JP7464634B2 - COMMUNICATION CIRCUIT, COMMUNICATION DEVICE, AND COMMUNICATION METHOD - Google Patents

Description

The present invention relates to a communication circuit and a communication method.

In a system having multiple devices, the electronic circuits that control each device may be connected by a bus, allowing communication between the devices. In such a system, the CAN (Controller Area Network) communication method, for example, is used as the communication method for the bus that connects the electronic circuits. The bus used in the CAN communication method is also called a CAN bus.

If an abnormality occurs in an electronic circuit connected to the bus, for example, the abnormal electronic circuit can be disconnected from the bus, allowing other electronic circuits to continue operating. To ensure stable operation of the entire system, it is desirable to be able to confirm in advance whether an electronic circuit will be disconnected from the network normally. For this reason, technology is being developed to confirm whether an electronic circuit can be disconnected from a network.

The automobile control device of Patent Document 1 has multiple control units connected via a bus. The automobile control device of Patent Document 1 checks for abnormalities in the control unit's disconnection function by sending signals from the other control units to the control unit to be checked via the bus.

JP 2014-91340 A

However, with the technology in Patent Document 1, it can be difficult to check for an abnormality in the network disconnection function within each control unit.

The present invention aims to provide a communication circuit etc. that can check for abnormalities in the disconnection function from the network without going through a bus.

To solve the above problems, the communication circuit of the present invention is a transceiver having a means for branching and receiving a signal to be transmitted to a bus, and is equipped with a control means for controlling the transition of the transceiver to standby mode, which transmits a high signal when transitioning to standby mode, an output means for outputting a signal for transmission to the transceiver, an input means for accepting input of a signal received by the transceiver, and a detection means for detecting the presence or absence of an abnormality in the transition to standby mode based on a signal input from the transceiver when the level of the signal for transmission is switched in a predetermined sequence after transition to standby mode.

The communication method of the present invention is a transceiver having a means for branching and receiving a signal to be transmitted to a bus, controls the transition of the transceiver to standby mode, which transmits a high signal when transitioning to standby mode, outputs a signal for transmission to the transceiver, accepts input of a signal received by the transceiver, and detects whether or not there is an abnormality in the transition to standby mode based on the signal input from the transceiver when the level of the signal for transmission is switched in a predetermined sequence after transition to standby mode.

This invention makes it possible to check for abnormalities in the network disconnection function without going through the bus.

1 is a diagram showing an outline of a configuration of a first embodiment of the present invention; FIG. 2 is a diagram illustrating an example of a configuration of a communication circuit according to a first exemplary embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a configuration of a transceiver according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating an example of signal levels according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a configuration of a transceiver according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating an example of an operation flow of the communication circuit according to the first exemplary embodiment of the present invention. FIG. 13 is a diagram showing an outline of the configuration of a second embodiment of the present invention. FIG. 11 is a diagram illustrating an example of an operation flow of a communication circuit according to a second exemplary embodiment of the present invention.

First Embodiment
A first embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a diagram showing an example of the configuration of a communication device 10 according to the present embodiment. The communication device 10 includes a communication circuit 20, a transceiver 30, and a switch 40.

The communication device 10 is connected to, for example, an electronic circuit that controls an in-vehicle device. The device controlled by the electronic circuit is not limited to an in-vehicle device. An electronic circuit that controls a device such as an in-vehicle device is also called an ECU (Electronic Control Unit). The electronic circuit is connected to, for example, the communication circuit 20 in FIG. 1. The communication device 10 is a device that transmits and receives signals between the electronic circuit and a communication device connected to the other electronic circuit when the electronic circuit communicates with the other electronic circuit. In other words, the electronic circuit communicates with the other electronic circuit via the communication function of the communication device 10.

The communication device 10 communicates with other communication systems via a bus. For example, the communication device 10 communicates with other communication devices using a CAN (Controller Area Network) communication method.

The communication device 10 has a function of disconnecting the connected electronic circuit from the network. The communication device 10 transitions the transceiver 30 to a standby mode, thereby transitioning the device to a state in which communication with other communication devices is not performed. The communication device 10 also has a function of checking whether there is an abnormality in the transition to the standby mode of the transceiver 30. The check for whether there is an abnormality in the transition to the standby mode is performed, for example, when a request for transition to the standby mode is received from the electronic circuit. The check for whether there is an abnormality in the transition to the standby mode may also be performed when a request for checking whether there is an abnormality in the transition to the standby mode is received from the electronic circuit. The check for whether there is an abnormality in the transition to the standby mode may also be performed at a preset date and time or at a preset time interval.

The configuration of the communication circuit 20 will now be described. As shown in FIG. 1, the communication circuit 20 further includes a control circuit 21 and a signal processing circuit 22.

The configuration of the control circuit 21 will be described. FIG. 2 is a diagram showing an example of the configuration of the control circuit 21. The control circuit 21 further includes a control unit 101, an output unit 102, an input unit 103, and a detection unit 104.

The control unit 101 controls the transition of the transceiver 30 to the standby mode. The transceiver 30 is a transceiver having a means for branching and receiving a signal to be transmitted to the bus. Furthermore, when the transceiver 30 transitions to the standby mode, it transmits a high signal to the bus.

When the control unit 101 transitions the transceiver 30 to the standby mode, the control unit 101 outputs a standby signal to the transceiver 30. For example, the control unit 101 outputs a signal to the transceiver 30 as a standby signal that sets the level of the signal transmitted by the transceiver 30 to High. The standby signal may be a signal of a level other than High. The signal level of the standby signal is set appropriately according to the specifications of the entire system.

The output unit 102 outputs a signal for transmission to the transceiver 30. The signal for transmission is a signal that the transceiver transmits to the bus. For example, when checking whether there is an abnormality in the transition to the standby mode, the output unit 102 outputs a signal indicating the level of the signal for transmission to the transceiver 30. The output unit 102 outputs a signal that controls the level of the signal transmitted by the transceiver 30 so that High and Low signals are transmitted from the transceiver 30 according to a predetermined sequence. The predetermined sequence is set as a sequence for checking whether there is an abnormality in the transition of the transceiver 30 to the standby mode. The predetermined sequence is, for example, information indicating the order of transmission of High and Low signals, the transmission time, and the transmission interval. The order of the signal levels High and Low is set in advance as a confirmation sequence. For example, the output unit 102 outputs a signal so that after transition to the standby mode, the signal for transmission is transmitted in the order of Low, High, and Low. The output unit 102 switches the signal between High and Low, for example, based on a request from the detection unit 104. The output unit 102 may switch the signal between High and Low at preset time intervals.

The input unit 103 accepts input of a signal received by the transceiver 30 when checking for the presence or absence of an abnormality in the transition to the standby mode. For example, when checking for the presence or absence of an abnormality in the standby mode, the input unit 103 accepts input of a signal indicating whether the signal received by the transceiver 30 is high or low. Furthermore, when checking for the presence or absence of an abnormality in the transition to the standby mode, the input unit 103 does not need to process the input signal.

The detection unit 104 detects whether there is an abnormality in the transition to the standby mode based on the signal input from the transceiver 30 when the level of the transmission signal is switched in a predetermined sequence after transition to the standby mode. That is, the detection unit 104 detects whether there is an abnormality in the transition to the standby mode based on the signal acquired by the input unit 103 indicating whether the signal received by the transceiver 30 is High or Low. The method by which the detection unit 104 checks whether there is an abnormality in the transition to the standby mode will be described later.

When the detection unit 104 starts checking for any abnormalities in the transition to the standby mode, the detection unit 104 may output a signal to start the check to the control unit 101, the output unit 102, and the input unit 103.

The detection unit 104 may output the result of the confirmation as to whether or not there is an abnormality in the transition to the standby mode to an electronic circuit connected to the communication device 10. The detection unit 104 may also output the result of the confirmation as to whether or not there is an abnormality in the transition to the standby mode to a device that manages multiple communication devices connected to the bus.

The detection unit 104 may control the switching of the switch element of the switch 40. When starting to check whether there is an abnormality in the standby mode, the detection unit 104 outputs a request to switch the switch to the switch 40. For example, when starting to check whether there is an abnormality in the standby mode, the detection unit 104 switches the switch element of the switch 40 so that the signal output from the output unit 102 is input to the transceiver 30. In addition, when the detection unit 104 outputs a request to switch the switch to the switch 40 at the start of the check, the detection unit 104 may output a request to switch the switch to the switch 40 when the check for the presence or absence of an abnormality in the standby mode is completed. For example, when the check for the presence or absence of an abnormality in the standby mode is completed, the detection unit 104 switches the switch element of the switch 40 so that the signal output from the signal processing circuit 22 is input to the transceiver 30.

This section describes an example of a method in which the detection unit 104 checks whether there is an abnormality in the transition to the standby mode. Figure 4 is a diagram that shows an example of the levels of each signal when checking whether there is an abnormality in the transition to the standby mode.

The signal processing circuit 22 converts the signal input from the electronic circuit into a signal format for transmission and outputs it to the transceiver 30. The signal processing circuit 22 converts the received signal input from the transceiver 30 into a signal format for the electronic circuit and outputs it. The signal processing circuit 22 does not need to process the input signal when the presence or absence of an abnormality in the transition of the transceiver 30 to the standby mode is being checked.

The control circuit 21 and the signal processing circuit 22 each use a semiconductor device. The control circuit 21 and the signal processing circuit 22 may use, for example, an FPGA (Field Programmable Gate Array). The control circuit 21 and the signal processing circuit 22 may be semiconductor devices other than an FPGA. The control circuit 21 and the signal processing circuit 22 may be an integrated semiconductor device. The control circuit 21 may also be, for example, a semiconductor device having a GPIO (General-purpose input/output) interface.

The configuration of the transceiver 30 will now be described. FIG. 3 is a diagram showing an example of the configuration of the transceiver 30. The transceiver 30 further includes a transmitter 31 and a receiver 32.

The transmitter 31 outputs the transmission signal input from the communication circuit 20 to the bus as a differential signal. The signal line between the transmitter 31 and the bus is branched and connected to the receiving terminal of the receiver 32. Therefore, the signal transmitted from the transmitter 31 is returned and input to the receiver 32 as well. The transmitter 31 also has an input terminal 33 for a standby signal. When a standby signal is input, the transmitter 31 transmits a high signal.

The signal to be transmitted by the transmitter 31 is input from the signal processing circuit 22 and the control circuit 21 via the switch 40. Depending on the state of the switch element of the switch 40, the signal to be transmitted by the transmitter 31 is selected and input from either the signal output by the signal processing circuit 22 or the signal output by the control circuit 21.

The receiver 32 converts the differential signal received via the bus into a bit signal and outputs it to the communication circuit 20. The signals received by the receiver 32 include the signal output by the transmitter 31. The signal output by the receiver 32 is input to the signal processing circuit 22 of the communication circuit 20 and to the input unit 103 of the control circuit 21. In addition, a switch may be provided between the receiver 32 and the signal processing circuit 22 and the control circuit 21 so that the signal output from the receiver 32 is input to only one of the signal processing circuit 22 and the control circuit 21.

The standby signal in (a) of FIG. 4 indicates the level of the standby signal output by the control unit 101 to the transceiver 30. The standby signal is output as a high signal in standby mode. The transmit signal in (b) of FIG. 4 indicates the level of the transmit signal sent by the output unit 102 to the transceiver 30. The receive signals in (c) and (d) of FIG. 4 indicate the level of the signal received by the transceiver 30 that is input to the input unit 103. (c) of FIG. 4 indicates the level of the received signal when the transition to standby mode is performed normally. (d) of FIG. 4 indicates the level of the received signal when an abnormality occurs in the transition to standby mode.

In the example of FIG. 4, when checking for anomalies begins, the output unit 102 outputs a low signal to the transceiver 30 for, for example, 100 microseconds. In the example of FIG. 4, the output unit 102 outputs a low signal to the transceiver 30 between T1 and T2. The time for which the low signal is output is not limited to 100 microseconds. The time for which the low signal is output is set, for example, to a length that can be distinguished from a normal signal. Also, if the transceiver is set with a timeout function that prevents the signal from becoming stuck at low, the length for which the low signal is output is set to be shorter than the time set for the timeout function. Also, the output unit 102 may output a high signal before outputting the low signal to prevent the timeout function from activating.

When a low signal is output for 100 microseconds, at time T2 in the example of FIG. 4, the control unit 101 outputs a standby signal to the transceiver 30. At this time, the high signal transmitted by the transmitter 31 of the transceiver 30 is returned and input to the receiver 32, so that if the transition to standby mode is normal, the signal input to the input unit 103 will be a high signal.

After the output of the standby signal has started, the output unit 102 outputs a low signal to the transceiver 30. Even if a low signal is output during standby mode, if the transition to standby mode is performed normally, the signal input to the input unit 103 indicates high. Therefore, if the signal input to the input unit 103 is low, the detection unit 104 determines that an abnormality has occurred in the transition to standby mode. The detection unit 104 detects that an abnormality has occurred in the transition to standby mode by determining that an abnormality has occurred in the transition to standby mode.

The detection unit 104 judges whether or not there is an abnormality in the transition to the standby mode when a preset time has elapsed after the output unit 102 outputs a Low signal. The detection unit 104 judges whether or not there is an abnormality in the transition to the standby mode, for example, 2 microseconds after the output unit 102 outputs a Low signal. The time from the output of the signal until the presence or absence of an abnormality is judged is not limited to 2 microseconds. The time from the output of the signal until the presence or absence of an abnormality is judged is set based on the time required for the output signal to be transmitted from the transmitter 31 of the transceiver 30, to be returned and received by the receiver 32, and for information on the level of the received signal to be input to the input unit 103. The setting of the time from the output of the signal by the output unit 102 until the detection unit 104 judges whether or not there is an abnormality is the same for the subsequent steps.

After the output unit 102 outputs a low signal, if the received signal input to the input unit 103 is high, the output unit 102 outputs a high signal at time T3 in the example of FIG. 4. The detection unit 104 determines whether or not there is an abnormality in the transition to the standby mode when a preset time has elapsed after the output unit 102 outputs a high signal. In the case of FIG. 4, the preset time is 2 microseconds. At this time, since both the standby signal and the transmission signal are high, if the transition to the standby mode is normal, the received signal will be high, as shown in FIG. 4(c). Therefore, if the signal input to the input unit 103 is low, as shown in FIG. 4(d), the detection unit 104 determines that there is an abnormality in the transition to the standby mode.

After the output unit 102 outputs a High signal, if the received signal input to the input unit 103 is High, the output unit 102 further outputs a Low signal at time T4 in the example of FIG. 4. The detection unit 104 determines whether or not there is an abnormality in the transition to the standby mode when a preset time has elapsed after the output unit 102 outputs a Low signal. At this time, since the standby signal is output, if the transition to the standby mode is normal, the received signal becomes High, as shown in FIG. 4(c). Therefore, if the signal input to the input unit 103 is Low, as shown in FIG. 4(d), the detection unit 104 determines that an abnormality has occurred in the transition to the standby mode. Also, since confirmation of each output pattern has been completed, if the signal input to the input unit 103 is High, the detection unit 104 determines that the transition to the standby mode is normal. The detection unit 104 detects that the transition to the standby mode is normal by determining that the transition to the standby mode is normal.

The transceiver may include an element that outputs a timeout signal. The timeout signal is a signal that is output when the signal becomes stuck at low to prevent the signal from becoming stuck at low.

Figure 5 shows an example of a transceiver equipped with an element that outputs a timeout signal, as transceiver 50. Transceiver 50 includes transmitter 31 and receiver 32. Time-out unit 51 outputs a high signal to transmitter 31 as a timeout signal, for example, if a low state continues for a preset period of time or longer. The duration of the low state before the timeout signal is output is set to, for example, between several hundred microseconds and several tens of milliseconds.

The switch 40 switches the signal path by switching the switch element based on a control signal input from the detection unit 104 of the control circuit 21. The switch 40 switches the switch element so that either the signal input from the control circuit 21 or the signal input from the signal processing circuit 22 is input to the transmitter 31 of the transceiver 30. The switch 40 may be formed as a switch element inside the communication circuit 20.

The operation of the communication device 10 of this embodiment when checking for an abnormality in transition to the standby mode will be described. Figure 6 is a diagram showing an example of the operation flow when the communication device 10 checks for an abnormality in transition to the standby mode.

When checking for a transition to standby mode begins, the detection unit 104 controls the switch 40 to switch the switch so that the signal output by the control circuit 21 is output to the transceiver 30 (step S101).

When the switch is changed over, the output unit 102 outputs a low signal to the transceiver 30 for a preset time (step S102). The signal output from the output unit 102 to the transceiver 30 is input to the transmitter 31. The transmitter 31 transmits a low signal to the bus based on the signal input from the output unit 102. The signal transmitted to the bus by the transmitter 31 is returned on the signal line connected to the bus and input to the receiver 32. The receiver 32 converts the received signal into a signal indicating the level of the received signal. After converting into a signal indicating the level of the received signal, the receiver 32 outputs a signal indicating the level of the received signal to the input unit 103.

After a preset time has elapsed, the output unit 102 outputs a standby signal to the transceiver 30, causing the transceiver 30 to transition to standby mode (step S103). Upon transitioning to standby mode, the transmitter 31 transmits a high signal to the bus based on the input standby signal. The signal transmitted by the transmitter 31 to the bus is returned on the signal line connected to the bus and input to the receiver 32. The receiver 32 converts the received signal into a signal indicating the level of the received signal. After converting into a signal indicating the level of the received signal, the receiver 32 outputs a signal indicating the level of the received signal to the input unit 103.

After the standby signal is output, the detection unit 104 checks the level of the received signal indicated by the signal input to the input unit 103. If the received signal input to the input unit 103 is low (No in step S104), the detection unit 104 determines that an abnormality has occurred in the transition to the standby mode (step S110).

When the level of the received signal indicated by the signal input to the input unit 103 is High (Yes in step S104), the detection unit 104 outputs a request to switch the level of the signal to be output to the output unit 102. Upon receiving the request to switch the level of the signal to be output, the output unit 102 outputs a High signal to the transceiver 30 (step S105).

The transmitter 31 of the transceiver 30 transmits a high signal to the bus based on the input high signal. The signal transmitted by the transmitter 31 to the bus is returned on a signal line connected to the bus and input to the receiver 32. The receiver 32 converts the received signal into a signal indicating the level of the received signal. After converting into a signal indicating the level of the received signal, the receiver 32 outputs the signal indicating the level of the received signal to the input unit 103.
After a preset time has elapsed since a High signal was output from output unit 102, detection unit 104 checks the level of the received signal indicated by the signal input to input unit 103. If the level of the received signal indicated by the signal input to input unit 103 is Low (No in step S106), detection unit 104 determines that an abnormality has occurred in the transition to the standby mode (step S110).

When the level of the received signal indicated by the signal input to the input unit 103 is High (Yes in step S106), the detection unit 104 outputs a request to switch the level of the signal to be output to the output unit 102. Upon receiving the request to switch the level of the signal to be output, the output unit 102 outputs a Low signal to the transceiver 30 (step S107).

The transmitter 31 of the transceiver 30 transmits a low signal to the bus based on the input low signal. At this point, since the standby signal is input, the transmitter 31 superimposes a high signal on the signal to be transmitted to the bus. Therefore, the signal transmitted by the transmitter 31 becomes a high signal. The signal transmitted by the transmitter 31 to the bus is folded back on the signal line connected to the bus and input to the receiver 32. The receiver 32 converts the received signal into a signal indicating the level of the received signal. After converting into a signal indicating the level of the received signal, the receiver 32 outputs a signal indicating the level of the received signal to the input unit 103.
After a preset time has elapsed since the output unit 102 outputted a low signal, the detection unit 104 checks the level of the received signal indicated by the signal input to the input unit 103. If the received signal indicated by the signal input to the input unit 103 is low (No in step S108), the detection unit 104 determines that an abnormality has occurred in the transition to the standby mode (step S110).

If the level of the received signal indicated by the signal input to the input unit 103 is high (Yes in step S108), the detection unit 104 determines that the transition to the standby mode has been performed normally (step S109).

For example, the detection unit 104 outputs the result of the confirmation as to whether or not the transceiver 30 has transitioned to the standby mode to an electronic circuit connected to the communication device 10. The detection unit 104 may also output the result of the confirmation as to whether or not there has been an abnormality in the transition to the standby mode to a management system that manages multiple communication devices connected to the bus.

In the communication device 10 of this embodiment, the output unit 102 of the communication circuit 20 outputs low and high signals to the transceiver 30 after transitioning to standby mode. The transceiver 30 transmits a signal for transmission based on the signal input from the output unit 102 and receives the returned signal. The transceiver 30 outputs a signal indicating the level of the received signal to the communication circuit 20. The input unit 103 of the communication circuit 20 accepts the input of the signal output by the transceiver 30. Then, the detection unit 104 detects whether there is an abnormality in the transition to standby mode based on the input signal. Therefore, the communication circuit 20 can detect whether there is an abnormality in the transition to standby mode based on the signal output by the transceiver 30. As a result, the communication circuit 20 can check whether there is an abnormality in the function of disconnecting from the network without going through a bus.

Second Embodiment
A second embodiment of the present invention will be described in detail with reference to the drawings. Fig. 7 is a diagram showing an outline of the configuration of a communication circuit 200 of this embodiment.

The communication circuit 200 includes a control unit 201, an output unit 202, an input unit 203, and a detection unit 204.

The control unit 201 is a transceiver having a means for branching and receiving a signal to be transmitted to the bus, and controls the transition of the transceiver, which transmits a High signal when transitioning to standby mode, to standby mode. The output unit 202 outputs a transmission signal to the transceiver. The input unit 203 accepts input of a signal to be received by the transceiver. The detection unit 204 detects whether there is an abnormality in the transition to standby mode based on the signal input from the transceiver when the level of the transmission signal is switched in a predetermined sequence after transition to standby mode.

Here, the control unit 101 of the first embodiment is an example of the control unit 201. Also, the control unit 201 is one aspect of the control means. The output unit 102 is an example of the output unit 202. Also, the output unit 202 is one aspect of the output means. The input unit 103 is an example of the input unit 203. Also, the input unit 203 is one aspect of the input means. The detection unit 104 is an example of the detection unit 204. Also, the detection unit 204 is one aspect of the detection means.

The operation of the communication circuit 200 will now be described. Figure 8 is a diagram showing an example of the operation flow of the communication circuit 200.

The control unit 201 is a transceiver having a means for branching and receiving a signal to be transmitted to the bus, and controls the transition of the transceiver, which transmits a high signal when transitioning to standby mode, to standby mode (step S201). The output unit 202, which controls the transition to standby mode, outputs a signal for transmission to the transceiver (step S202). After outputting the signal for transmission, the input unit 203 accepts input of a signal to be received by the transceiver (step S203). When a signal to be received by the transceiver is input, the detection unit 204 detects whether or not there is an abnormality in the transition to standby mode based on the signal input from the transceiver when the level of the signal for transmission is switched in a predetermined sequence after transition to standby mode (step S204).

The communication circuit 200 outputs a signal for transmission to a transceiver having a means for branching and receiving the signal to be transmitted to the bus. Then, the communication circuit 200 detects whether there is an abnormality in the transition to the standby mode based on the signal input from the transceiver when the signal level is switched in a predetermined sequence. Therefore, the communication circuit 200 can detect whether there is an abnormality in the transition to the standby mode based on the signal output by the communication circuit 200. As a result, the communication circuit 200 can check whether there is an abnormality in the function of disconnecting from the network without going through the bus.

REFERENCE SIGNS LIST 10 Communication device 20 Communication circuit 21 Control circuit 22 Signal processing circuit 30 Transceiver 31 Transmitter 32 Receiver 33 Input terminal 40 Switch 50 Transceiver 51 Time-out section 101 Control section 102 Output section 103 Input section 104 Detection section 200 Communication circuit 201 Control section 202 Output section 203 Input section 204 Detection section

Claims (10)

a control means for controlling the transition of the transceiver to a standby mode, the control means transmitting a high signal when the transceiver transitions to the standby mode;
an output means for outputting a signal for transmission to the transceiver;
an input means for receiving an input of a signal to be received by the transceiver;
and a detection means for detecting whether or not there is an abnormality in the transition to the standby mode based on a signal input from the transceiver when the level of the transmission signal is switched in a predetermined sequence after the transition to the standby mode. the detection means detects an abnormality in the transition to the standby mode when a signal input from the transceiver is Low after the transition to the standby mode.
2. The communication circuit according to claim 1. the predetermined sequence is set as an order of switching between High and Low levels of the transmission signal after transition to the standby mode,
the detection means detects that the transition to the standby mode has been performed normally when the signal input from the transceiver is High, regardless of whether it is High or Low;
3. A communication circuit according to claim 1 or 2. the predetermined sequence is a setting for outputting signals to the transceiver in the order of low, high, and low after transition to the standby mode;
4. The communication circuit according to claim 3. A switching unit is further provided for switching a path of a signal to be output to the transceiver.
the detection means controls the switching means to switch the signal path to a path for outputting either a signal for detecting the presence or absence of an abnormality in the transition to the standby mode or a signal to be transmitted via the bus.
A communication circuit according to any one of claims 1 to 4. The bus is a Controller Area Network bus.
A communication circuit according to any one of claims 1 to 5. a transceiver having a transmitting means for transmitting a signal to a bus and for transmitting a High signal when a transition to a standby mode is made, and a receiving means for receiving a signal transmitted on the bus and a signal obtained by branching off the signal transmitted by the transmitting means;
A communication circuit according to any one of claims 1 to 6,
the communication circuit detects whether or not there is an abnormality in the transition to the standby mode based on a signal received by the receiving means of the transceiver after the transceiver has transitioned to the standby mode.
Communication device. a transceiver having a means for branching and receiving a signal to be transmitted to a bus, the transceiver transmitting a High signal when transitioning to a standby mode being controlled;
outputting a signal for transmission to the transceiver;
Accepting an input of a signal to be received by the transceiver;
detecting whether or not there is an abnormality in the transition to the standby mode based on a signal input from the transceiver when the level of the transmission signal is switched in a predetermined sequence after the transition to the standby mode;
Communication method. when a signal input from the transceiver is low after the transition to the standby mode, an abnormality in the transition to the standby mode is detected;
The communication method according to claim 8. the predetermined sequence is set as an order of switching the level of the transmission signal between High and Low after transition to the standby mode, and when the signal input from the transceiver is High in both the High and Low states, it is detected that transition to the standby mode has been performed normally.
10. A communication method according to claim 8 or 9.

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