JP2011044945A - Communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology which enables a node failed in wakeup to be easily waken up. <P>SOLUTION: One of nodes constituting a communication system includes a wakeup potential setting circuit 40. The circuit 40 includes: a transistor Tr whose emitter is connected to the same 5V power source as a bus driver 30 and whose base is connected to an output port of a microcomputer 20; and an output line LO connecting a collector of the transistor Tr with buses LN1, LN2. A resistance value of each branch line in the output line LO is set to the same value. When output of an output port is switched to low and the transistor Tr is turned on, since the bus driver 30 is high impedance during a bus idle time, a potential of each bus is changed from 2.5V to 5V that is approximately equal to the output voltage of the power source. A node under a sleep state detects this potential change through auxiliary wakeup circuits 50, 60 and wakes up the microcomputer 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  In the present invention, communication between nodes is realized by connecting a plurality of nodes to a communication path composed of a pair of buses, and each node outputting a communication signal to the communication path using a differential transmission method. The present invention relates to a communication system.

  Conventionally, a FlexRay (registered trademark) standard communication system or a CAN (Controller Area Network) standard communication system is known as a communication system that performs communication using a differential transmission method. In the differential transmission method, a communication path is configured by a pair of buses, and signals having opposite phases are input to the buses, and communication signals transmitted between nodes are transmitted through the pair of buses (differential signals). This is a transmission method expressed by a potential difference of (signal).

  On the other hand, as a FlexRay standard communication system, a pseudo wakeup signal is output using a network idle time after a wakeup signal is transmitted in order to wake up a node that has failed to wake up and join the network. A communication system is known (see Patent Document 1).

  As is well known, in a FlexRay (registered trademark) communication system, a specific node receives a trigger signal from an external device via a path outside the communication path, wakes up, and sends a wake-up signal to the communication path. Then, the other nodes connected to the communication path are woken up from the sleep state.

  In an in-vehicle communication system, for example, a detection signal from a sensor that detects opening / closing (locking / unlocking) of a vehicle door is used as a trigger signal, and a node connected to the sensor wakes up. A wake-up signal for causing the node to wake up is output to the communication path.

  However, in this type of communication system, there is a possibility that a node that is disturbed by noise or the like and fails to wake up by a wakeup signal input from the communication path may occur. If the wakeup fails, the node cannot participate in the network.

In order to cope with such a problem, if a method of transmitting a wakeup signal multiple times is used, it takes time to start up the network.
That is, in FlexRay (registered trademark), after executing the wake-up process by transmitting the wake-up signal, the start-up process is executed, and the exchange of the specific signal between the cold start nodes is completed, and the time-triggered network is finally activated. However, normal communication between nodes is possible, but when a wakeup signal is transmitted multiple times, the startup process cannot be executed until the transmission of the wakeup signal is completed multiple times. It cannot be started quickly.

  Therefore, in Patent Document 1, in a FlexRay (registered trademark) standard communication system, a pseudo wakeup signal is not transmitted at a network idle time that does not interfere with communication between nodes after execution of startup processing without retransmitting the wakeup signal. By outputting to the communication path, the node that failed to wake up is woken up.

  In FlexRay (registered trademark), the communication cycle is composed of four segments. Specifically, a static segment, a dynamics segment, a symbol window, and a network idle time. The network idle time is a time domain for achieving global synchronization between nodes. In the network idle time, normal message transmission / reception is not performed, and message transmission / reception is performed in a static segment and a dynamics segment. In the technique described in Patent Document 1, a pseudo wakeup signal is transmitted at the network idle time using such a rule.

JP 2008-042888 A

However, the conventional method described above has the following problems.
That is, in the conventional method of transmitting a pseudo wakeup signal by a differential signal (in other words, by expressing a signal by a potential difference between a pair of buses) at the network idle time, the transmission timing of the pseudo wakeup signal deviates from the network idle time. If this happens, the pseudo wake-up signal interferes with normal message transmission and reception, and a communication error occurs.

  For this reason, it is necessary to put a pseudo wake-up signal in the network idle time. However, if the network idle time is increased to achieve this, the time area that can be used for normal message transmission / reception is reduced in the communication cycle. If the communication efficiency deteriorates and the network idle time is shortened, there is a problem that a pseudo wakeup signal must be transmitted at the network idle time with high time accuracy.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique that can wake up a node that has failed to wake up better than conventional methods.

  In order to achieve this object, the invention according to claim 1 is such that a plurality of nodes are connected to a communication path constituted by a pair of buses, and each node outputs a communication signal to the communication path by a differential transmission method. Thus, a communication system that realizes communication between nodes, each node is configured as follows.

  Each node constituting this communication system converts a signal to be transmitted output from the main device (microcomputer or the like) and the main device into an output signal to each bus and outputs it to each bus constituting the communication path. And a bus driver that converts a transmission signal of each bus constituting the communication path into an input signal to the main device and inputs the signal to the main device.

  Then, one of the nodes constituting the communication system is triggered by the input of a trigger signal input from an external device, the main device wakes up, and after wakeup, the main device enters the communication path through the bus driver. A wakeup signal for wakeup other connected nodes from the sleep state is output to the communication path. Hereinafter, this node is expressed as a wake-up node. After the wakeup signal is output, the wakeup node participates in a network in which nodes connected to the communication path participate and starts communication with other nodes.

  On the other hand, each node connected to the communication path excluding the wakeup node is configured to cause the bus driver to wake up the main device in response to the input of the wakeup signal input from the communication path in the sleep state. Yes.

  For example, a trigger signal is input to the main apparatus or a power supply IC that supplies power to the main apparatus to wake up the main apparatus. The main device that wakes up in this way joins the network through the bus driver after wakeup and starts communication with other nodes.

  When a plurality of wake-up nodes are provided in the communication system, it is uncertain which of the plurality of wake-up nodes wakes up first and transmits a wake-up signal. Therefore, in this case, the wakeup node may be provided with a function to wake up when the wakeup signal input from the communication path is input.

  In addition, as a feature of the present invention, one of the nodes constituting the communication system includes a wakeup potential setting circuit that changes the potential during the idle period of each bus to a wakeup potential common to each bus different from the specified potential. . In this type of node, the main device operates the wake-up potential setting circuit when a predetermined condition is satisfied after wake-up.

  In addition, as a feature of the present invention, each node connected to the communication path excluding the wakeup node and the node including the wakeup potential setting circuit is triggered by the fact that both potentials of the pair of buses are changed to the wakeup potential. In addition, a backup wake-up circuit for wake-up of the main device is provided, and the main device is configured to wake up by the operation of the backup wake-up circuit.

  The spare wakeup circuit can be configured to wake up the main device by inputting a trigger signal to the main device. Further, in a communication system including a plurality of wakeup nodes, a wakeup node may be provided with a spare wakeup circuit. Similarly, in a communication system in which a plurality of nodes including a wakeup potential setting circuit exist, a spare wakeup circuit may be provided in the node.

  The feature of the present invention configured as described above is that the pseudo wake-up signal is not output to the bus as a differential signal, but the potential of each bus during the bus idle period is set to a common wake-up potential. is there.

  In a differential transmission type bus driver, a signal flowing through a communication path is interpreted by a potential difference between the buses. That is, if the bus potential is common, even if the bus potential is changed to the wake-up potential, the potential difference between the buses becomes zero, which is the same as in the normal bus idle state, and the wake-up potential is applied to the bus driver. It is not interpreted as a meaningful signal. In short, the potential change to the wake-up potential has no effect on the signal transmission path through the bus driver.

  Therefore, even if the potential of each bus during the bus idle period is changed to the wake-up potential, normal communication is not hindered. Therefore, according to the present invention, it is possible to efficiently use the bus idle period and wake up a node that has failed to wake up without sending a pseudo wakeup signal at the network idle time.

  Further, according to the present invention, since the in-phase signal called the wake-up potential is used, in order to avoid communication abnormality due to interference as in the conventional method, the network wake-up signal is set to a long network idle time and the pseudo wake-up signal is There is no need to keep idle time.

Therefore, according to the present invention, it is possible to wake up a node that failed to wake up better (simpler) than the conventional method.
Further, according to the present invention, it is not necessary to determine a bus idle period and to turn on / off a circuit for changing the potential of each bus to a wake-up potential in accordance with a change in an idle period and a non-idle period. Thus, there is an effect that it is not necessary to perform complicated control in order to wake up a node that has failed to wake up. Specifically, the wakeup potential setting circuit can be configured as follows.

  In other words, the wake-up potential setting circuit is a line that is branched to a line for each bus and connected to each bus, and the resistance value of each branch line is set to the same value, and the input terminal is a power source. A switch circuit that is connected and whose output end is connected to the line, and in the operating state of the wakeup potential setting circuit, electrically connects the line and a power source, and In an operating state, it can be set as the structure provided with the switch circuit which cancels | releases the electrical connection of the said track | line and a power supply. By electrically connecting the line and the power source, both bus potentials during the idle period are set to a common wake-up potential, and by disconnecting the electrical connection between the line and the power source, the idle period The potential of each bus inside is set to a specified potential.

  Since the bus driver in the bus idle period is in an inactive state and is in a high impedance state, when the line and the power source are electrically connected by the switch circuit, the potential of each bus corresponds to the output voltage of the power source. Changes to wake-up potential.

  On the other hand, since the bus driver is in an active state during the non-bus idle period, the resistance value R of the branch line is very high even when the line and the power source are electrically connected by the switch circuit. Unless it is small, the current flowing through the line is very small. Even if the resistance value R is small, the potential difference between the buses (the amplitude of the differential signal) becomes small and the center potential of the amplitude changes. Therefore, in the bus driver, the communication signal represented by the potential difference is used. Can be interpreted normally. That is, in each bus, a communication signal can be transmitted in a non-bus idle period without being substantially affected by the operation / non-operation of the wakeup potential setting circuit.

  Therefore, according to the present invention, it is possible to wake up a node that has failed to wake up by a wakeup signal by turning on / off a simple wakeup potential setting circuit that does not require time accuracy.

  However, if the resistance value R of each branch line is too small with respect to the termination resistance connecting the pair of buses, the branch line works in the same way as the termination resistance, and as described above, the signal flowing through each bus at the time of non-bus idle. The potential difference becomes smaller. Therefore, the resistance value R is preferably set to a sufficiently large resistance value with respect to the termination resistance. Further, if the resistance value R of the branch line is too large with respect to the impedance of the bus driver at the time of bus idle, the wake-up potential approaches the specified potential, which is inconvenient. Therefore, the resistance value R is preferably set to an appropriate value in consideration of this point.

  The preliminary wake-up circuit in the communication system compares an average potential of a pair of buses with a threshold potential that is predetermined in a range higher than a specified potential and lower than the wake-up potential, and the average potential is the threshold potential. When the main device is woken up when it becomes higher, the main device is woken up when the electric potentials of the pair of buses are approximately changed to the wake-up potential. Good.

  If the spare wakeup circuit is configured in this way, the main device can be woken up with a simple circuit configuration when the potential of each bus changes to the wakeup potential. In addition, since the average potential of the pair of buses is used, it is possible to prevent the standby wakeup circuit from malfunctioning due to a signal flowing through the bus during the non-bus idle period even though the wakeup potential setting circuit is not activated. Can do.

  Since the signals flowing through the buses in the non-bus idle period are signals having opposite phases to each other, the average potential is small. Therefore, if the spare wakeup circuit is configured in this way, the malfunction of the spare wakeup circuit can be sufficiently avoided.

  In addition, the node having the wake-up potential setting circuit monitors a communication signal transmitted from each node connected to the communication path after wake-up, so that the node in the sleep state that has failed to wake up by the wake-up signal And a wake-up potential setting circuit may be activated when a sleep state node is detected.

  According to the communication system configured as described above, the wakeup potential setting circuit can be operated only when necessary, and a node that has not been woken up can be woken up. The generated radiation noise can be suppressed, and adverse effects due to the radiation noise can be suppressed.

  The wakeup potential setting circuit is preferably provided at a wakeup node. The wake-up potential setting circuit is not necessarily provided at the wake-up node, but the wake-up node is responsible for transmitting a wake-up signal and wakes up by an external trigger.

  Therefore, if a wakeup potential setting circuit is provided at the wakeup node, it is possible to avoid a situation in which the node itself including the wakeup potential setting circuit fails to wake up and the wakeup potential setting circuit does not function effectively. Necessary nodes can be woken up more reliably.

  When a wakeup potential setting circuit is provided at the wakeup node, the wakeup node may be configured to operate the wakeup potential setting circuit when transmission of a wakeup signal is started. According to the communication system configured as described above, there is an advantage that a node that has failed to wake up by a regular wakeup signal can be waked up quickly.

1 is a block diagram illustrating a configuration of a communication system 1. FIG. It is a block diagram showing the structure of electronic controller 10a, 10b, 10d, 10e. It is the graph which showed the signal waveform of bus | bath LN1, LN2. It is explanatory drawing which showed schematically the circuit structure around bus | bath LN1, LN2 when the transistor Tr is turned on. It is a flowchart showing the process which the microcomputer 20 performs after wakeup. It is a flowchart showing the preliminary | backup wakeup process which the microcomputer 20 performs. It is a flowchart showing the preliminary | backup wakeup process of a modification. It is a figure showing the structure of the wakeup electric potential setting circuit 40 '. It is the graph which showed the signal waveform etc. of bus | bath LN1, LN2 in a communication system provided with the wakeup electric potential setting circuit 40 '.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a communication system 1 according to the present embodiment. The communication system 1 according to the present embodiment is a communication system 1 in which a plurality of electronic control devices 10a, 10b, 10c, 10d, and 10e are connected to a common communication line LN. Hereinafter, the electronic control devices 10a, 10b, 10c, 10d, and 10e are collectively expressed as the electronic control device 10.

  The communication system 1 is mounted on a vehicle, for example. As an electronic control unit (ECU) mounted on a vehicle, an engine ECU that controls engine control, a brake ECU that controls brake control, a steering ECU that controls steering control, a suspension ECU that controls suspension control, and a light on / off control Various electronic control devices such as an ECU can be listed. In FIG. 1, only five electronic control devices 10 are illustrated, but it goes without saying that the number of electronic control devices 10 constituting the communication system 1 is not limited to this.

  In the communication system 1, the communication line LN includes a pair of buses LN1 and LN2, and each electronic control device 10 is connected to the respective buses LN1 and LN2 through connectors CNT (see FIG. 2). Each electronic control device 10 constituting the communication system 1 is configured to communicate with another electronic control device 10 by a differential transmission method.

  As communication protocols adopting the differential transmission method, for example, FlexRay (registered trademark) and CAN are known. In the following, it is assumed that FlexRay (registered trademark) is adopted as a communication protocol. However, it should be noted that the present invention is not limited to FlexRay (registered trademark).

  As is well known, in FlexRay (registered trademark), communication through a network between nodes is realized through the following process. That is, a process that wakes up each node connected to the communication line LN (hereinafter referred to as a wakeup process) and a process that determines a communication schedule and starts up a network (hereinafter referred to as a startup process).

  More specifically, in the wake-up process, a specific node that receives a wake-up trigger signal from an external device on a route outside the communication line LN wakes up from a sleep state when triggered by the trigger signal input from the external device. After the wake-up, a wake-up signal for waking up another node connected to the communication line LN from the sleep state is output to the communication line LN through the bus driver 30 (see FIG. 2). Then, the other node wakes up in response to the input of the wakeup signal input through the communication line LN and the bus driver 30.

  The wake-up process proceeds in such a procedure, but in the communication system 1 according to the present embodiment, a specific node (hereinafter referred to as a wake-up node) to which the electronic control devices 10a and 10b can transmit the wake-up signal. ) Is set. Specifically, assuming an in-vehicle communication system 1, examples of the wake-up node include a door ECU connected to a sensor that detects opening / closing (locking / unlocking) of a vehicle door as an external device. it can. For example, the sensor signal indicating the opening (unlocking) of the door is used as a trigger signal to wake up.

  On the other hand, the startup process proceeds after a cold start node that can start up the network wakes up. That is, in the startup process, a cold start node that is set in advance so that the network can be started up executes a predetermined startup process and starts up the network.

  As is well known, since FlexRay (registered trademark) is a time-triggered communication protocol, the FlexRay (registered trademark) standard communication system 1 performs time synchronization (also referred to as clock synchronization) prior to communication between nodes. It is necessary to establish a common time axis (in other words, to define a communication schedule) and to start the network. The startup process is a process for establishing time synchronization between a pair of cold start nodes and starting a network.

  Specifically, when the cold start node detects that the network is not activated after wakeup, the cold start node transmits a startup frame to the communication line LN a plurality of times in accordance with the period of the activated network as a startup process. .

  In this way, when one cold start node transmits a start-up frame, the cold start-up node that has received this transmits a response frame to the cold start node that has transmitted this start-up frame in accordance with the output of the start-up frame. To do. By exchanging such a start-up frame and response frame, these two cold start nodes establish time synchronization, thereby establishing a common time axis and starting the network.

  A node other than the cold start node (non-cold start node) is synchronized with the time-triggered network in which the cold start node participates based on a signal flowing through the communication line LN after the cold start node starts the network. Join the network.

  The startup process proceeds in such a procedure, but in the communication system 1 of this embodiment, the electronic control devices 10a, 10b, and 10c are set as cold start nodes. In this embodiment, the wake-up node is set as a cold start node. The reason for setting in this way is as follows.

  That is, in the electronic control devices 10c, 10d, and 10e that receive a wake-up signal from the wake-up node and wake up from the sleep state, there is a possibility that wake-up by the wake-up signal may fail due to noise or the like.

  On the other hand, in FlexRay (registered trademark), the network cannot be activated unless at least two cold start nodes wake up. Therefore, it is desirable to avoid the situation where the cold start node does not wake up as much as possible. For this reason, in this embodiment, a wakeup node that wakes up more reliably is set as a cold start node.

  Further, in this embodiment, in order to avoid a situation in which the electronic control device 10 that has failed to wake up by the wake-up signal due to the influence of noise or the like cannot subsequently enter the network without exiting the sleep state. The communication system 1 is provided with a function to wake up the electronic control device 10 that has failed to wake up by a pseudo wakeup signal. Hereinafter, a configuration for realizing this function will be described with reference to FIG. 2 together with a specific configuration of each electronic control device 10.

  However, hereinafter, a normal wakeup signal transmitted in the wakeup process is expressed as a “first wakeup signal”, and the pseudo wakeup signal unique to the communication system 1 of the present embodiment is expressed as “ It is expressed as “second wake-up signal”.

FIG. 2 is a block diagram illustrating a detailed configuration of the electronic control devices 10a and 10b and the electronic control devices 10d and 10e.
The electronic control devices 10a and 10b (wake-up nodes) of this embodiment include a microcomputer (hereinafter referred to as a microcomputer) 20, a bus driver 30, a wake-up potential setting circuit 40, a spare wake-up circuit 50, The connector CNT is connected to the communication line LN.

  The microcomputer 20 includes a communication controller 21 and an interrupt controller 23. The microcomputer 20 wakes up from a sleep state in accordance with an interrupt signal (trigger signal) input from the interrupt controller 23. After wakeup, FlexRay (registration) The communication control according to the trademark is realized by software processing by executing a program and hardware processing by the communication controller 21.

  Specifically, the microcomputer 20 is in a state where the supply of the clock signal is stopped in the sleep state, and the interrupt controller 23 starts the supply of the clock signal when the specific interrupt signal is input, The microcomputer 20 is woken up. In this embodiment, each electronic control device 10 including the electronic control devices 10 a and 10 b wakes up from the sleep state by the function of the interrupt controller 23.

  On the other hand, the bus driver 30 converts a transmission target signal output from the microcomputer 20 (communication controller 21) into an output signal to each of the buses LN1 and LN2 and outputs the output signal to each of the buses LN1 and LN2, and each bus. A signal flowing through LN1 and LN2 is converted into an input signal to the microcomputer 20 (communication controller 21) and input to the microcomputer 20, and a wake-up signal input from the communication line LN is detected and the interrupt controller 23 is detected. And a wakeup detection circuit 35 for inputting an interrupt signal (trigger signal).

  The transceiver 31 is composed of a known three-state driver that takes three states of signal output: high, low, and idle (high impedance), the input end is connected to the communication controller 21 of the microcomputer 20, and the output end is a connector CNT. Are connected to the buses LN1 and LN2 that are drawn through the terminal.

  The transceiver 31 is connected to a 5V power supply, and in the bus idle period, the transceiver 31 takes an inactive (high impedance) state, whereby the potential of each of the buses LN1 and LN2 is set to a specified potential (this embodiment). Then, it is set to 2.5 V which is an intermediate potential between the output voltage of the power source and the ground.

  On the other hand, during the non-bus idle period, the transceiver 31 converts the signal to be transmitted, which is input from the microcomputer 20 (communication controller 21), into a differential signal, and connects each of the buses LN1 and LN2 drawn through the connector CNT to each other. By outputting a signal having an opposite phase, a communication signal is output to the communication line LN.

  Specifically, as shown in the upper and lower graphs in FIG. 3A, a high / low signal with an amplitude center of 2.5 V is output to each of the buses LN1 and LN2. Note that the amplitude of the differential signal is determined by a termination resistor RT (see FIG. 1) connected to both ends of each of the buses LN1 and LN2.

  On the other hand, the receiver 33 is connected to the buses LN1 and LN2 drawn through the connector CNT, and is a well-known receiver that inputs a received signal corresponding to a potential difference between signals flowing through the buses LN1 and LN2 to the microcomputer 20. 33. A wakeup detection circuit 35 is provided at the output end of the receiver 33, and the received signal is input to the microcomputer 20 (communication controller 21) via the wakeup detection circuit 35.

  In addition, the wakeup detection circuit 35 monitors the input signal from the receiver 33 to detect the first wakeup signal output from the wakeup node. The microcomputer 20 is configured to wake up the microcomputer 20 by inputting an interrupt signal to the insertion controller 23.

  The bus driver 30 including the wakeup detection circuit 35 blocks the transmission of the received signal to the downstream (the microcomputer 20) until the first wakeup signal is detected by the wakeup detection circuit 35, and the first wakeup signal is detected. When the signal is detected, the microcomputer 20 is woken up by the method described above. Thereafter, when controlled by the microcomputer 20 and transiting to the normal mode, the transmission cutoff of the reception signal downstream is released, and in the normal mode, the reception signal output from the receiver 33 is transmitted downstream (the microcomputer 20).

  In addition, the wakeup potential setting circuit 40 is configured to operate in accordance with a high / low signal output from the output port of the microcomputer 20 and to output a second wakeup signal to the communication line LN. Specifically, when activated, the wakeup potential setting circuit 40 changes the potential of each of the buses LN1 and LN2 during the bus idle period from a specified potential (2.5V) to a wakeup potential (5V) higher than the specified potential. As a result, the second wakeup signal is output to the communication line LN.

  3A is a graph schematically showing signal waveforms of the buses LN1 and LN2 when the wakeup potential setting circuit 40 is not in operation (when a transistor Tr described later is turned off). FIG. 3B is a graph schematically showing signal waveforms of the buses LN1 and LN2 when the wakeup potential setting circuit 40 is operated (when a transistor Tr described later is turned on). It is.

  As shown in FIG. 2, the wake-up potential setting circuit 40 includes a PNP transistor Tr having an emitter connected to the same 5V power supply as the bus driver 30 and a base connected to the output port of the microcomputer 20 via a resistor R1. An output line LO connecting the collector of Tr and each of the buses LN1 and LN2.

  Since the base of the transistor Tr is connected to the output port of the microcomputer 20, the transistor Tr is set to an off state when a high signal is input from the output port, and is set to an on state when a low signal is input from the output port. .

  On the other hand, the output line LO branches from the collector of the transistor Tr and is connected to the buses LN1 and LN2, and the same resistance R2 is provided for each branch line. That is, the resistance value of each branch line is set to the same value. The reason why the resistance values of the branch lines are the same is to make the wake-up potentials of the buses LN1 and LN2 the same and to prevent potential differences between the buses LN1 and LN2 during the bus idle period. is there.

The resistance R2 is set to a resistance value sufficiently larger than the termination resistance RT and sufficiently smaller than the output impedance when the bus driver 30 is inactive.
The reason why the value of the resistor R2 is made sufficiently larger than the termination resistor RT is that when the value of the resistor R2 is small, the resistor R2 functions as the termination resistor RT, and the amplitude of the differential signal decreases according to the value of the resistor R2. It is because it ends. When the value of the resistor R2 is small, when the transistor Tr is in the on state, the average potential (the amplitude center of the differential signal) of the buses LN1 and LN2 during the non-bus idle period is the specified potential (2. This is because it becomes higher than 5V), and the detection of the wake-up potential is hindered.

  On the other hand, the reason why the value of the resistor R2 is set to a value sufficiently smaller than the output impedance when the bus driver 30 is inactive is as follows. That is, if the value of the resistor R2 is too large, the potentials (wake-up potentials) of the buses LN1 and LN2 during the bus idle period when the transistor Tr is in an on state are low, and the bus LN1 when the transistor Tr is in an off state. , LN2 and the specified potential (2.5 V) become small, and it becomes difficult to detect the wake-up potential that functions as the second wake-up signal.

  The wake-up potential setting circuit 40 according to the present embodiment has the above-described circuit configuration. When a high signal is input from the output port, the wake-up potential setting circuit 40 does not electrically connect the 5V power supply and the output line LO, When the average potential of the buses LN1 and LN2 is set to a specified potential (2.5V) and a low signal is input from the output port, the 5V power supply and the output line LO are electrically connected, and the bus The potentials of the buses LN1 and LN2 during the idle period are set to a common wake-up potential (5V) that is higher than the specified potential (2.5V).

  In this embodiment, as shown in FIG. 4A, the resistor R2 has a resistance value (eg, 1 kΩ) that is sufficiently smaller than the output impedance (eg, 300 kΩ) when the bus is idle (when the bus driver 30 is inactive). Therefore, almost no current flows from the power source to the bus driver 30 when the bus is idle. Therefore, when the transistor Tr is in the on state, the potentials (wake-up potentials) of the buses LN1 and LN2 at the time of bus idling are basically the same as the output voltage of the power supply and become approximately 5V. FIG. 4A is an explanatory diagram schematically showing a circuit configuration around the buses LN1 and LN2 when the transistor Tr is in an on state and the bus driver 30 is in an inactive state.

  FIG. 4B is an explanatory diagram schematically showing a circuit configuration around the buses LN1 and LN2 when the transistor Tr is in an on state and the bus driver 30 is in an active state. In this embodiment, as shown in FIG. 4B, the resistance R2 has a resistance value (for example, 1 kΩ) sufficiently larger than the output impedance (for example, 5Ω) at the time of non-bus idle (when the bus driver 30 is active). Since it is set, almost no current flows through the wake-up potential setting circuit 40 even when the transistor Tr is on during non-bus idling.

  Therefore, as shown in FIGS. 3A and 3B, during the non-bus idle period, the signal waveform of each bus depends on whether or not the wakeup potential setting circuit 40 is operating (depending on the state of the transistor Tr). There is basically no change, and the wake-up potential setting circuit 40 allows the potentials of the buses LN1 and LN2 to be selectively selected during the bus idle period while the operating state is continued (with the transistor Tr turned on). In addition, the specified potential can be changed to the wake-up potential.

  In the communication system 1 of the present embodiment, the second wakeup signal for wakeup of the electronic control device 10 that failed to wake up by the first wakeup signal is transmitted during the bus idle period.

  In addition, the standby wake-up circuit 50 is a circuit for detecting the output of the second wake-up signal and waking up its own node in the sleep state. As shown in FIG. 2, the preliminary wake-up circuit 50 is mainly configured by a comparator 51, and 3.5 V is input as a threshold potential to the negative input terminal of the comparator 51. The positive input terminal of the comparator 51 is connected upstream of the branch point of the output line LO. The positive input terminal has an average potential that is the average of the potentials of the buses LN1 and LN2 in the off state of the transistor Tr. Is input through an integration (filter) circuit.

  When a node including the wakeup potential setting circuit 40 is in the sleep state, the transistor Tr is maintained in the off state at that node. Therefore, when the electronic control devices 10a and 10b including the standby wake-up circuit 50 are in the sleep state, the comparator 51 compares the average potential of each of the buses LN1 and LN2 with the threshold potential of 3.5V, and each bus If the average potential of LN1 and LN2 is 3.5V or less, a low signal is output from the comparator 51, and if the average potential of each bus LN1 and LN2 exceeds 3.5V, a high signal is output from the comparator 51. Will be.

  The electronic control devices 10a and 10b of the present embodiment are configured such that the output of the comparator 51 is input to the interrupt controller 23 of the microcomputer 20. Accordingly, when the output of the comparator 51 is switched to a high signal while the microcomputer 20 is in the sleep state, the interrupt controller 23 supplies a clock signal, and the microcomputer 20 wakes up.

  This point will be described in detail. When the second wakeup signal is input from another node to the electronic control devices 10a and 10b in the sleep state, the potential of the signal input to the plus input terminal of the comparator 51 is as shown in FIG. b) As shown in the graph in the third stage, the average potential of each bus at the time of non-bus idle changes from 2.5 V to 5 V which is a wake-up potential. Therefore, when the second wake-up signal is input from another node, the output of the comparator 51 is switched to a high signal during the bus idle period as shown in the fourth graph of FIG. The microcomputer 20 of the electronic control devices 10a and 10b in the sleep state wakes up.

  With this operation, according to the present embodiment, even if the electronic control devices 10a and 10b are hindered by noise or the like and fail to wake up by the first wakeup signal, the electronic control device is activated by the second wakeup signal. 10a and 10b can be woken up and joined to the network.

  Although the hardware configuration of the electronic control devices 10a and 10b has been described above, the electronic control device 10c is basically configured in the same hardware configuration as the electronic control devices 10a and 10b. However, the electronic control device 10c does not have a function to wake up by an interrupt signal from an external device (sensor or the like). The electronic control device 10c is not configured as a wake-up node, and wakes up when the first wake-up signal and the second wake-up signal are input. This is different from the electronic control devices 10a and 10b.

  Next, the hardware configuration of the electronic control devices 10d and 10e will be described. The electronic control devices 10d and 10e have a hardware configuration similar to that of the electronic control devices 10a, 10b, and 10c, but are not configured as wake-up nodes, and the wake-up potential setting circuit 40 and the spare wake-up circuit 50 are not configured. Of these, only the circuit corresponding to the standby wake-up circuit 50 is provided, which is different from the electronic control units 10a, 10b, and 10c.

  Specifically, the hardware configuration of the electronic control devices 10d and 10e will be described. The electronic control devices 10d and 10e are connectors to which the microcomputer 20, the bus driver 30, the spare wake-up circuit 60, and the communication line LN are connected. It is the structure provided with CNT.

  The spare wake-up circuit 60 is configured such that 3.5 V is input as a threshold potential to the negative input terminal of the comparator 51, and input lines LI connected to the buses LN1 and LN2 are connected to the positive input terminal of the comparator 51. ing.

  The input line LI corresponds to the output line LO in the wakeup potential setting circuit 40 described above, branches from the connection side with the comparator 51 toward the connection side with the buses LN1 and LN2, and the bus LN1, It is configured to be connected to LN2. Each branch line is provided with the same resistor R2, and the resistance value of each branch line is set to the same value. The reason why the resistance values of the branch lines are the same is to input a signal corresponding to the average potential of the buses LN1 and LN2 to the plus input terminal of the comparator 51. Further, an integrating circuit is provided between the input line LI and the comparator 51.

  The spare wakeup circuit 60 configured in this way, like the spare wakeup circuit 50, compares the average potential of each of the buses LN1 and LN2 with the threshold potential of 3.5 V, and compares the average of each of the buses LN1 and LN2. If the potential is 3.5V or less, a low signal is input to the interrupt controller 23 of the microcomputer 20, and if the average potential of each bus LN1, LN2 exceeds 3.5V, a high signal is sent to the interrupt controller 23. 23.

  That is, when the average potential of each of the buses LN1 and LN2 exceeds 3.5V while in the sleep state, the microcomputer 20 wakes up by the operation of the interrupt controller 23. Therefore, even if the electronic control devices 10d and 10e fail to wake up by the first wake-up signal, the electronic control devices 10d and 10e wake up by the second wake-up signal output from another node (any one of the electronic control devices 10a, 10b, and 10c). Can be up.

  Therefore, according to the communication system 1 of the present embodiment, a node that has been disturbed by noise or the like and has failed to wake up by the first wakeup signal can be set in the bus idle period without using the network idle time. It can be used to wake up efficiently.

  Further, it is not necessary to turn on / off the wake-up potential setting circuit 40 according to the switching between the non-idle period and the idle period of the bus, and the second wake-up signal can be easily controlled without hindering normal communication. To wake up a node that is blocked by noise or the like and failed to wake up by the first wakeup signal.

  Furthermore, according to the present embodiment, in a state where the wakeup potential setting circuit 40 is operated, every time a frame is transmitted (in other words, every time the bus idle period and the non-bus idle period are switched), The comparator output repeats high / low intermittently. Therefore, for the microcomputer 20 that detects the edge of the comparator output as an interrupt signal, the signal output of the comparator can increase the probability that the microcomputer 20 will wake up, and the microcomputer 20 can be woken up more reliably. Can be made.

  Then, the content of the process which each microcomputer 20 of the electronic control apparatus 10 performs is demonstrated using FIGS. FIG. 5A is a flowchart showing processing executed when the microcomputer 20 of the electronic control devices 10a and 10b wakes up by an interrupt signal from an external device (sensor or the like).

  When the microcomputer 20 wakes up by an interrupt signal from an external device, the microcomputer 20 executes an initial process such as initializing the communication controller 21 (S110), and then performs a communication line LN according to a procedure defined in Flexray (registered trademark). The first wake-up signal is transmitted through the bus driver 30 (S120), and after this transmission, the startup process described above is executed (S130), and time synchronization is established by exchanging signals with other cold start nodes, Set a common time axis (communication schedule) and start the network. Then, when the network is activated, it joins the time-triggered network, starts communication with other nodes participating in the network, and starts the preliminary wake-up process shown in FIG. 6 (S140). Transition to the state (normal state).

  On the other hand, when the microcomputer 20 of the electronic control device 10a, 10b, 10c wakes up when the bus driver 30 of its own device receives the first wakeup signal, as shown in FIG. (S110), the startup process is executed without transmitting the first wakeup signal, and the network is activated in cooperation with other cold start nodes (S130).

  Then, when the network is activated, it participates in the time trigger type network, starts communication with other nodes participating in the network, and starts the preliminary wake-up process shown in FIG. 6 (S140). Transition to the communication state (normal state). FIG. 5B is a flowchart showing processing executed when the microcomputer 20 of the electronic control devices 10a, 10b, and 10c wakes up by the first wakeup signal transmitted from the wakeup node.

  In addition, when the microcomputer 20 of the electronic control devices 10d and 10e wakes up when the bus driver 30 of the own device receives the first wakeup signal, as shown in FIG. 5C, the initial processing is performed. After the execution (S110), it joins the network activated by the cold start node (S150), starts communication with other nodes, and shifts to a normal communication state (normal state). FIG. 5C is a flowchart showing processing executed when the microcomputer 20 of the electronic control devices 10d and 10e wakes up by the first wakeup signal transmitted from the wakeup node.

  The preliminary wake-up process executed by the microcomputer 20 of the electronic control devices 10a, 10b, and 10c in S140 is performed according to the following procedure. FIG. 6 is a flowchart showing the preliminary wake-up process executed by the microcomputer 20 of the electronic control apparatuses 10a, 10b, and 10c in S140.

  When the preliminary wake-up process is started, the microcomputer 20 determines whether or not a predetermined time has elapsed after joining the network (S210). The predetermined time is determined in advance by the designer in consideration of the time required for the node that has received the first wake-up signal to wake up to join the network and start frame transmission.

  If it is determined that the predetermined time has elapsed (Yes in S210), whether or not a frame having the node as a transmission source has been received for each node other than the own node based on the received frame obtained through the bus driver 30. Is determined (S220).

  Specifically, the electronic control device 10a determines whether or not each of the electronic control devices 10b, 10c, 10d, and 10e has received a frame from the electronic control device. Similarly, the electronic control device 10b determines whether or not each of the electronic control devices 10a, 10c, 10d, and 10e has received a frame from the electronic control device, and the electronic control device 10c performs electronic control. For each of the devices 10a, 10b, 10d, and 10e, it is determined whether or not a frame can be received from the electronic control device.

  The reception waiting time of the frame used for the determination in S220 can be arbitrarily determined by the designer. For example, the determination in S220 may be performed based on a reception result for one communication cycle period, or may be performed based on a reception result for a plurality of communication cycle periods.

  If it is determined in S220 that all the nodes other than the own node have received the frame having the node as the transmission source, it is determined that there is no sleep state node that does not participate in the network ( No in S230), the process proceeds to S260.

  On the other hand, if it is determined in S220 that any of the nodes other than the own node cannot receive a frame having the node as a transmission source, it is determined that there is a sleep state node that does not participate in the network. (Yes in S230), the process proceeds to S240.

  When the process proceeds to S240, the microcomputer 20 determines whether or not the second wakeup signal is already being transmitted. If the transmission of the second wakeup signal has not yet started (No in S240), the process proceeds to S250. Then, the output signal of the output port is switched from the high signal to the low signal.

  By this process, the microcomputer 20 activates the wake-up potential setting circuit 40 of the own device (in other words, turns on the transistor Tr) and starts transmitting the second wake-up signal. Thereafter, the process proceeds to S220.

On the other hand, if the second wakeup signal is already being transmitted (Yes in S240), the process proceeds to S220 while maintaining the output signal of the output port as a low signal.
Here, when the transmission of the second wakeup signal is started as described above, in the electronic control device 10 in the sleep state, the signal input to the plus output terminal of the comparator 51 becomes 5 V in the bus idle period, and the microcomputer 20 Will wake up.

  Specifically, the microcomputer 20 of the electronic control device 10 that wakes up upon receipt of the second wakeup signal is the same as that in the case of the electronic control devices 10d and 10e receiving the first wakeup signal shown in FIG. By executing the process shown in c), the network joins the already activated network and transmits a frame in the slot assigned to the own node.

That is, after the second wakeup signal transmission is started, it is normally determined No in S230 as time elapses.
In this way, the microcomputer 20 determines No in S230 and proceeds to S260 to determine whether the second wake-up signal is currently being transmitted, and if the second wake-up signal is being transmitted ( After the output signal of the output port is switched to a high signal and the wakeup potential setting circuit 40 is deactivated (S270), the preliminary wakeup process is terminated. On the other hand, if the second wake-up signal is not being transmitted (No in S260), the preliminary wake-up process is terminated while maintaining the output of the output port at the high signal.

With such a procedure, the second wake-up signal is transmitted in the communication system 1 of the present embodiment.
According to the present embodiment, as described above, even if the wakeup potential setting circuit 40 is operated, normal communication is basically not disturbed, so that the wakeup potential setting circuit 40 is always operated. It can also be.

  However, radiation noise may increase due to transmission of the second wakeup signal. In this embodiment, for this reason, the electronic control device 10 in the sleep state is detected by monitoring the communication signal (frame) flowing through the communication line LN, and the electronic device in the sleep state not participating in the network is detected. The second wakeup signal is transmitted only when the control device 10 exists.

  However, in the above method, it takes time until the electronic control device 10 in the sleep state is detected, and the node that has failed to wake up due to the first wakeup signal cannot escape from the sleep state for a while. . In other words, in the above method, it takes time until the network starts up normally.

  Therefore, the preliminary wake-up process may be executed according to the procedure shown in FIG. FIG. 7 is a flowchart showing a preliminary wake-up process according to a modification. However, this preliminary wake-up process is executed by a wake-up node that is woken up by an interrupt signal (trigger signal) from an external device.

  When the preliminary wake-up process shown in FIG. 7 is started, the microcomputer 20 initializes a parameter N indicating the number of times of transmission of the second wake-up signal to zero (S310), and at the same time as the transmission of the first wake-up signal is started. (Yes in S320), by switching the output signal of the output port from the high signal to the low signal, the wakeup potential setting circuit 40 is operated to start the transmission of the second wakeup signal (S330). That is, in the modification, transmission of the second wakeup signal is started simultaneously with the first wakeup signal.

  In the modified example, since the transmission of the second wakeup signal is started simultaneously with the first wakeup signal, the preliminary wakeup process is started in parallel with the process in S120 after the completion of the initial process (S110). Will do.

  After that, the microcomputer 20 starts measuring a transmission time that is an elapsed time from the start of transmission of the second wakeup signal (S340), and when the transmission time exceeds a predetermined upper limit (Yes in S350). ), The transmission time measurement ends (S360), the output signal of the output port is switched from the low signal to the high signal, the wakeup potential setting circuit 40 is deactivated, and the transmission of the second wakeup signal is stopped. (S370). The upper limit value in S350 is set to a time longer than at least the frame length so that the bus idle period arrives during transmission of the second wakeup signal.

  When the process in S370 is completed, the microcomputer 20 updates the parameter N to a value obtained by adding 1 (S375), and determines whether or not the updated value is equal to or greater than a predetermined upper limit of the number of transmissions. Judgment is made (S380). If it is determined that the value is equal to or greater than the upper limit (Yes in S380), the preliminary wake-up process is terminated. The upper limit value used here is set in advance to a value at which all of the electronic control devices 10 in the communication system 1 wake up with a sufficiently high probability.

  On the other hand, if it is determined that the value of parameter N is less than the upper limit value of the number of transmissions (No in S380), the measurement of the waiting time until the next transmission of the second wakeup signal is started (S390) When the time exceeds a predetermined upper limit (Yes in S400), after measuring the waiting time (S410), the process proceeds to S330, and the second wakeup signal is transmitted again.

  In this way, in the modification, the second wakeup signal is intermittently transmitted immediately after the wakeup, and the node that has failed to wake up by the first wakeup node is quickly joined to the network.

  The communication system 1 of the present embodiment including the modification has been described above. In the present embodiment, a pseudo wakeup signal (second wakeup signal) is output as an in-phase signal instead of a differential signal, and a wakeup potential is output. By simply turning on / off the setting circuit 40, a node that has failed to wake up by the first wakeup signal can be woken up using the bus idle period.

  Therefore, unlike the conventional case, it is not necessary to set the network idle time long in order to store the pseudo wakeup signal in the network idle time. There's no need to keep it out of idle time.

  In other words, in this embodiment, it is not necessary to switch the wake-up potential setting circuit 40 on / off with high time accuracy in order to avoid the occurrence of communication abnormality due to interference that the prior art has, and network idle There is no need to transmit a pseudo wake-up signal at the time, and it is not necessary to set a long network idle time to decrease the communication efficiency as in the prior art. Therefore, according to the present embodiment, it is possible to wake up a node that has failed to wake up better than the conventional method.

  Further, according to this embodiment, since the pseudo wakeup signal (second wakeup signal) is not a differential signal but an in-phase signal, the potential difference during the bus idle period can be set to zero, which is the same as that during idling. In addition, an error such as a NIT (network idle time) error is not detected as in the conventional system, and unnecessary error processing need not be executed.

  More specifically, since the network idle time is a time region in which normal message transmission / reception is not performed, if a pseudo wake-up signal is transmitted as in the conventional method using this region, communication according to the FlexRay (registered trademark) standard is performed. According to the system, a NIT error is detected in a node that has already been woken up, and unnecessary error processing is executed. That is, since a signal that should not flow flows during the network idle time, the node detects that it is abnormal.

  Therefore, in the conventional method, it is necessary to change the communication system from the normal FlexRay (registered trademark) specification so that the NIT error is not detected when the pseudo wakeup signal is received. There was a problem of cost.

  On the other hand, according to the present embodiment, since such a problem does not occur, it is not necessary to change the specification of the node so that the pseudo wakeup signal is not detected as an error as in the conventional method (it takes a NIT error or the like). A communication system that can wake up a node that has failed to wake up can be configured at low cost.

  The main device described in “Claims” corresponds to the microcomputer 20 included in each electronic control device 10 in the above embodiment, and a trigger signal input from the external device is sent from the external device to the interrupt controller 23. Corresponds to the input interrupt signal. In addition, the switch circuit and the line included in the wakeup potential setting circuit correspond to the transistor Tr and the output line LO in the above embodiment.

  In addition, the microcomputer 20 executes an operation of operating the wakeup potential setting circuit when a node having the wakeup potential setting circuit detects a node in a sleep state that has failed to wakeup by the wakeup signal. This is realized by a preliminary wake-up process. In addition, the operation in which the wake-up node operates the wake-up potential setting circuit at the same time as the start of transmission of the wake-up signal is realized by the preliminary wake-up process of the modified example.

  Further, the present invention is not limited to the above-described embodiments, and can take various forms. For example, the present invention is not limited to the in-vehicle communication system 1 and can be applied to various communication systems. In addition, the present invention is not limited to FlexRay (registered trademark) as long as the communication protocol adopts a differential transmission method, and various communication protocols can be employed.

  In addition, in the above embodiment, the second wakeup is performed by changing the potential of each of the buses LN1 and LN2 during the bus idle period from the specified potential (2.5V) to the wakeup potential (5V) higher than the specified potential. The signal is output to the communication line LN, but the wakeup potential setting circuit 40 wakes up the potentials of the buses LN1 and LN2 during the bus idle period from the specified potential (2.5V) to a level lower than the specified potential. The second wake-up signal may be output to the communication line LN by changing the potential to 0 V (for example, 0 V).

  Specifically, as shown in FIG. 8, a wake-up potential setting circuit 40 'can be configured. FIG. 8 is a diagram illustrating the configuration of the wake-up potential setting circuit 40 '. The wake-up potential setting circuit 40 ′ includes an NPN transistor Tr ′ whose emitter is grounded and whose base is connected to the output port of the microcomputer 20 via the resistor R1, a collector of the transistor Tr ′, and the buses LN1 and LN2. The connecting line LO '.

  In the wake-up potential setting circuit 40 ′, the base of the transistor Tr ′ is connected to the output port of the microcomputer 20, so that when a low signal is input from the output port, the transistor Tr ′ is set to OFF and from the output port, When is entered, it is set to on.

  That is, when a low signal is input from the output port, the wake-up potential setting circuit 40 ′ sets the average potential of each of the buses LN1 and LN2 during the bus idle period to the specified potential (2) without grounding the line LO ′. .5V), and when a high signal is input from the output port, the line LO ′ is grounded, and the potentials of the buses LN1 and LN2 during the bus idle period are set from the specified potential (2.5V). Is set to a common wake-up potential (0 V).

  In the communication system in which the wake-up potential setting circuit 40 ′ is configured in this way, the comparator 51 receives a threshold potential (for example, 1.5 V) lower than the specified potential at the positive input terminal and the negative input terminal. The average potentials of the buses LN1 and LN2 are input.

  In the communication system configured in this way, for example, as shown in FIG. 9, the potentials of the buses LN1 and LN2, the input to the comparator 51, and the output of the comparator 51 change. Therefore, even if the communication system is configured in this way, it is possible to wake up the electronic control device that has failed to wake up by the first wakeup signal in the same manner as in the above-described embodiment.

  In the above embodiment, the microcomputer 20 is woken up by inputting an interrupt signal to the microcomputer 20. However, as a wakeup method, in addition to the power supply IC that controls the power supply to the microcomputer 20. And a method of waking up the microcomputer 20 by inputting a trigger signal. That is, the above-described embodiment may be realized by adopting such a method to realize the configuration of the invention described in “Claims”.

  In addition, when the electronic control device 10 is configured to include two microcomputers, and one of the microcomputers includes the communication controller 21, the microcomputer not including the communication controller 21 is connected to a trigger line or bus connected to the external device. The electronic control device 10 may be configured to wake up by a trigger signal input through the driver 30 and to wake up a microcomputer including the communication controller 21 in accordance with a command from the waked-up microcomputer. That is, various modes are conceivable for the trigger signal input path.

DESCRIPTION OF SYMBOLS 1 ... Communication system, LN ... Communication line, LN1, LN2 ... Bus, RT ... Termination resistance 10, 10a, 10b, 10c, 10d, 10e ... Electronic control unit, CNT ... Connector, 20 ... Microcomputer, 21 ... Communication controller, DESCRIPTION OF SYMBOLS 23 ... Interrupt controller, 30 ... Bus driver, 31 ... Transceiver, 33 ... Receiver, 35 ... Wake-up detection circuit, 40, 40 '... Wake-up potential setting circuit, Tr, Tr' ... Transistor, R1, R2 ... Resistance, LI, LO, LO '... lines, 50, 60 ... spare wake-up circuit, 51 ... comparator

Claims (6)

A communication system in which a plurality of nodes are connected to a communication path constituted by a pair of buses, and each node outputs a communication signal to the communication path by a differential transmission method, thereby realizing communication between the nodes. There,
Each node converts a main device and a signal to be transmitted output from the main device into an output signal to each bus and outputs the output signal to each bus constituting the communication path, and transmission of each bus A bus driver that converts a signal into an input signal to the main device and inputs the signal to the main device;
One of the nodes constituting the communication system is waked up by the main device in response to a trigger signal input from an external device, and after the wakeup, the main device transmits the communication through the bus driver. Configured as a wake-up node that outputs a wake-up signal to wake up other nodes connected to the path from the sleep state to the communication path;
Each node connected to the communication path excluding the wake-up node is configured to cause the bus driver to wake up the main device when the wake-up signal is input from the communication path.
Further, one of the nodes constituting the communication system includes a wake-up potential setting circuit that changes a potential during an idle period of each bus to a wake-up potential common to each bus different from a specified potential, Later, when the predetermined condition is satisfied, the main device is configured to operate the wake-up potential setting circuit,
Each node connected to the communication path excluding the wake-up node and a node having the wake-up potential setting circuit causes the main device to be triggered by the change in both potentials of the pair of buses to the wake-up potential. A communication system comprising a backup wake-up circuit for wake-up, wherein the main device is also woken up by the operation of the backup wake-up circuit. The wake-up potential setting circuit includes:
A line branched to a line for each bus and connected to each bus, and a resistance value of each branch line is set to the same value;
A switch circuit in which an input end is connected to a power source and an output end is connected to the line. When the wake-up potential setting circuit is in an operating state, the line and the power source are electrically connected to each other. In the non-operating state of the up potential setting circuit, a switch circuit for releasing the electrical connection between the line and the power source;
And electrically connecting the line and the power source, thereby setting both potentials of the buses to the wake-up potential during the idle period, and releasing the electrical connection between the line and the power source. Thus, the communication system according to claim 1, wherein the potential of each bus during the idle period is set to the specified potential. The preliminary wake-up circuit compares the average potential of the pair of buses with a threshold potential that is predetermined in a range higher than the specified potential and lower than the wake-up potential, and the average potential is higher than the threshold potential. When the main device is waked up, the main device is woken up when the potentials of the pair of buses are approximately changed to wake-up potentials. The communication system according to claim 1 or 2, characterized in that: The node including the wake-up potential setting circuit monitors a communication signal transmitted from each node connected to the communication path after the wake-up, so that the wake-up by the wake-up signal still fails to sleep. The wake-up potential setting circuit is configured to operate upon detection of a state node and detection of the sleep state node. The communication system described. The communication system according to any one of claims 1 to 4, wherein the wake-up potential setting circuit is provided in the wake-up node. The wakeup potential setting circuit is provided in the wakeup node,
The communication system according to any one of claims 1 to 3, wherein the wake-up node is configured to operate the wake-up potential setting circuit when transmission of the wake-up signal is started.

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