JP2012028865A - Node - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a node which has simple structure and is capable of communication between nodes in a normal mode without activating a node in a sleep mode, and capable of quickly activating a node in the sleep mode as necessary.SOLUTION: Each ECU 10 comprises a first transceiver 12 used for communication between its own ECU 10 and another ECU 10 and, in addition, a second transceiver 13 for transmitting and receiving a differential signal having reversed polarity on a communication path LN relative to a differential signal having normal polarity used for its communication. An ECU 10 uses the second transceiver 13 to transmit and receive an activation signal to transition an operation mode from a sleep mode to a normal mode. In addition, if dominants of a differential signal of the normal polarity and a differential signal of the reversed polarity collide with each other, the dominant of the normal polarity is dominant. This makes it possible to transmit the activation signal at any timing without affecting communication between an ECU 10 in the normal mode and an ECU 10 in the normal mode.

Description

  The present invention relates to a node constituting a communication system having a communication path composed of a pair of buses and performing communication using differential signals.

  2. Description of the Related Art Conventionally, a CAN (Controller Area Network) standard communication system is known as one of communication systems that use a differential signal as a transmission signal of a communication path composed of a pair of buses (see, for example, Patent Document 1).

  In the CAN standard (ISO11898-1), there are dominant (dominant) and recessive (inferior) signal levels on a communication path. For example, a case where a differential signal is equal to or higher than a predetermined threshold (for example, 0.9 V). , Dominant and less than threshold are recognized as recessive. When any one node outputs a dominant signal, the signal level on the communication path is set to be dominant.

  Further, the CAN standard defines a sleep mode that is an operation mode for stopping a communication function for power saving, and a node in the sleep mode is defined to wake up when a dominant is detected on a communication path. Yes.

JP 2008-131514 A

  By the way, in such a CAN standard communication system, when there is a node in the sleep mode (hereinafter referred to as a dormant node), the node in the normal mode that is the normal operation mode while the dormant node is in the sleep state. There is a problem that it is not possible to use the communication only with each other (hereinafter referred to as an activation node).

That is, performing communication means that a dominant appears on the communication path, so that when the activation nodes communicate with each other, the dormant node is activated.
If the node is configured such that the idle node ignores the signal level of the communication path, it is possible to perform communication between the activation nodes while the idle node is in the sleep state.

  However, in this case, in order to wake up (activate) the dormant node, it is necessary to either restart the entire node or provide a means for transmitting a wake-up signal separately from the communication path. In the former case, since it takes a long time to start, there is a problem that it cannot be applied to a system that requires real-time processing, and in the latter case, there is a problem that the system configuration becomes complicated.

  In order to solve the above problems, the present invention enables communication between nodes in the normal mode without activating the node in the sleep mode with a simple configuration, and promptly connects the node in the sleep mode as necessary. The object is to provide a bootable node.

  The node of the present invention has a communication path composed of a pair of buses, and is used in a communication system using a differential signal for communication between nodes connected to the communication path. In normal mode, which is the operation mode that can perform the communication, if a request to shift to sleep mode that stops communication and puts it into a low power consumption state occurs, the operation mode changes from normal mode to sleep mode, and the operation mode When a differential signal having a polarity opposite to the normal polarity that is used for communication is sent to the communication path in the sleep mode, the operation mode returns from the sleep mode to the normal mode.

  The node of the present invention includes a first transceiver that transmits and receives a differential signal having a normal polarity via a communication path, and a second transceiver that transmits and receives a differential signal having a polarity opposite to the normal polarity via the communication path. And an invalidating means for invalidating the function of the first transceiver when the operation mode is the sleep mode, and an input / output terminal of a second transceiver provided for inputting / outputting a differential signal is provided in the second transceiver When the differential signal transmitted by the signal collides with the differential signal of the normal polarity on the communication path, the differential signal is connected to the communication path via a resistor for making the differential signal of the normal polarity dominant.

  Here, the polarity of the differential signal means that the signal level of the differential signal is positive with respect to the reference level when the signal level of one of the pair of buses constituting the communication path is the reference level ( It means whether it becomes positive (negative polarity) or negative (negative polarity).

  In the node of the present invention configured as described above, when the operation mode is the normal mode, communication with other nodes is performed using the first transceiver. When it is necessary to activate another node in the sleep mode, a signal (activation signal) is transmitted using the second transceiver.

  On the other hand, when the operation mode is the sleep mode, the function of the first transceiver is invalidated by the invalidating means, so that communication between other nodes in the normal mode is not received, and the second transceiver When the activation signal is received, the normal mode is restored.

  Therefore, in the communication system configured using the nodes of the present invention, communication can be performed between nodes in the normal mode while keeping the nodes in the sleep mode in the sleep mode.

In addition, when starting a node in the sleep mode, it is only necessary to send a signal to the communication path using the second transceiver, so that a quick start can be realized.
Moreover, when the signal transmitted from the first transceiver and the signal transmitted from the second transceiver collide, the transmission signal of the first transceiver is dominant, so that communication between nodes in the normal mode is not disturbed. The activation signal can be transmitted at an arbitrary timing, and the sleep mode node can be activated.

  The first transceiver and the second transceiver may be configured for exclusive use, respectively. However, as shown in claim 2, the same configuration is used to input and output differential signals. By changing the connection relationship between the input / output terminals provided in each transceiver and the pair of buses constituting the communication path between the first transceiver and the second transceiver, the polarity of the differential signal to be transmitted and received is inverted. Also good.

  In addition, the first transceiver and the second transceiver may transmit a signal having an asymmetric waveform to a pair of buses constituting the communication path, but it is desirable to transmit a signal having a symmetrical waveform.

  Specifically, for example, as shown in claim 3, one of the pair of buses sends a binary signal composed of a preset reference voltage and a voltage higher than the reference voltage, On the other hand, a binary signal composed of a reference voltage and a voltage lower than the reference voltage may be transmitted, and the two binary signals may be configured to have a symmetrical waveform with respect to the reference voltage.

  Next, as described in claim 4, the node according to the present invention transmits a signal via the second transceiver when a preset activation condition is satisfied, whereby another node whose operation mode is the sleep mode is transmitted. There may be provided other node activation means for activating.

  The node of the present invention configured as described above can be suitably used as a node having a function of returning another node from the sleep mode to the normal mode when configuring the communication system.

  According to a fifth aspect of the present invention, the node includes a return unit for returning the operation mode to the normal mode when the second transceiver receives a predetermined signal when the operation mode is the sleep mode. It may be.

The node of the present invention configured as described above can be suitably used as a node capable of transitioning to the normal mode and the sleep mode when configuring the communication system.
In addition, as described in claim 6, the node according to the present invention complements a missing portion generated in the received signal of the second transceiver due to a collision of differential signals having different polarities on the communication path, and shapes the received signal. A shaping circuit may be provided.

  According to the node of the present invention configured as described above, the reception signal of the second transceiver can be used not only as an activation signal but also for communication between the nodes, and therefore, in parallel with the communication using the first transceiver. Thus, communication using the second transceiver can be realized, that is, multiplex communication can be realized.

  However, in this case, in order to ensure the accuracy of processing in the shaping circuit, in communication using the first transceiver, the maximum number of bits that are continuously transmitted at a level different from the reference voltage is N, and the bit width is 1 As for W, in communication using the second transceiver, it is desirable to use a signal having a bit width of 3 times or more (preferably 10 times or more) of N × W.

  In this case, the activation signal needs to be configured to use a unique pattern that is not used for communication so that it can be clearly distinguished from the signal used for communication using the second transceiver.

The block diagram which shows the whole structure of a communication system. The block diagram which shows the structure of the electronic control unit in 1st Embodiment. The wave form diagram which shows the waveform in each part of a communication system. The flowchart which shows the content of the other node starting process performed when starting another electronic control unit. The flowchart which shows the content of the sleep process performed when changing to sleep mode, and the wake-up process performed when changing to normal mode. The block diagram which shows the structure of the electronic control unit in 2nd Embodiment. The circuit diagram which shows the detailed structure of a shaping circuit. The timing diagram which shows operation | movement of a shaping circuit.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
<Overall configuration>
FIG. 1 is a block diagram showing a configuration of an in-vehicle communication system 1 in which a CAN (Controller Area Network) is used as a communication protocol.

  As shown in FIG. 1, the communication system 1 connects a plurality of electronic control units 10a, 10b, 10c,... Mounted on a vehicle so that they can communicate with each other via a common communication path LN. Each of these electronic control units 10a, 10b, 10c,... Functions as a node. In the following, the electronic control unit is referred to as an ECU, and the ECUs 10a, 10b, 10c,.

  Among these, the communication path LN is composed of a pair of buses LN1 and LN2, and both ends thereof are terminated by termination resistors R and R, respectively. In the communication path LN, a differential signal expressing a dominant (for example, 0) or recessive (for example, 1) signal level is transmitted by the potential difference between the two buses LN1 and LN2.

  Specifically, the ECUs 10a, 10b, 10c,... Control the engine ECU that controls the engine, the brake ECU that controls the brake control, the steering ECU that controls the steering control, the suspension ECU that controls the suspension control, and the light on / off control. Various electronic control devices such as an ECU can be listed. In FIG. 1, only three ECUs 10 are illustrated, but it goes without saying that the number of ECUs 10 constituting the communication system 1 is not limited to this.

  Further, one of the ECUs 10 (in this case, the ECU 10a) is configured such that an external event serving as a trigger for starting the entire communication system 1 is input from an in-vehicle device (not shown).

  The external event may be generated, for example, when a door of the vehicle is opened or closed, or may be generated when a switch provided for starting up the communication system 1 is operated.

  Further, the ECU 10 is configured to transition between a normal mode, which is a normal operation mode when controlling a control target, and a sleep mode, which is an operation mode provided to reduce power consumption.

<ECU>
FIG. 2 is a block diagram showing a part of the configuration of the ECU 10, specifically, a configuration related to communication via the communication path LN, and all the ECUs 10 have a common configuration.

  As shown in FIG. 2, the ECU 10 includes a microcomputer (hereinafter referred to as “microcomputer”) 11 that executes a control process for controlling each part of the vehicle and a process for communicating with another ECU, and a communication path LN. A pair of transceivers 12 and 13 for connecting data (transmission frame) given from the microcomputer 11 to the communication path LN and inputting data (reception frame) on the communication path LN to the microcomputer 11 are provided. .

  The input / output terminals T1 and T2 of one transceiver (hereinafter referred to as “first transceiver”) 12 are directly connected to a pair of buses LN1 and LN2 constituting the communication path LN, respectively, and the other transceiver (hereinafter referred to as “first transceiver”). Input / output terminals T1 and T2 of 13) are connected to buses LN1 and LN2 via resistors 14 and 14, respectively.

  Specifically, the input / output terminal T1 of the first transceiver 12 and the input / output terminal T2 of the second transceiver 13 are connected to the bus LN1, and the input / output terminal T2 of the first transceiver 12 and the input / output terminal T1 of the second transceiver 13 are connected. Is connected to the bus LN2.

  That is, the first transceiver 12 and the second transceiver 13 are connected to the communication path LN so that the differential signals that can be transmitted and received by the transceivers 12 and 13 are opposite to each other on the communication path LN. Polarity.

<Transceiver>
The first transceiver 12 converts a transmission signal input from the transmission terminal TX into a differential signal and outputs the differential signal from the input / output terminals T1 and T2, and receives the differential signal input from the input / output terminals T1 and T2 as a reception signal. When the dominant signal is detected after the recession continues in the differential signal input to the input / output terminals T1 and T2 for a predetermined period or longer after the signal is converted into the signal and output from the receiving terminal RX, the microcomputer 11 detects the frame. It has a frame detection function for outputting the signal FR1.

  Further, the first transceiver 12 functions effectively when the standby signal ST1 is at an inactive level according to the standby signal ST1 from the microcomputer 11, and has a sleep function that stops the function when the standby signal ST1 is at an active level. Have.

  Among these, a signal conversion function etc. are demonstrated with reference to the waveform of each part of the communication system 1 shown in FIG. First, when the input (transmission signal) to the transmission terminal TX is “1”, the first transceiver 12 sets the voltages VoT1 and VoT2 of the input / output terminals T1 and T2 to the reference voltage VM (for example, 2.5 V). When the input to the transmission terminal TX is “0”, the voltage VT1 of the input / output terminal T1 is set to a high level VH (for example, 3.5 V) set higher than the reference voltage VM, and the input / output terminal T2 The voltage VT2 is set to a low level VL (for example, 1.5 V) set to a voltage lower than the reference voltage VM.

  As a result, the voltage level ΔVo (= VoT1−VoT2) of the differential signal output from the input / output terminals T1 and T2 is “1” when the input to the transmission terminal TX is “1” based on the potential of the input / output terminal T2. At this time, ΔVo = 0 [V] (recessive), and when the input to the transmission terminal TX is “0”, ΔVo = 2 [V] (dominant).

  Further, the first transceiver 12 is configured such that when the voltage level ΔVin (= VLN1−VLN2) of the differential signal input to the input / output terminals T1 and T2 is equal to or higher than a predetermined threshold TH (for example, 0.9V), The reception terminal RX is set to “0”, and when the voltage level ΔVin of the input differential signal is less than the threshold value TH, the reception terminal RX is set to “1”.

Note that these functions of the first transceiver 12 are well known in the CAN transceiver.
The second transceiver 13 is configured in the same manner as the first transceiver 12. However, the frame detection signal output to the microcomputer 11 is represented by FR2, and the standby signal from the microcomputer 11 is represented by ST2.

  The signal transmitted by the second transceiver 13 is set to have a bit width larger than that of the signal transmitted by the first transceiver 12. Specifically, the bit width of the signal transmitted by the second transceiver 13 is set to be longer than the maximum continuous length defined for the transmission frame from the first transceiver 12.

  When the voltage level ΔVin (= VLN2−VLN1) of the differential signal (opposite polarity with respect to the first transceiver 12) input to the input / output terminals T1 and T2 is equal to or higher than the threshold value TH, the second transceiver 13 receives the reception terminal RX. Is set to “0”, and when the voltage level ΔVin of the input differential signal is less than the threshold value TH, the receiving terminal RX is set to “1”.

  Further, since the second transceiver 13 is connected to the buses LN1 and LN2 via the resistors 14 and 14, the output voltages VoT1 and VoT2 from the input / output terminals T1 and T2 are directly applied to the buses LN1 and LN2. Rather, the signal level divided by the resistance values of the resistors 14 and 14 and the termination resistance R of the communication path LN is applied. In the present embodiment, the amplitude with respect to the reference voltage VM is set to be about 1/3 of the magnitude (VH-VM, VM-VL) at the input / output terminals T1, T2.

  Further, due to the presence of the resistors 14 and 14, when the dominant output from the first transceiver 12 and the dominant output from the second transceiver 13 collide on the communication path LN, they are directly connected to the communication path LN. The dominant output from the first transceiver 12 is dominant.

  Therefore, the reception signal output from the reception terminal RX of the first transceiver 12 is correctly restored even if the dominant collides, while the reception signal output from the reception terminal RX of the second transceiver 13 collides with the dominant. The part is missing.

<Microcomputer>
In addition to the well-known configuration of a microcomputer comprising a CPU, ROM, RAM, IO port, etc., the microcomputer 11 transmits and receives frames according to the CAN protocol, arbitration control for determining which frames are preferentially processed, and communication errors. A communication controller 111 that executes processing and the like is provided.

  Further, the microcomputer 11 includes a clock circuit (not shown) that generates an operation clock for operating a CPU (not shown), and shuts off the power supply to the clock circuit, thereby operating the clock circuit (and thus the CPU). It is configured such that its own operation) can be stopped.

The operation mode when the clock circuit is operating is the normal mode, and the operation mode when the clock circuit is stopped is the sleep mode.
In addition, when the microcomputer 11 is in the sleep mode and receives the frame detection signal FR2 from the second transceiver 13, the clock circuit is activated and the CPU starts operating, and transitions to the normal mode (wakes up). It is configured as follows.

<Other node startup processing>
Here, the other node activation process executed by the microcomputer 11 of the ECU 10 having the function of waking up another ECU will be described with reference to the flowchart shown in FIG.

  This process is activated when a predetermined activation condition is satisfied during execution of the vehicle control assigned to the ECU 10. In particular, the ECU 10a is activated after execution of a wake-up process, which will be described later, even when an external event is input in the sleep mode.

  Therefore, at the start of this process, the operation mode of the ECU 10 is the normal mode, the standby signal ST1 is set to inactive, the standby signal ST2 is set to active, and only the first transceiver 12 is in a communicable state. .

  When this processing is started, the standby signal ST2 is set to be active to make the second transceiver 13 communicable (S110), and the start signal including at least one bit dominant is transmitted using the second transceiver 13. Transmit (S120).

Thereafter, by setting the standby signal ST2 to inactive, the second transceiver 13 is stopped (S130), and this process is terminated.
<Sleep / Wake-up>
Next, sleep processing and wake-up processing executed by the microcomputer 11 of the ECU 10 will be described with reference to the flowchart shown in FIG.

FIG. 5A is a flowchart showing the contents of the sleep process executed when the operation state of the ECU 10 transitions from the normal mode to the sleep mode.
This sleep process is activated when a predetermined sleep condition is satisfied while vehicle control assigned to the ECU 10 is being executed (that is, when the operation mode is the normal mode). In the normal mode, the standby signal ST1 is set to inactive, and the standby signal ST2 is set to active except when the above-described other node activation process is executed.

  When this processing starts, as shown in FIG. 5A, first, the first transceiver 12 is stopped and the second transceiver 13 is started by switching the standby signal ST1 to active and the standby signal ST2 to inactive. (S210).

  As a result, the operation mode of the ECU 10 becomes the sleep mode, and a differential signal having a polarity opposite to the normal polarity on the communication path LN can be received via the second transceiver 13.

Thereafter, the power supply to the clock circuit of the microcomputer 11 is interrupted, and the microcomputer 11 itself is stopped, thereby causing the ECU 10 to transition to the sleep mode (S220).
Next, FIG. 5B is a flowchart showing the contents of the wake-up process executed when the operation state of the ECU 10 transitions from the sleep mode to the normal mode.

  In this wake-up process, a frame detection signal FR2 from the second transceiver 13 is input to the microcomputer 11 (all ECUs 10 are applicable) or an external event is input by sending an activation signal on the communication path LN. When the clock circuit is activated and the CPU starts operating, the activation is performed in an initialization process executed by the CPU.

  When this process is activated, the first transceiver 12 is activated and the second transceiver 13 is deactivated by switching the standby signal ST1 to inactive and the standby signal ST2 to be active (S310), and the process is terminated.

As a result, the operation mode of the ECU 10 becomes a normal mode, and a differential signal having a normal polarity on the communication path LN can be transmitted / received via the first transceiver 12.
<Operation>
In the communication system 1 configured as described above, the ECU 10 in the normal mode performs communication with each other via the activated first transceiver 12.

On the other hand, the ECU 10 in the sleep mode monitors whether or not the activation signal is sent to the communication path LN by the activated second transceiver 13.
At this time, since the second transceiver 13 recognizes the differential signal with a polarity opposite to that of the first transceiver 12, it receives a differential signal (transmitted and received by the first transceiver 12) used for communication between the ECUs 10 in the normal mode. However, this is not recognized as a dominant, that is, since the frame detection signal FR2 is not generated, the ECU 10 in the sleep mode is not shifted to the normal mode.

  The ECU 10 for which the activation condition is satisfied, or the ECU 10a that has been woken up by the input of an external event temporarily operates the second transceiver 13, and the polarity of the differential signal on the communication path LN is opposite to the normal polarity. Send an activation signal with polarity. When the dominant signal collides between the normal polarity differential signal and the reverse polarity differential signal, the normal polarity differential signal is dominant. That is, the communication between the ECUs 10 in the normal mode is not affected by the activation signal.

  When the activation signal is sent to the communication path LN, the ECU 10 in the sleep mode generates the frame detection signal FR2 by the second transceiver 13 that has detected this, so that the operation mode returns to the normal mode.

<Effect>
As described above, in the communication system 1, each ECU 10 has a normal polarity differential signal used for communication in addition to the first transceiver 12 used for communication between the ECUs 10 on the communication path LN. A second transceiver 13 that transmits and receives a differential signal having a reverse polarity is provided, and the second transceiver 13 is used to transmit and receive an activation signal that changes the operation mode from the sleep mode to the normal mode. In addition, when the dominant signal collides between the normal polarity differential signal and the reverse polarity differential signal, the normal polarity dominant signal is dominant.

  Therefore, according to the communication system 1, the activation signal is sent on the LN at any timing without affecting the communication between the ECUs 10 in the normal mode, and the sleep mode ECU 10 is returned to the communication mode (wake). Up).

<Correspondence with Invention>
In this embodiment, S210 is an invalidation means, other node activation processing (S110 to S130) is another node activation means, and the wake-up processing (processing is executed by the microcomputer 11 when the frame detection signal FR2 is input in the sleep mode. (Including control for restarting the power supply to the clock circuit executed before starting) corresponds to the return means.

[Second Embodiment]
Next, a second embodiment will be described.
<Overall configuration>
FIG. 6 is a block diagram showing a configuration of the ECU 20 that constitutes the communication system 2 of the present embodiment.

  The ECU 20 does not use the second transceiver 13 only for wakeup, but enables communication by the second transceiver 13 and realizes multiplex communication together with the first transceiver 12.

Since the ECU 20 is only partially different in configuration from the ECU 10, the following description will be made in detail with respect to the different portions.
As shown in FIG. 6, in addition to the microcomputer 21, the first and second transceivers 12, 13, and the resistors 14, 14, the ECU 20 receives the reception signal RD1 and the second signal output from the reception terminal RX of the first transceiver 12. The reception signal RD2 output from the reception terminal RX of the transceiver 13 is used as an input, and a missing portion is generated in the reception signal RD2 when the dominant collides between the normal polarity differential signal and the reverse polarity differential signal (see FIG. 3). ) And a shaping circuit 15 for supplying the received signal RD2 shaped by the complementation to the microcomputer 21 as an output.

  Unlike the case of the first embodiment, the second transceiver 13 is configured to always operate without stopping even in the sleep mode. That is, the processes executed by the microcomputer 21 of the ECU 20 (another node activation process, a sleep process, and a wake-up process) start and stop the second transceiver 13 from the processes in the first embodiment shown in FIGS. The processing to be performed is omitted.

  In addition, when the frame detection signal FR2 is input from the second transceiver 13, the microcomputer 21 does not immediately determine that it is the activation signal, but uses a pattern specific to the activation signal (using the second transceiver 13). In the first embodiment, the operation is performed in the same manner as when the frame detection signal FR2 is detected.

<Shaping circuit>
Here, FIG. 7 is a circuit diagram showing a detailed configuration of the shaping circuit 15, and FIG. 8 is a timing chart showing the operation of the shaping circuit 15.

  As shown in FIG. 7, the shaping circuit 15 includes an AND circuit 31 that receives an operation clock CK and a reception signal RD2 supplied from a clock circuit (not shown), and a reception signal RD2 according to a clock GCK that is an output of the AND circuit 31. A D-type flip-flop (D-FF) circuit 32 that latches the signal level and a D-FF circuit 33 that latches the output of the D-FF circuit 32 according to the clock GCK are provided.

  Further, the shaping circuit 15 is a set input of an AND circuit 34 that receives both outputs X1 and X2 of the D-FF circuits 32 and 33, a NOR circuit 35 that receives X1 and X2, and an output XS of the AND circuit 34. , And an SR type flip-flop (SR-FF) circuit 36 using the output XR of the NOR circuit 35 as a reset input.

  As shown in FIG. 8, the AND circuit 31 temporarily stops the supply of the operation clock CK to the D-FF circuits 32 and 33 while the reception signal RD1 is dominant (L level here). Yes, using the clock GCK generated by the AND circuit 31, the D-FF circuits 32 and 33 latch the reception signal RD2.

  Thus, the signal levels of X1 and X2 are held at the signal level of the immediately preceding reception signal RD2 while the reception signal RD1 is dominant, that is, the missing portion is complemented. The reason why the D-FF circuits 32 and 33 that latch the reception signal RD2 are two stages is to provide a digital filter function (removal of spike noise).

  The output XS of the AND circuit 34 having X1 and X2 as inputs rises at a timing when the reception signal RD2 changes from dominant (L level) to recessive (H level), and is also NOR having X1 and X2 as inputs. The output XR of the circuit 35 rises at a timing when the reception signal RD2 changes from recessive (H level) to dominant (L level). Therefore, by inputting these signals XS and XR to the SR-FF circuit 36, a signal from which the influence of the recessive collision is removed is reproduced.

<Effect>
As described above, according to the communication system 2, as in the case of the communication system 1, it is possible to realize the communication between the ECUs 20 in the normal mode without activating the ECUs 20 in the sleep mode, By using it, the ECU 20 in the sleep mode can be returned to the normal mode at an arbitrary timing.

  In particular, according to the communication system 2, each ECU 20 can realize multiplex communication using not only the first transceiver 12 but also the second transceiver 13 in the normal mode.

  When performing multiplex communication, for example, the first transceiver 12 can realize high-speed communication according to the CAN protocol, and the second transceiver 13 can realize low-speed communication according to the LIN protocol. .

  However, the communication by the second transceiver 13 needs to be sufficiently slow compared to the communication by the first transceiver 12, and it is desirable that the speed is at least 1/3, preferably 1/10 or less.

[Other Embodiments]
As mentioned above, although several embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects. .

  For example, in the above-described embodiment, the communication system 1 is configured using the ECU 10 and the communication system 2 is configured using the ECU 20. However, the ECUs 10 and 20 may be mixed in one communication system.

DESCRIPTION OF SYMBOLS 1, 2 ... Communication system 10, 20 ... Electronic control unit (ECU) 11, 21 ... Microcomputer (microcomputer) 12, 13 ... Transceiver 14 ... Resistor 15 ... Shaping circuit 31, 34 ... AND circuit 32, 33 ... D type Flip-flop (D-FF) circuit 35... NOR circuit 36... SR-type flip-flop (SR-FF) circuit 111.

Claims (6)

It is used in a communication system having a communication path composed of a pair of buses and using a differential signal for communication between nodes connected to the communication path, and in an operation mode capable of executing communication via the communication path. When a request to shift to a sleep mode to stop communication and enter a low power consumption state occurs in a certain normal mode, the operation mode shifts from the normal mode to the sleep mode, and when the operation mode is the sleep mode, When a differential signal having a polarity opposite to the normal polarity that is the polarity used for the communication is sent to the communication path, the operation mode is a node that returns from the sleep mode to the normal mode,
A first transceiver for transmitting and receiving the normal polarity differential signal via the communication path;
A second transceiver for transmitting and receiving a differential signal having a polarity opposite to the normal polarity via the communication path;
When the operation mode is a sleep mode, invalidating means for invalidating the function of the first transceiver;
And the input / output terminal of the second transceiver provided for inputting / outputting the differential signal causes a differential signal transmitted by the second transceiver to collide with a differential signal having a normal polarity on the communication path. In this case, the node is connected to the communication path via a resistor for making the differential signal of normal polarity dominant.   The first transceiver and the second transceiver have the same configuration, and a connection relationship between an input / output terminal provided to input / output the differential signal and a pair of buses constituting the communication path, The node according to claim 1, wherein the polarity of the differential signal to be transmitted and received is inverted by making the first transceiver different from the second transceiver.   The first transceiver and the second transceiver send a binary signal composed of a preset reference voltage and a voltage higher than the reference voltage to one of a pair of buses constituting the communication path. On the other hand, a binary signal composed of the reference voltage and a voltage lower than the reference voltage is sent out, and these two binary signals have a symmetrical waveform with respect to the reference voltage. The node according to claim 1 or claim 2.   The remote node activation means for activating another node whose operation mode is a sleep mode by transmitting a signal through the second transceiver when a preset activation condition is satisfied. The node according to any one of claims 1 to 3.   5. The apparatus according to claim 1, further comprising a return unit configured to return the operation mode to a normal mode when the second transceiver receives a predetermined signal when the operation mode is a sleep mode. The node according to item 1.   2. A shaping circuit that shapes a received signal by complementing a missing portion generated in the received signal of the second transceiver due to a collision of differential signals having different polarities on the communication path. 6. The node according to any one of 5 above.

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