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 1 circuit Vehicle CAN communication 2 circuit Vehicle CAN communication 3 circuit	BCM	SYSTEM DESCRIPTION
Between the following circuits. Vehicle CAN communication 3 circuit ITS CAN communication 1 circuit ITS CAN communication 4 circuit Chassis CAN communication 3 circuit Drivetrain CAN communication 2 circuit IT CAN communication circuit Diagnostic CAN communication circuit	8CH CAN gateway	8CH CAN Gateway COMPONENT DESCRIPTION
Between the following circuits. ITS CAN communication 1 circuit ITS CAN communication 2 circuit ITS CAN communication 3 circuit ITS CAN communication 4 circuit	ADAS control unit 2	ADAS CONTROL UNIT 2
Between the following circuits. Chassis CAN communication 1 circuit Chassis CAN communication 2 circuit Chassis CAN communication 3 circuit Chassis CAN communication 4 circuit Drivetrain CAN communication 1 circuit	Chassis control module	SYSTEM DESCRIPTION
Between the following circuits. ITS CAN communication 1 circuit ITS CAN communication 4 circuit ITS CAN communication 5 circuit	Around view monitor control unit	AROUND VIEW MONITOR CONTROL UNIT
ITS CAN communication 4 circuit ↔ ITS CAN communication 5 circuit	Sonar control unit	SONAR CONTROL UNIT
Chassis CAN communication 2 circuit ↔ Chassis CAN communication 4 circuit	ABS actuator and electric unit	SYSTEM DESCRIPTION
Between the following circuits. Drivetrain CAN communication 1 circuit Drivetrain CAN communication 2 circuit Engine CAN communication circuit	PHEV-ECU	GENERAL INFORMATION

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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No.	Message name	Description
1	Start of frame (1 bit)	Start of message.
2	Arbitration of field (11 bit)	Priorities of message-sending are shown when there is a possibility that multiple messages are sent at the same time.
3	Control field (6 bit)	Signal quantity in data field is shown.
4	Data field (0-64 bit)	Actual signal is shown.
5	CRC field (16 bit)	The transmitting control unit calculates sending data in advance and writes the calculated value in a message. The receiving control unit calculates received data and judges that the data reception is normal when the calculated value is the same as the value written in the sent data.
6	ACK field (2 bit)	The completion of normal reception is sent to the transmitting unit.
7	End of frame (7 bit)	End of message.