In-vehicle device, communication method, and communication program
Patent Information
- Application Number
- PCT/JP2026/010579
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-27
- Filing Date
- 2026-03-18
- Publication Date
- 2026-10-01
Smart Images
Figure JP2026010579_01102026_PF_FP_ABST
Abstract
Description
In-vehicle device, communication method and communication program
[0001] The present disclosure relates to an in-vehicle device, a communication method and a communication program. This application claims priority based on Japanese Patent Application No. 2025-53074 filed on March 27, 2025, the entire disclosure of which is incorporated herein by reference.
[0002] Patent Document 1 (Japanese Unexamined Patent Publication No. 2023-23504) discloses the following communication device. That is, the communication device is connected to a communication bus to which a plurality of communication devices are connected, and includes a data transmission unit that transmits data and a processing unit that executes processing. The order in which the plurality of communication devices and the data transmission unit transmit data via the communication bus is predetermined. A start signal indicating the start of data transmission is repeatedly transmitted via the communication bus. When the start signal is transmitted, the data transmission unit transmits data in accordance with the order, and the processing unit changes the transmission interval of the start signal.
[0003] Japanese Unexamined Patent Publication No. 2023-23504
[0004] The in-vehicle device of the present disclosure is an in-vehicle device in an in-vehicle communication system including a plurality of in-vehicle devices connected to a bus, comprising: a communication unit that receives a beacon signal via the bus and transmits a communication signal to the bus at a transmission opportunity set based on the reception timing of the beacon signal; a monitoring unit that monitors the beacon signal transmitted to the bus by another in-vehicle device; and a backup transmission unit that transmits the beacon signal to the bus in place of the other in-vehicle device when the monitoring unit detects that the beacon signal from the other in-vehicle device has been interrupted.
[0005] One aspect of the present disclosure can be implemented not only as an in-vehicle device including such a characteristic processing unit, but also as a semiconductor integrated circuit that implements part or all of the in-vehicle device, or as a system including the in-vehicle device.
[0006] Figure 1 is a diagram showing the configuration of an in-vehicle communication system according to the first embodiment of this disclosure. Figure 2 is a diagram showing an example of a PLC cycle in an in-vehicle communication system according to the first embodiment of this disclosure. Figure 3 is a flowchart defining an example of the operation procedure when an in-vehicle ECU according to the first embodiment of this disclosure starts and stops transmitting a beacon signal. Figure 4 is a diagram showing an example of a communication sequence in an in-vehicle communication system according to the first embodiment of this disclosure. Figure 5 is a diagram showing the configuration of an in-vehicle communication system according to Modification 1 of the first embodiment of this disclosure. Figure 6 is a diagram showing the configuration of an in-vehicle communication system according to Modification 2 of the first embodiment of this disclosure. Figure 7 is a diagram showing the configuration of an in-vehicle communication system according to the second embodiment of this disclosure. Figure 8 is a diagram showing an example of a communication sequence in an in-vehicle communication system according to the second embodiment of this disclosure.
[0007] Conventionally, in an in-vehicle communication system equipped with multiple in-vehicle devices connected to a bus, technologies have been disclosed for avoiding collisions of communication signals transmitted by the in-vehicle devices.
[0008] [Problems this disclosure aims to solve] Beyond the technology described in Patent Document 1, there is a need for a technology that can provide more stable communication in an in-vehicle communication system equipped with multiple in-vehicle devices connected to a bus.
[0009] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide an in-vehicle device, a communication method, and a communication program that enable more stable communication in an in-vehicle communication system equipped with multiple in-vehicle devices connected to a bus.
[0010] [Effects of this disclosure] According to this disclosure, in an in-vehicle communication system equipped with multiple in-vehicle devices connected to a bus, more stable communication can be achieved.
[0011] [Description of Embodiments of the Disclosure] First, the contents of embodiments of the disclosure will be listed and described. (1) An in-vehicle device according to an embodiment of the disclosure is an in-vehicle device in an in-vehicle communication system comprising a plurality of in-vehicle devices connected to a bus, comprising: a communication unit that receives a beacon signal via the bus and transmits a communication signal to the bus at a transmission opportunity set based on the timing of reception of the beacon signal; a monitoring unit that monitors the beacon signal transmitted to the bus by other in-vehicle devices; and a backup transmitting unit that transmits the beacon signal to the bus on behalf of the other in-vehicle devices when the monitoring unit detects that the beacon signal from the other in-vehicle devices has been interrupted.
[0012] In this way, if the beacon signal transmitted to the bus is interrupted, the system is configured to transmit the beacon signal on behalf of the on-board device that should transmit the beacon signal. This ensures that even if the on-board device stops due to a malfunction or other reason, the supply of beacon signals to each on-board device in the on-board communication system can be maintained. Therefore, each on-board device can communicate with other on-board devices using a communication mode that transmits communication signals based on the timing of the beacon signal. This reduces delays in communications related to vehicle operation, etc., compared to a configuration that switches to a CSMA / CD (Carrier Sense Multiple Access / Collision Detection) communication mode when, for example, the on-board device that should transmit the beacon signal stops. Consequently, more stable communication can be achieved in an on-board communication system equipped with multiple on-board devices connected to a bus.
[0013] (2) In (1) above, if the beacon signal from the other in-vehicle device is interrupted, the communication unit may switch from the first communication mode in which it transmits the communication signal at the transmission opportunity to the second communication mode in which it transmits the communication signal according to the CSMA / CD method, and the communication unit may switch from the second communication mode to the first communication mode when the transmission of the beacon signal by the backup transmission unit is started.
[0014] This configuration allows for communication in the second communication mode during the period between the interruption of the beacon signal and the start of beacon signal transmission by the backup transmitter. Furthermore, regardless of the timing of the original source's beacon signal transmission, communication in the first communication mode can be resumed using the beacon signal transmitted by the backup transmitter.
[0015] (3) In (1) or (2) above, if the auxiliary transmitting unit detects a beacon signal from another vehicle-mounted device by the monitoring unit after the start of transmitting the beacon signal, the auxiliary transmitting unit may stop transmitting the beacon signal.
[0016] This configuration allows for the transmission of beacon signals from a single source, enabling normal communication according to a set transmission order using beacon signals from that single source.
[0017] (4) In the above (3), the in-vehicle communication system may repeatedly transmit the beacon signal, and each in-vehicle device may be given the opportunity to transmit in a predetermined transmission order between the transmission timings of two consecutive beacon signals, and the monitoring unit may detect the beacon signal from another in-vehicle device, determined by using the last transmission opportunity in the transmission order as a reference after the start of transmission of the beacon signal by the backup transmitting unit.
[0018] With this configuration, after the backup transmitter starts transmitting a beacon signal, it is possible to distinguish between the beacon signal that serves as the reference for transmission opportunities and beacon signals from a different source than the source of the said beacon signal, thereby enabling more accurate detection of multiple beacon signals from multiple sources.
[0019] (5) In (3) or (4) above, if the monitoring unit starts transmitting the beacon signal by the auxiliary transmitting unit, it may determine whether or not there is a beacon signal from another in-vehicle device after a waiting period corresponding to the identifier given to the communication unit has elapsed.
[0020] With this configuration, in an in-vehicle communication system that provides redundancy for in-vehicle devices equipped with backup transmitters, the number of backup transmitters that transmit beacon signals can be narrowed down to one, and normal communication can be performed according to the transmission order set using beacon signals from that single backup transmitter.
[0021] (6) In any of (1) to (5) above, the communication unit may transmit the communication signal in accordance with 10BASE-T1S at the transmission opportunity set based on the reception timing of the beacon signal used for PLCA (Physical Layer Collision Avoidance).
[0022] With this configuration, half-duplex communication between multiple in-vehicle devices can be performed in accordance with 10BASE-T1S, while preventing collisions of communication signals on the bus.
[0023] (7) A communication method according to an embodiment of the present disclosure is a communication method in an in-vehicle device in an in-vehicle communication system comprising a plurality of in-vehicle devices connected to a bus, comprising the steps of: receiving a beacon signal via the bus and transmitting a communication signal to the bus at a transmission opportunity set based on the timing of reception of the beacon signal; monitoring the beacon signal transmitted to the bus by other in-vehicle devices; and, when detecting that the beacon signal from the other in-vehicle devices has been interrupted, transmitting the beacon signal to the bus on behalf of the other in-vehicle devices.
[0024] In this way, if the beacon signal transmitted to the bus is interrupted, the system transmits the beacon signal on behalf of the on-board device that should transmit the beacon signal. This configuration ensures that even if the on-board device that should transmit the beacon signal stops due to a malfunction or other reason, the beacon signal can still be transmitted to the bus. Therefore, even if the on-board device that should transmit the beacon signal stops, the communication mode, which transmits communication signals based on the timing of the beacon signal, can be maintained. This reduces delays in communication related to vehicle operation, etc., compared to a configuration that switches to the CSMA / CD communication mode when, for example, the on-board device that should transmit the beacon signal stops. Consequently, more stable communication can be achieved in an on-board communication system equipped with multiple on-board devices connected to a bus.
[0025] (8) The communication program according to the embodiment of the present disclosure is a communication program used in an in-vehicle device in an in-vehicle communication system comprising a plurality of in-vehicle devices connected to a bus, and is a program for causing a computer to function as: a communication unit that receives a beacon signal via the bus and transmits a communication signal to the bus at a transmission opportunity set based on the timing of reception of the beacon signal; a monitoring unit that monitors the beacon signal transmitted to the bus by other in-vehicle devices; and a backup transmitting unit that transmits the beacon signal to the bus on behalf of the other in-vehicle devices when the monitoring unit detects that the beacon signal from the other in-vehicle devices has been interrupted.
[0026] In this way, if the beacon signal transmitted to the bus is interrupted, the system transmits the beacon signal on behalf of the on-board device that should transmit the beacon signal. This configuration ensures that even if the on-board device that should transmit the beacon signal stops due to a malfunction or other reason, the beacon signal can still be transmitted to the bus. Therefore, even if the on-board device that should transmit the beacon signal stops, the communication mode, which transmits communication signals based on the timing of the beacon signal, can be maintained. This reduces delays in communication related to vehicle operation, etc., compared to a configuration that switches to the CSMA / CD communication mode when, for example, the on-board device that should transmit the beacon signal stops. Consequently, more stable communication can be achieved in an on-board communication system equipped with multiple on-board devices connected to a bus.
[0027] Embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated. Furthermore, at least some of the embodiments described below may be combined in any way.
[0028] [Configuration and Basic Operation] Figure 1 is a diagram showing the configuration of an in-vehicle communication system according to a first embodiment of the present disclosure. Referring to Figure 1, the in-vehicle communication system 201 comprises an in-vehicle ECU (Electronic Control Unit) 101 and N in-vehicle ECUs 111, where N is an integer of 2 or more. The in-vehicle ECUs 101 and 111 are examples of in-vehicle devices. The in-vehicle communication system 201 is mounted on a vehicle 1.
[0029] The in-vehicle ECUs 101 and 111 are connected to bus 2. More specifically, the in-vehicle ECUs 101 and 111 are multidrop connected to bus 2. For example, bus 2 is a cable conforming to Ethernet®. More specifically, bus 2 is a single twisted-pair cable conforming to IEEE 802.3cg. The in-vehicle communication system 201 may further include a relay device (not shown) connected to bus 2 that relays communication signals between the in-vehicle ECUs 101 and 111 and equipment connected to a transmission line different from bus 2.
[0030] The in-vehicle ECU 111 comprises a data processing unit 11, a MAC processing unit 12, a PHY processing unit 13, and a communication port 14. Compared to the in-vehicle ECU 111, the in-vehicle ECU 101 further comprises a PHY processing unit 15 and a communication port 16. The PHY processing unit 15 is stopped in the initial state of the in-vehicle communication system 201. Hereinafter, the MAC processing unit 12 of the in-vehicle ECU 101 will also be referred to as the MAC processing unit 12A. The MAC processing unit 12A is an example of a monitoring unit. The PHY processing unit 13 is an example of a communication unit. The PHY processing unit 15 is an example of a backup transmission unit. Some or all of the data processing unit 11, MAC processing unit 12, and PHY processing units 13, 15 are implemented, for example, by a processing circuit (Circuitry) including one or more processors. The communication ports 14, 16 are connectors or terminals to which the bus 2 is connected.
[0031] As an example, in the in-vehicle ECU 101, the data processing unit 11 and the MAC processing unit 12A are implemented by a microcontroller, while the PHY processing units 13 and 15 are implemented by two separate ICs (Integrated Circuits) distinct from the microcontroller. In the in-vehicle ECU 111, the data processing unit 11 and the MAC processing unit 12 are implemented by a microcontroller, while the PHY processing unit 13 is implemented by a separate IC. The IC implementing the PHY processing unit 13 is connected to the communication port 14 on the board, and the IC implementing the PHY processing unit 15 is connected to the communication port 16 on the board.
[0032] Each PHY processing unit 13, 15 is pre-assigned a node ID, which is an identifier. For example, the node ID of each PHY processing unit 13 is a distinct integer from zero to N. The node ID of PHY processing unit 15 is "zero". Hereinafter, PHY processing units 13 with node IDs 0, 1, 2, 3...N will also be referred to as PHY processing unit 13_0, 13_1, 13_2, 13_3, ... 13_N, respectively. For example, the in-vehicle ECU 101 includes PHY processing unit 13_1, which is a PHY processing unit 13 with node ID "1".
[0033] The in-vehicle ECUs 101 and 111 perform one-to-many half-duplex communication according to 10BASE-T1S. That is, the PHY processing unit 13 transmits a communication signal Cs to other PHY processing units 13 via the bus 2.
[0034] More specifically, the data processing unit 11 periodically or irregularly generates communication information destined for other data processing units 11 in the in-vehicle communication system 201 and outputs the generated communication information to the MAC processing unit 12. The MAC processing unit 12 generates a frame containing the communication information received from the data processing unit 11. The MAC processing unit 12 outputs the generated frame to the PHY processing unit 13, for example, according to the MII (Media Independent Interface) communication protocol. The frame length of the frame generated by the MAC processing unit 12 is less than a predetermined value and is variable.
[0035] The PHY processing unit 13 generates an analog communication signal Cs that includes the frame received from the MAC processing unit 12, and transmits the generated communication signal Cs to the bus 2 via the communication port 14.
[0036] When the PHY processing unit 13 receives a communication signal Cs from another PHY processing unit 13 in the in-vehicle communication system 201 via the bus 2 and communication port 14, it acquires a frame from the received communication signal Cs. The PHY processing unit 13 outputs the acquired frame to the MAC processing unit 12, for example, according to the MII communication protocol.
[0037] The MAC processing unit 12 acquires communication information from the frame received from the PHY processing unit 13 and outputs the acquired communication information to the data processing unit 11. The data processing unit 11 uses the communication information received from the MAC processing unit 12 to perform predetermined processing.
[0038] (PLCA) In the in-vehicle communication system 201, a beacon signal Bc used for PLCA is repeatedly transmitted. Between the transmission timings of two consecutive beacon signals Bc, the in-vehicle ECUs 101 and 111 are given an opportunity to transmit a communication signal Cs according to a predetermined transmission order.
[0039] More specifically, the PHY processing unit 13_0 in the in-vehicle ECU 111 transmits the beacon signal Bc to the bus 2 via the communication port 14. For example, the beacon signal Bc is a signal with a predetermined pattern.
[0040] In the in-vehicle ECU 101, PHY processing units 13 other than PHY processing unit 13_0 receive the beacon signal Bc via bus 2. More specifically, in the in-vehicle communication system 201, PHY processing units 13 other than PHY processing unit 13_0 receive the beacon signal Bc from PHY processing unit 13_0 via bus 2 and the corresponding communication port 14.
[0041] Each PHY processing unit 13 in the in-vehicle communication system 201 is given a transmission opportunity in ascending order of node ID, for example, according to the PLC in 10BASE-T1S. Hereinafter, the cycle of transmission opportunities from PHY processing unit 13_0 to PHY processing unit 13_N will also be referred to as the PLC cycle. In the in-vehicle communication system 201, the PLC cycle is repeated multiple times. The beacon signal Bc is a synchronization signal that indicates the start of the PLC cycle.
[0042] The PHY processing unit 13_0 operates in communication mode Md1, transmitting the communication signal Cs according to 10BASE-T1S at transmission opportunities set based on the transmission timing of the beacon signal Bc. Other PHY processing units operate in communication mode Md1 at transmission opportunities set based on the reception timing of the beacon signal Bc. Communication mode Md1 is an example of a first communication mode.
[0043] More specifically, the PHY processing unit 13 waits to transmit the generated communication signal Cs until a transmission opportunity for the PHY processing unit 13 arrives. The PHY processing unit 13 is capable of transmitting the communication signal Cs to the bus 2 via the communication port 14 at the transmission opportunity set for the PHY processing unit 13. The transmission opportunity shifts to the next PHY processing unit 13 when the PHY processing unit 13 does not transmit the communication signal Cs or when the PHY processing unit 13 completes transmission of the communication signal Cs. For example, the communication signal Cs includes an ESD (End of Stream Delimiter) indicating the end of the communication signal Cs. The PHY processing unit 13 determines completion of transmission of the communication signal Cs by another PHY processing unit 13 based on the ESD.
[0044] Figure 2 is a diagram showing an example of a PLCA cycle in the in-vehicle communication system according to the first embodiment of the present disclosure. In Figure 2, the horizontal axis represents time. In Figure 2, the numbers in parentheses indicate the node IDs of the PHY processing units 13 having transmission opportunities.
[0045] Referring to Figure 2, the PHY processing unit 13_0 transmits a beacon signal Bc during a period from time t0B to time t00. PHY processing units 13 other than the PHY processing unit 13_0 receive the beacon signal Bc via the bus 2 and the communication port 14.
[0046] The PHY processing unit 13 includes a timer (not shown). For example, the timer is a count-up timer. When the PHY processing unit 13_0 completes transmission of the beacon signal Bc at time t00, it resets the timer to zero. Further, when PHY processing units 13 other than the PHY processing unit 13_0 complete reception of the beacon signal Bc at time t00, they reset their timers to zero. This enables synchronization of the timers of the respective PHY processing units 13 in the in-vehicle communication system 201. Each PHY processing unit 13 determines the node ID of the PHY processing unit 13 granted a transmission opportunity based on the time indicated by the timer.
[0047] More specifically, at time t00 when the transmission of the beacon signal Bc is completed, a transmission opportunity is granted to the PHY processing unit 13_0. For example, since the PHY processing unit 13_0 does not have a communication signal Cs to be transmitted, it does not transmit the communication signal Cs during its transmission opportunity.
[0048] Next, at time t01 when a waiting time Tm of a predetermined length has elapsed from time t00 when the transmission opportunity was granted to the PHY processing unit 13_0, a transmission opportunity is granted to the PHY processing unit 13_1. The waiting time Tm is, for example, 2 microseconds. The PHY processing unit 13_1 refers to a timer and waits for its transmission opportunity, that is, time t01. Then, at time t01, the PHY processing unit 13_1 starts transmitting the communication signal Cs and stops counting up the timer. Furthermore, the PHY processing units 13 other than the PHY processing unit 13_1 receive the communication signal Cs at time t01 and stop counting up the timers.
[0049] Next, at time t02 when the transmission of the communication signal Cs by the PHY processing unit 13_1 is completed, a transmission opportunity is granted to the PHY processing unit 13_2. The PHY processing unit 13_1 completes the transmission of the communication signal Cs at time t02 and resumes counting up the timer. Furthermore, the PHY processing units 13 other than the PHY processing unit 13_1 determine the completion of transmission of the communication signal Cs by the PHY processing unit 13_1 at time t02, and resume counting up the timers. For example, since the PHY processing unit 13_2 does not have a communication signal Cs to be transmitted, it does not transmit the communication signal Cs during its transmission opportunity.
[0050] Next, at time t03, after a waiting period Tm has elapsed from time t02, when the PHY processing unit 13_2 was given a transmission opportunity, the PHY processing unit 13_3 is given a transmission opportunity. The PHY processing unit 13_3 refers to the timer and waits for its transmission opportunity, i.e., time t03. For example, if the PHY processing unit 13_3 has a communication signal Cs and cannot start transmitting the communication signal Cs at time t03, it transmits a commit signal Cm of a predetermined pattern during the period until it can start transmitting the communication signal Cs. At time t03, the PHY processing unit 13_3 starts transmitting the commit signal Cm and stops the timer counting up. Also, the PHY processing units 13 other than the PHY processing unit 13_3 receive the commit signal Cm at time t03 and stop the timer counting up. After that, when it becomes possible for the PHY processing unit 13_3 to transmit the communication signal Cs, it starts transmitting the communication signal Cs instead of the commit signal Cm.
[0051] Next, at time t04, when the transmission of the communication signal Cs by the PHY processing unit 13_3 is completed, the PHY processing unit 13_4 is given an opportunity to transmit. The PHY processing unit 13_3 completes the transmission of the communication signal Cs at time t04 and resumes counting up the timer. In addition, the PHY processing units 13 other than the PHY processing unit 13_3 determine at time t04 that the transmission of the communication signal Cs by the PHY processing unit 13_3 is complete and resume counting up the timer. For example, since the PHY processing unit 13_4 does not have a communication signal Cs to transmit, it does not transmit the communication signal Cs during its transmission opportunity.
[0052] Next, at time t05, after a waiting period Tm has elapsed from time t04, when PHY processing unit 13_4 was given a transmission opportunity, PHY processing unit 13_5 is given a transmission opportunity. PHY processing unit 13_5 refers to the timer and waits for its transmission opportunity, i.e., time t05. Then, at time t05, PHY processing unit 13_5 starts transmitting the communication signal Cs and stops the timer counting up. Also, PHY processing units 13 other than PHY processing unit 13_5 receive the communication signal Cs at time t05 and stop the timer counting up.
[0053] Subsequently, at time t0N, the PHY processing unit 13_N is given an opportunity to transmit. The PHY processing unit 13_0 transmits the beacon signal Bc again when the waiting time Tm has elapsed from time t0N or when the PHY processing unit 13_N has finished transmitting the communication signal Cs.
[0054] More specifically, the PHY processing unit 13_0 is given in advance the number of PHY processing units 13 in the in-vehicle communication system 201, i.e., a value of "N+1". The PHY processing unit 13_0 transmits a beacon signal Bc during the period from time t1B, when a waiting time Tm has elapsed from time t0N or when the transmission of the communication signal Cs by the PHY processing unit 13_N is completed, until time t10.
[0055] [Problem] In the in-vehicle communication system 201, there is a need for technology that enables more stable communication. More specifically, in the in-vehicle communication system 201, if, for example, the PHY processing unit 13_0 stops due to a malfunction or the like, the beacon signal Bc from the PHY processing unit 13_0 may be interrupted.
[0056] In this case, each PHY processing unit 13 cannot transmit the communication signal Cs at the transmission timing according to the PLCA cycle, so the communication signals Cs transmitted by multiple PHY processing units 13 may collide on the bus 2.
[0057] Therefore, the in-vehicle ECU 101 according to the first embodiment of this disclosure solves the above problem with the following configuration.
[0058] (Start of transmission of beacon signal Bc by PHY processing unit 15) The PHY processing unit 13 includes a register RgA that indicates whether or not the beacon signal Bc is being repeatedly transmitted to bus 2.
[0059] PHY processing units 13 other than PHY processing unit 13_0 set the value of register RgA to "1" if they receive the next beacon signal Bc before a predetermined timeout period Tout has elapsed after receiving the previous beacon signal Bc. Also, PHY processing unit 13_0 sets the value of register RgA to "1" if it transmits the next beacon signal Bc before a predetermined timeout period Tout has elapsed after transmitting the previous beacon signal Bc. PHY processing unit 13 operates in communication mode Md1 when the value of register RgA is "1".
[0060] On the other hand, if a PHY processing unit 13 other than PHY processing unit 13_0 does not receive a beacon signal Bc within the timeout period Tout after receiving the beacon signal Bc, it sets the value of register RgA to "zero". Also, if PHY processing unit 13_0 fails to transmit the next beacon signal Bc within the timeout period Tout after transmitting the previous beacon signal Bc, it sets the value of register RgA to "zero". When the value of register RgA is "zero", PHY processing unit 13 operates in communication mode Md2.
[0061] For example, in the in-vehicle communication system 201, if the beacon signal Bc from PHY processing unit 13_0 is interrupted due to the shutdown of PHY processing unit 13_0, the PHY processing unit 13 other than PHY processing unit 13_0 will transition from the above-described communication mode Md1 to communication mode Md2, which transmits a communication signal Cs according to the CSMA / CD method. Also, for example, if the PHY processing unit 13_0's function to transmit the beacon signal Bc is stopped, but it is still able to transmit the communication signal Cs, it will transition from communication mode Md1 to communication mode Md2, similar to the other PHY processing units 13. Communication mode Md2 is an example of a second communication mode. More specifically, in the in-vehicle communication system 201, each PHY processing unit 13 will transition from communication mode Md1 to communication mode Md2 if the value of register RgA is rewritten from "1" to "zero".
[0062] In communication mode Md2, the PHY processing unit 13 transmits a communication signal Cs according to the CSMA / CD scheme. More specifically, after generating a communication signal Cs, the PHY processing unit 13 checks the transmission status of the communication signal Cs on bus 2. If another PHY processing unit 13 has transmitted a communication signal Cs to bus 2, the PHY processing unit 13 waits to transmit the generated communication signal Cs. If no other PHY processing unit 13 has transmitted a communication signal Cs to bus 2, the PHY processing unit 13 transmits the generated communication signal Cs to bus 2 via communication port 14. If the transmitted communication signal Cs 13 collides with a communication signal Cs transmitted by another PHY processing unit 13 on bus 2, the PHY processing unit 13 retransmits the communication signal Cs after a random waiting period.
[0063] The MAC processing unit 12A in the in-vehicle ECU 101 monitors the beacon signal Bc transmitted to the bus 2 by the in-vehicle ECU 111. More specifically, the MAC processing unit 12A, for example, at a monitoring timing according to a predetermined monitoring period Cy1, accesses the PHY processing unit 13_1 according to the SMI (Serial Management Interface) communication protocol and obtains the value of register RgA in the PHY processing unit 13_1. If the obtained value is "1", the MAC processing unit 12A determines that the beacon signal Bc has been successfully transmitted from the PHY processing unit 13_0.
[0064] On the other hand, if the acquired value is "zero", the MAC processing unit 12A determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted. If the MAC processing unit 12A determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted, it activates the PHY processing unit 15.
[0065] When the MAC processing unit 12 detects that the beacon signal Bc from another in-vehicle ECU 111 has been interrupted, the PHY processing unit 15 transmits the beacon signal Bc to the bus 2 on behalf of the in-vehicle ECU 111. For example, the PHY processing unit 15, like the PHY processing unit 13_0, is given in advance the number of PHY processing units 13 in the in-vehicle communication system 201, i.e., a value of "N+1". When activated by the MAC processing unit 12A, the PHY processing unit 15 transmits the beacon signal Bc to the bus 2 via the communication port 16 in the same manner as the PHY processing unit 13_0.
[0066] For example, when the PHY processing unit 15 starts transmitting a beacon signal Bc, the PHY processing unit 13 switches from communication mode Md2 to communication mode Md1. More specifically, each PHY processing unit 13 in the in-vehicle communication system 201 receives a beacon signal Bc from the PHY processing unit 15 via the bus 2 and the corresponding communication port 14. Each PHY processing unit 13 transmits a communication signal Cs to the bus 2 via the communication port 14 at a transmission opportunity set based on the timing of receiving the beacon signal Bc received from the PHY processing unit 15, in the same manner as when it receives a beacon signal Bc from PHY processing unit 13_1.
[0067] (Stopping transmission of beacon signal Bc by PHY processing unit 15) In the in-vehicle communication system 201, if the PHY processing unit 13_0 recovers after the PHY processing unit 15 has started transmitting the beacon signal Bc, the PHY processing unit 13_0 will resume transmitting the beacon signal Bc.
[0068] For example, the PHY processing unit 15 includes a register RgB that indicates whether or not the beacon signal Bc has been transmitted to the bus 2 by the PHY processing unit 13_0. In its initial state, the PHY processing unit 15 sets the value of register RgB to "zero".
[0069] After the start of transmission of the beacon signal Bc, the PHY processing unit 15 determines whether the beacon signal Bc has been transmitted to bus 2 by the PHY processing unit 13_0 by using the last transmission opportunity in the PLCA cycle as a reference. More specifically, if the PHY processing unit 15 receives the beacon signal Bc via bus 2 and communication port 16 at a timing different from the end timing of the (N+1)th transmission opportunity in the PLCA cycle, it determines that the beacon signal Bc was transmitted by the PHY processing unit 13_0 and rewrites the value of register RgB from "zero" to "1". Here, the (N+1)th transmission opportunity in the PLCA cycle is the last transmission opportunity in the transmission order of each PHY processing unit 13 in the PLCA cycle.
[0070] The MAC processing unit 12A monitors the beacon signal Bc transmitted to the bus 2 by the onboard ECU 111 after the PHY processing unit 15 is activated.
[0071] If the MAC processing unit 12A detects the beacon signal Bc from the in-vehicle ECU 111 after the start of transmission of the beacon signal Bc, the PHY processing unit 15 stops transmitting the beacon signal Bc.
[0072] For example, the MAC processing unit 12A detects the beacon signal Bc from the in-vehicle ECU 111, which is determined by using the (N+1)th transmission opportunity in the PLCA cycle as a reference, after the PHY processing unit 15 has started transmitting the beacon signal Bc. More specifically, after the PHY processing unit 15 is started, the MAC processing unit 12A obtains the value of the register RgB of the PHY processing unit 15 by accessing the PHY processing unit 15 according to the SMI communication protocol at a monitoring timing according to a predetermined monitoring period Cy2, for example. If the obtained value is "1", the MAC processing unit 12A determines that the PHY processing unit 13_0 has recovered and that the transmission of the beacon signal Bc by the PHY processing unit 13_0 has resumed. If the MAC processing unit 12A determines that the transmission of the beacon signal Bc by the PHY processing unit 13_0 has resumed, it stops the PHY processing unit 15.
[0073] [Operation Flow] Figure 3 is a flowchart that shows an example of the operation procedure when an in-vehicle ECU according to the first embodiment of this disclosure starts and stops transmitting a beacon signal.
[0074] Referring to Figure 3, first, the MAC processing unit 12A in the in-vehicle ECU 101 monitors the beacon signal Bc transmitted to the bus 2 by the PHY processing unit 13_0. More specifically, the MAC processing unit 12A waits for a monitoring timing according to the monitoring period Cy1 (NO in step S11), and when the monitoring timing arrives (YES in step S11), it obtains the value of the register RgA of the PHY processing unit 13_1 (step S12).
[0075] Next, if the value of register RgA is "1" (NO in step S13), the MAC processing unit 12A determines that the beacon signal Bc has been successfully transmitted from the PHY processing unit 13_0 and waits for a new monitoring timing according to the monitoring cycle Cy1 (NO in step S11).
[0076] On the other hand, if the value of register RgA is "zero" (YES in step S13), the MAC processing unit 12A determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted and activates the PHY processing unit 15 (step S14).
[0077] Next, the PHY processing unit 15 takes over from the PHY processing unit 13_0 and starts transmitting the beacon signal Bc (step S15).
[0078] Next, the MAC processing unit 12A waits for a monitoring timing according to the monitoring period Cy2 (NO in step S16), and when the monitoring timing arrives (YES in step S16), it obtains the value of register RgB of the PHY processing unit 15 (step S17).
[0079] Next, if the value of register RgB is "zero" (NO in step S18), the MAC processing unit 12A determines that the transmission of the beacon signal Bc by the PHY processing unit 13_0 has not resumed and waits for a new monitoring timing according to the monitoring cycle Cy2 (NO in step S16).
[0080] On the other hand, if the value of register RgB is "1" (YES in step S18), the MAC processing unit 12A determines that the transmission of the beacon signal Bc from the PHY processing unit 13_0 has resumed and stops the PHY processing unit 15 (step S19). Next, the MAC processing unit 12A waits for a new monitoring timing according to the monitoring cycle Cy1 (NO in step S11).
[0081] Figure 4 is a diagram showing an example of a communication sequence in an in-vehicle communication system according to the first embodiment of the present disclosure. In Figure 4, the PHY processing units 13_0, 13_1, 13_N and the PHY processing unit 15 are typically shown.
[0082] Referring to Figure 4, first, the PHY processing unit 13_0 transmits the beacon signal Bc to the bus 2 (step S21).
[0083] Next, the PHY processing unit 13_0 transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_0 in the PLCA cycle (step S22).
[0084] Next, the PHY processing unit 13_1 transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_1 in the PLCA cycle (step S23).
[0085] Next, the PHY processing unit 13_N transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_N in the PLCA cycle (step S24).
[0086] Next, for example, the PHY processing unit 13_0 stops due to a malfunction or other reason (step S25).
[0087] Next, for example, the PHY processing unit 13_1 determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted and switches from communication mode Md1 to communication mode Md2. Then, the PHY processing unit 13_1 transmits a communication signal Cs according to the CSMA / CD scheme (step S26).
[0088] Next, the MAC processing unit 12A in the in-vehicle ECU 101 determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted and activates the PHY processing unit 15 (step S27).
[0089] Next, the PHY processing unit 15 transmits the beacon signal Bc to the bus 2 on behalf of the PHY processing unit 13_0 (step S28).
[0090] Next, the PHY processing unit 13_1 transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_1 in the PLCA cycle (step S29).
[0091] Next, the PHY processing unit 13_N transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_N in the PLCA cycle (step S30).
[0092] Next, for example, the PHY processing unit 13_0 recovers and transmits the beacon signal Bc to the bus 2 (step S31).
[0093] Next, the PHY processing unit 13_0 transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_0 in the PLCA cycle (step S32).
[0094] Next, the PHY processing unit 13_1 transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_1 in the PLCA cycle (step S33).
[0095] Next, the PHY processing unit 13_N transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_N in the PLCA cycle (step S34).
[0096] Next, the MAC processing unit 12A in the in-vehicle ECU 101 determines that the transmission of the beacon signal Bc by the PHY processing unit 13_0 has resumed, and stops the PHY processing unit 15 (step S35).
[0097] In the in-vehicle communication system 201 according to the first embodiment of this disclosure, the PHY processing unit 13 is configured to transmit a communication signal Cs in accordance with 10BASE-T1S at a transmission opportunity set based on the reception timing of the beacon signal Bc, but it is not limited to this. The PHY processing unit 13 may be configured to transmit the communication signal Cs in accordance with a standard different from 10BASE-T1S.
[0098] Furthermore, in the in-vehicle communication system 201 according to the first embodiment of this disclosure, the PHY processing unit 13 is configured to transition from communication mode Md1 to communication mode Md2, which transmits a communication signal Cs according to the CSMA / CD method, but the invention is not limited to this. PHY processing units 13 other than PHY processing unit 13_0 may be configured not to transition from communication mode Md1 to communication mode Md2 if the beacon signal Bc from PHY processing unit 13_0 is interrupted. Also, PHY processing unit 13_0 may be configured not to transition from communication mode Md1 to communication mode Md2 if the beacon signal Bc transmission function stops.
[0099] Furthermore, although the in-vehicle ECU 101 according to the first embodiment of this disclosure is configured to include a PHY processing unit 13_1 which is a PHY processing unit 13 with node ID "1", it is not limited thereto. The in-vehicle ECU 101 may also be configured to include a PHY processing unit 13 with node ID "2" or higher instead of the PHY processing unit 13_1.
[0100] Furthermore, in the in-vehicle ECU 101 according to the first embodiment of this disclosure, the MAC processing unit 12A is configured to monitor the beacon signal Bc transmitted to the bus 2 by the in-vehicle ECU 111 after the PHY processing unit 15 is started, and to stop the PHY processing unit 15 when it determines that the transmission of the beacon signal Bc by the PHY processing unit 13_0 has resumed. However, the MAC processing unit 12A may be configured not to monitor the beacon signal Bc transmitted to the bus 2 by the in-vehicle ECU 111 after the PHY processing unit 15 is started.
[0101] Furthermore, in the in-vehicle ECU 101 according to the first embodiment of this disclosure, the PHY processing unit 15 is configured to determine whether or not the beacon signal Bc has been transmitted to the bus 2 by the PHY processing unit 13_0 by using the last transmission opportunity in the PLCA cycle as a reference after the start of transmission of the beacon signal Bc, but it is not limited to this. The PHY processing unit 15 may also be configured to determine whether or not the beacon signal Bc has been transmitted to the bus 2 by the PHY processing unit 13_0 by using the transmission timing of the beacon signal Bc of the PHY processing unit 15 as a reference. More specifically, if the time difference between the timing of transmission of the beacon signal Bc and the timing of reception of the beacon signal Bc is greater than or equal to a predetermined value, the PHY processing unit 15 determines that the received beacon signal Bc was transmitted by the PHY processing unit 13_0 and rewrites the value of register RgB from "zero" to "1". If the value of register RgB in the PHY processing unit 15 is "1", the MAC processing unit 12A determines that the transmission of the beacon signal Bc by the PHY processing unit 13_0 has resumed and stops the PHY processing unit 15.
[0102] Figure 5 shows the configuration of an in-vehicle communication system according to Modification 1 of the first embodiment of the present disclosure. Referring to Figure 5, the in-vehicle ECU 102 according to Modification 1 is equipped with a MAC processing unit 12B instead of a MAC processing unit 12A, and further equipped with a MAC processing unit 17, compared to the in-vehicle ECU 101. MAC processing units 12B and 17 are examples of monitoring units. For example, in the in-vehicle ECU 102, the data processing unit 11 and MAC processing units 12B and 17 are implemented by a single microcontroller.
[0103] Unlike MAC processing unit 12A, MAC processing unit 12B does not start or stop PHY processing unit 15. More specifically, MAC processing unit 12B obtains the value of register RgA of PHY processing unit 13_1 in the same manner as MAC processing unit 12A, and if the obtained value is "zero", it determines that the beacon signal Bc from PHY processing unit 13_0 has been interrupted. If MAC processing unit 12B determines that the beacon signal Bc from PHY processing unit 13_0 has been interrupted, it outputs a start command to MAC processing unit 17.
[0104] The MAC processing unit 17 receives a start command from the MAC processing unit 12B and starts the PHY processing unit 15. For example, after the start of transmission of the beacon signal Bc by the PHY processing unit 15, the MAC processing unit 17 detects the beacon signal Bc from the in-vehicle ECU 111, which is determined by using the (N+1)th transmission opportunity in the PLCA cycle as a reference. More specifically, similar to the MAC processing unit 12A, after the start of the PHY processing unit 15, the MAC processing unit 17 accesses the PHY processing unit 15 according to the SMI communication protocol at a monitoring timing according to the monitoring cycle Cy2, and obtains the value of the register RgB of the PHY processing unit 15. If the obtained value is "1", the MAC processing unit 17 determines that the PHY processing unit 13_0 has recovered and transmission of the beacon signal Bc by the PHY processing unit 13_0 has resumed. If the MAC processing unit 17 determines that the transmission of the beacon signal Bc by the PHY processing unit 13_0 has resumed, it stops the PHY processing unit 15.
[0105] Figure 6 shows the configuration of an in-vehicle communication system according to Modification 2 of the first embodiment of the present disclosure. Referring to Figure 6, the in-vehicle ECU 103 according to Modification 2 does not have a communication port 16 compared to the in-vehicle ECU 101. The ICs that implement the PHY processing unit 13_1 and the IC that implement the PHY processing unit 15 are connected to the communication port 14 on the board. When the PHY processing unit 15 is activated by the MAC processing unit 12A, it transmits a beacon signal Bc to the bus 2 via the communication port 14.
[0106] Next, other embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.
[0107] <Second Embodiment> [Configuration and Basic Operation] This embodiment relates to an in-vehicle communication system 202 that includes a plurality of in-vehicle ECUs 101, compared to the in-vehicle communication system 201 according to the first embodiment. Except for the contents described below, it is the same as the in-vehicle communication system 201 according to the first embodiment.
[0108] Figure 7 is a diagram showing the configuration of an in-vehicle communication system according to a second embodiment of the present disclosure. Referring to Figure 7, the in-vehicle communication system 202, compared to the in-vehicle communication system 201, comprises in-vehicle ECUs 101A and 101B, which are in-vehicle ECUs 101, and (N-1) in-vehicle ECUs 111.
[0109] The in-vehicle ECU 101A comprises a data processing unit 11, a MAC processing unit 12C_1 which is a MAC processing unit 12, a PHY processing unit 13_1 which is a PHY processing unit 13 with node ID "1", a PHY processing unit 15_1 which is a PHY processing unit 15, and communication ports 14 and 16. The in-vehicle ECU 101B comprises a data processing unit 11, a MAC processing unit 12C_2 which is a MAC processing unit 12, a PHY processing unit 13_2 which is a PHY processing unit 13 with node ID "2", a PHY processing unit 15_2 which is a PHY processing unit 15, and communication ports 14 and 16. Hereinafter, MAC processing units 12C_1 and 12C_2 will also be referred to as MAC processing unit 12C.
[0110] The MAC processing unit 12C_1, like the MAC processing unit 12A, accesses the PHY processing unit 13_1 according to the SMI communication protocol at the monitoring timing according to the monitoring cycle Cy1, and obtains the value of the register RgA of the PHY processing unit 13_1. If the obtained value is "zero", the MAC processing unit 12C_1 determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted and activates the PHY processing unit 15_1. When activated by the MAC processing unit 12C_1, the PHY processing unit 15_1 transmits the beacon signal Bc to the bus 2 via the communication port 16.
[0111] The MAC processing unit 12C_2, like the MAC processing unit 12A, accesses the PHY processing unit 13_2 according to the SMI communication protocol at the monitoring timing according to the monitoring cycle Cy1, and obtains the value of the register RgA of the PHY processing unit 13_2. If the obtained value is "zero", the MAC processing unit 12C_2 determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted and activates the PHY processing unit 15_2. When activated by the MAC processing unit 12C_2, the PHY processing unit 15_2 transmits the beacon signal Bc to the bus 2 via the communication port 16.
[0112] [Problem] In the in-vehicle communication system 202, if the beacon signal Bc from the PHY processing unit 13_0 is interrupted, the PHY processing unit 15 can transmit the beacon signal Bc in place of the PHY processing unit 13_0. Furthermore, even if the PHY processing unit 15 that transmits the beacon signal Bc in place of the PHY processing unit 13_0 stops due to a malfunction or other reason, another PHY processing unit 15 can transmit the beacon signal Bc. By making the PHY processing units 15 redundant in this way, more stable communication can be achieved.
[0113] However, if multiple PHY processing units 15 each transmit multiple beacon signals Bc, normal communication following the PLCA cycle may not occur.
[0114] Therefore, the in-vehicle communication system 202 according to the second embodiment of this disclosure solves the above problems with the following configuration.
[0115] (Stopping transmission of beacon signal Bc by PHY processing unit 15) When the transmission of beacon signal Bc by the PHY processing unit 15 is started, the MAC processing unit 12C in the vehicle ECU 101 determines whether or not there are beacon signals Bc from other vehicle ECUs 101, 111 after a waiting time Tw corresponding to the node ID given to the PHY processing unit 13 in the vehicle ECU 101 has elapsed.
[0116] More specifically, in the in-vehicle ECU 101A, the MAC processing unit 12C_1 waits for a waiting time Tw1 to elapse, which is, for example, a waiting time Tw obtained by multiplying the node ID of the PHY processing unit 13_1 by a predetermined value Vx, after the PHY processing unit 15_1 has been started.
[0117] Furthermore, after the startup of the PHY processing unit 15, the MAC processing unit 12C_2 in the in-vehicle ECU 101B waits for a waiting time Tw2 to elapse, which is a waiting time Tw obtained by multiplying the node ID of the PHY processing unit 13_2 by a predetermined value Vx. Here, since the node ID of the PHY processing unit 13_2 is greater than the node ID of the PHY processing unit 13_1, the waiting time Tw2 is longer than the waiting time Tw1.
[0118] For example, at time tm0, MAC processing units 12C_1 and 12C_2 determine that the beacon signal Bc from PHY processing unit 13_0 has been interrupted, and activate PHY processing units 15_1 and 15_2, respectively. Then, PHY processing units 15_1 and 15_2 begin transmitting the beacon signal Bc.
[0119] The MAC processing unit 12C_1 starts monitoring the beacon signal Bc transmitted by the other in-vehicle ECUs 101 and 111 at time tm1, after the waiting time Tw1 has elapsed from time tm0. Then, at the monitoring timing according to the monitoring cycle Cy2, the MAC processing unit 12C_1 accesses the PHY processing unit 15_1 according to the SMI communication protocol and obtains the value of the register RgB of the PHY processing unit 15_1. Here, at time tm1, the transmission of the beacon signal Bc by the PHY processing unit 15_2 has already started, so the value of the register RgB of the PHY processing unit 15_1 is "1". Since the obtained value of register RgB is "1", the MAC processing unit 12C_1 determines that the transmission of the beacon signal Bc is being performed by either the PHY processing unit 15_2 or the PHY processing unit 13_0, and stops the PHY processing unit 15_1.
[0120] At time tm2, after the waiting time Tw2 has elapsed from time tm0, the MAC processing unit 12C_2 begins monitoring the beacon signal Bc transmitted by the other in-vehicle ECUs 101 and 111. Then, the MAC processing unit 12C_2 accesses the PHY processing unit 15_2 according to the SMI communication protocol and obtains the value of the register RgB of the PHY processing unit 15_2. Here, at time tm2, which is later than time tm1, the beacon signal Bc from the PHY processing unit 13_0 has been interrupted, and the PHY processing unit 15_1 has been stopped by the MAC processing unit 12C_1 and is not transmitting the beacon signal Bc, so the value of the register RgB of the PHY processing unit 15_1 is "zero". The MAC processing unit 12C_2 determines that the value of the acquired register RgB is "zero," and therefore the PHY processing units 15_2 and 13_0 have not transmitted the beacon signal Bc, and maintain the activated state of the PHY processing unit 15_1.
[0121] [Operation Flow] Figure 8 is a diagram showing an example of a communication sequence in an in-vehicle communication system according to a second embodiment of the present disclosure. In Figure 8, PHY processing units 13_0 and 13_N and PHY processing units 15_1 and 15_2 are typically shown.
[0122] Referring to Figure 8, first, the PHY processing unit 13_0 transmits the beacon signal Bc to the bus 2 (step S41).
[0123] Next, the PHY processing unit 13_0 transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_0 in the PLCA cycle (step S42).
[0124] Next, the PHY processing unit 13_N transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_N in the PLCA cycle (step S43).
[0125] Next, for example, the PHY processing unit 13_0 stops due to a malfunction or other reason (step S44).
[0126] Next, for example, the PHY processing unit 13_N determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted and switches from communication mode Md1 to communication mode Md2. Then, the PHY processing unit 13_N transmits a communication signal Cs according to the CSMA / CD scheme (step S45).
[0127] Next, the MAC processing unit 12C_1 in the in-vehicle ECU 101A determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted and activates the PHY processing unit 15_1 (step S46).
[0128] Furthermore, the MAC processing unit 12C_2 in the in-vehicle ECU 101B determines that the beacon signal Bc from the PHY processing unit 13_0 has been interrupted and activates the PHY processing unit 15_2 (step S47).
[0129] Next, the PHY processing unit 15_1 transmits the beacon signal Bc to the bus 2 on behalf of the PHY processing unit 13_0 (step S48).
[0130] Furthermore, the PHY processing unit 15_2 transmits the beacon signal Bc to the bus 2 on behalf of the PHY processing unit 13_0 (step S49).
[0131] Next, at time tm1, after the waiting time Tw1 has elapsed since the start timing of the PHY processing unit 15_1, the MAC processing unit 12C_1 begins monitoring the beacon signal Bc transmitted by the other in-vehicle ECUs 101 and 111. Based on the value of register RgB of the PHY processing unit 15_1, the MAC processing unit 12C_1 determines that the beacon signal Bc is being transmitted by the PHY processing unit 15_2 or the PHY processing unit 13_0, and stops the PHY processing unit 15_1 (step S50).
[0132] Next, the PHY processing unit 13_N transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_N in the PLCA cycle (step S51).
[0133] Next, for example, the PHY processing unit 13_0 recovers and transmits the beacon signal Bc to the bus 2 (step S52).
[0134] Next, the PHY processing unit 13_0 transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_0 in the PLCA cycle (step S53).
[0135] Next, the PHY processing unit 13_N transmits the communication signal Cs to the bus 2 during the transmission opportunity of the PHY processing unit 13_N in the PLCA cycle (step S54).
[0136] Next, the MAC processing unit 12C_2 in the in-vehicle ECU 101B determines that the transmission of the beacon signal Bc by the PHY processing unit 13_0 has resumed, and stops the PHY processing unit 15_2 (step S55).
[0137] The embodiments described above should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and all modifications within the meaning and scope of the claims are intended to be included.
[0138] Each process (each function) of the above-described embodiment is implemented by a processing circuit (Circuitry) including one or more processors. The processing circuit may consist of an integrated circuit, etc., which combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors. The one or more memories store programs (instructions) that cause the one or more processors to execute each of the above processes. The one or more processors may execute each of the above processes according to the programs read from the one or more memories, or they may execute each of the above processes according to logic circuits that have been designed in advance to execute each of the above processes. The above-mentioned processor may be various processors suitable for computer control, such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), and ASIC (Application Specific Integrated Circuit). Furthermore, multiple physically separated processors may cooperate with each other to perform the above-mentioned processes. For example, processors installed in multiple physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), WAN (Wide Area Network), and the Internet to perform the above-mentioned processes. The above program may be installed on the above memory via the above network from an external server device, or it may be distributed on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), or semiconductor memory, and then installed on the above memory from the above recording medium.
[0139] The above description includes the following features. [Note 1] An in-vehicle device in an in-vehicle communication system comprising a plurality of in-vehicle devices connected to a bus, comprising: a communication unit that receives a beacon signal via the bus and transmits a communication signal to the bus at a transmission opportunity set based on the timing of reception of the beacon signal; a monitoring unit that monitors the beacon signal transmitted to the bus by other in-vehicle devices; and a backup transmitting unit that transmits the beacon signal to the bus on behalf of the other in-vehicle devices when the monitoring unit detects that the beacon signal from the other in-vehicle devices has been interrupted, wherein the communication unit is implemented by a first processing circuit, the backup transmitting unit is implemented by a second processing circuit, the monitoring unit monitors the beacon signal from the other in-vehicle devices by accessing the first processing circuit in accordance with the SMI communication protocol before the backup transmitting unit starts transmitting the beacon signal, and the monitoring unit monitors the beacon signal from the other in-vehicle devices by accessing the second processing circuit in accordance with the SMI communication protocol after the backup transmitting unit starts transmitting the beacon signal.
[0140] [Note 2] An in-vehicle device in an in-vehicle communication system comprising a plurality of in-vehicle devices connected to a bus, comprising a processing circuit, the processing circuit receiving a beacon signal via the bus, transmitting a communication signal to the bus at a transmission opportunity set based on the timing of reception of the beacon signal, monitoring the beacon signal transmitted to the bus by other in-vehicle devices, and transmitting the beacon signal to the bus on behalf of the other in-vehicle devices when it is detected that the beacon signal from the other in-vehicle devices has been interrupted.
[0141] 1 Vehicle 2 Bus 11 Data Processing Unit 12, 12A, 12B, 12C, 17 MAC Processing Unit 13, 15 PHY Processing Unit 14, 16 Communication Port 101, 101A, 101B, 102, 103, 111 In-vehicle ECU 201, 202 In-vehicle Communication System t0B, t00, t01, t02, t03, t04, t05, t0N, t10, t11 Time Bc Beacon Signal Cm Commit Signal Cs Communication Signal Tm Waiting Time
Claims
1. An in-vehicle device in an in-vehicle communication system comprising a plurality of in-vehicle devices connected to a bus, comprising: a communication unit that receives a beacon signal via the bus and transmits a communication signal to the bus at a transmission opportunity set based on the timing of reception of the beacon signal; a monitoring unit that monitors the beacon signal transmitted to the bus by other in-vehicle devices; and a backup transmitting unit that transmits the beacon signal to the bus on behalf of the other in-vehicle devices when the monitoring unit detects that the beacon signal from the other in-vehicle devices has been interrupted.
2. The in-vehicle device according to claim 1, wherein, when the beacon signal from the other in-vehicle device is interrupted, the communication unit transitions from a first communication mode in which it transmits the communication signal at the transmission opportunity to a second communication mode in which it transmits the communication signal according to the CSMA / CD (Carrier Sense Multiple Access / Collision Detection) method, and when the transmission of the beacon signal by the backup transmission unit is started, the communication unit transitions from the second communication mode to the first communication mode.
3. The in-vehicle device according to claim 1 or 2, wherein the auxiliary transmitting unit stops transmitting the beacon signal if the monitoring unit detects the beacon signal from another in-vehicle device after the start of transmitting the beacon signal.
4. The in-vehicle communication system, wherein the beacon signal is transmitted repeatedly, and between the transmission timings of two consecutive beacon signals, each of the in-vehicle devices is given the opportunity to transmit according to a predetermined transmission order, and the monitoring unit detects the beacon signal from another in-vehicle device, determined by using the last transmission opportunity in the transmission order as a reference, after the start of transmission of the beacon signal by the backup transmitting unit.
5. The in-vehicle device according to claim 3 or 4, wherein, when the backup transmitting unit starts transmitting the beacon signal, the monitoring unit determines whether or not there is a beacon signal from another in-vehicle device after a waiting time corresponding to the identifier given to the communication unit has elapsed.
6. The in-vehicle device according to any one of claims 1 to 5, wherein the communication unit transmits the communication signal in accordance with 10BASE-T1S at the transmission opportunity set based on the reception timing of the beacon signal used in PLCA (Physical Layer Collision Avoidance).
7. A communication method in an in-vehicle device in an in-vehicle communication system comprising a plurality of in-vehicle devices connected to a bus, the method comprising: receiving a beacon signal via the bus and transmitting a communication signal to the bus at a transmission opportunity set based on the timing of reception of the beacon signal; monitoring the beacon signal transmitted to the bus by other in-vehicle devices; and, when detecting that the beacon signal from the other in-vehicle devices has been interrupted, transmitting the beacon signal to the bus on behalf of the other in-vehicle devices.
8. A communication program used in an in-vehicle device in an in-vehicle communication system comprising a plurality of in-vehicle devices connected to a bus, the program causing a computer to function as: a communication unit that receives a beacon signal via the bus and transmits a communication signal to the bus at a transmission opportunity set based on the timing of reception of the beacon signal; a monitoring unit that monitors the beacon signal transmitted to the bus by other in-vehicle devices; and a backup transmitting unit that transmits the beacon signal to the bus on behalf of the other in-vehicle devices when the monitoring unit detects that the beacon signal from the other in-vehicle devices has been interrupted.