JP2011244264A - Communication apparatus and method of canceling sleep state of communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cancel a sleep state of a node of which the sleep state is not canceled by a wake-up signal, without providing a node with means for detecting the node of which the sleep state is not canceled or means for transmitting a special signal pattern via a communication bus.SOLUTION: In a communication system, each of a plurality of ECUs 100 is configured to transmit/receive a frame via a communication bus 10, and in accordance with a wake-up signal transmitted from the ECU 100 of which the sleep state is canceled by an internal event, the sleep state of the other ECU 100 is canceled. The ECU 100 includes a frame detection circuit 130 which outputs a high-level signal in the case where a signal level of the communication bus 10 changes continuously specific times or more at intervals not exceeding a specific time. In the case where the high-level signal is outputted from the frame detection circuit 130 to an external interrupt terminal of a microcomputer 110, the microcomputer 110 cancels the sleep state of the relevant ECU 100.

Description

  The present invention relates to a communication device that functions as a node in a communication system configured such that a plurality of nodes can transmit and receive frames via a communication bus, and a sleep state canceling method for such a communication device.

  Conventionally, as a communication system of this type, a node is in a sleep state (a low power consumption state in which a clock or partial power supply is stopped) in a situation where communication is not necessary. One configured to cancel the sleep state is known.

  For example, a node of a communication system using FlexRay (registered trademark) as a communication protocol is released from a sleep state by an internal event in response to a switch operation or the like and transitions to a normal operation state (wakes up), and other nodes Send a wake-up signal. Then, the other nodes receive the wake-up signal to cancel the sleep state and shift to the normal operation state (wake up). In this way, when the node is released from the sleep state and transits to the normal operation state, frame transmission / reception via the communication bus is started.

  However, in such a communication system, a node that cannot normally receive a wake-up signal from another node due to a temporary factor such as noise mixing or voltage fluctuation will remain in a sleep state. .

  Thus, a communication system has been proposed in which a node has a function of canceling a sleep state of a node whose sleep state has not been canceled by a wake-up signal from another node (see Patent Document 1). Specifically, the node of the communication system stores information related to the other node in the internal memory, and the node that has not been released from the sleep state based on the frame transmitted from the other node via the communication bus ( The presence of an unwakened node is detected. When the presence of an unwakened node is detected, a pseudo wakeup signal having the same pattern as the wakeup signal is communicated during the network idle time during which no frame transfer is performed in the communication cycle. Send over the bus. Thereby, it becomes possible to cancel the sleep state of the node whose sleep state has not been canceled by the wakeup signal.

JP 2008-42888 A

  However, in the configuration described in Patent Document 1 described above, a special signal pattern (pseudo wakeup signal) is communicated at a timing different from the communication protocol stipulations or means for detecting the presence of a node whose sleep state has not been released. Since it is necessary to provide the node with means for transmitting via the bus, the configuration of the node becomes complicated.

  The present invention has been made in view of these problems, and without providing a node with a means for detecting the presence of a node whose sleep state has not been released or a means for transmitting a special signal pattern via a communication bus. An object of the present invention is to provide a communication device and a communication device sleep state canceling method that can cancel a sleep state of a node whose sleep state has not been canceled by a wakeup signal.

  The communication device according to claim 1 of the present invention made to achieve the above object is configured such that a plurality of nodes are configured to be able to transmit and receive frames via a communication bus, and from a node whose sleep state is canceled by an internal event. It functions as a node in a communication system in which a sleep state of another node is canceled by a transmitted wakeup signal.

  The communication device includes a detection circuit that outputs a specific signal when the signal level of the communication bus continuously changes a specified number of times at intervals not exceeding the specified time, and the detection circuit outputs a specific signal. In the case of being canceled, the canceling unit cancels the sleep state of the communication device.

  That is, this communication apparatus is configured to be released from the sleep state when the signal level of the communication bus changes continuously a predetermined number of times at intervals not exceeding the predetermined time. For this reason, even when the sleep state is not canceled by the wake-up signal, the sleep state can be canceled by starting transmission of a normal data communication signal (frame) via the communication bus. It becomes possible.

  Therefore, according to the communication system in which such a communication device functions as a node, the sleep state of the node whose sleep state has not been canceled by the wakeup signal can be canceled. In addition, since it is only necessary to add a detection circuit, it is not necessary to provide the node with a means for detecting the presence of a node whose sleep state has not been canceled or a means for transmitting a special signal pattern via the communication bus.

  On the other hand, if the signal level of the communication bus does not change continuously for a specified number of times at an interval that does not exceed the specified time, the sleep state is not canceled, so a communication bus with noise pulses that can occur transiently when communication is not started It is possible to prevent the sleep state from being canceled due to a change in the signal level.

  By the way, the prescribed time may be set to a time longer than the longest time in which the signal level allowed in the frame does not change, as described in claim 2, for example. In this way, it can be prevented that the change is not detected as a continuous change when the signal level does not change in the frame for a long time.

  Further, the specified number of times may be set to be equal to or less than the minimum change number of the signal level included in the frame, for example, as described in claim 3. In this way, it is possible to cancel the sleep state by transmitting one frame via the communication bus. In particular, if the specified time is set to a time longer than the longest time that the signal level allowed for the frame does not change as described in claim 2, one frame is transmitted via the communication bus. The sleep state can be canceled without fail.

  Next, according to a fourth aspect of the present invention, there is provided a method for canceling a sleep state of a communication apparatus, wherein a plurality of nodes are configured to be able to transmit and receive frames via a communication bus, and are transmitted from a node whose sleep state is canceled by an internal event In a communication system in which a sleep state of another node is canceled by an up signal, the sleep state of a node whose sleep state has not been canceled by a wakeup signal from another node is canceled. In this sleep state cancellation method, the sleep state is canceled when the signal level of the communication bus continuously changes a predetermined number of times at intervals not exceeding the predetermined time.

  According to such a sleep state canceling method, it is possible to obtain the same effect as that of the communication system in which the communication device according to claim 1 functions as a node.

It is a block diagram showing the schematic structure of the communication system of embodiment. It is a timing chart showing circuit operation of ECU. It is explanatory drawing showing the frame format of FlexRay (trademark).

Hereinafter, an embodiment in which the present invention is applied to an in-vehicle communication system using FlexRay (registered trademark) as a communication protocol will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a schematic configuration of a communication system according to an embodiment.

  In this communication system, a plurality of electronic control units (hereinafter referred to as “ECUs”) 100, 100,... Mounted on a vehicle are configured to be able to transmit and receive frames via a communication bus 10. It functions as a node (communication device). The communication bus 10 used in this communication system is a two-wire type comprising two communication lines, and a differential signal (data communication) expressing a signal level of “0” or “1” by a potential difference between the two lines. Signal) is transmitted and received between the ECUs 100. 1, the circuit configuration is shown for only one of the plurality of ECUs 100, 100,..., But this circuit configuration is common to all the ECUs 100.

As shown in FIG. 1, the ECU 100 includes a microcomputer 110, a transceiver 120, and a frame detection circuit 130.
The microcomputer 110 executes processing for communication control. The communication circuit 111 is built in the microcomputer 110, and the TxD output port and the RxD input port of the communication circuit 111 are connected to the TxD input port and the RxD output port of the transceiver 120, respectively. The external interrupt terminal of the microcomputer 110 is connected to the frame detection circuit 130.

  The transceiver 120 functions as an interface between the communication bus 10 and the microcomputer 110. Specifically, the transceiver 120 converts a transmission signal (TxD signal) input from the TxD input port into a differential signal and outputs the differential signal to the communication bus 10, and receives the differential signal input from the communication bus 10 as a reception signal ( RxD signal) and output from the RxD output port.

  The frame detection circuit 130 receives a reception signal output from the RxD output port of the transceiver 120, and outputs a high-level signal to an external interrupt terminal of the microcomputer 110 at a specific timing based on this reception signal. Specifically, the frame detection circuit 130 includes a buffer 131, an XOR circuit 132, a diode 133, a capacitor 134, a resistor 135, an inverting circuit 136, and a counter 137.

  The XOR circuit 132 receives a reception signal output from the RxD output port of the transceiver 120 and a delay signal obtained by delaying the reception signal by the buffer 131. The anode of the diode 133 is connected to the output side of the XOR circuit 132, and a capacitor 134 and a resistor 135 are connected in parallel between the cathode of the diode 133 and the ground. An envelope detection circuit is configured by the resistor 135.

  In addition, an inverting circuit 136 is connected to the cathode of the diode 133, and an output signal of the envelope detection circuit (hereinafter referred to as “detection signal”) is inverted by the inverting circuit 136 and then input to the counter 137. The inverting circuit 136 outputs a low level signal when the level of the detection signal is equal to or higher than the threshold potential Vth, and outputs a high level signal when it is lower than the threshold potential Vth.

  On the other hand, the counter 137 receives the output signal from the XOR circuit 132 as a clock and counts the number of pulses. A signal of the fifth bit (Q4 shown in FIG. 1) of the count value is input to the external interrupt terminal of the microcomputer 110. That is, when the count value reaches “16”, a high level signal is output from the counter 137 to the external interrupt terminal of the microcomputer 110. The counter 137 receives the output signal of the inverting circuit 136 as a clear signal, and clears the count value to 0 when a high level signal is input from the inverting circuit 136.

Next, a flow when the ECU 100 transitions from the sleep state to the normal operation state (wakes up) in the communication system of the present embodiment will be described.
The ECU 100 in the sleep state is released from the sleep state by an internal event corresponding to a switch operation performed by a vehicle occupant, and transitions to the normal operation state. Then, ECU 100 whose sleep state has been canceled by an internal event transmits a wake-up signal to another ECU 100 via communication bus 10.

  On the other hand, when the ECU 100 in the sleep state receives a wake-up signal from another ECU 100 via the communication bus 10, the sleep state is canceled and the ECU 100 transitions to the normal operation state. Specifically, in the ECU 100 in the sleep state, the microcomputer 110 accepts only the wake-up signal for the reception signal input from the RxD input port, and the wake-up signal from the other ECU 100 passes through the transceiver 120. To cancel the sleep state.

  That is, when any one ECU 100 in the communication system transitions from the sleep state to the normal operation state due to an internal event, the other ECU 100 also transitions from the sleep state to the normal operation state by the wakeup signal transmitted by the ECU 100.

  However, if the ECU 100 in the sleep state cannot normally receive the wakeup signal due to temporary factors such as noise or voltage fluctuation, the sleep state may not be released and communication may not start.

  Therefore, in the communication system of the present embodiment, the ECU 100 does not normally receive the wake-up signal due to a temporary factor, and even when the sleep state is not released, the other ECU 100 performs normal data communication signals (frames). ) Is started, the sleep state is canceled. Hereinafter, the circuit operation of the ECU 100 in which the sleep state has not been canceled because the wakeup signal cannot be normally received will be described with reference to the timing chart of FIG.

  Even in the sleep state, the transceiver 120 converts the differential signal input from the communication bus 10 into a received signal and outputs the received signal from the RxD output port. FIG. 2 shows an example in which a low level or high level reception signal (a logic signal of “0” or “1”) is output depending on the presence or absence of a potential difference between two wires of the communication bus 10. It is not limited to.

  The reception signal output from the transceiver 120 is input to the microcomputer 110 and the frame detection circuit 130. However, as described above, the microcomputer 110 in the sleep state has received signals other than the wake-up signal from the RxD input port. Does not accept signals.

  On the other hand, in the frame detection circuit 130, a reception signal from the transceiver 120 and a delay signal obtained by delaying the reception signal by the buffer 131 are input to the XOR circuit 132, and an edge signal that is an exclusive OR of these signals is output. . That is, an edge signal that becomes high level at the timing when the signal level of the communication bus 10 changes is output from the XOR circuit 132.

  The edge signal from the XOR circuit 132 is input to an envelope detection circuit constituted by a diode 133, a capacitor 134 and a resistor 135. In this envelope detection circuit, the capacitor 134 is charged while the edge signal is at a high level, and the charge charged in the capacitor 134 is gradually passed through the resistor 135 while the edge signal is at a low level. Discharged. For this reason, the detection signal output from the envelope detection circuit increases when the signal level of the communication bus 10 changes, and gradually decreases when the signal level of the communication bus 10 does not change.

  The detection signal is inverted by the inverting circuit 136 and then input to the counter 137. As described above, the output signal (inverted signal) of the inverting circuit 136 is low when the level of the detection signal is equal to or higher than the threshold potential Vth, and is high when the level of the detection signal is lower than the threshold potential Vth. Become a level.

  On the other hand, the edge signal from the XOR circuit 132 is also input to the counter 137, and the counter 137 counts the number of pulses of the edge signal. When the count value reaches “16”, a high level signal is output to the external interrupt terminal of the microcomputer 110. In the counter 137, the count value is cleared to 0 when the output signal (inverted signal) from the inverting circuit 136 becomes high level.

  That is, when the change in the signal level of the communication bus 10 continues 16 times or more at an interval where the level of the detection signal does not fall below the threshold potential Vth, the high level is output from the frame detection circuit 130 to the external interrupt terminal of the microcomputer 110. Is output. Thereby, the microcomputer 110 cancels the sleep state of the ECU 100 and makes a transition to the normal operation state.

  In this frame detection circuit 130, the time from when the detection signal rises to a high level until it falls below the threshold potential Vth is set to a time longer than the longest time that the signal level allowed for the frame does not change. Has been. In addition, the count value (16 in this embodiment) that sets the output to the external interrupt terminal to a high level is set to a value that is less than or equal to the minimum value of the number of signal level changes assumed in one frame. For this reason, when a normal frame is transmitted from the other ECU 100 via the communication bus 10, a high level signal is always output from the frame detection circuit 130 to the external interrupt terminal of the microcomputer 110.

  Here, the minimum value of the number of changes in the signal level included in the frame transmitted from the ECU 100 in the communication system according to the present embodiment will be described by taking a case where the payload segment is 0 bytes as an example.

  As shown in FIG. 3, in the FlexRay (registered trademark) frame format, a frame is composed of a 5-byte header segment, a 0-254 byte payload segment, and a 3-byte trailer segment. Therefore, the frame length when the payload segment is 0 byte is 8 bytes.

  When this frame is transmitted through the communication circuit 111 of the microcomputer 110, TSS (transmission start sequence), FSS (frame start sequence), FES (frame end) are encoded by the communication circuit 111 as shown in FIG. Sequence) and a signal with BSS (byte start sequence) added for each byte. For this reason, even if all the data in the frame is “0” or all “1”, the number of changes in the signal level in this frame is “18”. That is, the signal level changes at least 18 times in one frame.

In the communication system of the present embodiment, the longest time that the signal level allowed in the frame does not change is 9 bit time.
For this reason, in the frame detection circuit 130 of this embodiment, the time from when the detection signal rises to a high level until it falls below the threshold potential Vth is set longer than 9 bit time (for example, 10 bit time). In addition, the count value for setting the output to the external interrupt terminal to the high level is set to a value of 18 or less (16 in this embodiment). In this embodiment, the count value for setting the output to the external interrupt terminal to high level is 16 in order to make it difficult to cancel the sleep state due to temporary factors such as noise. The value is set as large as possible. That is, even if a transient noise pulse is detected as a change in the signal level of the communication bus 10, it is unlikely that a large number of changes will be detected continuously, and the state in which the signal level does not change has a predetermined interval. If exceeded, the count value of the counter 137 is cleared to 0, so that the sleep state is prevented from being canceled due to temporary factors such as noise.

  As described above, the ECU 100 functioning as a node in the communication system according to the present embodiment outputs a high-level signal when the signal level of the communication bus 10 continuously changes a specified number of times at intervals not exceeding the specified time. A frame detection circuit 130 is provided. When a high level signal is output from the frame detection circuit 130 to the external interrupt terminal of the microcomputer 110, the microcomputer 110 cancels the sleep state of the ECU 100.

  In particular, in the present embodiment, the specified time is set to a time longer than the longest time that the signal level allowed for the frame does not change (in this embodiment, 10 bit time), and the signal that includes the specified number of times in the frame. It is set to be equal to or less than the minimum level change number (in this embodiment, 16 times).

  Therefore, even when the sleep state is not canceled by the wake-up signal, the ECU 100 is released from the sleep state by starting transmission of a normal data communication signal (frame) via the communication bus 10.

  Therefore, according to the communication system of the present embodiment in which the ECU 100 functions as a node, the sleep state of the node whose sleep state has not been canceled by the wakeup signal can be canceled. In addition, since it is only necessary to add the frame detection circuit 130 to the configuration of the communication device that realizes the prescribed communication protocol, means for detecting the presence of the ECU 100 whose sleep state has not been released, and a special signal pattern are provided. There is no need to provide the ECU 100 with means for transmitting via the communication bus 10.

  On the other hand, if the signal level of the communication bus 10 does not change continuously for a specified number of times at intervals that do not exceed the specified time, the sleep state is not released, so communication using noise pulses that can occur transiently when communication is not started It is possible to prevent the sleep state from being canceled due to a change in the signal level of the bus 10.

  In the communication system of this embodiment, the ECU 100 corresponds to the communication device (node) of the present invention, the frame detection circuit 130 corresponds to the detection circuit of the present invention, and the microcomputer 110 corresponds to the release means of the present invention.

As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention can take a various form, without being limited to the said embodiment.
For example, in the above embodiment, the frame detection circuit 130 is provided separately from the microcomputer 110 and the transceiver 120. However, the present invention is not limited to this, and the frame detection circuit 130 can be built in the microcomputer 110 and the transceiver 120. is there.

  In addition, the present invention can be applied to various communication protocols other than FlexRay (registered trademark). For example, in the case of CAN, the maximum time during which the signal level allowed for a frame does not change is 5 bit times, and therefore the time from when the detection signal rises to a high level until it falls below the threshold potential Vth is 5 bit times. It may be set longer (for example, 6 bit time).

  DESCRIPTION OF SYMBOLS 10 ... Communication bus, 100 ... ECU, 110 ... Microcomputer, 111 ... Communication circuit, 120 ... Transceiver, 130 ... Frame detection circuit, 131 ... Buffer, 132 ... XOR circuit, 133 ... Diode, 134 ... Capacitor, 135 ... Resistance, 136 ... Inversion circuit, 137 ... Counter

Claims (4)

In a communication system in which a plurality of nodes are configured to be able to transmit and receive frames via a communication bus, and a sleep state of another node is canceled by a wakeup signal transmitted from a node whose sleep state is canceled by an internal event. A communication device that functions as:
A detection circuit that outputs a specific signal when the signal level of the communication bus continuously changes a specified number of times at intervals not exceeding a specified time;
Cancellation means for canceling the sleep state of the communication device when the specific signal is output by the detection circuit;
A communication apparatus comprising: The communication apparatus according to claim 1, wherein the specified time is set to a time longer than a longest time during which the signal level allowed in the frame does not change. The communication apparatus according to claim 1, wherein the specified number of times is set to be equal to or less than a minimum number of signal level changes included in the frame. In a communication system in which a plurality of nodes are configured to be able to transmit and receive frames via a communication bus, and a sleep state of another node is canceled by a wakeup signal transmitted from a node whose sleep state is canceled by an internal event. A method for canceling a sleep state of a node whose sleep state has not been canceled by a wake-up signal from the node,
A method for canceling a sleep state of a communication device, wherein the sleep state is canceled when the signal level of the communication bus changes continuously a predetermined number of times at intervals not exceeding a predetermined time.

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