 finishes sending data frames, the first ECU 11 sends a beacon signal again.

[0169] Assume a fault occurs in the third ECU 12, causing it to stop transmitting data frames. In this case, after a standby period has elapsed since the second ECU 12 stopped transmitting data frames, the third ECU 12 does not transmit any data frames. Therefore, after another standby period has elapsed, the fourth ECU 12 transmits data frames. Thus, after two standby periods have elapsed since the second ECU 12 stopped transmitting data frames, the fourth ECU 12 begins transmitting data frames.

[0170] In the event of a fault in the third ECU 12, the third ECU 12 does not send a data frame, so the first ECU 11 can detect the fault in the third ECU 12. When the first ECU 11 detects a fault in the third ECU 12, the fault data is updated, and the third ECU 12 is displayed as the malfunctioning ECU 12. The first ECU 11 sends a transmission frame containing the fault data, notifying the second, fourth, and fifth ECUs of the fault in the third ECU 12. As a result, the order shown in the sequence table for the first ECU 11 and the second, fourth, and fifth ECUs 12 is updated.

[0171] As a result, ECU11 and (N-2) ECU12 transmit data frames in the order shown in the updated sequence table. Since there are no two standby periods, the interval between beacon signal transmissions is shortened. The amount of data transmitted per unit time via communication bus B is almost the same as the amount of data transmitted before the fault occurred.

[0172] (Implementation Method 2)

[0173] In Implementation 1, the standby period remains unchanged. However, the standby period can also be changed depending on the number of second ECUs 12 that have malfunctioned.

[0174] The differences between Embodiment 2 and Embodiment 1 will be explained below. Since the structures other than those described later are common to Embodiment 1, the same reference numerals will be used for the structural parts common to Embodiment 1, and their descriptions will be omitted.

[0175] <Structure of ECU11>

[0176] Figure 15 This is a block diagram showing the main structure of the first ECU 11 in Embodiment 2. The IC storage unit 33 of the first ECU 11 stores a standby period table and device quantity data. Hereinafter, the number of normal ECUs in the first ECU 11 and (N-1) second ECUs 12 is referred to as the device quantity. The device quantity data represents the device quantity. The device quantity represented by the device quantity data is changed by the IC control unit 31.

[0177] Figure 16 This is a chart showing the contents of a standby period table. The standby period table shows the relationship between the number of devices and the standby period. For example... Figure 16 As shown, the smaller the number of devices, the longer the standby time. Figure 16 The example shown is where N is 5. The standby period of the IC control unit 31 of the first ECU11 is the standby period corresponding to the number of devices represented by the device quantity data.

[0178] <Structure of ECU12>

[0179] The IC storage unit 33 of the second ECU 12 also stores a standby period table and device quantity data. The standby period tables stored in the IC storage units 33 of the first ECU 11 and (N-1) second ECUs 12 are the same. The standby period of the IC control unit 31 of the second ECU 12 is also the standby period corresponding to the number of devices represented by the device quantity data.

[0180] <Update the order table>

[0181] Figure 17 This is a flowchart illustrating the steps of the update process. Similar to Embodiment 1, the update process is performed by the IC control unit 31 of the first ECU 11 and (N-1) second ECUs 12. In Embodiment 2, the IC control unit 31 performs steps S61 to S63 of the update process in the same manner as in Embodiment 1. Therefore, the explanation of steps S61 to S63 is omitted. After performing step S63, the IC control unit 31 adjusts the number of devices represented by the device quantity data to a value calculated by subtracting the number of second ECUs 12 represented by the fault data from N (step S71). After performing step S71, the IC control unit 31 ends the update process. After ending the update process, the IC control unit 31 performs the update process again.

[0182] As described in Embodiment 1, the IC control unit 31 of the first ECU 11 updates the fault data when it is determined multiple times consecutively that the target communication device has not sent a data frame. The IC control unit 31 of the first ECU 11 further instructs the bit communicator 35 to send the updated fault data to the remaining second ECUs 12, excluding the target communication device. As a result, the fault data of the remaining second ECUs 12 is updated and becomes consistent with the fault data of the first ECU 11. With the fault data already updated in both the first ECU 11 and the normal second ECUs 12, the number of devices is reduced. Consequently, the standby time of the first ECU 11 and the normal second ECUs 12 is extended.

[0183] <The Effects of Communication System 1>

[0184] Figure 18 This is an explanatory diagram illustrating the effect of communication system 1. In Figure 18 The example shown is where N is 5. Similarly to Embodiment 1, if the first ECU 11 and (N-1) second ECUs 12 are operating normally, as shown... Figure 18 As shown in the upper part, whenever the first ECU11 sends a beacon signal, the first ECU11 and (N-1) second ECUs12 send data frames in the order shown in the sequence table.

[0185] In the event of a fault in the third ECU12, after two standby periods following the end of data frame transmission by the second ECU12, the fourth ECU12 begins transmitting data frames. Subsequently, the fault data is updated, and the first ECU11 and (N-2) normal ECUs12 transmit data frames in the order shown in the sequence table.

[0186] In Implementation 2, if a fault is detected in the third ECU12, the number of devices changes from N to (N-1), and the standby period is extended. This prevents a decrease in the transmission interval of the beacon signal. The standby period in the standby period table is set so that the transmission interval remains constant regardless of the number of devices.

[0187] The communication system 1 in embodiment 2 also has the same effects as the communication system 1 in embodiment 1, except for the effect of maintaining the standby period at a constant value regardless of the number of devices.

[0188] <Features of Communication System 1 in Embodiments 1 and 2>

[0189] Figure 19 This is an explanatory diagram illustrating the features of communication system 1 in embodiments 1 and 2. Figure 19 The image shows the transmission of data frames after the order table has been updated in both Embodiment 1 and Embodiment 2 (see reference). Figure 14 and Figure 18 (Lower part). In embodiments 1 and 2, it is assumed that there is no faulty second ECU12, and the first ECU11 and (N-2) second ECU12s send data frames in sequence.

[0190] In communication bus B, the voltage difference between conductor W1 and conductor W2 is switched between a low-level voltage and a high-level voltage. The sum of the number of switches from high-level to low-level voltage and the number of switches from low-level to high-level voltage is recorded as the number of voltage switches in communication bus B. When the voltage of communication bus B is switched, interference noise is generated. Interference noise is noise that interferes with signals output via conductors different from those on communication bus B. In cases of high interference noise, it is possible to incorrectly read signals output via conductors different from those on communication bus B, such as action signals.

[0191] In communication system 1 of embodiment 1, when a fault occurs in a second ECU 12, the standby period remains unchanged, so the beacon signal transmission interval decreases. As a result, the amount of data transmitted per unit time is almost the same as the amount of data before the fault occurred. However, because the beacon signal transmission interval decreases, the number of switching operations per unit time in communication bus B increases. Therefore, the intensity of interference noise increases.

[0192] On the other hand, in communication system 1 of embodiment 2, when a fault occurs in a second ECU 12, the standby period is extended, so the amount of data transmitted per unit time decreases compared to the amount of data before the fault occurred. However, the transmission interval of the beacon signal does not change, so the number of switching times per unit time in communication bus B remains almost unchanged. As a result, the intensity of interference noise also remains almost unchanged.

[0193] Figure 20 These are explanatory diagrams illustrating other features of communication system 1 in embodiments 1 and 2. Figure 20 The image shows the spectrum of the signal (data) transmitted via communication bus B before the fault occurred in ECU12. Frequency and intensity are shown on the horizontal and vertical axes, respectively. Figure 20 As shown, multiple spectra are excited, and the frequency interval of the excited spectra is represented by the reciprocal of the transmission interval of the beacon signal.

[0194] In the communication system 1 of Embodiment 1, when a fault occurs in the second ECU 12, as described above, the transmission interval of the beacon signal decreases. Therefore, the frequency interval of the spectrum increases. Consequently, the number of excited spectra decreases, and thus the intensity of each spectrum increases. As a result, the intensity of the spectrum that functions as interference noise increases.

[0195] On the other hand, in communication system 1 of embodiment 2, even if a fault occurs in the second ECU 12, as described above, the transmission interval of the beacon signal does not change. Therefore, even if a fault occurs in the second ECU 12, the spectrum of the signal (data) propagated via the communication bus B does not change. As a result, the intensity of the spectrum acting as interference noise does not change.

[0196] (Implementation Method 3)

[0197] In Implementation 2, the beacon signal transmission interval is maintained regardless of the number of faulty second ECUs 12. However, maintaining the beacon signal transmission interval regardless of the number of faulty second ECUs 12 is unnecessary.

[0198] The differences between Embodiment 3 and Embodiment 2 will be explained below. Since the structures other than those described later are common to Embodiment 2, the same reference numerals will be used for the structural parts common to Embodiment 2, and their descriptions will be omitted.

[0199] <Data Frame Transmission Method>

[0200] Figure 21 This is an explanatory diagram of the data frame transmission method in Embodiment 3. Figure 21In the example shown, N is 5. In the communication system 1 of embodiment 3, when the beacon signal transmission interval is greater than or equal to a predetermined interval, the intensity of interference noise is small, so the possibility of erroneously reading signals output via wires different from the communication bus B is low. Furthermore, the predetermined interval is shorter than the beacon signal transmission interval before the failure in the second ECU 12.

[0201] When the normal number of second ECUs 12 is P or more, the beacon signal transmission interval is a predetermined interval or more. Therefore, in the communication system 1 of Embodiment 3, when the normal number of second ECUs 12 is P or more, the beacon signal transmission interval is decreased, similar to Embodiment 1. When the normal number of second ECUs 12 is less than P, the beacon signal transmission interval is maintained, similar to Embodiment 2. This suppresses the decrease in the amount of data transmitted per unit time and maintains the beacon signal transmission interval at a value greater than the predetermined interval. Figure 21 The example shown is where P is 2. P is less than (N-1).

[0202] <Contents of the standby table>

[0203] Figure 22 This is a chart showing the contents of the standby period table. The contents of the standby period table differ when comparing Embodiments 2 and 3. As described in the description of Embodiment 2, the number of devices represented by the device quantity data is the number of normal ECUs in the first ECU 11 and (N-1) second ECUs 12. Figure 22 The example shown illustrates N and P being 8 and 4 respectively. Figure 22 As shown, when the number of devices is (P+1) or more, the standby period is a common value. Therefore, when a fault occurs in the second ECU12, and the number of normal second ECUs12 is (P+1) or more, the beacon signal transmission interval decreases without changing the standby period.

[0204] When the number of devices is P or less, the smaller the number of normal second ECUs 12, the longer the standby period. Therefore, when a fault occurs in the second ECU 12, the standby period is prolonged when the number of normal second ECUs 12 is (P-1) or less.

[0205] <The Effects of Communication System 1>

[0206] In the communication system 1 of embodiment 3, the decrease in the amount of data transmitted per unit time is suppressed and the transmission interval of the beacon signal is maintained at a value above a predetermined interval.

[0207] The communication system 1 in embodiment 3 also has the same effect as the communication system 1 in embodiments 1 and 2.

[0208] <Modifications of Implementation Methods 2 and 3>

[0209] In communication system 1 of embodiments 2 and 3, the method for maintaining the beacon signal transmission interval is not limited to the method of extending the standby period. Instead of extending the standby period, the beacon signal transmission interval can also be maintained, for example, by increasing the data size of the data frame. Increasing the data size of the data frame can be achieved, for example, by increasing the data size of the main data.

[0210] (Implementation Method 4)

[0211] In implementation 1, the first ECU 11 and (N-1) second ECUs 12 transmit pseudo frames. However, the first ECU 11 and (N-1) second ECUs 12 may also include ECUs that do not transmit pseudo frames.

[0212] The differences between Embodiment 4 and Embodiment 1 will be explained below. Since the structures other than those described later are common to Embodiment 1, the same reference numerals will be used for the structural parts common to Embodiment 1, and their descriptions will be omitted.

[0213] <Data Frame Transmission Method>

[0214] Figure 23 This is an explanatory diagram of the data frame transmission method in Embodiment 4. Figure 23 In the example shown, N is 5. Similar to Embodiment 3, when the beacon signal transmission interval is greater than or equal to a predetermined interval, the intensity of interference noise is low, therefore, the possibility of incorrectly reading signals output via wires different from the communication bus B is low. In the communication system 1 of Embodiment 4, when U ECUs transmit data frames, the beacon signal transmission interval is greater than or equal to a predetermined interval. U is a natural number, less than N. Figure 23 The example shown is where U is 3.

[0215] In the communication system 1 of embodiment 4, in the first ECU 11 and (N-1) second ECUs 12, each of the (N-U) ECUs does not transmit pseudo-frames. If a fault occurs in one of the U ECUs, one of the (N-U) ECUs begins transmitting pseudo-frames. This maintains the beacon signal transmission interval at a value greater than a predetermined interval.

[0216] <Steps for sending a data frame>

[0217] In the structure where the first ECU11 transmits pseudo-frames, the IC control unit 31 of the first ECU11 performs the transmission process in the same way as in Embodiment 1.

[0218] In the configuration where the first ECU 11 does not send pseudo-frames, the IC control unit 31 of the first ECU 11 similarly executes steps S21 to S26 of the transmission process performed by the IC control unit 31 of the first ECU 11 that sends pseudo-frames during the transmission process. If the IC control unit 31 determines that no transmission frame is stored in the IC storage unit 33 (S24: "No"), it does not execute step S27 and ends the transmission process.

[0219] In the structure where the second ECU12 transmits pseudo-frames, the IC control unit 31 of the second ECU12 performs the transmission process in the same way as in Embodiment 1.

[0220] In the configuration where the second ECU 12 does not send pseudo-frames, the IC control unit 31 of the second ECU 12 similarly executes steps S31 to S36 of the transmission process performed by the IC control unit 31 of the second ECU 12 that sends pseudo-frames during the transmission process. If the IC control unit 31 determines that no transmission frame is stored in the IC storage unit 33 (S34: "No"), it does not execute step S37 and ends the transmission process.

[0221] In the communication system 1 of embodiment 4, each of the U ECUs sends a pseudo frame when there is no transmission frame in the IC storage unit 33. Each of the (N-U) ECUs does not send a pseudo frame when there is no transmission frame in the IC storage unit 33.

[0222] When the first ECU 11 is included in U ECUs, the IC control unit 31 of the first ECU 11 performs the transmission process in the same way as in Embodiment 1. When the first ECU 11 is included in (N-U) ECUs, the IC control unit 31 of the first ECU 11 performs the transmission process without step S27. In this case, the first ECU 11 functions as a non-transmission device.

[0223] When the second ECU 12 is included in U ECUs, the IC control unit 31 of the second ECU 12 included in U ECUs performs the transmission process in the same way as in Embodiment 1. When the second ECU 12 is included in (N-U) ECUs, the IC control unit 31 of the second ECU 12 included in (N-U) ECUs performs the transmission process in which step S37 is omitted. The second ECU 12 included in (N-U) ECUs functions as a non-transmission device.

[0224] <Fault Detection and Handling>

[0225] Figure 24This is a flowchart illustrating the steps of the fault detection process. Similar to Embodiment 1, the IC control unit 31 of the first ECU 11 performs the fault detection process. Figure 24 The example shown illustrates the transmission of pseudo-frames by the first to the Uth ECUs in the first ECU 11 and (N-1)th second ECUs 12. In Embodiment 4, the IC control unit 31 of the first ECU 11 executes steps S41-S48, S50, and S51 in the same manner as in Embodiment 1. Therefore, the description of steps S41-S48, S50, and S51 is omitted.

[0226] After executing step S48, the IC control unit 31 of the first ECU11 determines whether the value of the integer K is U (step S81). If the IC control unit 31 determines that the value of the integer K is not U (S81: "No"), it executes step S42. If the IC control unit 31 determines that the value of the integer K is U (S81: "Yes"), it executes step S50.

[0227] As described above, the IC control unit 31 of the first ECU11 detects the occurrence of faults in each of the (U-1) second ECUs12.

[0228] <Update the order table>

[0229] The IC control units 31 of the first ECU11 and the second ECU12 that send the pseudo-frame perform the update process in the same way as in Embodiment 1.

[0230] Figure 25 This is a flowchart illustrating the update process steps of the second ECU 12 that does not send pseudo-frames. In the update process, the IC control unit 31 of the second ECU 12 that does not send pseudo-frames similarly executes steps S61 to S63 of the update process performed by the IC control unit 31 of the second ECU 12 that sends pseudo-frames. Therefore, the explanation of steps S61 to S63 is omitted.

[0231] After executing step S63, the IC control unit 31 of the second ECU 12 that does not send pseudo-frames determines whether to change the transmission process to sending pseudo-frames (step S91). For example, if the number of faulty second ECUs 12 is 1 (U+1), the IC control unit 31 of the second ECU 12 determines to change the transmission process. If the number of faulty second ECUs 12 is 2 (U+2), the IC control unit 31 of the second ECU 12 determines to change the transmission process.

[0232] If the IC control unit 31 determines that the transmission process needs to be changed (S91: "Yes"), it changes the transmission process to the transmission process of sending pseudo-frames (step S92). If the IC control unit 31 determines that the transmission process should not be changed (S91: "No"), or after executing step S92, it ends the update process. After ending the update process, the IC control unit 31 executes the update process again.

[0233] As described in Embodiment 1, in the first ECU 11, the IC control unit 31 updates the fault data stored in the IC storage unit 33 when it determines that the target communication device has not sent a data frame a predetermined number of times consecutively. Further, the IC control unit 31 of the first ECU 11 instructs the bit communicator 35 to send a transmission frame containing the fault data to (N-1) second ECUs 12. Consequently, the IC control unit 31 of the second ECUs 12, which does not send dummy frames, performs an update process and changes the transmission process. As described above, when the IC control unit 31 determines that the target communication device has not sent a data frame a predetermined number of times consecutively, it causes the second ECUs 12, which does not send dummy frames, to begin sending dummy frames.

[0234] <The Effects of Communication System 1>

[0235] In the communication system 1 of embodiment 4, when a fault is detected in the target communication device, the second ECU 12, which does not send pseudo-frames, begins to send pseudo-frames. Therefore, it is possible to prevent a decrease in the beacon signal transmission interval.

[0236] The communication system 1 in embodiment 4 also has the same effect as the communication system 1 in embodiment 1.

[0237] <Modifications of Implementation Method 4>

[0238] In embodiment 4, the first to Uth ECUs may include ECUs that do not send dummy frames. In this case, the remaining ECUs include ECUs that send dummy frames. The IC control unit 31 of the first ECU 11 sequentially determines whether a fault has occurred for each of the (U-1)th second ECUs 12 that send dummy frames. Alternatively, the first ECU 11 may also be an ECU that does not send dummy frames. In this case, the first ECU 11 performs the same update process as the update process of the second ECU 12 that does not send dummy frames.

[0239] <Variations of Embodiments 1-4>

[0240] In embodiments 1 to 4, the pseudo-frame can also be a data frame whose destination and source are the same. In this case, when the bit communicator 35 receives a data frame, the IC control unit 31 of the first ECU 11 and (N-1) second ECUs 12 discards the received data frame if the destination and source of the received data frame are the same. Furthermore, if the destination of the data frame is limited to one, it is impossible to notify the normal second ECU 12 of the fault by sending a single frame containing fault data. In this case, the first ECU 11 notifies the fault by sending multiple frames with different destinations.

[0241] Furthermore, if the IC control unit 31 of the first ECU 11 determines that the target communication device has not sent a data frame a predetermined number of times, it may also change the order of sending data frames to the order in which the target communication device is removed. In this case, the determination number of the Kth second ECU 12 is the total number of times that the Kth second ECU 12 has not sent a data frame. Alternatively, the predetermined number may be 1. In this case, steps S44, S45, and S47 of the fault detection process are omitted. In the fault detection process, if the IC control unit 31 of the first ECU 11 determines that the Kth second ECU 12 has not sent a data frame (S43: "No"), it executes step S46. If the IC control unit 31 determines that the Kth second ECU 12 has sent a data frame (S43: "Yes"), it executes step S48.

[0242] The ECU that detects the fault is not limited to the first ECU 11; it can also be the second ECU 12. In this case, the first ECU 11 functions as a second communication device. The destination of the transmission frame containing fault data is a normal ECU. The second ECU 12 that detects the fault functions as a communication device for changing the order. The number of ECUs that detect the fault is not limited to one. It is also possible for the first ECU 11 and (N-1) second ECUs 12 to each detect the fault of the second ECU 12 that sends a pseudo-frame. In this case, it is not necessary to transmit a data frame containing fault data. When the IC control unit 31 of the first ECU 11 and (N-1) second ECUs 12 detects a fault in the second ECU 12, if the order of the faulty second ECU 12 is earlier than the order of this device, it changes the order of this device to the previous one.

[0243] In both the first ECU 11 and the second ECU 12, the transmission processing can be performed by the device control unit 25 instead of the IC control unit 31. Alternatively, in both the first ECU 11 and the second ECU 12, the device control unit 25 and the IC control unit 31 can cooperate to perform the transmission processing. Furthermore, the device connected to the communication bus B is not limited to an ECU. Any communication device that transmits data via the communication bus B is acceptable.

[0244] The method for determining the timing of the end of data frame transmission is not limited to methods based on data length. When an EOF field indicating the end of transmission is set at the end of the data frame, the timing of the end of transmission of the EOF field is the timing of the end of data frame transmission. EOF is an abbreviation for End Of Frame. The waveform of the EOF field is predetermined.

[0245] It should be considered that the disclosed embodiments 1 to 4 are exemplary in all respects and not restrictive. The scope of the invention is indicated not by the foregoing meaning but by the claims, and is intended to include all modifications of the same meaning and scope as the claims.

[0246] The above description includes the features noted below.

[0247] [Note 1]

[0248] In communication system 1, after the beacon signal has been transmitted, the first ECU 11 and multiple second ECUs 12 transmit data frames via communication bus B in a predetermined order. Pseudo-frames with destinations different from those of the first ECU 11 and multiple second ECUs 12 are also transmitted via communication bus B. The first ECU 11 determines whether the second ECU 12 has transmitted a data frame at a predetermined time. If the first ECU 11 determines that the second ECU 12 has not transmitted a data frame, it changes the transmission order.

[0249] Explanation of reference numerals in the attached figures

[0250] 1 Communication System

[0251] 11. First ECU (Communication Device, Second Communication Device, Non-transmitting Device)

[0252] 12. Second ECU (Communication Device, Second Communication Device, Target Communication Device, Non-transmitting Device)

[0253] 21communication IC

[0254] 22 Input Section

[0255] 23 Output Section

[0256] 24. Device Storage Section

[0257] 25. Device Control Unit

[0258] 26 Device Bus

[0259] 31IC Control Department (Processing Department)

[0260] 32-interface

[0261] 33 IC Storage Division

[0262] 34 Clock Section

[0263] 35-bit communicator (data transmission unit, signal transmission unit)

[0264] 36IC bus

[0265] Resistors 41a, 41b, and 42

[0266] Capacitors 43, 44a, and 44b

[0267] 45 Common Mode Choke Coil

[0268] 45a First Inductor

[0269] 45b Second Inductor

[0270] 46. ​​Conversion Section

[0271] A storage medium

[0272] B Communication Bus

[0273] G1 first conductor

[0274] G2, second conductor

[0275] M vehicle

[0276] P Computer Program

[0277] W1 first conductor

[0278] W2 second conductor

[0279] Wa and Wb are the equipment wires.

Claims

1. A communication device for transmitting data via a communication bus, The communication device includes a processing unit that performs processing. The processing unit is configured such that, When a beacon signal is transmitted, for one piece of data transmitted via the communication bus by the communication device itself and a plurality of second communication devices in a predetermined order, the timing of the transmission of the target communication device included in the plurality of second communication devices determines whether the target communication device has transmitted data. If it is determined that the target communication device has not transmitted data, the order is changed. The data transmitted via the communication bus includes pseudo-data whose destination differs from that of the communication device itself and the plurality of second communication devices, except for the source communication device. The communication device includes a data transmission unit for transmitting data. The data transmission unit transmits data after a first predetermined standby period elapsed since the beacon signal transmission ended, or after a second predetermined standby period elapsed since the data transmission of the preceding second communication device ended. If the processing unit determines that the target communication device has not sent data, it extends the first predetermined standby period or the second predetermined standby period.

2. The communication device according to claim 1, wherein, The processing unit changes the order if it determines that the target communication device has not sent data multiple times in a row.

3. The communication device according to claim 1 or 2, wherein, The communication device includes a signal transmitting unit that repeatedly transmits the beacon signal.

4. A communication system comprising multiple communication devices connected to a communication bus. When the multiple communication devices are given beacon signals, they transmit data via the communication bus in a predetermined order. If the target communication device among the plurality of communication devices does not have data to be sent to any of the other communication devices besides the target communication device, it sends pseudo-data whose destination is different from that of the other communication devices. Among the plurality of communication devices, the communication device that is different from the target communication device has a processing unit that performs the processing. The processing unit determines at the scheduled time that the target communication device has sent data whether it has sent data. If it determines that the target communication device has not sent data, it changes the order. The plurality of communication devices includes a non-transmitting device that does not transmit the pseudo-data. If the processing unit determines that the target communication device has not sent data, it causes the non-transmitting device to start sending the pseudo data to prevent the transmission interval of the beacon signal from decreasing.

Images