Communication device, communication system, and communication method

Abstract

A first ECU (11) and a plurality of second ECUs (12) are connected to a communication bus (B). The first ECU (11) repeatedly transmits a beacon signal via the communication bus (B). The first ECU (11) and the plurality of second ECUs (12) each transmit data in a predetermined order in a case where the beacon signal is transmitted. The first ECU (11) or the second ECU (12) transmits dummy data different from the remaining ECUs in a case where there is no transmission data transmitted to one of the remaining ECUs other than the device.

Description

Technical Field

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

[0002] This application claims priority based on Japanese Application No. 2021-078007, filed on April 30, 2021, and invokes all the contents of that Japanese application. Background Technology

[0003] Patent Document 1 discloses a communication system for a vehicle in which multiple communication devices are connected to a communication bus. 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 data transmission device, wherein the communication device includes a transmitting unit connected to a communication bus of multiple second communication devices and transmitting data thereon. The order in which the multiple second communication devices and the transmitting unit transmit data via the communication bus is predetermined. The communication device repeatedly transmits a beacon signal indicating the start of data transmission via the communication bus. When the beacon signal is transmitted, the transmitting unit transmits data in the predetermined order. In the absence of data to be transmitted to the second communication devices, the transmitting unit transmits pseudo-data whose destination is different from that of the multiple second communication devices.

[0008] One aspect of the communication system disclosed herein includes multiple communication devices connected to a communication bus. One of the multiple communication devices repeatedly transmits a beacon signal indicating the start of data transmission via the communication bus. When the beacon signal is transmitted, the multiple communication devices transmit data via the communication bus in a predetermined order. At least one of the multiple communication devices transmits pseudo-data whose destination is different from that of the other communication devices when there is no data to be transmitted to any of the other communication devices.

[0009] One aspect of this disclosure relates to a communication method for a data transmission device, wherein the communication device is connected to a communication bus to which a plurality of second communication devices are connected, the order in which the communication device and the plurality of second communication devices transmit data via the communication bus is predetermined, the communication device repeatedly transmits a beacon signal indicating the start of data transmission via the communication bus, and the communication device performs the following steps: when the beacon signal is transmitted, transmitting data in the order stated thereon; and when there is no data to be transmitted to the second communication devices, transmitting pseudo-data whose destination is different from that of the plurality of second communication devices.

[0010] 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

[0011] Figure 1 This is a block diagram showing the main structural components of the communication system in Embodiment 1.

[0012] Figure 2 This is an illustration of the data frame transmission method.

[0013] Figure 3 It is a diagram showing the ID, function, and transmission position of the first ECU and multiple second ECUs.

[0014] Figure 4 This is a waveform diagram of the beacon signal.

[0015] Figure 5 This is an illustration of the contents of a data frame.

[0016] Figure 6 This is a block diagram showing the main structural components of the first ECU.

[0017] Figure 7 This is a circuit diagram of a bit-based communicator.

[0018] Figure 8 This is a flowchart illustrating the sequence of preparations for transmitting a frame.

[0019] Figure 9 This is a flowchart showing the sequence of transmission processes performed by the IC control unit of the first ECU.

[0020] Figure 10 This is a flowchart showing the sequence of transmission processes performed by the IC control unit of the second ECU.

[0021] Figure 11 This is an illustration of the effects of the communication system.

[0022] Figure 12 These are additional diagrams illustrating the effects of the communication system.

[0023] Figure 13 This is an explanatory diagram of the data frame transmission method in Implementation Method 2.

[0024] Figure 14 This is a flowchart showing the sequence of transmission processes performed by the IC control unit of the first ECU that does not send pseudo-frames.

[0025] Figure 15 This is a flowchart showing the sequence of transmission processes performed by the IC control unit of the second ECU that does not send pseudo-frames.

[0026] Figure 16 This is an explanatory diagram of the data frame transmission method in Implementation Method 3.

[0027] Figure 17 This is a graph showing the conditions for sending pseudo-frames.

[0028] Figure 18 This is a flowchart showing the sequence of transmission processing performed by the IC control unit of the second ECU that transmits pseudo-frames. Detailed Implementation

[0029] [The problem this disclosure aims to solve]

[0030] Data is transmitted by adjusting the voltage of the communication bus every 1-bit interval. When the voltage of the communication bus changes, the current flowing through it fluctuates, generating electromagnetic waves. Inside the vehicle, various signals are output via wires different from the communication bus. The electromagnetic waves generated from the communication bus act as interference noise. If the interference noise is strong, the signal may not be properly read.

[0031] Therefore, the objective is to provide a communication device, communication system, and communication method that can prevent the generation of strong interference noise.

[0032] [The Effects of This Disclosure]

[0033] According to this disclosure, it is possible to prevent the generation of strong interference noise.

[0034] [Description of embodiments of this disclosure]

[0035] First, embodiments of this disclosure will be described by way of example. At least some of the embodiments described below may be combined arbitrarily.

[0036] (1) One aspect of the present disclosure relates to a communication device for transmitting data, wherein the communication device includes a transmitting unit connected to a communication bus of a plurality of second communication devices and transmitting data thereon, the order in which the plurality of second communication devices and the transmitting unit transmit data via the communication bus is predetermined, the communication device repeatedly transmits a beacon signal indicating the start of data transmission via the communication bus, the transmitting unit transmits data in the order indicated when the beacon signal is transmitted, and when there is no data to be transmitted to the second communication devices, the transmitting unit transmits pseudo data whose destination is different from that of the plurality of second communication devices.

[0037] In the above method, when a beacon signal is transmitted via the communication bus, the transmitting unit transmits data via the communication bus in a predetermined order. When no data is being transmitted, the transmitting unit transmits dummy data. Therefore, the transmission interval of the transmitted beacon signal is long.

[0038] In traditional communication systems where multiple communicators are connected to a communication bus, each communicator does not transmit data unless it has data to send to other communicators. Therefore, the transmission interval of beacon signals is short. Beacon signals are transmitted by adjusting the voltage of the communication bus every 1-bit interval. This voltage change generates interference noise. Because the transmission interval of beacon signals is short, the voltage of the communication bus switches many times per unit time, resulting in high intensity interference noise.

[0039] However, in the above method, the beacon signal transmission interval is long, so the number of voltage switching operations on the communication bus per unit time is small. Therefore, the intensity of interference noise is low, preventing the generation of strong interference noise.

[0040] (2) In a communication device according to one aspect of the present disclosure, the structure of the transmitting unit conforms to IEEE 802.3cg (IEEE is a registered trademark) 10BASE-T1S.

[0041] In the above method, the transmitting unit transmits a baseband signal with a data transmission rate of 10 Mbps via a twisted pair cable.

[0042] (3) In a communication device according to one aspect of the present disclosure, a determination unit is provided, which determines whether to send the pseudo data based on the amount of data sent via the communication bus from the time the beacon signal is sent until the time of data transmission when no data is sent.

[0043] In the above method, when the beacon signal transmission interval is greater than a predetermined interval, strong interference noise is prevented. When no data is being transmitted, the transmitting unit sends pseudo-data as needed, thus efficiently transmitting pseudo-data.

[0044] (4) The communication system according to one aspect of the present disclosure has multiple communication devices connected to a communication bus. One of the multiple communication devices repeatedly sends a beacon signal indicating the start of data transmission via the communication bus. When the beacon signal is sent, the multiple communication devices transmit data via the communication bus in a predetermined order. At least one of the multiple communication devices transmits pseudo data with a destination different from the other communication devices when there is no data to be transmitted to one of the other communication devices other than itself.

[0045] In the above method, at least one of the multiple communication devices connected to the communication bus transmits spurious data when no actual data is being transmitted. Therefore, the transmission interval of the beacon signal is long. As a result, strong interference noise is prevented.

[0046] (5) In a communication system according to one aspect of this disclosure, the plurality of communication devices respectively transmit the pseudo data in the absence of the transmitted data.

[0047] In the above method, because all communication devices transmit pseudo-data, the transmission interval of the beacon signal is very long. Therefore, the intensity of interference noise generated from the communication bus is very small.

[0048] (6) In a communication system according to one aspect of this disclosure, at least one of the plurality of communication devices does not transmit data via the communication bus in the absence of the transmission data.

[0049] In the above method, one or more communication devices transmit spurious data. The remaining communication devices do not transmit spurious data. This is to prevent strong interference noise, assuming the beacon signal transmission interval is greater than a predetermined interval. By maintaining the beacon signal transmission interval at a value greater than the predetermined interval using one or more communication devices, strong interference noise is prevented. The remaining communication devices do not transmit data, for example, if no data is being transmitted. In this case, efficient data transmission can be achieved.

[0050] (7) One aspect of the present disclosure relates to a communication method of a communication device for transmitting data, wherein the communication device is connected to a communication bus to which a plurality of second communication devices are connected, the order in which the communication device and the plurality of second communication devices transmit data via the communication bus is predetermined, and a beacon signal indicating the start of data transmission is repeatedly transmitted via the communication bus, and the communication device performs the following steps: when the beacon signal is transmitted, transmitting data in the order thereon; and when there is no data to be transmitted to the second communication devices, transmitting pseudo-data whose destination is different from that of the plurality of second communication devices.

[0051] In the above method, when a beacon signal is transmitted via the communication bus, the communication device transmits data in a predetermined order via the communication bus. When no data is being transmitted, the communication device transmits spurious data. Therefore, the transmission interval of the transmitted beacon signal is long, resulting in fewer voltage switching cycles on the communication bus per unit time. Consequently, the intensity of interference noise is low, preventing the generation of strong interference noise.

[0052] [Details of the embodiments disclosed herein]

[0053] 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 indicated by the claims, which are intended to encompass all modifications within the meaning and scope equivalent to the claims.

[0054] (Implementation Method 1)

[0055] <Structure of Communication Systems>

[0056] 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 a plurality of second ECUs 12. ECU is an abbreviation for Electronic Control Unit. The first ECU 11 and the plurality of second ECUs 12 are connected to a communication bus B.

[0057] Electrical devices and sensors are connected to the first ECU 11 and multiple second ECUs 12, respectively. Illustrations of the electrical devices and sensors are omitted. The sensors detect vehicle-related values ​​and output the detected values ​​to the first ECU 11 or the multiple second ECUs 12 connected to the sensors. For example, when the sensor detection values ​​are input, the first ECU 11 and the multiple 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.

[0058] When one ECU connected to communication bus B sends a data frame, all ECUs connected to communication bus B receive the data frame. The first ECU 11 and multiple second ECUs 12, upon receiving a data frame, discard the received data frame if its destination is not their own device.

[0059] Upon receiving a data frame, the first ECU 11 and the plurality of second ECUs 12, when the data frame's destination is this device, determine the action to be performed by the electrical equipment connected to this device based on the master data contained in the received data frame. After determining the action to be performed by the electrical equipment, the first ECU 11 and the plurality of second ECUs 12 output an action signal indicating the determined action to the electrical equipment. When an action signal is input to the electrical equipment, the electrical equipment performs the action indicated by the input action signal.

[0060] <Data Frame Transmission Method>

[0061] Figure 2 This is an illustration of the data frame transmission method. Figure 3 This is a diagram showing the IDs, functions, and transmission positions of the first ECU 11 and multiple second ECUs 12. ID is an abbreviation for Identification Data. Figure 2 and Figure 3 The image shows an example of a first ECU 11 and four second ECUs 12 transmitting data frames.

[0062] When one of the first ECU 11 and one of the plurality of second ECUs 12 transmits a data frame via communication bus B, and other ECUs also transmit data frames via communication bus B, multiple data frame collisions occur. In the event of multiple data frame collisions, data frame transmission fails. Therefore, to avoid multiple data frame collisions, the first ECU 11 and the second ECU 12 transmit data frames according to, for example, PLCA (Physical Layer Collision Avoidance).

[0063] like Figure 2 As shown, beacon signals are repeatedly transmitted via communication bus B using the PLCA method. 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 through the ECU, which acts as the master unit. Figure 3 As shown, the first ECU 11 acts as the master unit. Therefore, the first ECU 11 repeatedly sends beacon signals via the communication bus B. Multiple second ECUs 12 act as slave devices.

[0064] When the first ECU 11 sends a beacon signal, the first ECU 11 and multiple second ECUs 12 send data frames in a predetermined order. For example... Figure 3 As shown, IDs are pre-assigned to the first ECU 11 and multiple second ECUs 12. Figure 3 In this example, the ID of the first ECU11 is 001. One of the four second ECUs12 is assigned a number from 002 to 005. Figure 3 In this configuration, the transmission order of 001 to 005 is set from first to fifth. The host's transmission order is first.

[0065] When the first ECU 11 sends a beacon signal, firstly, the first ECU 11 with ID 001 sends a data frame. Next, the second ECU 12 with ID 002 sends a data frame. Then, the three second ECUs 12 corresponding to IDs 003 to 005 send data frames sequentially. After the second ECU 12 with ID 005 has finished sending its data frame, the first ECU 11 sends the beacon signal again.

[0066] The first ECU 11 remains in standby mode until a constant period has elapsed since the beacon signal was transmitted. After the constant period has elapsed, the first ECU 11 transmits a data frame. Each second ECU 12 remains in standby mode until a constant period has elapsed since the data frame transmission was completed. After the constant period has elapsed, each second ECU 12 transmits a data frame. The first ECU 11 and the second ECU 12 function as either a communication device or a second communication device, respectively.

[0067] Furthermore, when the number of second ECUs 12 is different from 4, similarly to the case where the number of second ECUs 12 is 4, multiple second ECUs 12 send data frames sequentially after the first ECU 11 sends a data frame.

[0068] In addition to PLAC (PLA) communication, another communication method via the communication bus is CSMA / CD (Carrier Sense Multiple Access / Collision Detection). Similar to PLAC, in CSMA / CD, multiple ECUs transmit data frames via the communication bus. If multiple data frame collisions occur, each ECU detects the collisions. The multiple ECUs that sent the conflicting data frames then retransmit their own data frames. The timing of these data frame transmissions by the multiple ECUs is different from each other. Therefore, collisions between multiple data frames are avoided.

[0069] With CSMA / CD, the delay time of data frames resulting from multiple data frame collisions is uncertain. However, with PLCA, the transmission periods for data frames are allocated separately for the first ECU 11 and multiple second ECUs 12. Therefore, data frame collisions do not occur. As a result, PLCA can guarantee the maximum delay time. With the maximum delay time guaranteed, the design of the in-vehicle network is easier.

[0070] <Beacon Signal>

[0071] 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. In communication bus B, there is a first conductor W1 and a second conductor 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 ECU 11 and multiple second ECUs 12, each time a one-bit period elapses, adjust the voltage difference between the first wire W1 and the second wire W2 in the communication bus B to a high level or a low level, thereby transmitting the beacon signal. Figure 4 In this context, H and L represent high-level voltage and low-level voltage, respectively.

[0072] The first ECU11 and the plurality of second ECUs12 adjust the voltage difference between the first wire W1 and the second wire W2 contained in the communication bus B to a high level voltage or a low level voltage each time a 1-bit period has elapsed, thereby sending a data frame.

[0073] At each bit, a high-level voltage or a low-level voltage is indicated. Figure 4 In the example, the beacon signal consists of 7 bits. Figure 4 The beacon signal shown is output by alternating between high and low voltage levels. Furthermore, the number of bits constituting the beacon signal is not limited to 7.

[0074] 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. For example, each second ECU 12 adjusts the rise or fall timing to, for example, the end time of the beacon signal.

[0075] Here, a structure that performs processing at the rising point of the clock signal adjusts the rising point of the clock signal. A structure that performs processing at the falling point of the clock signal adjusts the falling point of the clock signal.

[0076] Synchronization between the first ECU 11 and the multiple second ECUs 12 is achieved by adjusting the rise or fall times of the clock signal in each of the second ECUs 12. Therefore, the processing times of the first ECU 11 and the multiple second ECUs 12 are substantially consistent. Furthermore, the waveform of the beacon signal is not limited to... Figure 4 The waveform shown.

[0077] <Content of the data frame>

[0078] 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. At each bit, a high-level voltage or a low-level voltage is output. For example, a bit value of 1 and 0 correspond to a high-level voltage and a low-level voltage, respectively.

[0079] The destination field of the data frame indicates the destination of the data frame. For example, the 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 may represent, 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 measured in bits.

[0080] Regarding data frames, the number of bits constituting the portion outside the data fields is fixed. If the length of the master data is determined, then the length of the data frame is also determined. The number of bits constituting the master data varies. However, the upper limit of the number of bits constituting the master data is predetermined.

[0081] The first ECU 11 and multiple second ECUs 12 respectively transmit data frames whose destination is in the ECU connected to the communication bus B and exists in the other ECUs besides the sending source. Hereinafter, this data frame will be referred to as a transmission frame. A transmission frame is equivalent to transmitting data.

[0082] like Figure 3 As shown, with 5 IDs assigned, the destination of the transmission frame sent by the first ECU11 with ID 001 is 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 one of the first ECU11 corresponding to ID 001 and one of the three second ECUs12 corresponding to IDs 003 to 005.

[0083] The first ECU 11 and the plurality of second ECUs 12 further transmit data frames whose destination does not exist in the ECU connected to the communication bus B. This data frame will be referred to below as a pseudo-frame. A pseudo-frame is equivalent to pseudo-data; that is, data without a destination is pseudo-data.

[0084] like Figure 3 As shown, with 5 IDs assigned, the destination of the pseudo-frame is different from any of the first ECU11 corresponding to 001 and any of the four second ECUs12 corresponding to 002 to 005. For example, the destination of the pseudo-frame could be the ECU with ID 999.

[0085] As described above, when the first ECU 11 and the plurality of 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 the plurality of second ECUs 12 discard the received spurious frame.

[0086] As described 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 is in the ECU connected to communication bus B, and is different from any of the other ECUs besides the sending source.

[0087] <Structure of the first ECU11>

[0088] 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 a device bus 26. The communication IC 21 is further connected to a 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.

[0089] The sensor outputs its detected value to the input unit 22. For example, when the sensor's detected value is 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.

[0090] 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, communication IC21 discards any received spurious frames.

[0091] When the 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. In other words, when the communication IC 21 receives a transmission frame whose destination is this device, it provides the received transmission frame to the device control unit 25.

[0092] 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.

[0093] The device storage unit 24 is, for example, a non-volatile memory. The 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 computer program P, thereby performing the transmission frame generation process and the signal output process in parallel. 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.

[0094] 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.

[0095] <Structure of Communication IC21>

[0096] 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.

[0097] 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. 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.

[0098] 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.

[0099] Bit communicator 35 transmits a 1-bit signal or data provided by IC control unit 31 each time the clock signal rises. Bit communicator 35 transmits the 1-bit 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 voltage or a low-level voltage. The voltage difference is maintained at a high-level voltage or a low-level voltage throughout one cycle of the clock signal. The cycle of the clock signal corresponds to the period of 1 bit.

[0100] Bit communicator 35 detects the voltage difference between the first wire W1 and the second wire W2 included in the communication bus B whenever the clock signal rises, thereby receiving 1 bit of signal or data. Bit communicator 35 notifies the IC control unit 31 of the received 1 bit of signal or data.

[0101] 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.

[0102] 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.

[0103] 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, and receive 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.

[0104] <Structure of Bit Communicator 35>

[0105] 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 respectively wound around the magnetic body.

[0106] 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.

[0107] A capacitor 44a and a common-mode choke coil 45 are disposed midway along the device wire Wa, along with a first inductor 45a. The capacitor 44a is disposed on the first wire W1 side of the first inductor 45a. Similarly, a capacitor 44b and a second inductor 45b, along with a common-mode choke coil 45, are disposed midway along the device wire Wb. The capacitor 44b is disposed on the second wire W2 side of the second inductor 45b.

[0108] 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 node 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 first conductor G1. First conductor G1 is disposed within the first ECU11.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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 0 or 1. For example, if the voltage difference is a low-level voltage, the bit value is zero. If the voltage difference is a high-level voltage, the bit value is 1. 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 0 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 disposed within the first ECU 11 and is different from the first conductor G1.

[0113] 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.

[0114] 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.

[0115] The bit communicator 35 conforms to the IEEE 802.3cg 10BASE-T1S standard. 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 a registered trademark and is an abbreviation for the Institute of Electrical and Electronics Engineers.

[0116] <Structure of the second ECU12>

[0117] In the structure of the second ECU 12, except for the structure related to the transmission of the beacon signal, 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.

[0118] In the second ECU 12, the IC control unit 31 does not provide the 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. The rising point of the clock signal is adjusted by a structure that performs processing at the rising point of the clock signal. The falling point of the clock signal is adjusted by a structure that performs processing at the falling point of the clock signal.

[0119] The IC control unit 31 of the second ECU 12 performs write processing, transmit processing, and receive processing in the same way as the IC control unit 31 of the first ECU 11. However, in the transmit processing 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, and then causes the bit communicator 35 to transmit a transmit frame or a pseudo frame.

[0120] <Order of Data Frames Sent>

[0121] Figure 8 This is a flowchart illustrating the sequence of preparations for transmitting a frame. The same preparations for transmitting a frame are performed in both the first ECU 11 and the second ECU 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.

[0122] 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 input to the input unit 22. If the device control unit 25 determines that a transmission frame should not be generated (S1: "No"), it executes step S1 again and waits until the time for generating the transmission frame arrives.

[0123] 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 that generates a transmission frame with a predetermined data length, 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.

[0124] 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.

[0125] 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.

[0126] 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 to 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.

[0127] 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.

[0128] Figure 9This is a flowchart illustrating the sequence of transmission processes performed by the IC control unit 31 of the first ECU 11. In the transmission process, the IC control unit 31 first determines whether to transmit a beacon signal (step S21). The moment the beacon signal is transmitted is the moment when the second ECU 12, which is the last ECU in sequence, finishes transmitting the data frame. As described above, the data length field of the data frame indicates the length of the main data. Based on the data length indicated in the data length field of the data frame transmitted by the last ECU 12, the IC control unit 31 can determine the moment when the transmission of the data frame ends.

[0129] If the IC control unit 31 determines that it will not send a beacon signal (S21: "No"), it executes step S21 again and waits until the time to send the beacon signal arrives. If the IC control unit 31 determines that it will send a beacon signal (S21: "Yes"), it instructs the bit communicator 35 to send 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.

[0130] After executing step S22, the IC control unit 31 determines whether it is time to start transmitting 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 constant period has elapsed since the end of the beacon signal transmission. The moment when a constant period has elapsed is the start time of transmission. If the IC control unit 31 determines that it is not time to start transmission (S23: "No"), it executes step S23 again and waits until the start time of transmission arrives.

[0131] 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 (step S25). The bit communicator 35 functions as a transmission unit. After executing step S25, the IC control unit 31 deletes the transmitted frame from the IC storage unit 33 (step S26).

[0132] 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.

[0133] Figure 10 This is a flowchart illustrating the sequence of transmission processes performed by the IC control unit 31 of the second ECU 12. Steps S34 to S37 of the transmission processes performed by the IC control unit 31 of the second ECU 12 are the same as steps S24 to S27 of the transmission processes performed by the IC control unit 31 of the first ECU 11. Therefore, the explanation of steps S34 to S37 is omitted.

[0134] 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.

[0135] 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 time to start transmitting a data frame (step S33).

[0136] like Figure 3 As shown, when the transmission order is assigned, in step S33, the IC control unit 31 determines whether a constant period has elapsed since the first ECU 11 or the second ECU 12 with the previous transmission order ended transmitting the data frame. The moment when the constant period has elapsed is the moment when transmission begins. Regarding the second ECU 12 with ID 002, the ECU preceding it is the first ECU 11 with ID 001. Regarding the second ECU 12 with ID 003, the ECU preceding it is the second ECU 12 with ID 002.

[0137] Based on the data length shown in the data length field of the data frame sent by the first ECU 11 or the second ECU 12 that is preceding it, the IC control unit 31 can determine the time when the first ECU 11 or the second ECU 12 ends the transmission of the data frame.

[0138] If the IC control unit 31 determines that it is not the time to start transmitting the data frame (S33: "No"), it executes step S33 and waits until the time to start transmitting the data frame arrives. If the IC control unit 31 determines that it is the time to start transmitting the data frame (S33: "Yes"), it executes step S34. After ending the transmission process, the IC control unit 31 executes the transmission process again.

[0139] As described above, when there is no transmission frame in the IC storage unit 33 for sending to other ECUs different from this device, the bit communicator 35 of the first ECU 11 and the plurality of second ECUs 12 will send a pseudo frame. Therefore, when it is the turn of transmission, the bit communicator 35 of the first ECU 11 and the plurality of second ECUs 12 will definitely send a transmission frame or a pseudo frame.

[0140] Additionally, regarding the first ECU 11 and the multiple second ECUs 12, the order in which the data frames are sent is as follows: Figure 3 As shown, this is predetermined. Therefore, when the bit communicators 35 of the first ECU 11 and the plurality of second ECUs 12 are sent with beacon signals, they transmit data frames via the communication bus B in a predetermined order.

[0141] <The Effects of Communication System 1>

[0142] Figure 11 This is an explanatory diagram illustrating the effect of communication system 1. First, a conventional communication system connecting five ECUs to the communication bus will be described. In this conventional system, when it is each ECU's turn to transmit, if no transmission frame is available in the IC storage unit 33, it does not transmit a data frame. After a constant period has elapsed since the completion of beacon signal transmission, if the first ECU has not transmitted a data frame, the second ECU remains idle until another constant period has elapsed. If the second ECU has not transmitted a data frame, the third ECU remains idle until another constant period has elapsed. The remaining three ECUs also remain idle until a constant period has elapsed. If, despite the constant period elapsed, the fifth ECU has still not transmitted a data frame, the beacon signal is transmitted again.

[0143] As a result, in the case where there are no transmission frames in the IC storage unit 33 for each of the five ECUs, such as Figure 11As shown on the upper side, a beacon signal is transmitted every 5 constant intervals. The transmission interval of the beacon signal is short. With a short transmission interval, the voltage of communication bus B is switched more frequently to change the voltage difference to a high or low level. This switching of the voltage of communication bus B generates interference noise. The higher the number of switching times per unit time, the stronger the interference noise. In this case, it is possible to incorrectly read signals output via wires different from communication bus B, such as action signals.

[0144] However, in communication system 1, if there are no transmission frames in the IC storage unit 33 for the first ECU 11 and the four second ECUs 12 respectively, such as Figure 11 As shown on the lower side, the first ECU 11 and the plurality of second ECUs 12 each necessarily transmit pseudo-frames. Therefore, the transmission interval of the transmitted beacon signal is long. With a long transmission interval, the number of voltage switching operations on the communication bus B is small. In this case, the intensity of interference noise is low. As a result, the generation of strong interference noise is prevented.

[0145] In communication system 1, the first ECU 11 and four second ECUs 12 all send pseudo frames, so the transmission interval of the beacon signal is very long. Therefore, the intensity of the interference noise generated from the communication bus B is very small.

[0146] Even when the number of second ECUs 12 is different from 4, the communication system 1 achieves the same effect as described above.

[0147] Furthermore, all bit values ​​of the main data constituting the pseudo-frame are preferably identical. In this case, the number of voltage switching times per unit time is reduced.

[0148] Figure 12 This is another explanatory diagram of the effect of communication system 1. Here, the effect of communication system 1 is explained using the spectrum of the signal (data) propagated via communication bus B. In conventional communication systems, when there are no transmission frames in the IC storage unit 33 for each of the five ECUs, a beacon signal is transmitted every time a constant transmission interval has elapsed. As a result, the same waveform appears repeatedly periodically. In this case, the spectrum is excited at frequency intervals of (1 / transmission interval). Regarding conventional communication systems, because the transmission interval is short, as in Figure 12 As shown on the left, the frequency intervals of the excitation spectrum are large.

[0149] In communication system 1, when there are no transmission frames in the IC storage unit 33 for the first ECU 11 and the second ECU 12 respectively, as in the conventional case, a beacon signal is transmitted every time a constant transmission interval has elapsed. Therefore, the frequency spectrum is excited at frequency intervals of (1 / transmission interval). Regarding communication system 1, because the transmission interval is long, therefore, as... Figure 12 As shown on the right, the frequency intervals of the excitation spectrum are short.

[0150] In conventional communication systems, the number of excitation spectra within a constant frequency range is small. Therefore, the intensity of each spectrum is high. As a result, there are spectra that function as strong interference noise. On the other hand, in communication system 1, the number of excitation spectra within a constant frequency range is large. Therefore, the intensity of each spectrum is low. Therefore, there are no spectra that function as strong interference noise. As a result, the generation of strong interference noise is prevented.

[0151] (Implementation Method 2)

[0152] In embodiment 1, all ECUs connected to the communication bus B transmit pseudo-frames. This prevents the generation of strong interference noise. However, the structure for preventing the generation of strong interference noise is not limited to the structure where all ECUs transmit pseudo-frames.

[0153] The differences between Embodiment 2 and Embodiment 1 will now be explained. All other structures, except those described later, are the same as in Embodiment 1; therefore, the same reference numerals will be used for the structural parts common to Embodiment 1, and their descriptions will be omitted.

[0154] <Data Frame Transmission Method>

[0155] Figure 13 This is an explanatory diagram of the data frame transmission method in Embodiment 2. Figure 13 The image shows an example of a first ECU 11 and four second ECUs 12 transmitting data frames. The IDs, functions, and transmission order of the first ECU 11 and the four second ECUs 12 are shown below. Figure 3 The location is determined as shown.

[0156] In the communication system 1 of Embodiment 2, no strong interference noise is generated when the beacon signal transmission interval is greater than or equal to a predetermined interval. The predetermined interval is a constant value. Furthermore, the predetermined interval is shorter than the maximum transmission interval when all four second ECUs 12 have transmitted data frames.

[0157] exist Figure 13In the example, when three of the four second ECUs (ECU 11 and ECU 12) send data frames, the transmission interval is greater than a predetermined interval. In this case, the remaining two ECUs do not need to send pseudo-frames.

[0158] In communication system 1, the number of ECUs connected to communication bus B is denoted as N. N is an integer greater than or equal to 3. The N ECUs consist of a first ECU 11 and (N-1) second ECUs 12. The number of ECUs sending pseudo-frames is denoted as P. P is a natural number less than N. The number of ECUs not sending pseudo-frames is denoted as Q. Q is a natural number, calculated using (N-P). Figure 13 In the example, N, P, and Q are 5, 3, and 2, respectively.

[0159] As described above, when P ECUs send data frames, the beacon signal transmission interval is greater than a predetermined interval. Q ECUs do not need to send pseudo-frames. The Q ECUs that do not send pseudo-frames can be any one of the first ECU 11 and (N-1) second ECUs 12.

[0160] <Order of Data Frames Sent>

[0161] The IC control unit 31 of the first ECU 11 that sends the pseudo-frame performs the transmission process in the same way as in Embodiment 1. However, regarding step S21 of the transmission process, if the second ECU 12, which is the last in the order of the last position after a constant period of time has elapsed, has not started transmitting the data frame, this time point is the moment when the beacon signal is transmitted.

[0162] Figure 14 This is a flowchart illustrating the sequence of transmission processes performed by the IC control unit 31 of the first ECU 11 that does not send dummy frames. In the transmission process, the IC control unit 31 of the first ECU 11 that does not send dummy frames similarly performs steps S21 to S26 of the transmission process performed by the IC control unit 31 of the first ECU 11 that sends dummy frames. Therefore, the explanation of steps S21 to S26 is omitted.

[0163] If the IC control unit 31 of the first ECU 11, which does not send pseudo-frames, determines that no transmission frame is stored in the IC storage unit 33 (S24: "No"), it terminates the transmission process. If the transmission process has been terminated, the IC control unit 31 will execute the transmission process again.

[0164] The IC control unit 31 of the second ECU 12 that sends the pseudo-frame performs the transmission process in the same way as in Embodiment 1. However, regarding step S33 of the transmission process, if the first ECU 11 or the second ECU 12, which is the previous one after a constant period of time has elapsed, has not started transmitting the data frame, the time point after a further constant period of time from that point is the time when the transmission of the data frame begins.

[0165] Figure 15 This is a flowchart illustrating the sequence of transmission processes performed by the IC control unit 31 of the second ECU 12 that does not send dummy frames. In the transmission process, the IC control unit 31 of the second ECU 12 that does not send dummy frames similarly performs steps S31 to S36 of the transmission process performed by the IC control unit 31 of the second ECU 12 that sends dummy frames. The explanation of steps S31 to S36 is omitted.

[0166] If the IC control unit 31 of the second ECU12, which does not send pseudo-frames, determines that no transmission frame is stored in the IC storage unit 33 (S34: "No"), it terminates the transmission process. If the transmission process has been terminated, the IC control unit 31 will execute the transmission process again.

[0167] In the communication system 1 of embodiment 2, P ECUs transmit pseudo frames when no transmission frame is available in the IC storage unit 33. Q ECUs do not transmit pseudo frames when no transmission frame is available in the IC storage unit 33.

[0168] When the first ECU 11 is included in P 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 Q ECUs, the IC control unit 31 of the first ECU 11 performs... Figure 14 The sending process is shown below.

[0169] When the second ECU 12 is included in P ECUs, the IC control unit 31 of the second ECU 12 included in the P ECUs performs the transmission process in the same way as in Embodiment 1. When the second ECU 12 is included in Q ECUs, the IC control unit 31 of the second ECU 12 included in the Q ECUs performs... Figure 15 The sending process is shown below.

[0170] <The Effects of Communication System 1>

[0171] In the communication system 1 of embodiment 2, the transmission interval of the beacon signal is maintained at a value greater than or equal to a predetermined interval by the P ECUs, thus preventing the generation of strong interference noise. Each of the Q ECUs' bit communicators 35 does not transmit data frames when there are no transmission frames in the IC storage unit 33. Therefore, efficient transmission of transmission frames is achieved.

[0172] (Implementation Method 3)

[0173] In embodiment 2, the bit communicator 35 of the Q ECUs may not necessarily send pseudo frames if there are no transmission frames in the IC storage unit 33.

[0174] The differences between Embodiment 3 and Embodiment 2 will now be explained. All other structures, except those described later, are the same as in Embodiment 2; therefore, the same reference numerals will be used for the structural parts common to Embodiment 2, and their descriptions will be omitted.

[0175] <Data Frame Transmission Method>

[0176] Figure 16 This is an explanatory diagram of the data frame transmission method in Embodiment 3. Figure 16 The example shown illustrates a first ECU 11 and four second ECUs 12 transmitting data frames. In Embodiment 3, similar to Embodiment 2, when P ECUs transmit data frames, the beacon signal transmission interval is a predetermined interval or more. Figure 16 In the example, P is 3.

[0177] In the communication system 1 of embodiment 2, each of the P ECUs transmits a pseudo-frame when no transmission frame is stored in the IC storage unit 33. However, for example, if one of the Q ECUs transmits a transmission frame, pseudo-frames are transmitted by (P-1) ECUs, thereby achieving a transmission interval of more than a predetermined interval.

[0178] In the communication system 1 of embodiment 3, the last P second ECUs 12 function as ECUs for transmitting pseudo-frames. The last P second ECUs 12 adjust the transmission interval to make it a predetermined interval or higher. Figure 16 In the example, the three second ECUs 12 corresponding to 003 to 005 adjust their transmission intervals. The bit position of the data frame transmitted by the bit communicator 35 of each of the P second ECUs 12 is after the second bit.

[0179] Figure 17 This is a graph showing the conditions for sending pseudo-frames. Figure 17 The sending conditions shown correspond to Figure 16 The structure. That is, in Figure 17The diagram illustrates the transmission conditions of communication system 1, where N, P, and Q are 5, 3, and 2, respectively. Among the Q ECUs, there is a first ECU 11 with ID 001 and a second ECU 12 with ID 002. The bit communicator 35 of the first Q ECUs does not transmit pseudo-frames if no transmission frame is present in the IC storage unit 33.

[0180] Among the P ECUs, there is a second ECU 12 corresponding to 003 to 005. When the second ECU 12 with ID 003 does not have a transmission frame in the IC storage unit 33, it transmits a pseudo frame when the number of data frames transmitted by the first Q ECUs is 0. When the second ECU 12 with ID 003 does not have a transmission frame in the IC storage unit 33, it does not transmit a data frame when the number of data frames transmitted by the first Q ECUs is 1 or more. When the number of data frames is 1 or more, the last (P-1) ECUs can adjust the transmission interval to make the transmission interval a predetermined interval or higher.

[0181] When the second ECU 12 with ID 004 has no transmission frames in the IC storage unit 33, it transmits a pseudo-frame if the number of data frames transmitted by the first (Q+1) ECUs is 1. When the second ECU 12 with ID 004 has no transmission frames in the IC storage unit 33, it does not transmit any data frames if the number of data frames transmitted by the first (Q+1) ECUs is 2 or more. When the number of data frames is 2, the last (P-2) ECUs can adjust the transmission interval to make the transmission interval a predetermined interval or higher. When the number of data frames is 3 (=P), the transmission interval is already a predetermined interval or higher, so there is no need to transmit a pseudo-frame.

[0182] When the second ECU 12 with ID 005 has no transmission frames in the IC storage unit 33, it transmits a pseudo frame if the number of data frames transmitted by the first (Q+2) ECUs is 2. When the second ECU 12 with ID 004 has no transmission frames in the IC storage unit 33, it does not transmit a data frame if the number of data frames transmitted by the first (Q+2) ECUs is 3 or more (=P). When the number of data frames is 3 or more, the transmission interval is already greater than the predetermined interval, so there is no need to transmit a pseudo frame.

[0183] <Order of Data Frames Sent>

[0184] In the communication system 1 of Embodiment 3, the bit communicator 35 of the first ECU 11 does not transmit data frames when there are no transmission frames in the IC storage unit 33. Therefore, the IC control unit 31 of the first ECU 11 in Embodiment 3 executes... Figure 14 The sending process is shown below.

[0185] The bit communicator 35 of the second ECU 12 with ID 002 does not send a pseudo-frame when there is no transmission frame in the IC storage unit 33. The IC control unit 31 of the second ECU 12, which does not send pseudo-frames, performs the same operation as in Embodiment 2. Figure 15 The sending process is shown below.

[0186] Figure 18 This is a flowchart illustrating the sequence of transmission processes performed by the IC control unit 31 of the second ECU 12 that transmits pseudo-frames. In the transmission process, the IC control unit 31 of the second ECU 12 that transmits pseudo-frames similarly executes steps S31 to S36 of the transmission process performed by the IC control unit 31 of the second ECU 12 in Embodiment 2. Therefore, the explanation of steps S31 to S36 is omitted.

[0187] In the transmission process, the IC control unit 31 of the second ECU 12, when determining that no transmission frame is stored in the IC storage unit 33 (S34: "No"), determines whether to transmit a pseudo-frame based on the number of data frames transmitted via the communication bus B from the transmitted beacon signal until the turn of a data frame transmission (step S41). For example, in step S41 of the transmission process of the second ECU 12 with ID 003, as follows... Figure 17 As shown, if the number of data frames sent by the first Q ECUs is 0, the IC control unit 31 determines that a pseudo-frame has been sent. If the number of data frames sent by the first Q ECUs is 1 or more, the IC control unit 31 determines that a pseudo-frame has not been sent.

[0188] Even if the amount of data contained in the data field of a data frame varies, the amount of data in a data frame remains essentially constant because the variation is small. Therefore, the number of data frames transmitted via communication bus B is equivalent to the amount of data transmitted via communication bus B. The IC control unit 31 functions as a determination unit.

[0189] If the IC control unit 31 determines that a pseudo-frame should be sent (S41: "Yes"), it instructs the bit communicator 35 to send the pseudo-frame stored in the IC storage unit 33 bit by bit (step S42). If the IC control unit 31 determines that a pseudo-frame should not be sent (S41: "No"), or after executing step S42, it ends the transmission process. After ending the transmission process, the IC control unit 31 executes the transmission process again.

[0190] <The Effects of Communication System 1>

[0191] Each of the P second ECUs 12's bit communicators 35 transmits pseudo-frames as needed, thus transmitting pseudo-frames efficiently.

[0192] The communication system 1 in embodiment 3 also has the same effect as the communication system 1 in embodiment 2.

[0193] <Modifications of Implementation Method 3>

[0194] In Embodiment 3, when the data volume of the data frame varies greatly, the IC control unit 31 of the second ECU 12 that sends the pseudo-frame can also perform the transmission processing step S41 in the following manner. In step S41, the IC control unit 31 determines whether to send a pseudo-frame based on the data volume of the data transmitted via the communication bus B from the transmitted beacon signal until the turn of the data frame transmission.

[0195] As described above, in Embodiment 3, two types of ECUs are connected to the communication bus B. These are an ECU that does not send dummy frames and an ECU that determines whether to send a dummy frame based on the amount of data transmitted via the communication bus B when no dummy frame is sent. In the communication system 1 of Embodiment 3, as described in Embodiments 1 and 2, an ECU that always sends a dummy frame when no dummy frame is sent can also be connected to the communication bus B. Furthermore, in Embodiment 3, when P is 1, the second ECU 12 is not included among the P ECUs.

[0196] <Variations of Embodiments 1-3>

[0197] In the first ECU 11 and the second ECU 12 of embodiments 1 to 3, the transmission process may be performed by the device control unit 25 instead of the IC control unit 31. Furthermore, in the first ECU 11 and the second ECU 12, the device control unit 25 and the IC control unit 31 may cooperate in performing the transmission process. Further, the destination of the pseudo-frame can also be the transmission source. In this case, when the first ECU 11 and the multiple second ECUs 12 receive a data frame, they discard the received data frame if the destination and transmission source of the received data frame are the same. Additionally, the device connected to the communication bus B is not limited to an ECU. It is acceptable as long as the device connected to the communication bus B is a communication device that transmits data via the communication bus B.

[0198] The method for determining the end time 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 end time of the EOF field is the end time of the data frame transmission. EOF is an abbreviation for End Of Frame. The waveform of the EOF field is predetermined.

[0199] It should be considered that the disclosed embodiments 1 to 3 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 within the meaning and scope equivalent to the claims.

[0200] Explanation of reference numerals in the attached figures

[0201] 1. Communication System

[0202] 11 First ECU (Communication Device, Second Communication Device)

[0203] 12 Second ECU (Communication Device, Second Communication Device)

[0204] 21 Communication IC

[0205] 22 Input Section

[0206] 23 Output Section

[0207] 24. Device Storage Section

[0208] 25. Device Control Unit

[0209] 26 Device Bus

[0210] 31 IC Control Unit (Decision Unit)

[0211] 32-interface

[0212] 33 IC Storage Division

[0213] 34 Clock Section

[0214] 35-bit communicator (transmitter)

[0215] 36 IC bus

[0216] Resistors 41a, 41b, and 42

[0217] Capacitors 43, 44a, and 44b

[0218] 45 Common mode choke coil

[0219] 45a First Inductor

[0220] 45b Second Inductor

[0221] 46. ​​Conversion Section

[0222] A storage medium

[0223] B Communication Bus

[0224] G1 First Conductor

[0225] G2 Second Conductor

[0226] M vehicle

[0227] P Computer Program

[0228] W1 First Conductor

[0229] W2 Second Conductor

[0230] Wa, Wb equipment wires

Claims

1. A communication device for transmitting data, The communication device includes a transmitting unit connected to a communication bus to which multiple second communication devices are connected, and transmits data. The order in which the plurality of second communication devices and transmitting units transmit data via the communication bus is predetermined. The communication device repeatedly sends beacon signals indicating the start of data transmission via the communication bus. The transmitting unit transmits data in the specified order upon receiving the beacon signal. The transmitting unit transmits pseudo-data whose destination is different from the plurality of second communication devices when there is no data to be transmitted to the second communication devices. The communication device includes a determination unit that, in the absence of transmitted data, determines whether to transmit the spurious data based on the amount of data transmitted via the communication bus from the time the beacon signal was transmitted until the turn of data transmission.

2. The communication device according to claim 1, wherein, The structure of the transmitting unit conforms to IEEE 802.3cg 10BASE-T1S.

3. A communication system, The communication system includes multiple communication devices connected to the communication bus. One of the multiple communication devices repeatedly transmits a beacon signal indicating the start of data transmission via the communication bus. The plurality of communication devices transmit data via the communication bus in a predetermined order upon receiving the beacon signal. At least one of the plurality of communication devices transmits pseudo-data whose destination is different from the other communication devices, even when there is no data to be transmitted to any of the other communication devices besides itself. In the absence of transmitted data, the communication system determines whether to transmit the false data based on the amount of data transmitted via the communication bus from the time the beacon signal was transmitted until the turn for data transmission.

4. The communication system according to claim 3, wherein, Each of the plurality of communication devices sends the pseudo data in the absence of the actual data to be transmitted.

5. The communication system according to claim 3, wherein, At least one of the plurality of communication devices does not transmit data via the communication bus in the absence of the transmission data.

6. A communication method, which is a communication method of a communication device for transmitting data. The communication device is connected to a communication bus that connects to multiple second communication devices. The order in which the communication device and the plurality of second communication devices transmit data via the communication bus is predetermined. The communication device repeatedly sends beacon signals indicating the start of data transmission via the communication bus. The communication device performs the following steps: If the beacon signal is transmitted, data is transmitted in the specified order; In the absence of data to be transmitted to the second communication device, pseudo-data with a destination different from the plurality of second communication devices is transmitted; and In the absence of the data to be transmitted, the decision to transmit the spurious data is made based on the amount of data transmitted via the communication bus from the moment the beacon signal was transmitted until the turn for data transmission.

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