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DE-112017004406-B4 - COMMUNICATION SYSTEM, COMMUNICATION DEVICE, FORWARDING DEVICE, COMMUNICATION IC, CONTROL IC AND COMMUNICATION METHOD

DE112017004406B4DE 112017004406 B4DE112017004406 B4DE 112017004406B4DE-112017004406-B4

Abstract

Communication system in which several communication devices (1, 301, 401, 510) are interconnected via a two-wire bus (10), wherein the communication devices (1, 301, 401, 510) are configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, wherein the first line (10a) and the second line (10b) are connected to a common potential via their respective first resistors (R21, R22), each of the communication devices (1, 301, 401, 510) has: a communication processing unit (21) for generating a message to be sent and for sequentially outputting binary information that constitutes the generated message; and a first switch (SW1) configured to be switched between a closed and an open state based on the binary information output by the communication processing unit (21) and to bring the bus (10) into the first state by connecting the first line (10a) to a first potential that is greater than the common potential and by connecting the second line (10b) to a second potential that is less than the common potential, at least one communication device (1, 301, 401, 510) has an anomaly detection unit (22) for detecting an anomaly in a message sent on the bus (10), and characterized by the fact that at least two communication devices (1, 301, 401, 510) including at least one communication device (1, 301, 401, 510): a switching control unit (4) for switching, if the anomaly detection unit (22) has detected an anomaly, the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) configured to switch between a closed and an open state based on the binary information output by the communication processing unit (21), if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state by connecting the first line (10a) and the second line (10b) via a second resistor (R41).

Inventors

  • Masayuki Inoue

Assignees

  • AUTONETWORKS TECHNOLOGIES, LTD.
  • SUMITOMO WIRING SYSTEMS, LTD.
  • SUMITOMO ELECTRIC INDUSTRIES, LTD.

Dates

Publication Date
20260513
Application Date
20170824
Priority Date
20160902

Claims (20)

  1. A communication system in which several communication devices (1, 301, 401, 510) are interconnected via a two-wire bus (10), wherein the communication devices (1, 301, 401, 510) are configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R21, R22), each of the communication devices (1, 301, 401, 510) comprises: a communication processing unit (21) for generating a message to be sent and for sequentially outputting binary information that represents the generated Form a message; and a first switch (SW1) configured to switch between a closed and an open state based on the binary information output by the communication processing unit (21) and to bring the bus (10) into the first state by connecting the first line (10a) to a first potential greater than the common potential and by connecting the second line (10b) to a second potential less than the common potential, at least one communication device (1, 301, 401, 510) comprising an anomaly detection unit (22) for detecting an anomaly in a message transmitted on the bus (10), and characterized in that at least two communication devices (1, 301, 401, 510), including the at least one communication device (1, 301, 401, 510), comprise: a switching control unit (4) for switching if the anomaly detection unit (22) detects an anomaly has the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) which is configured to be switched between a closed and an open state based on the binary information output by the communication processing unit (21) if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state by connecting the first line (10a) and the second line (10b) via a second resistor (R41).
  2. Communication system according to Claim 1 , where the first switch (SW1) connects the first line (10a) to the first potential that is greater than the common potential, connects and connects the second line (10b) to the second potential, which is smaller than the common potential, if a value of the binary information output by the communication processing unit (21) is a first value, and the first switch (SW1) disconnects the first line (10a) from the first potential and disconnects the second line (10b) from the second potential, if the value of the binary information output by the communication processing unit (21) is a second value, and the second switch (SW2) disconnects the first line (10a) and the second line (10b) from each other, if the anomaly detection unit (22) has not detected an anomaly, the second switch (SW2) connects the first line (10a) and the second line (10b) via the second resistor (R41), if the anomaly detection unit (22) has detected an anomaly and the value of a message to be sent is the first value, and the second switch (SW2) connects the first line (10a) and the second line (10b) separates from each other if the anomaly detection unit (22) has detected an anomaly and the value of the message to be sent is the second value.
  3. Communication system according to Claim 1 or 2 , wherein the at least two communication devices (1, 301, 401, 510) have an output destination switching unit (4) for switching the output destination of the binary information output by the communication processing unit (21) to the first switch (SW1) if the anomaly detection unit (22) has not detected an anomaly, and to the second switch (SW2) if the anomaly detection unit (22) has detected an anomaly.
  4. Communication system according to one of the Claims 1 until 3 , wherein each of the communication devices (1, 301, 401, 510) has a comparator (31) for comparing the potential of the first line (10a) with the potential of the second line (10b) and for outputting a value corresponding to the potential difference, wherein the communication device (1, 301, 401, 510) that receives a message from the communication processing unit (21) receives the value output from the comparator (31), and the at least two communication devices (1, 301, 401, 510) have an inverter (61) for inverting the logic of the value output from the comparator (31) and for receiving a message from the communication processing unit (21) that receives a value output from the inverter (61) if the anomaly detection unit (22) has detected an anomaly.
  5. Communication system according to one of the Claims 1 until 4 , wherein the at least one communication device (1, 301, 401, 510) comprising the anomaly detection unit (22) comprises an anomaly notification unit for notifying another communication device (1, 301, 401, 510) of the anomaly if the anomaly detection unit (22) has detected an anomaly.
  6. Communication system according to one of the Claims 1 until 5 , wherein the at least two communication devices (1, 301, 401, 510) comprise a communication IC (3, 303, 603) comprising the first switch (SW1), the second switch (SW2) and the switching control unit (4).
  7. Communication system according to one of the Claims 1 until 5 , wherein the at least two communication devices (1, 301, 401, 510) include a control IC (2, 402, 502) comprising the communication processing unit (21), the second switch (SW2) and the switching control unit (4).
  8. Communication system according to one of the Claims 1 until 7 , wherein several buses (10) are connected to the at least one communication device (1, 301, 401, 510) and the at least one communication device (1, 301, 401, 510) has a forwarding device (510) for forwarding a message between the buses (10).
  9. A communication system in which several communication devices (1, 301, 401, 510) are interconnected via a two-wire bus (10), wherein the communication devices (1, 301, 401, 510) are configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R21, R22), each of the communication devices (1, 301, 401, 510) comprises: a communication processing unit (21) for generating a message to be sent and for sequentially outputting binary information that represents the generated form a message; and a first switch (SW1) that is configured based on the binary information output by the communication processing unit (21). to be switched between a closed and an open state and to bring the bus (10) into the first state by connecting the first line (10a) to a first potential that is greater than the common potential and by connecting the second line (10b) to a second potential that is less than the common potential, at least one communication device (1, 301, 401, 510) has an anomaly detection unit (22) for detecting an anomaly in a message sent on the bus (10), and characterized in that at least two communication devices (1, 301, 401, 510) including the at least one communication device (1, 301, 401, 510) have: a switching control unit (4) for switching, if the anomaly detection unit (22) has detected an anomaly, the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) configured to be switched between a closed and an open state based on the binary information output by the communication processing unit (21) if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state by connecting the first line (10a) to the second potential and the second line (10b) to the first potential.
  10. Communication system according to Claim 9 , wherein the at least two communication devices (1, 301, 401, 510) comprise a first communication IC (3) comprising the first switch (SW1) and a second communication IC (603) comprising the second switch (SW2).
  11. Communication system according to Claim 10 , wherein each of the communication devices (1, 301, 401, 510) has at least one comparator (31) for comparing the potential of the first line (10a) with the potential of the second line (10b) and for outputting a value corresponding to the potential difference, wherein the communication device (1, 301, 401, 510) that receives a message from the communication processing unit (21) receives the value output from the comparator (31), and the first communication IC (3) and the second communication IC (603) have the respective comparators (31), the at least two communication devices (1, 301, 401, 510) have an inverter (61) for inverting the logic of the value output from the comparator (31) of the second communication IC (603), and the at least two communication devices (1, 301, 401, 510) are configured to: receive a message from the communication processing unit (21) that receives a value output by the comparator (31) of the first communication IC (3) if the anomaly detection unit (22) has not detected an anomaly, and receive a message from the communication processing unit (21) that receives a value output by the inverter (61) if the anomaly detection unit (22) has detected an anomaly.
  12. A communication system in which several communication devices (1, 301, 401, 510) are interconnected via a two-wire bus (10), wherein the communication devices (1, 301, 401, 510) are configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R21, R22), each of the communication devices (1, 301, 401, 510) comprises: a communication processing unit (21) for generating a message to be sent and for sequentially outputting binary information that represents the generated Form a message; and a first switch (SW1) configured to switch between a closed and an open state based on the binary information output by the communication processing unit (21) and to bring the bus (10) into the first state by connecting the first line (10a) to a first potential greater than the common potential and by connecting the second line (10b) to a second potential less than the common potential, at least one communication device (1, 301, 401, 510) comprising an anomaly detection unit (22) for detecting an anomaly in a message transmitted on the bus (10), and characterized in that at least two communication devices (1, 301, 401, 510), including the at least one communication device (1, 301, 401, 510), comprise: a switching control unit (4) for switching if the anomaly detection unit (22) detects an anomaly has, of the first switch (SW1) such that the first line (10a) is connected to the first potential is connected and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) which is configured to be switched between a closed and an open state on the basis of the binary information output by the communication processing unit (21) if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state.
  13. Communication device (1, 301, 401, 510) to which a two-wire bus (10) is connected and which is configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R21, R22) and the communication device (1, 301, 401, 510) comprises: a communication processing unit (21) for generating a message to be sent and for sequentially outputting binary information that constitutes the generated message; a first switch (SW1) configured to be switched between a closed and an open state based on the binary information output by the communication processing unit (21) and to bring the bus (10) into the first state by connecting the first line (10a) to a first potential greater than the common potential and by connecting the second line (10b) to a second potential less than the common potential; and an anomaly detection unit (22) for detecting an anomaly in a message sent on the bus (10), characterized in that the communication device (1, 301, 401, 510) further comprises: a switching control unit (4) for switching, if the anomaly detection unit (22) has detected an anomaly, the first switch (SW2) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) configured to switch between a closed and an open state based on the binary information output by the communication processing unit (21) if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state by connecting the first line (10a) and the second line (10b) via a second resistor (R41).
  14. Communication device (1, 301, 401, 510) to which a two-wire bus (10) is connected and which is configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R21, R22) and the communication device (1, 301, 401, 510) comprises: a communication processing unit (21) for generating a message to be sent and for sequentially outputting binary information that constitutes the generated message; and a first switch (SW1) configured to switch between a closed and an open state based on the binary information output by the communication processing unit (21) and to bring the bus (10) into the first state by connecting the first line (10a) to a first potential greater than the common potential and by connecting the second line (10b) to a second potential less than the common potential, an anomaly detection unit (22) for detecting an anomaly in a message transmitted on the bus (10), characterized in that the communication device (1, 301, 401, 510) further comprises a switching control unit (4) for switching, if the anomaly detection unit (22) has detected an anomaly, the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby opening the bus (10) is brought into the first state; and a second switch (SW2) configured to be switched between a closed and an open state based on the binary information output by the communication processing unit (21) if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state by connecting the first line (10a) to the second potential and connecting the second line (10b) to the first potential.
  15. Communication device (1, 301, 401, 510) to which a two-wire bus (10) is connected and which is configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R21, R22) and the communication device (1, 301, 401, 510) comprises: a communication processing unit (21) for generating a message to be sent and for sequentially outputting binary information that constitutes the generated message; a first switch (SW1) configured to be switched between a closed and an open state based on the binary information output by the communication processing unit (21) and to bring the bus (10) into the first state by connecting the first line (10a) to a first potential greater than the common potential and by connecting the second line (10b) to a second potential less than the common potential; and an anomaly detection unit (22) for detecting an anomaly in a message transmitted on the bus (10), characterized in that the communication device (1, 301, 401, 510) further comprises: a switching control unit (4) for switching, if the anomaly detection unit (22) has detected an anomaly, the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) configured to switch between a closed and an open state based on the binary information output by the communication processing unit (21), if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state.
  16. A forwarding device (510) to which several two-wire buses (10) are connected and which is configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, and to forward the message between the buses (10), wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R21, R22), and the forwarding device (510) comprises: a forwarding processing unit (521) for receiving a message and forwarding the received message by generating a message to be sent and sequentially outputting binary information that constitutes the generated message; a first switch (SW1) configured to be switched between a closed and an open state based on the binary information output by the forwarding processing unit (521) and to bring the corresponding bus (10) into the first state by connecting the first line (10a) to a first potential greater than the common potential and by connecting the second line (10b) to a second potential less than the common potential; and an anomaly detection unit (22) for detecting an anomaly in a message sent on the bus (10), characterized in that the forwarding device (510) further comprises: a switching control unit (4) for switching, if the anomaly detection unit (22) has detected an anomaly, the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) configured to switch between a closed and an open state based on the binary information output by the forwarding processing unit (521) if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state by connecting the first line (10a) and the second line (10b) via a second resistor (R41).
  17. Forwarding device (510) to which several two-wire buses (10) are connected and which is configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that forms the message, and to forwarding the message between the buses (10), wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R41) and the forwarding device (510) comprises: a forwarding processing unit (521) for receiving a message and forwarding the received message by generating a message to be sent and sequentially outputting binary information that constitutes the generated message; a first switch (SW1) configured to be switched between a closed and an open state based on the binary information output by the forwarding processing unit (521) and to bring the corresponding bus (10) into the first state by connecting the first line (10a) to a first potential that is greater than the common potential and by connecting the second line (10b) to a second potential that is less than the common potential; and an anomaly detection unit (22) for detecting an anomaly in a message sent on the bus (10), characterized in that the forwarding device (510) further comprises: a switching control unit (4) for switching, if the anomaly detection unit (22) has detected an anomaly, the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) configured to switch between a closed and an open state based on the binary information output by the forwarding processing unit (521) if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state by connecting the first line (10a) to the second potential and connecting the second line (10b) to the first potential.
  18. A forwarding device (510) to which several two-wire buses (10) are connected and which is configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that constitutes the message, and to forward the message between the buses (10), wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R21, R22), and the forwarding device (510) comprises: a forwarding processing unit (521) for receiving a message and forwarding the received message by generating a message to be sent and sequentially outputting binary information that constitutes the generated message; a first switch (SW1) configured to be switched between a closed and an open state based on the binary information output by the forwarding processing unit (521) and to bring the corresponding bus (10) into the first state by connecting the first line (10a) to a first potential greater than the common potential and by connecting the second line (10b) to a second potential less than the common potential; and an anomaly detection unit (22) for detecting an anomaly in a message transmitted on the bus (10), characterized in that the forwarding device (510) further comprises a switching control unit (4) for switching, if the anomaly detection unit (22) has detected an anomaly, the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and a second switch (SW2) configured to switch between a closed and an open state based on the binary information output by the forwarding processing unit (521) if the anomaly detection unit (22) has detected an anomaly, and to bring the bus (10) into the second state.
  19. A communication IC (3, 303, 603) to which a two-wire bus (10) is connected and which is configured to send and receive a message using a differential communication scheme by assigning a first state, in which a potential difference between a first line (10a) and a second line (10b) of the bus (10) is large, and a second state, in which the potential difference is small, to binary information that forms the message, wherein the first line (10a) and the second line (10b) are connected to a common potential via respective first resistors (R41), and the communication IC (3, 303, 603) comprises: a first switch (SW1) which is configured to connect the bus (10) by connecting the first line (10a) to a first potential that is greater than the common potential, and by connecting the second line (10b) to a second potential, to bring the bus (10) into the first state, which is smaller than the common potential, characterized in that the communication IC (3, 303, 603) further comprises: a second switch (SW2) configured to bring the bus (10) into the second state by connecting the first line (10a) and the second line (10b) via a second resistor (R41); a switching control unit (4) for switching, if an anomaly has been detected in a message transmitted on the bus (10), the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential, thereby bringing the bus (10) into the first state; and an output destination switching unit (4) into which binary information is input which forms a transmit message and which is configured to switch an output destination of the input binary information to the first switch (SW1) if no anomaly has been detected, and to the second switch (SW2) if such an anomaly has been detected.
  20. A control IC (2, 402, 502) that sends a message to a communication IC (3, 303, 603) having a first switch (SW1) by outputting a signal to control the first switch (SW1) to be in a closed or an open state, wherein the first switch (SW1) is configured to connect a first line (10a) of a two-wire bus (10) to a first potential greater than the common potential and to connect a second line (10b) of the two-wire bus (10) to a second potential less than the common potential, wherein the first line (10a) and the second line (10b) of the two-wire bus (10) are connected to a common potential via respective first resistors (R21, R22), wherein the control IC (2, 402, 502) comprises: a communication processing unit (21) for generating a message to be sent and for the sequential output of binary information constituting the generated message, characterized in that the control IC (2, 402, 502) further comprises: a second switch (SW2) for connecting the first line (10a) and the second line (10b) via a second resistor (R41); a switching control unit (4) for switching, if an anomaly has been detected in a message transmitted on the bus (10), the first switch (SW1) such that the first line (10a) is connected to the first potential and the second line (10b) is connected to the second potential; and an output destination switching unit (4) for switching an output destination of the binary information from the communication processing unit (21) to the first switch (SW1) if no anomaly has been detected, and to the second switch (SW2) if such an anomaly has been detected.

Description

TECHNICAL AREA The present invention relates to a communication system, a communication device, a forwarding device, an integrated communication circuit (communication IC), a control IC and a communication method that enable communication via a two-wire bus according to a differential communication scheme. TECHNICAL BACKGROUND Vehicles are known to contain several communication devices, such as electronic control units (ECUs), which are interconnected via a vehicle-integrated network, such as a Controller Area Network (CAN). The ECUs send and receive messages to and from each other via this network, thereby coordinating their operation to perform various functions, such as controlling the vehicle's driving. Such a vehicle-integrated network carries the risk that, for example, an unauthorized message could be sent to it if an unauthorized device is connected to it. JP 2013 - 098 719 A This reveals a communication system in which ECUs each count how often a message of individual CAN IDs is sent; an ECU that sends a message generates a message authentication code (MAC) based on the data field, CAN ID and the message count value and sends the generated MAC as a MAC message, and an ECU that has received the message compares a generated MAC based on the data field, CAN ID and the count value of the received message with the MAC contained in the MAC message and determines the permissibility or validity of the message. The JP 2014 - 187 445 A Disclosing a network monitoring device that monitors the communication state of a communication bus, and if the reception time of a monitored message is shorter than a regular reception time, the network monitoring device determines that the communication state of the monitored message is abnormal, and if the time is longer than the regular reception time, the network monitoring device determines that the communication state of a message that is not the monitored message is abnormal. The US 2003/158983 A1 Disclosing a method and a device for monitoring a bus system with at least two users, at least one of whom is structured as an authorized user and monitors the data transmission on the bus system, wherein an identifier is transmitted for each data transmission on the bus system and the identifier is uniquely assignable to a user. The at least one authorized user advantageously compares the identifier with a predetermined identifier and, if both identifiers match, initiates measures to prevent the execution of the data to be transmitted if the data transmission is initiated by someone other than the at least one authorized user. The measures include, for example, grounding a bus of the bus system. US 2013/0104231 A1 Disclosing the prevention of spoofing in a motor vehicle network comprises monitoring data packets on a bus in the motor vehicle network by an electronic control unit. After determining, in response to the monitoring, that a data packet originates from a source other than the electronic control unit, the prevention of spoofing in the motor vehicle network comprises generating and sending a diagnostic message to at least one module in the motor vehicle network via the bus, wherein the diagnostic message instructs the at least one module not to take any action with respect to the data packet. Also disclosed is a dominant Dominant overriding of data fields or causing a network error for every message on the bus with the identifier. DE 11 2014 003 345 T5 This discloses an ECU with a data exclusion function if, during data reception, a continuous dominant of 6 bits or greater is received. A data exclusion device is connected to a bus to which the ECU is connected. If an ID of data received through the bus matches an ID of an unauthorized ECU detected by a theft sensor, the data exclusion device 5 outputs a continuous 7-bit dominant to bus 3 and then stops outputting the dominant. The US 2015/0172298 A1 discloses a network device connected via a bus to a plurality of network devices, comprising: an authentication unit that performs authentication based on message authentication information contained in data transmitted over the bus by one of the plurality of network devices acting as a sending device; and a processing unit that invalidates the data explained if it is determined that unauthorized data has been transmitted by the sending device, which is impersonating another network device among the multitude of network devices, in case authentication fails. The DE 11 2015 006 541 T5 Disclosure is made of an attack detection device that detects an attack against a communication network between facilities. The attack detection device comprises a CAN (Controller Area Network) that transmits a signal to a multitude of nodes by means of a differential voltage between two signal lines, and a short-circuit detector that monitors the signal transmitted through the two signal lines of the CAN and detects a short circuit between the two signal lines based on a change in the signal