System Description: Description

• CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only.
• The following control units include a gateway function and communicate signals between the different CAN communication circuits.

  CAN communication circuit	Gateway control unit	Reference
  Between the following circuits Vehicle CAN communication circuit IT CAN communication circuit Diagnostic CAN communication circuit	3CH CAN gateway	System Description
  Between the following circuits Vehicle CAN communication circuit 1 circuit Vehicle CAN communication circuit 2 circuit IT CAN communication circuit Diagnostic CAN communication circuit	6CH CAN gateway	System Description
  Vehicle CAN communication 2 circuit <=> ITS CAN communication circuit	ADAS control unit	System Description
  Vehicle CAN communication 2 circuit <=> Chassis CAN communication circuit	Chassis control module	System Description

CAN Communication Signal Generation 

• Termination circuits (resistors) are connected across the CAN communication system. When transmitting a CAN communication signal, each control unit passes a current to the CAN-H line and the current returns to the CAN-L line.

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• The current flows separately into the termination circuits connected across the CAN communication system and the termination circuits drop voltage to generate a potential difference between the CAN-H line and the CAN-L line.

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  NOTE: A signal with no current passage is called "Recessive" and one with current passage is called "Dominant".
• The system produces digital signals for signal communications, by using the potential difference.

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The Construction of CAN Communication Signal (Message) 

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