Nissan Versa Note. Manual - part 544

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[CAN]

SYSTEM

SYSTEM

CAN COMMUNICATION SYSTEM
CAN COMMUNICATION SYSTEM : System Description

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SYSTEM DIAGRAM

DESCRIPTION

CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle mul-

tiplex communication line with high data communication speed and excellent error detection ability. Many elec-

tronic 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.

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 cir-

cuits drop voltage to generate a potential difference between the

CAN-H line and the CAN-L line.

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.

The Construction of CAN Communication Signal (Message)

CAN Communication Line

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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 pos-
sibility 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 ad-

vance and writes the calculated value in a message.

• The receiving control unit calculates received data and judg-

es that the data reception is normal when the calculated val-
ue 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.

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[CAN]

SYSTEM

The CAN communication line is a twisted pair wire consisting of

strands of CAN-H (1) and CAN-L (2) and has noise immunity.

NOTE:

The CAN communication system has the characteristics of noise-resistant because this system produces dig-

ital signals by using the potential difference between the CAN-H line and the CAN-L line and has the twisted

pair wire structure.

Since the CAN-H line and the CAN-L line are always adjacent to

each other, the same degree of noise occurs, respectively, when a

noise (1) occurs. Although the noise changes the voltage, the poten-

tial difference (2) between the CAN-H line and the CAN-L line is

insensitive to noise. Therefore, noise-resistant signals can be

obtained.

CAN Signal Communications

Each control unit of the CAN communication system transmits signals through the CAN communication con-

trol circuit included in the control unit and receives only necessary signals from each control unit to perform

various kinds of control.

• Example: Transmitted signals

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• Example: Received signals

NOTE:

The above signal names and signal communications are provided for reference purposes. For CAN communi-

cations signals of this vehicle, refer to 

LAN-29, "CAN COMMUNICATION SYSTEM : CAN Communication

Signal Chart"

.

CAN COMMUNICATION SYSTEM : CAN Communication Control Circuit

INFOID:0000000008968388

CAN communication control circuit is incorporated into the control unit and transmits/receives CAN communi-

cation signals.

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Component

System description

CAN controller

It controls CAN communication signal transmission and reception, error detection, etc.

Transceiver IC

It converts digital signal into CAN communication signal, and CAN communication signal into digital 
signal.