Communication device, communication system, and communication method

Abstract

A communication device has a data transmitting section which is connected to a communication bus and transmits data, and a processing section which performs processing. The communication bus is connected to a plurality of communication apparatuses. The order in which the plurality of communication apparatuses and the data transmitting section transmit data via the communication bus is determined. A start signal indicating the start of data transmission is repeatedly transmitted via the communication bus. The data transmitting section transmits data in accordance with the order when the start signal is transmitted. The processing section changes the transmission interval of the start signal.

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. 2021-129095, filed on August 5, 2021, and invokes all the contents of that Japanese application. Background Technology

[0003] Patent Document 1 discloses a vehicle communication system 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 the communication apparatus disclosed herein includes: a data transmission unit connected to a communication bus and transmitting data, the communication bus being connected to a plurality of communication devices; and a processing unit performing processing, wherein the order in which the plurality of communication devices and the data transmission unit transmit data via the communication bus is determined, a start signal is repeatedly transmitted via the communication bus, the start signal indicating the start of data transmission, the data transmission unit transmitting data in the order indicated by the start signal being transmitted, and the processing unit changing the transmission interval of the start signal.

[0008] One aspect of the communication system disclosed herein includes multiple communication devices connected to a communication bus. One of the multiple communication devices has a signal transmitting unit that repeatedly transmits a start signal via the communication bus, the start signal indicating the start of data transmission. Each of the multiple communication devices has a data transmitting unit that transmits data via the communication bus in a predetermined order after the start signal has been transmitted. At least one of the multiple communication devices also has a processing unit that performs processing and changes the transmission interval of the start signal.

[0009] One aspect of this disclosure relates to a communication method of a communication device that transmits data. The communication device is connected to a communication bus, which is connected to multiple communication devices. The order in which the communication device and the multiple communication devices transmit data via the communication bus is determined. A start signal is repeatedly transmitted via the communication bus, indicating the start of data transmission. The communication device performs the following steps: upon receiving the start signal, transmitting data according to the specified order; and changing the transmission interval of the start signal.

[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 a communication device, or as a communication system that includes a 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 IDs, functions, and transmission order 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 a block diagram showing the main structural components of the first ECU.

[0016] Figure 6 This is a circuit diagram of a bit-based communicator.

[0017] Figure 7 This is a flowchart showing the sequence of changes during standby.

[0018] Figure 8 This is a flowchart illustrating the sequence of steps for preparing to send a data frame.

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

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

[0021] Figure 11This is an illustrative diagram showing the relationship between transmission interval and interference noise.

[0022] Figure 12 This is another illustrative diagram showing the relationship between transmission interval and interference noise.

[0023] Figure 13 This is a block diagram showing the main structural components of the communication system in Embodiment 2.

[0024] Figure 14 This is a flowchart showing the sequence of changes during standby.

[0025] Figure 15 This is a block diagram showing the main structural components of the communication system in Embodiment 3.

[0026] Figure 16 It is a chart that shows the contents of sequential data.

[0027] Figure 17 This is an illustration of the transmission of data frames.

[0028] Figure 18 This is a block diagram showing the main structural components of the first ECU.

[0029] Figure 19 This is a flowchart showing the order in which the sequence changes.

[0030] Figure 20 This is an illustration of the transmission interval when no data frames are being transmitted.

[0031] Figure 21 This is a block diagram showing the main structural components of the communication system in Embodiment 4.

[0032] Figure 22 This is a flowchart showing the sequence of changes to the data during the final period. Detailed Implementation

[0033] [The problem this disclosure aims to solve]

[0034] Data is transmitted by adjusting the voltage of the communication bus each 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.

[0035] This disclosure was made in view of the above circumstances, and its purpose is to provide a communication device, communication system, and communication method capable of preventing the generation of strong interference noise.

[0036] [The Effects of This Disclosure]

[0037] The above method can prevent the generation of strong interference noise.

[0038] [Description of embodiments of this disclosure]

[0039] First, embodiments of this disclosure will be described by way of example. At least some of the embodiments described below may be combined arbitrarily.

[0040] (1) A communication device according to one aspect of the present disclosure includes: a data transmission unit connected to a communication bus and transmitting data, the communication bus being connected to a plurality of communication devices; and a processing unit that performs processing, wherein the order in which the plurality of communication devices and the data transmission unit transmit data via the communication bus is determined, a start signal is repeatedly transmitted via the communication bus, the start signal indicating the start of data transmission, the data transmission unit transmitting data in the order in which the start signal is transmitted, and the processing unit changing the transmission interval of the start signal.

[0041] In the above method, a start signal is sent by adjusting the voltage of the communication bus every bit interval. This voltage change generates interference noise. When the start signal transmission interval is short, the voltage of the communication bus switches many times per unit time, resulting in strong interference noise. The processing unit changes the start signal transmission interval. Therefore, the processing unit can prevent the generation of strong interference noise.

[0042] (2) In a communication device according to one aspect of the present disclosure, the data transmission unit is in standby mode when it is time to transmit data, and the data transmission unit starts transmitting data when the standby period becomes longer than the standby period. The transmission interval of the start signal increases correspondingly to the increase of the standby period, and the processing unit changes the transmission interval of the start signal by changing the standby period.

[0043] In the above method, the processing unit changes the standby period. This, in turn, changes the interval between the start signal transmissions.

[0044] (3) In a communication device according to one aspect of the present disclosure, the processing unit obtains the number of devices connected to the communication bus from the outside, and the processing unit changes the standby period based on the obtained number of devices.

[0045] In the above method, for example, a reference interval for the transmission interval of the start signal is predetermined and set. In this case, as an example, the processing unit subtracts the period consumed by transmitting the start signal from the reference interval. The processing unit divides the subtraction value obtained by the subtraction by the number of devices. The processing unit, for example, changes the standby period to the division value obtained by the division. For example, if a standby period is set for all devices connected to the communication bus, the standby period of each device is changed to the division value. At this time, even if all devices do not transmit data, the transmission interval of the start signal is the reference interval. The transmission interval of the start signal will not become a value lower than the reference interval. Therefore, even when the reference interval is long, strong interference noise will not be generated.

[0046] (4) One aspect of the communication device disclosed herein includes a signal transmitting unit that transmits the start signal via the communication bus. The signal transmitting unit is in standby mode when the last communication device in the order of data transmission among the plurality of communication devices has finished transmitting data or when the last communication device has not transmitted data. When the standby period becomes a second standby period or longer, the signal transmitting unit transmits the start signal again. The processing unit changes the transmission interval of the start signal by changing the second standby period.

[0047] In the above method, the processing unit changes the second standby period. This changes the transmission interval of the start signal.

[0048] (5) In a communication device according to one aspect of the present disclosure, the processing unit obtains period data related to the second standby period from the outside, and the processing unit changes the second standby period based on the obtained period data.

[0049] In the above method, the processing unit changes the second standby period based on the acquired period data.

[0050] (6) In a communication device according to one aspect of the present disclosure, when the signal transmitting unit finishes transmitting the start signal, the data transmitting unit starts transmitting data after a standby period, the processing unit obtains the period data representing an integer exceeding the number of devices connected to the communication bus, and the processing unit changes the second standby period to the product of the standby period and a value obtained by subtracting the number of devices from the integer represented by the period data.

[0051] In the above method, the processing unit changes the second standby period to a value corresponding to the integer represented by the period data.

[0052] (7) In a communication device according to one aspect of the present disclosure, the structure of the data transmission unit conforms to IEEE 802.3cg 10BASE-T1S.

[0053] In the above method, the data transmission unit transmits a baseband signal with a data rate of 10 Mbps via a twisted pair cable.

[0054] (8) A communication system according to one aspect of the present disclosure includes multiple communication devices connected to a communication bus. One of the multiple communication devices has a signal transmitting unit that repeatedly transmits a start signal via the communication bus, the start signal indicating the start of data transmission. Each of the multiple communication devices has a data transmitting unit that transmits data via the communication bus in a predetermined order after the start signal has been transmitted. At least one of the multiple communication devices also has a processing unit that performs processing and changes the transmission interval of the start signal.

[0055] In the above-described manner, as mentioned above, the intensity of interference noise is high when the transmission interval of the start signal is short. One or more processing units in one or more communication devices change the transmission interval of the start signal. Therefore, one or more processing units can prevent the generation of high-intensity interference noise.

[0056] (9) In a communication system according to one aspect of the present disclosure, one or more of the processing units change the transmission interval of the start signal to a value of 60 μs or more.

[0057] In the above method, the transmission interval of the start signal is more than 60μs, so as to prevent the generation of strong interference noise caused by the transmission interval of the start signal.

[0058] (10) In a communication system according to one aspect of the present disclosure, one or more of the processing units change the transmission interval of the start signal to a value of 6500 μs or less.

[0059] In the above method, the transmission interval of the start signal is less than 6500μs, thus preventing communication delay caused by the transmission interval of the start signal.

[0060] (11) One aspect of the present disclosure relates to a communication method of a communication device that transmits data, wherein the communication device is connected to a communication bus, the communication bus is connected to multiple communication devices, the order in which the communication device and the multiple communication devices transmit data via the communication bus is determined, a start signal is repeatedly transmitted via the communication bus, the start signal indicating the start of data transmission, and the communication device performs the following steps: in the case of the start signal being transmitted, transmitting data in the order stated thereon; and changing the transmission interval of the start signal.

[0061] In the above-described method, as mentioned above, the intensity of interference noise is high when the transmission interval of the start signal is short. The communication device changes the transmission interval of the start signal. Therefore, the communication device can prevent the generation of high-intensity interference noise.

[0062] [Details of the embodiments disclosed herein]

[0063] Hereinafter, with reference to the accompanying drawings, specific examples of communication systems involved in embodiments of the present disclosure will be described. Furthermore, the present disclosure is not limited to these examples, but is intended to include all modifications within the meaning and scope equivalent to the claims, as indicated by the claims themselves.

[0064] (Implementation Method 1) <Structure of Communication System 1>

[0065] 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.

[0066] Electrical devices and sensors are connected to the first ECU 11 and the plurality of 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 plurality of second ECUs 12 connected to the sensors. For example, when the sensor detection values ​​are input, the first ECU 11 and the plurality of second ECUs 12 respectively transmit data frames containing the sensor detection values ​​as main data via communication bus B. The data frames contain transmission object data indicating the transmission object. Furthermore, the main data is not limited to the sensor detection values. The data frames are data.

[0067] 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 the intended recipient is not their own device.

[0068] Upon receiving a data frame, the first ECU 11 and the plurality of second ECUs 12, when the data frame is destined for 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.

[0069] <Data Frame Transmission Method>

[0070] 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 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 the first ECU 11 and four second ECUs 12 transmitting data frames.

[0071] 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 plurality of second ECUs 12 transmit data frames according to PLCA (Physical Layer Collision Avoidance).

[0072] like Figure 2 As shown, in PLCA mode, 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 equivalent to a start signal. The beacon signal is transmitted by 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.

[0073] When the first ECU 11 sends a beacon signal, the first ECU 11 and multiple second ECUs 12 transmit data frames via communication bus B. The order in which the first ECU 11 and multiple second ECUs 12 transmit data frames via communication bus B is predetermined. Figure 3 As shown, IDs are pre-assigned to the first ECU 11 and the multiple second ECUs 12. Figure 3 In this example, the ID of the first ECU11 is 001. The four second ECUs12 are each assigned one of IDs from 002 to 005. Figure 3 In this configuration, the transmission order of 001 through 005 is set to first through fifth. The host transmits the data first.

[0074] This describes the actions of the first ECU 11 and the four second ECUs 12 when they respectively send data frames. The first ECU 11 and the four second ECUs 12 each store common standby period data representing the standby period.

[0075] When the first ECU 11 sends a beacon signal, firstly, the first ECU 11 with ID 001 remains in standby mode until the standby period represented by the standby period data has elapsed. After the standby period, the first ECU 11 sends a data frame. Next, the second ECU 12 with ID 002 remains in standby mode until the standby period represented by the standby period data has elapsed since the previous ECU, i.e., the first ECU 11, ended sending its data frame. After the standby period, the second ECU 12 with ID 002 sends a data frame.

[0076] Next, the second ECU 12 with ID 003 remains in standby mode until the standby period represented by the standby data period ends, starting from the end of the data frame transmission of the preceding ECU, i.e., the second ECU 12 with ID 002. After the standby period, the second ECU 12 with ID 003 transmits a data frame. Then, the two second ECUs corresponding to 004 and 005 transmit data frames in the same manner as the second ECU 12 with ID 002 or 003, respectively. The first ECU 11 transmits a beacon signal again when the last second ECU 12 in the sequence, i.e., the second ECU 12 with ID 005, finishes transmitting a data frame. The first ECU 11 and the second ECU 12 function as communication devices or communication equipment, respectively.

[0077] If the first ECU 11 does not send a data frame, the second ECU 12 with ID 002 remains in standby mode until the standby period has elapsed again after the beacon signal was sent. If a data frame to be sent is available, the second ECU 12 with ID 002 sends the data frame after the standby period has elapsed.

[0078] Each second ECU 12 remains in standby mode until another standby period has elapsed after the standby period of the preceding ECU has ended, provided that a data frame is available. If a data frame is available, the second ECU 12 transmits the data frame after the standby period has elapsed. If the last second ECU 12 in the sequence does not transmit a data frame, the first ECU 11 transmits the beacon signal again after the standby period of the last second ECU 12 has elapsed.

[0079] Furthermore, in cases where the number of second ECUs 12 is different from four, similarly to cases where the number of second ECUs 12 is four, multiple second ECUs 12 sequentially send data frames after the first ECU 11 sends a data frame.

[0080] The number of ECUs connected to communication bus B will be denoted as the number of devices. When no data frames are being transmitted, the beacon signal transmission interval is the sum of multiple standby periods. The number of standby periods is the same as the number of devices. When one or more data frames are being transmitted, the beacon signal transmission interval is the sum of the periods consumed by the multiple standby periods and the transmission of one or more data frames. Therefore, the beacon signal transmission interval increases correspondingly to an increase in a standby period.

[0081] like Figure 1 As shown, a common device quantity data representing the number of devices is input from an external source to the first ECU 11 and the plurality of second ECUs 12. The first ECU 11 and the plurality of second ECUs 12 each calculate a standby period value based on the device quantity represented by the input device quantity data. The first ECU 11 and the plurality of second ECUs 12 then change their stored standby period data to standby period data representing the calculated value. Thus, the standby period represented by the standby period data is changed to the calculated value.

[0082] <Advantages of PLCA>

[0083] In addition to PLAC (PLA) communication, another communication method via the communication bus is CSMA / CD (Carrier Sense Multiple Access / Collision Detection). In CSMA / CD, similar to PLAC, multiple ECUs transmit data frames via the communication bus. If multiple data frame collisions occur, each ECU detects the collisions. The ECUs that were the sources of the colliding data frames then retransmit the data frames. The timing of the data frame transmissions by the multiple ECUs is different from each other. Therefore, collisions between multiple data frames are avoided.

[0084] In the CSMA / CD method, the delay time of the data frames resulting from the collisions is uncertain when multiple data frame collisions occur. However, in the PLCA method, the transmission period for data frames is allocated separately for the first ECU 11 and the multiple second ECUs 12. Therefore, data frame collisions are avoided. As a result, the maximum delay time can be guaranteed in the PLCA method. With the maximum delay time guaranteed, the design of the in-vehicle network is simplified.

[0085] <Beacon Signal>

[0086] Figure 4 This is a waveform diagram of the beacon signal. (The diagram is shown in...) Figure 4 The vertical and horizontal axes show the voltage difference and time. Figure 4 The waveform of the beacon signal shown is an example. Communication bus B includes a first conductor W1 and a second conductor W2 (see reference). Figure 6 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 transmit the beacon signal by adjusting the voltage difference between the first wire W1 and the second wire W2 contained in the communication bus B to a high level or a low level each time a bit has elapsed. Figure 4 In this context, H and L represent high-level voltage and low-level voltage, respectively.

[0087] The data frame also consists of multiple bits. Each time a bit period elapses, the first ECU11 and the multiple second ECUs12 transmit a data frame by adjusting 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.

[0088] For each bit, indicate either a high-level voltage or a low-level voltage. Figure 4 In the example, the beacon signal consists of seven bits. Regarding Figure 4 The beacon signal shown is output alternately with high and low voltage levels. Furthermore, the number of bits constituting the beacon signal is not limited to seven.

[0089] 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.

[0090] Here, for structures that perform processing at the rising point of the clock signal, the rising point of the clock signal is adjusted. For structures that perform processing at the falling point of the clock signal, the falling point of the clock signal is adjusted.

[0091] 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.

[0092] <Structure of the first ECU11>

[0093] Figure 5 This is a block diagram showing the main structural components of the first ECU 11. The first ECU 11 includes a communication IC 21, a detection value input unit 22, a signal output unit 23, a data input unit 24, a device storage unit 25, and a device control unit 26. These are connected to a device bus 27. IC is an abbreviation for Integrated Circuit. The communication IC 21 is further connected to the communication bus B. The detection value input unit 22 is further connected to a sensor. The signal output unit 23 is further connected to electrical equipment. Illustrations of the sensor and electrical equipment are omitted.

[0094] The sensor outputs the detected value to the detection value input unit 22. For example, when the sensor's detected value is input to the detection value input unit 22, the device control unit 26 generates a data frame containing the sensor's detected value as master data. The device control unit 26 assigns the generated data frame to the communication IC 21. Upon receiving the data frame, the communication IC 21 transmits the assigned data frame via the communication bus B.

[0095] Communication IC 21 receives data frames transmitted via communication bus B. If the intended recipient of the received data frame is different from the first ECU 11, communication IC 21 discards the received data frame. If the intended recipient of the received data frame is the first ECU 11, communication IC 21 assigns the received data frame to the device control unit 26.

[0096] When the device control unit 26 receives a received data frame, it determines the operation to be performed by the electrical equipment based on the master data of the received data frame. Once the device control unit 26 has determined the operation to be performed by the electrical equipment, the instruction signal output unit 23 outputs an operation signal indicating the determined operation to the electrical equipment. As described above, when an operation signal is input, the electrical equipment performs the operation indicated by the input operation signal.

[0097] Communication IC 21 transmits data frames according to PLCA. Standby period data is stored in Communication IC 21. Communication IC 21 repeatedly transmits beacon signals. Communication IC 21 remains in standby mode until the standby period represented by the standby period data has elapsed since the end of beacon signal transmission. After the standby period elapses, Communication IC 21 transmits data frames. If no data frame is due, Communication IC 21 does not transmit a data frame. As described above, the second ECU 12, which is the second in sequence, remains in standby mode until the standby period represented by the standby period data has elapsed after the standby period of the first ECU 11.

[0098] The device quantity data is input to the data input unit 24. The device control unit 26 calculates the standby period value based on the device quantity data input to the data input unit 24. The device control unit 26 assigns the standby period data representing the calculated value as the standby period to the communication IC 21. The communication IC 21 changes its stored standby period data to the standby period data assigned by the communication IC 21. Thus, the standby period is changed to the value calculated by the device control unit 26.

[0099] The device storage unit 25 is composed of, for example, non-volatile memory and volatile memory. A computer program P is stored in the device storage unit 25. The device control unit 26 has a processing element that performs processing, such as a CPU (Central Processing Unit). The device control unit 26 functions as a processing unit. The processing element of the device control unit 26 executes, in parallel, period calculation processing, frame generation processing, and signal output processing by executing the computer program P. In the period calculation processing, the device control unit 26 calculates the value of the standby period. In the frame generation processing, the device control unit 26 generates a data frame as described above and assigns the generated data frame to the communication IC 21. In the signal output processing, the device control unit 26 instructs the signal output unit 23 to output an operation signal as described above.

[0100] 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 readable. Storage medium A is, for example, a portable memory. Examples of portable memory include CD-ROM, USB (Universal Serial Bus) memory, SD card, micro SD card, or CF card (CompactFlash) (registered trademark). When storage medium A is a portable memory, the processing element of the device control unit 26 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 25. 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 26 obtains the computer program P via the communication unit. The obtained computer program P is then stored in the device storage unit 25.

[0101] The device control unit 26 may have two or more processing elements. In this case, the multiple processing elements of the device control unit 26 may cooperate to perform tasks such as periodic calculation processing, frame generation processing, and signal output processing.

[0102] <Structure of Communication IC21>

[0103] The communication IC 21 of the first ECU 11 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 the IC bus 36. The interface 32 is further connected to the device bus 27. The clock unit 34 is further connected to the bit communicator 35. The bit communicator 35 is further connected to the communication bus B.

[0104] The device control unit 26 assigns a data frame to the IC control unit 31 via the interface 32. The IC control unit 31 has a processing element, such as a CPU, for performing processing. When a data frame is assigned, the IC control unit 31 writes the assigned data frame to the IC storage unit 33. The IC storage unit 33 is composed of, for example, non-volatile memory and volatile memory.

[0105] The clock unit 34 outputs a clock signal to the bit communicator 35. The IC control unit 31 assigns data frames stored in the IC storage unit 33 bit by bit to the bit communicator 35. The IC control unit 31 assigns beacon signals bit by bit to the bit communicator 35.

[0106] The bit communicator 35 transmits a one-bit signal or data assigned by the IC control unit 31 each time the clock signal rises. The bit communicator 35 transmits a one-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 during one cycle of the clock signal. The cycle of the clock signal corresponds to the period of one bit.

[0107] Each time the clock signal rises, the bit communicator 35 receives a bit of signal or data by detecting the voltage difference between the first wire W1 and the second wire W2 contained in the communication bus B. The bit communicator 35 then notifies the IC control unit 31 of the received bit of signal or data.

[0108] Furthermore, the bit communicator 35 can also transmit a one-bit signal or data assigned by the IC control unit 31 whenever the clock signal falls. Additionally, the bit communicator 35 can also receive a one-bit signal or data by detecting the voltage difference on the communication bus B whenever the clock signal falls.

[0109] The IC control unit 31 controls the operation of the bit communicator 35 via PLCA communication. The bit communicator 35 sends a beacon signal. The bit communicator 35 remains in standby mode until the standby period represented by the standby period data has elapsed since the end of the beacon signal transmission. The standby period data is stored in the IC memory unit 33.

[0110] When the bit communicator 35 receives a data frame, if the intended recipient of the received data frame is not the first ECU 11, the IC control unit 31 discards the received data frame. When the bit communicator 35 receives a data frame, if the intended recipient of the received data frame is the first ECU 11, the IC control unit 31 transmits the received data frame to the device control unit 26 via the interface 32. As described above, the device control unit 26 uses the master data of the data frame transmitted from the IC control unit 31 when determining the operation of the electrical equipment.

[0111] The IC storage unit 33 stores a computer program (not shown). The IC control unit 31 executes the computer program to perform standby period change processing, frame writing processing, frame transmission processing, and frame reception processing in parallel. In the standby period change processing, the IC control unit 31 changes the standby period data stored in the IC storage unit 33. When the standby period data is changed, the standby period is changed. In the frame writing processing, the IC control unit 31 writes a data frame to the IC storage unit 33 as described above. In the frame transmission 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 data frame. In the frame reception processing, the IC control unit 31 performs processing related to the data frame received by the bit communicator 35 as described above.

[0112] <Structure of Bit Communicator 35>

[0113] Figure 6 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.

[0114] 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.

[0115] A capacitor 44a and a first inductor 45a of a common-mode choke coil 45 are positioned midway along the device lead Wa. The capacitor 44a is positioned on the first lead W1 side of the first inductor 45a. Similarly, a capacitor 44b and a second inductor 45b of a common-mode choke coil 45 are positioned midway along the device lead Wb. The capacitor 44b is positioned on the second lead W2 side of the second inductor 45b.

[0116] 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.

[0117] 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.

[0118] Two capacitors 44a and 44b remove the DC component from the two voltages input from the two device leads Wa and Wb, respectively. The two voltages with the DC component removed from them are then output from capacitors 44a and 44b to the common-mode choke coil 45.

[0119] 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 the common-mode noise removed to the conversion unit 46.

[0120] 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, a bit value of 0 is output. If the voltage difference is a high-level voltage, a bit value of 1 is output. 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, for example, a high-level voltage and a low-level voltage of the reference potential, which is the second conductor G2. The second conductor G2 is disposed within the first ECU 11 and is different from the first conductor G1.

[0121] As described above, the bit communicator 35 transmits a one-bit signal or data. The IC control unit 31 assigns a one-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 one-bit signal or data assigned by the IC control unit 31.

[0122] 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.

[0123] 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 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.

[0124] <Structure of the second ECU12>

[0125] Each of the second ECUs 12 is configured similarly to the first ECU 11. Therefore, each of the multiple second ECUs 12 has a bit communicator 35 connected to the communication bus B. When comparing the second ECUs 12 with the first ECU 11, the timing of data frame transmission by the bit communicator 35 of the communication IC 21 and the structure associated with the beacon signal are different.

[0126] In the communication IC 21 of the second ECU 12, the IC control unit 31 also controls the operation of the bit communicator 35 by sending data frames via the bit communicator 35 in a PLCA manner. The communication IC 21 of the second ECU 12 also stores standby period data. The bit communicator 35 of the second ECU 12 does not send beacon signals. The bit communicator 35 of the second ECU 12 remains in standby mode until the standby period indicated by the standby period data has elapsed since the last data frame sent by either the first ECU 11 or the second ECU 12 in sequence.

[0127] After a standby period, the bit communicator 35 of the second ECU 12 sends a data frame. If no data frame is due to be sent, the bit communicator 35 of the second ECU 12 does not send a data frame. As described above, the second ECU 12 in sequence remains in standby mode until the standby period represented by the standby period data has elapsed after the standby period has elapsed.

[0128] In the second ECU 12, the IC control unit 31 does not send a beacon signal to the bit communicator 35. The bit communicator 35 receives the beacon signal. Upon receiving the beacon signal, the IC control unit 31 adjusts the rise or fall time of the clock signal based on the received beacon signal, as described in the beacon signal description. For structures that perform processing at the rise time of the clock signal, the rise time of the clock signal is adjusted. For structures that perform processing at the fall time of the clock signal, the fall time of the clock signal is adjusted.

[0129] The IC control unit 31 of the second ECU 12, like the IC control unit 31 of the first ECU 11, executes standby change processing, frame writing processing, frame transmission processing, and frame receiving processing by executing a computer program. However, in the frame transmission 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. After adjusting the clock signal, the IC control unit 31 causes the bit communicator 35 to transmit data frames.

[0130] <Order of changes during standby>

[0131] Figure 7 This is a flowchart illustrating the sequence of changes during the standby period. The changes during the standby period are performed similarly in both the first ECU 11 and the multiple second ECUs 12. Figure 7 The diagram shows the period calculation processing of the device control unit 26 and the standby period change processing of the IC control unit 31. Reference interval data representing a constant reference interval is stored in the device storage unit 25 of each of the first ECU 11 and the plurality of second ECUs 12.

[0132] During the calculation process, the device control unit 26 determines whether device quantity data should be input to the data input unit 24 from an external source (step S1). For example, a user operates a data output device that outputs device quantity data. In this case, the data output device outputs device quantity data to the data input unit 24. If the device control unit 26 determines that device quantity data has not been input to the data input unit 24 (S1: "No"), it executes step S1 again. The device control unit 26 remains in standby mode until device quantity data is input to the data input unit 24.

[0133] When the device control unit 26 determines that device quantity data should be input to the data input unit 24 (S1: "Yes"), it acquires the device quantity data input from the outside to the data input unit 24 (step S2). Acquiring the device quantity data is equivalent to acquiring the device quantity. Next, the device control unit 26 reads the reference interval data from the device storage unit 25 (step S3). Next, the device control unit 26 calculates the value of the standby period based on the device quantity data acquired in step S2 and the reference interval data read in step S3 (step S4).

[0134] Let Tb represent the beacon signal transmission period. The beacon signal transmission interval is the period from the start of beacon signal transmission to the end of transmission. Let Nd represent the number of devices represented by device quantity data. Let Tr represent the reference interval represented by reference interval data. In this case, in step S4, for example, the device control unit 26 calculates the value Tc of the standby period according to the following formula.

[0135] Tc = (Tr - Tb) / Nd

[0136] Furthermore, errors can also be considered in step S4. Errors may arise, for example, when there is a delay in the start of beacon signal or data frame transmission. In the case where E represents the absolute value of the error, the standby period value Tc calculated in step S3 is (((Tr-Tb) / Nd)+E) or (((Tr-Tb) / Nd)-E).

[0137] Next, the device control unit 26 transmits standby period data, representing the value calculated in step S4, to the IC control unit 31 via interface 32 (step S5). After executing step S5, the device control unit 26 ends the period calculation process. After ending the period calculation process, the device control unit 26 executes the period calculation process again.

[0138] During the standby period change process, the IC control unit 31 determines whether standby period data has been assigned from the device control unit 26 (step S11). If the IC control unit 31 determines that standby period data has not been assigned (S11: "No"), it executes step S11 again. The IC control unit 31 remains in standby mode until standby period data is assigned from the device control unit 26.

[0139] If the IC control unit 31 determines that standby time data has been assigned (S11: "Yes"), it changes the standby time data stored in the IC storage unit 33 to the assigned standby time data (step S12) and ends the standby time change process. After ending the standby time change process, the IC control unit 31 executes the standby time change process again.

[0140] As described above, when the standby period data stored in the IC storage unit 33 is changed, the standby period is changed. Therefore, the device control unit 26 changes the standby period by executing step S5. Figure 2 As shown, the beacon signal transmission interval is changed when the standby period is changed.

[0141] <Order of Data Frames Sent>

[0142] Figure 8 This is a flowchart illustrating the sequence of data frame transmission preparations. Data frame transmission preparations are performed similarly in both the first ECU 11 and the plurality of second ECUs 12. Figure 8 The image shows the frame generation process of the device control unit 26 and the frame writing process of the IC control unit 31.

[0143] In the frame generation process, the device control unit 26 first determines whether to generate a data frame (step S21). In step S21, the device control unit 26 determines that a data frame should be generated, for example, when the sensor's detection value is input to the detection value input unit 22. In this case, the main data of the data frame is the sensor's detection value input to the detection value input unit 22. If the device control unit 26 determines that a data frame should not be generated (S21: "No"), it executes step S21 again and waits until the time for generating a data frame arrives.

[0144] If the device control unit 26 determines that a data frame needs to be generated (S21: "Yes"), it generates a data frame (step S22). Next, the device control unit 26 transmits the data frame generated in step S22 to the IC control unit 31 via interface 32 (step S23). After executing step S23, the device control unit 26 ends the frame generation process. After ending the frame generation process, the device control unit 26 executes the frame generation process again.

[0145] In the frame writing process, the IC control unit 31 first determines whether a data frame has been assigned from the device control unit 26 (step S31). If the IC control unit 31 determines that no data frame has been assigned (S31: "No"), it executes step S31 again and waits until a data frame is assigned from the device control unit 26.

[0146] If the IC control unit 31 determines that a data frame has been assigned by the device control unit 26 (S31: "Yes"), it writes the assigned data frame to the IC storage unit 33 (step S32). After executing step S32, the IC control unit 31 ends the frame writing process. After ending the frame writing process, the IC control unit 31 executes the frame writing process again.

[0147] As described above, when the device control unit 26 generates a data frame, the generated data frame is written to the IC storage unit 33. The data frame stored in the IC storage unit 33 is then transmitted via the communication bus B.

[0148] Figure 9 This is a flowchart illustrating the sequence of frame transmission processing performed by the IC control unit 31 of the first ECU 11. In the frame transmission processing, the IC control unit 31 first determines whether to transmit a beacon signal (step S41). If the second ECU 12, being the last in the sequence, does not transmit a data frame, the beacon signal is transmitted at the point when the standby period of the last second ECU 12 has elapsed. The determination of whether the standby period has elapsed is, for example, made using a timer.

[0149] When the second ECU 12 is the last in the sequence to send a data frame, the beacon signal is sent at the moment when the second ECU 12 finishes sending the data frame. In the data frame, length data indicating the length of the main data is configured before the main data. Based on the data length of the data frame, the IC control unit 31 can determine the end time of data frame transmission.

[0150] If the IC control unit 31 determines that it will not send a beacon signal (S41: "No"), it executes step S41 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 (S41: "Yes"), it instructs the bit communicator 35 to send the beacon signal via the communication bus B (step S42). 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.

[0151] Regarding the first ECU 11, the data frame is transmitted first. Therefore, regarding the first ECU 11, the data frame transmission order takes place after the beacon signal transmission ends. After executing step S42, the IC control unit 31 determines whether the standby period indicated by the standby period data has elapsed since the end of the beacon signal transmission (step S43). If the IC control unit 31 determines that the standby period has not elapsed (S43: "No"), it executes step S43 again, and the standby continues until the standby period has elapsed. The elapsed standby period means that the standby period has become longer than the standby period.

[0152] If the IC control unit 31 determines that a standby period has elapsed (S43: "Yes"), it determines whether a data frame is stored in the IC storage unit 33 (step S44). If the IC control unit 31 determines that a data frame is stored in the IC storage unit 33 (S44: "Yes"), it instructs the bit communicator 35 to transmit the data frame stored in the IC storage unit 33 bit by bit via the communication bus B (step S45). The bit communicator 35 functions as a data transmission unit. After executing step S45, the IC control unit 31 deletes the transmitted data frame from the IC storage unit 33 (step S46).

[0153] If the IC control unit 31 determines that no data frame is stored in the IC storage unit 33 (S44: "No"), or after executing step S46, it terminates the frame transmission process. When no data frame is stored in the IC storage unit 33, the IC control unit 31 terminates the frame transmission process without causing the bit communicator 35 to transmit a data frame. After terminating the frame transmission process, the IC control unit 31 executes the frame transmission process again. The IC control unit 31 remains in standby mode until the time for transmitting the beacon signal arrives.

[0154] As described above, the IC control unit 31 of the first ECU 11 instructs the bit communicator 35 to repeatedly transmit beacon signals via the communication bus B. The bit communicator 35 of the first ECU 11 also functions as a signal transmitter. When a beacon signal is transmitted, the IC control unit 31, according to a predetermined sequence, for example… Figure 3 The diagram enables bit communicator 35 to send data frames.

[0155] Figure 10 This is a flowchart illustrating the sequence of frame transmission processing performed by the IC control unit 31 of the second ECU 12. Steps S55 to S57 of the frame transmission processing performed by the IC control unit 31 of the second ECU 12 are the same as steps S44 to S46 of the frame transmission processing performed by the IC control unit 31 of the first ECU 11. Therefore, the explanation of steps S55 to S57 is omitted.

[0156] In the frame transmission process, the IC control unit 31 of the second ECU12 first determines whether the bit communicator 35 has received a beacon signal (step S51). If the IC control unit 31 determines that the bit communicator 35 has not received a beacon signal (S51: "No"), it executes step S51 again and waits until the bit communicator 35 receives a beacon signal.

[0157] When the IC control unit 31 determines that the bit communicator 35 has received a beacon signal (S51: "Yes"), it adjusts the clock signal output by the clock unit 34 (step S52). In step S52, the IC control unit 31 adjusts the rise or fall time of the clock signal as described above. After executing step S52, the IC control unit 31 determines whether the transmission sequence of the data frames has arrived (step S53).

[0158] When the bit communicator 35 of the preceding first ECU 11 or second ECU 12 sends a data frame, the transmission order arrives at the end of the transmission of that data frame. When the bit communicator 35 of the preceding first ECU 11 or second ECU 12 does not send a data frame, the transmission order arrives after the standby period of the preceding first ECU 11 or second ECU 12 has elapsed.

[0159] If the IC control unit 31 determines that the transmission sequence has not arrived (S53: "No"), it executes step S53 again. The IC control unit 31 remains in standby mode until the transmission sequence arrives. If the IC control unit 31 determines that the transmission sequence has arrived (S53: "Yes"), it determines whether the standby period represented by the standby period data has elapsed since the transmission sequence arrived (step S54). If the IC control unit 31 determines that the standby period has not elapsed (S54: "No"), it executes step S54 again. The IC control unit 31 remains in standby mode until the standby period has elapsed.

[0160] If the IC control unit 31 determines that the standby period has elapsed (S54: "Yes"), it executes step S55. Therefore, if a data frame is stored in the IC storage unit 33, the bit communicator 35 transmits a data frame. Subsequently, the IC control unit 31 deletes the data frame transmitted by the bit communicator 35 from the IC storage unit 33, ending the frame transmission process. If no data frame is stored in the IC storage unit 33, the IC control unit 31 does not instruct the bit communicator 35 to transmit a data frame and ends the frame transmission process. After ending the frame transmission process, the IC control unit 31 executes the frame transmission process again.

[0161] <Relationship between transmission interval and interference noise>

[0162] Figure 11 This is an illustrative diagram showing the relationship between transmission interval and interference noise. Here, it is assumed that the error is zero. Figure 11 The example shown illustrates a scenario where the number of second ECUs 12 is four. The number of devices is five. As described above, the beacon signal transmission period, standby period, and number of devices are represented by Tb, Tc, and Nd, respectively. The standby period data is changed to the calculated value Tc. Therefore, Tc represents the standby period.

[0163] like Figure 11 As shown, when neither the first ECU11 nor any of the second ECUs12 transmits data frames, the beacon signal transmission interval is the shortest. At this time, the beacon signal transmission interval is (Tb + (Nd·Tc)), consistent with the reference interval Tr. "·" indicates a product. With a short transmission interval, the bit communicator 35 of the first ECU11 switches the voltage of the communication bus B the most times, changing the voltage difference to a high or low level. When the voltage of the communication bus B is switched, interference noise is generated. With a high number of switches per unit time, the intensity (peak value) of the interference noise is large.

[0164] When a portion of the first ECU 11 and multiple second ECUs 12 transmit data frames, the time consumed by transmitting one or more data frames is added to (Tb + (Nd·Tc)). Therefore, the transmission interval of the beacon signal is extended. Consequently, the number of switching operations per unit time is reduced, and thus, the intensity of interference noise is also reduced. Figure 11 In the example, the first ECU 11 and two second ECUs 12, which are the fourth and fifth in sequence, transmit data frames. With all data frames transmitted by the first ECU 11 and multiple second ECUs 12, the beacon signal transmission interval is the longest. Therefore, the number of switching operations per unit time is minimized, and the intensity of interference noise is reduced.

[0165] Figure 12 This is another illustration of the relationship between transmission interval and interference noise. Here, the spectrum of the signal (data) propagated via communication bus B is used to illustrate the relationship between transmission interval and interference noise. When the same waveform is repeated with a constant transmission interval, the spectrum is excited at frequency intervals of (1 / transmission interval). Therefore, the shorter the transmission interval, the larger the frequency interval of the spectrum. Figure 12 and Figure 11 Similarly, an example is shown where the number of second ECU12 is four.

[0166] When none of the first ECU 11 and the multiple second ECUs 12 transmit data frames, as described above, the beacon signal transmission interval is the shortest. Therefore, the frequency interval of the spectrum is the largest. When only a portion of the first ECU 11 and the multiple second ECUs 12 transmit data frames, as described above, the beacon signal transmission interval is extended. Therefore, the frequency interval of the spectrum is reduced. When all of the first ECU 11 and the multiple second ECUs 12 transmit data frames, as described above, the beacon signal interval is the shortest. Therefore, the frequency interval of the spectrum is the smallest.

[0167] The larger the frequency interval, i.e., the shorter the transmission interval of the beacon signal, the fewer spectra are excited within a constant frequency range. Therefore, with the overall intensity fixed, the shorter the transmission interval of the beacon signal, the greater the intensity of each spectrum. Consequently, when the transmission interval of the beacon signal is short, there exists a spectrum that functions as strong interference noise.

[0168] When the beacon signal transmission interval is minimized, the beacon signal transmission interval is the reference interval. For example... Figure 12 As shown, in communication system 1, when the beacon signal transmission interval is the reference interval, the intensity of the spectrum is lower than the permissible level for interference noise. Therefore, in communication system 1, interference noise with an intensity exceeding the permissible level will not be generated.

[0169] As described above, reference interval data is stored in the IC storage unit 33 of each of the first ECU 11 and the plurality of second ECUs 12. The reference interval represented by the reference interval data is, for example, 60 μs or more. In this case, the device control unit 26 of each of the first ECU 11 and the plurality of second ECUs 12 changes the beacon signal transmission interval to a value of 60 μs or more by changing the standby period during the period calculation process. When the beacon signal transmission interval is 60 μs or more, the generation of strong interference noise caused by the beacon signal transmission interval is prevented.

[0170] The device control units 26 of each of the first ECU 11 and the plurality of second ECUs 12 preferably change the beacon signal transmission interval to a value of 60 μs or more and 6500 μs or less. The maximum value of the beacon signal transmission interval is determined by the maximum value of the beacon signal transmission period, the number of devices, the standby period, and the data length of the data frame. The more devices there are, the larger the maximum value of the beacon signal transmission interval. For example, by limiting the number of devices, the device control units 26 of each of the first ECU 11 and the plurality of second ECUs 12 can change the beacon signal transmission interval to a value of 6500 μs or less. When the beacon signal transmission interval is 6500 μs or less, communication delay caused by the beacon signal transmission interval is prevented.

[0171] <The Effects of Communication System 1>

[0172] As described above, the device control units 26 of the first ECU 11 and the plurality of second ECUs 12 change the beacon signal transmission interval by changing the standby period. This changes the beacon signal transmission interval to a value greater than or equal to a reference interval. As a result, strong interference noise is prevented.

[0173] <Modifications of Implementation Method 1>

[0174] The standby periods corresponding to the first ECU 11 and the plurality of second ECUs 12 may also be inconsistent. Each standby period may also differ from at least one of the remaining standby periods. Furthermore, the standby periods of a portion of the first ECU 11 and the plurality of second ECUs 12 may be fixed. In this case, the device control unit 26 of each of the remaining one or more ECUs changes the beacon signal transmission interval by changing the standby period. In this case, all one or more device control units 26 change the beacon signal transmission interval to a value greater than or equal to a reference interval.

[0175] (Implementation Method 2)

[0176] In Embodiment 1, the data input to the data input unit 24 is device quantity data. However, the data input to the data input unit 24 is not limited to device quantity data.

[0177] The differences between Embodiment 2 and Embodiment 1 will now be explained. Regarding structures other than those described later, since they 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.

[0178] <Structure of Communication System 1>

[0179] Figure 13 This is a block diagram showing the main structure of the communication system 1 in Embodiment 2. In the communication system 1 of Embodiment 2, instead of device quantity data, common standby time data indicating the standby time is input to the data input section 24 of each of the first ECU 11 and the plurality of second ECUs 12.

[0180] <Structure of the first ECU11 and the second ECU12>

[0181] In Embodiment 2, the device control unit 26 of each of the first ECU 11 and the plurality of second ECUs 12 executes a standby period data assignment process by executing a computer program P instead of a period calculation process, and assigns standby period data to the IC control unit 31.

[0182] <Order of changes during standby>

[0183] Figure 14 This is a flowchart illustrating the sequence of changes during the standby period. The changes during the standby period are performed similarly in both the first ECU 11 and the multiple second ECUs 12. Figure 14 The diagram shows the standby data assignment process of the device control unit 26 and the standby time change process of the IC control unit 31. The standby time change process is performed in the same manner as in Embodiment 1.

[0184] During standby data assignment, the device control unit 26 determines whether standby data should be input to the data input unit 24 from an external source (step S61). If the device control unit 26 determines that standby data has not been input to the data input unit 24 (S61: "No"), it executes step S61 again. Thus, the device control unit 26 remains in standby mode until standby data is input to the data input unit 24.

[0185] When the device control unit 26 determines that standby data should be input to the data input unit 24 (S61: "Yes"), it acquires the standby data input from the outside to the data input unit 24 (step S62). Acquiring the standby data is equivalent to acquiring the standby period. Next, the device control unit 26 assigns the standby data acquired in step S62 to the IC control unit 31 via the interface 32 (step S63). After executing step S63, the device control unit 26 ends the standby data assignment process. After ending the standby data assignment process, the device control unit 26 executes the standby data assignment process again.

[0186] As described in Embodiment 1, when the IC control unit 31 is given standby time data from the device control unit 26, it changes the standby time data stored in the IC storage unit 33 to the standby time data given by the device control unit 26. Thus, the standby time is changed to the value (standby time) represented by the standby time data input to the data input unit 24. Therefore, the device control unit 26 changes the standby time by executing step S63. When the standby time is changed, the beacon signal transmission interval is changed. The standby time data represents a standby time where the beacon signal transmission interval becomes a reference interval, for example, 60 μs or more. Preferably, the standby time represented by the standby time data is a period where the beacon signal transmission interval becomes a value of 60 μs or more and 6500 μs or less. For example, the upper limit of the standby time represented by the standby time data is set corresponding to the number of devices such that the beacon signal transmission interval becomes 6500 μs or less.

[0187] <The Effects of Communication System 1>

[0188] The first ECU 11 and the plurality of second ECUs 12 each perform the same effect as in embodiment 1.

[0189] <Modifications of Implementation Method 2>

[0190] Alternatively, it is not necessary to input common standby period data to the first ECU 11 and the plurality of second ECUs 12. The standby period data input to the first ECU 11 and the plurality of second ECUs 12 may also differ from at least one of the other standby period data. In this case, one standby period differs from at least one of the remaining standby periods. Furthermore, a portion of the standby periods of the first ECU 11 and the plurality of second ECUs 12 may be fixed. In this case, standby period data is input to the data input section 24 of the remaining one or more ECUs to change these standby periods. The one or more standby period data respectively represent standby periods where the beacon signal transmission interval becomes a value greater than or equal to a reference interval.

[0191] (Implementation Method 3)

[0192] In Embodiment 1, the beacon signal transmission interval is changed by altering the standby period of at least one of the first ECU 11 and the plurality of second ECUs 12. However, the method for changing the beacon signal transmission interval is not limited to the method for changing the standby period.

[0193] The differences between Embodiment 3 and Embodiment 1 will be explained below. Regarding structures other than those described later, since they 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.

[0194] <Structure of Communication System 1>

[0195] Figure 15 This is a block diagram showing the main structural components of the communication system 1 in Embodiment 3. In Embodiment 3, common standby data is stored in the IC storage units 33 of each of the first ECU 11 and the plurality of second ECUs 12. The standby data stored in each IC storage unit 33 is not changed. In addition, the IC storage units 33 of each of the first ECU 11 and the plurality of second ECUs 12 store common sequence data indicating the order in which the first ECU 11 and the plurality of second ECUs 12 transmit data frames via the communication bus B. The first ECU 11 and the plurality of second ECUs 12 transmit data frames via the communication bus B according to the order indicated by the sequence data stored in the IC storage units 33.

[0196] In Embodiment 3, instead of device quantity data, sequential data is input to the data input units 24 of each of the first ECU 11 and the plurality of second ECUs 12. When sequential data is input to the data input units 24 in both the first ECU 11 and the plurality of second ECUs 12, the IC control unit 31 changes the sequential data stored in the IC storage unit 33 to the sequential data input to the data input units 24. This changes the sequence related to the transmission of data frames.

[0197] Figure 16 It is a chart showing the contents of sequential data. In Figure 16 The example shown illustrates a scenario where there are two second ECUs 12. The number of devices is three. (Example:) Figure 16 As shown, in sequential data, corresponding assignments and data frame transmission sequences are established with multiple IDs respectively.

[0198] Similar to implementation method 1, the ECU with ID 001 is the first ECU 11. The first ECU 11 acts as the master. The first ECU 11 sends data first. The two ECUs with IDs 002 and 003 are the second ECUs 12. The second ECUs 12 act as slave devices. The sending orders corresponding to 002 and 003 are the second and third, respectively.

[0199] In the sequential data, the function and transmission order are specified for the four IDs corresponding to the four hypothetical ECUs. Hypothetical ECUs are non-existent ECUs. Therefore, hypothetical ECUs do not send data frames. The four ECUs with IDs 991 to 994 are hypothetical ECUs. The function of the four hypothetical ECUs is to act as slave devices. The order of 991, 992, 993, and 994 is fourth, fifth, sixth, and seventh, respectively. Assuming the presence of hypothetical ECUs, the first ECU 11 and multiple second ECUs 12 will each perform actions. Furthermore, the number of hypothetical ECUs is not limited to four. The number of hypothetical ECUs can be any natural number.

[0200] Figure 17 This is an illustration of the transmission of data frames. Figure 17 and Figure 16 Similarly, an example is shown where the number of second ECU12 is two. Figure 17 The diagram shows the state where the first ECU 11 and multiple (two) second ECUs 12 have all transmitted data frames. As mentioned above, if a hypothetical ECU does not exist, it does not transmit data frames. Therefore, if the bit communicator 35 of the first ECU 11 is the last among the multiple second ECUs to transmit data frames, and the bit communicator 35 of the last ECU has finished transmitting data frames, it will remain in standby mode until (the number of hypothetical ECUs) * (standby period) has elapsed. The last ECU corresponds to the last communication device. Figure 17 In the example, the last ECU is the second ECU 12 with ID 003. The first ECU 11 sends a beacon signal after (the number of hypothetical ECUs) * (standby period). The passage of the final period means that the standby period becomes more than the final period.

[0201] If the last ECU does not send a data frame, the bit communicator 35 of the first ECU 11 remains in standby mode until (number of hypothetical ECUs) * (standby period) has elapsed since the last ECU's standby period. After (number of hypothetical ECUs) * (standby period), the bit communicator 35 of the first ECU 11 sends a beacon signal. The period between two consecutive beacon signals is recorded as the final standby period of the first ECU 11. The final period is (number of hypothetical ECUs) * (standby period), equivalent to the second standby period. Sequential data represents the number (integer) of IDs exceeding the number of devices connected to the communication bus B. The number of IDs is associated with the final period. Sequential data is equivalent to period data.

[0202] <Structure of the first ECU11>

[0203] Figure 18 This is a block diagram showing the main structural components of the first ECU 11. In the first ECU 11 of Embodiment 3, sequential data is input to the data input unit 24 from the outside. The sequential data is stored in the IC storage unit 33 of the communication IC 21. The device control unit 26 executes a computer program P to perform sequential data assignment processing, which assigns sequential data to the IC control unit 31 of the communication IC 21, instead of the standby period change processing. The IC control unit 31 executes a sequence change processing, which changes the sequence data, instead of the standby period change processing, by executing a computer program stored in the IC storage unit 33. When the sequence data is changed, the order in which the data frames are transmitted is changed.

[0204] <Structure of the second ECU12>

[0205] Similar to the first ECU 11, in the second ECU 12, sequential data is input to the data input unit 24 from the outside. The sequential data is stored in the IC storage unit 33 of the communication IC 21. The device control unit 26 performs sequential data assignment processing by executing the computer program P, replacing the standby period change processing. The IC control unit 31 performs sequential change processing by executing the computer program stored in the IC storage unit 33, replacing the standby period change processing.

[0206] <Order of Change>

[0207] Figure 19 This is a flowchart illustrating the sequence of changes in order. The same sequence change is performed in both the first ECU 11 and the plurality of second ECUs 12. Figure 19 The diagram shows the sequential data assignment processing of the device control unit 26 and the sequential change processing of the IC control unit 31.

[0208] During the sequential data assignment process, the device control unit 26 determines whether sequential data should be input to the data input unit 24 from an external source (step S71). If the device control unit 26 determines that sequential data has not been input to the data input unit 24 (S71: "No"), it executes step S71 again. As a result, the device control unit 26 remains in standby mode until sequential data is input to the data input unit 24.

[0209] When the device control unit 26 determines that sequential data should be input to the data input unit 24 (S71: "Yes"), it acquires the sequential data input from the outside to the data input unit 24 (step S72). Acquiring the sequential data is equivalent to acquiring the order of data frame transmission. Next, the device control unit 26 assigns the sequential data acquired in step S72 to the IC control unit 31 via the interface 32 (step S73). After executing step S73, the device control unit 26 ends the sequential data assignment process. After ending the sequential data assignment process, the device control unit 26 executes the sequential data assignment process again.

[0210] During the sequence change process, the IC control unit 31 determines whether sequence data has been assigned from the device control unit 26 (step S81). If the IC control unit 31 determines that no sequence data has been assigned (S81: "No"), it executes step S81 again. The IC control unit 31 remains in standby mode until sequence data is assigned from the device control unit 26.

[0211] If the IC control unit 31 determines that sequential data has been assigned (S81: "Yes"), it changes the sequential data stored in the IC storage unit 33 to the assigned sequential data (step S82) and ends the sequence change process. After ending the sequence change process, the IC control unit 31 executes the sequence change process again.

[0212] As described above, when the sequence data stored in the IC storage unit 33 is changed, the number of IDs represented by the sequence data, i.e., the number of hypothetical ECUs, is changed. When the number of hypothetical ECUs is changed, the final period is changed. Therefore, the device control unit 26 changes the final period by executing step S73. When the final period is changed, the transmission interval of the beacon signal is changed. The execution of step S73 is equivalent to changing the final period based on the sequence data obtained by the device control unit 26.

[0213] As described in Embodiment 1, Nd represents the number of ECUs connected to the communication bus B. Tc represents the standby period. Further, Nv represents the number of hypothetical ECUs. When the device control unit 26 performs step S73, the final period is changed to the product of the standby period Tc and the number of hypothetical ECUs Nv. The number of hypothetical ECUs Nv is a value obtained by subtracting the number of devices Nd from the number of IDs represented by sequential data (Nd+Nv).

[0214] Figure 20 This is a diagram illustrating the transmission interval when no data frames are being transmitted. Figure 20 The diagram shows the transmission interval of the beacon signals and the spectrum of the signals (data) propagated via communication bus B. Figure 20 In this context, Tmin represents the minimum value of the data frame transmission interval.

[0215] As described in Embodiment 1, when no data frames are transmitted, the data frame transmission interval is the shortest, and the intensity (peak value) of the interference noise is the greatest. The minimum transmission interval Tmin is expressed by the following formula.

[0216] Tmin=(Nd+Nv)·Tc

[0217] Let (Nd + Nv) represent the number of IDs represented by sequential data. The minimum transmission interval Tmin varies correspondingly to the number (integer) of IDs represented by sequential data. The number of IDs represented by sequential data is preferably an integer whose spectral intensity is lower than the permissible level of interference noise intensity. The larger the number of IDs represented by sequential data, the longer the minimum transmission interval Tmin. The longer the minimum transmission interval, the smaller the intensity (peak value) of the interference noise. Therefore, by increasing the number of IDs represented by sequential data, i.e., the number of hypothetical ECUs Nv, the intensity of interference noise can be reduced.

[0218] The number of sequential data representation IDs output to the data input unit 24 is preferably an integer value where the minimum transmission interval Tmin becomes 60 μs or more. When the number of sequential data representation IDs input to the data input unit 24 is an integer value where the minimum transmission interval Tmin becomes 60 μs or more, the device control unit 26 of the first ECU 11 changes the transmission interval of the beacon signal to a value of 60 μs or more. Furthermore, the device control unit 26 of the first ECU 11 preferably changes the transmission interval of the beacon signal to a value of 60 μs or more and 6500 μs or less. For example, the upper limit of the number of sequential data representation IDs is set such that the transmission interval of the beacon signal becomes 6500 μs or less.

[0219] <The Effects of Communication System 1>

[0220] The first ECU 11 and the plurality of second ECUs 12 each perform the same effect as in embodiment 1.

[0221] (Implementation Method 4)

[0222] In embodiment 3, the data input to the data input unit 24 is sequential data. However, the data input to the data input unit 24 is not limited to sequential data.

[0223] The differences between Embodiment 4 and Embodiment 3 will be explained below. Regarding structures other than those described later, since they are common to Embodiment 3, the same reference numerals will be used for the structural parts common to Embodiment 3, and their descriptions will be omitted.

[0224] <Structure of Communication System 1>

[0225] Figure 21 This is a block diagram showing the main structural components of the communication system 1 in Embodiment 4. In the communication system 1 of Embodiment 2, instead of sequential data, final period data representing the final period is input to the data input section 24 of the first ECU 11. Common sequential data, excluding the IDs of hypothetical ECUs, is stored in the IC storage sections 33 of both the first ECU 11 and the plurality of second ECUs 12.

[0226] The IC storage unit 33 of the first ECU 11 stores final period data representing the final period. When the last ECU in the sequence of the multiple second ECUs 12 sends a data frame, the bit communicator 35 of the first ECU 11 sends a beacon signal after the final period represented by the final period data has elapsed, once the last ECU has finished sending the data frame. When the last ECU does not send a data frame, the bit communicator 35 sends a beacon signal after the final period represented by the final period data has elapsed, once the last ECU's standby period has elapsed.

[0227] <Structure of the first ECU11>

[0228] In Embodiment 4, the device control unit 26 of the first ECU 11 executes a final period data assignment process, which assigns the final period data to the IC control unit 31, instead of a sequential data assignment process, by executing a computer program P. The IC control unit 31 of the first ECU 11 executes a final period modification process, which modifies the final period data stored in the IC storage unit 33, by executing a computer program stored in the IC storage unit 33.

[0229] <Order of Changes During the Final Period>

[0230] Figure 22This is a flowchart showing the sequence of changes during the final period. Figure 22 The diagram shows the final period data assignment processing of the device control unit 26 and the final period change processing of the IC control unit 31.

[0231] During the final period data assignment process, the device control unit 26 determines whether to input the final period data to the data input unit 24 from an external source (step S91). If the device control unit 26 determines that the final period data has not been input to the data input unit 24 (S91: "No"), it executes step S91 again. As a result, the device control unit 26 remains in standby mode until the final period data is input to the data input unit 24.

[0232] When the device control unit 26 determines that final period data should be input to the data input unit 24 (S91: "Yes"), it acquires the final period data input from the outside to the data input unit 24 (step S92). Acquiring the final period data is equivalent to acquiring the final period. Next, the device control unit 26 assigns the final period data acquired in step S92 to the IC control unit 31 via the interface 32 (step S93). After executing step S93, the device control unit 26 ends the final period data assignment process. After ending the final period data assignment process, the device control unit 26 executes the final period data assignment process again.

[0233] In the final period change process, the IC control unit 31 determines whether final period data has been assigned from the device control unit 26 (step S101). If the IC control unit 31 determines that final period data has not been assigned (S101: "No"), it executes step S101 again. The IC control unit 31 waits until final period data is assigned from the device control unit 26.

[0234] If the IC control unit 31 determines that final period data has been assigned (S101: "Yes"), it changes the final period data stored in the IC storage unit 33 to the assigned final period data (step S102) and ends the final period change process. After ending the final period change process, the IC control unit 31 executes the sequence change process again.

[0235] As described above, when the final period data stored in the IC storage unit 33 is changed, the final period is changed. Therefore, the device control unit 26 changes the final period by executing step S93. When the final period is changed, the transmission interval of the beacon signal is changed.

[0236] The final period of the final period data output to the data input unit 24 is preferably a period during which the minimum value of the transmission interval Tmin becomes 60 μs or more. When the number of IDs in the final period data output to the data input unit 24 is during a period when the minimum value of the transmission interval Tmin becomes 60 μs or more, the device control unit 26 of the first ECU 11 changes the transmission interval of the beacon signal to a value of 60 μs or more. Furthermore, the device control unit 26 of the first ECU 11 preferably changes the transmission interval of the beacon signal to a value of 60 μs or more and 6500 μs or less. For example, the upper limit of the final period of the final period data is set corresponding to the number of devices so that the transmission interval of the beacon signal becomes 6500 μs or less.

[0237] <The Effects of Communication System 1>

[0238] The first ECU11 and the plurality of second ECUs12 each perform the same effects as in embodiment 3.

[0239] <Modifications of Implementation Methods 3 and 4>

[0240] In embodiments 3 and 4, at least one of the first ECU 11 and the plurality of second ECUs 12 can also have its standby period changed in the same way as in embodiments 1 or 2. In this case, one or more standby periods and the final period are changed such that the beacon signal transmission interval becomes, for example, a value of 60 μs or more and 6500 μs or less. In embodiment 3, regarding the transmission of data frames, the order of the hypothetical ECUs is not limited to after the order of the last ECU. The order of the hypothetical ECUs can also be configured, for example, between the order of the second and last ECUs. In this case, the standby period of the second ECU 12 that transmits data frames after the hypothetical ECUs is extended. In addition, when there are two or more hypothetical ECUs, some hypothetical ECUs can be configured between the order of the second and last ECUs, and the remaining hypothetical ECUs can be configured after the order of the last ECU.

[0241] <Variations of Embodiments 1-4>

[0242] In embodiments 1-4, some or all of the processing performed by the IC control unit 31 in the first ECU 11 and the plurality of second ECUs 12 may also be performed by the device control unit 26. Furthermore, in embodiments 1-4, some or all of the processing performed by the device control unit 26 may also be performed by the IC control unit 31. Additionally, the transmission of data frames is not limited to transmission according to the PLCA method. There is no problem if the data frames are transmitted sequentially by the first ECU 11 and the plurality of second ECUs 12 after the beacon signal is transmitted. Furthermore, the device connected to the communication bus B is not limited to an ECU. There is no problem if the device connected to the communication bus B is a communication device that transmits data via the communication bus B.

[0243] 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.

[0244] The technical features (structural elements) described in embodiments 1 to 4 can be combined with each other to form new technical features.

[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 defined by the claims, not by the foregoing meaning, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0246] Label Explanation

[0247] 1. Communication System

[0248] 11 First ECU (Communication Device, Communication Equipment)

[0249] 12 Second ECU (Communication Device, Communication Equipment)

[0250] 21 Communication IC

[0251] 22 Detection Value Input Section

[0252] 23 Signal Output Section

[0253] 24 Data Input Section

[0254] 25. Device storage section

[0255] 26. Device Control Unit (Processing Unit)

[0256] 27 Device Bus

[0257] 31 IC Control Section

[0258] 32-interface

[0259] 33 IC Storage Division

[0260] 34 Clock Section

[0261] 35-bit communicator (data transmission unit, signal transmission unit)

[0262] 36 IC bus

[0263] Resistors 41a, 41b, and 42

[0264] Capacitors 43, 44a, and 44b

[0265] 45 Common mode choke coil

[0266] 45a First Inductor

[0267] 45b Second Inductor

[0268] 46. ​​Conversion Section

[0269] A storage medium

[0270] B Communication Bus

[0271] G1 First Conductor

[0272] G2 Second Conductor

[0273] M vehicle

[0274] P Computer Program

[0275] W1 First Conductor

[0276] W2 Second Conductor

[0277] Wa and Wb are equipment wires.

Claims

1. A communication device, wherein, The communication device includes: A data transmitting unit, connected to a communication bus, transmits data; the communication bus is connected to multiple communication devices; and Processing Department, Execute Processing The order in which the plurality of communication devices and data transmission units transmit data via the communication bus is determined. A start signal is repeatedly sent via the communication bus, indicating the start of data transmission. When the start signal is received, the data transmission unit transmits data in the specified order. The processing unit changes the transmission interval of the start signal. The data transmission unit stands by when it is time to transmit data. The data transmission unit begins transmitting data when the standby period becomes longer than the standby period. The transmission interval of the start signal increases correspondingly to the increase in the standby period. The processing unit changes the transmission interval of the start signal by changing the standby period.

2. The communication device according to claim 1, wherein, The processing unit obtains the number of devices connected to the communication bus from an external source. The processing unit changes the standby period based on the number of devices obtained.

3. A communication device, wherein, The communication device includes: A data transmitting unit, connected to a communication bus, transmits data; the communication bus is connected to multiple communication devices; and Processing Department, Execute Processing The order in which the plurality of communication devices and data transmission units transmit data via the communication bus is determined. A start signal is repeatedly sent via the communication bus, indicating the start of data transmission. When the start signal is received, the data transmission unit transmits data in the specified order. The processing unit changes the transmission interval of the start signal. The communication device includes a signal transmitting unit that transmits the start signal via the communication bus. The signal transmitting unit stands standby when the order of data transmission among the plurality of communication devices is the last one, and when the last communication device has finished transmitting data, or when the last communication device has not transmitted data. If the standby period becomes a second standby period or longer, the signal transmitting unit transmits the start signal again. The processing unit changes the transmission interval of the start signal by changing the second standby period.

4. The communication device according to claim 3, wherein, The processing unit obtains period data related to the second standby period from an external source. The processing unit changes the second standby period based on the acquired period data.

5. The communication device according to claim 4, wherein, When the signal transmitting unit finishes transmitting the start signal, the data transmitting unit begins transmitting data after a standby period. The processing unit acquires the period data, which represents an integer indicating the number of devices exceeding the number of devices connected to the communication bus. The processing unit changes the second standby period to the product of the standby period and the number of devices obtained by subtracting the number of devices from an integer represented by the period data.

6. The communication device according to any one of claims 1 to 5, wherein, The structure of the data transmission unit conforms to IEEE 802.3cg 10BASE-T1S.

7. A communication system, wherein, The communication system includes multiple communication devices connected to a communication bus. One of the plurality of communication devices has a signal transmitting unit that repeatedly transmits a start signal via the communication bus, the start signal indicating the start of data transmission. Each of the plurality of communication devices has a data transmission unit, which transmits data via the communication bus in a predetermined order upon receiving the start signal. At least one of the plurality of communication devices further includes a processing unit that performs processing. The processing unit changes the transmission interval of the start signal. The data transmission unit stands by when it is time to transmit data. The data transmission unit begins transmitting data when the standby period becomes longer than the standby period. The transmission interval of the start signal increases correspondingly to the increase in the standby period. The processing unit changes the transmission interval of the start signal by changing the standby period.

8. A communication system, wherein, The communication system includes multiple communication devices connected to a communication bus. One of the plurality of communication devices has a signal transmitting unit that repeatedly transmits a start signal via the communication bus, the start signal indicating the start of data transmission. Each of the plurality of communication devices has a data transmission unit, which transmits data via the communication bus in a predetermined order upon receiving the start signal. At least one of the plurality of communication devices further includes a processing unit that performs processing. The processing unit changes the transmission interval of the start signal. The at least one communication device includes a signal transmitting unit that transmits the start signal via the communication bus. The signal transmitting unit stands standby when the last communication device in the sequence of data transmission among the multiple communication devices connected to the communication bus finishes transmitting data, or when the last communication device has not transmitted data. If the standby period becomes a second standby period or longer, the signal transmitting unit transmits the start signal again. The processing unit changes the transmission interval of the start signal by changing the second standby period.

9. The communication system according to claim 7 or 8, wherein, One or more of the processing units collectively change the transmission interval of the start signal to a value of 60 μs or more.

10. The communication system according to claim 9, wherein, One or more of the processing units collectively change the transmission interval of the start signal to a value of 6500 μs or less.

11. A communication method, which is a communication method of a communication device, wherein the communication device transmits data, wherein... The communication device is connected to a communication bus, which in turn connects to multiple communication devices. The order in which the communication device and multiple communication equipment transmit data via the communication bus is determined. A start signal is repeatedly sent via the communication bus, indicating the start of data transmission. The communication device performs the following steps: Upon receiving the start signal, data is transmitted in the specified order; and Change the transmission interval of the start signal. Standby when it is time to send data. Data transmission begins when the standby period becomes longer than the standby period. The transmission interval of the start signal increases correspondingly to the increase in the standby period. The transmission interval of the start signal is changed by changing the standby period.

12. A communication method, which is a communication method of a communication device, wherein the communication device transmits data, wherein... The communication device is connected to a communication bus, which in turn connects to multiple communication devices. The order in which the communication device and multiple communication equipment transmit data via the communication bus is determined. A start signal is repeatedly sent via the communication bus, indicating the start of data transmission. The communication device performs the following steps: Upon receiving the start signal, data is transmitted in the specified order; and Change the transmission interval of the start signal. The start signal is sent via the communication bus. When the data transmission order among the multiple communication devices is the last one, and the last communication device has finished transmitting data, or when the last communication device has not transmitted data, the device is in standby mode. If the standby period becomes a second standby period or longer, the start signal is sent again. The transmission interval of the start signal is changed by changing the second standby period.

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