Nissan Leaf. Manual - part 892

LAN-30

< SYSTEM DESCRIPTION >

[CAN]

COMPONENT PARTS

SYSTEM DESCRIPTION

COMPONENT PARTS

Component Parts Location

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Air bag diagnosis sensor unit

AV control unit

A/C auto amp.

TCU

Around view monitor control unit

Approaching vehicle sound for pe-
destrians (VSP) control unit

ABS actuator and electric unit (con-
trol unit)

VCM
(Electric shift control module includ-
ed)

PDM (Power Delivery Module)

Traction motor inverter

Electrically-driven intelligent brake 
unit

IPDM E/R

BCM

EPS control unit

Combination meter

Steering angle sensor

Data link connector

Li-ion battery

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< SYSTEM DESCRIPTION >

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SYSTEM

CAN COMMUNICATION SYSTEM
CAN COMMUNICATION SYSTEM : System Description

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SYSTEM DIAGRAM

NOTE:

VCM includes electric shift control module.

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.

• VCM includes a gateway function and communicates signals between the CAN communication circuit and

EV system CAN circuit. Refer to 

EVC-18, "VCM"

.

CAN Communication Signal Generation

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< SYSTEM DESCRIPTION >

[CAN]

SYSTEM

• 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.

• 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)

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CAN COMMUNICATION LINE

The CAN communication line is a twisted pair wire consisting of
strands of CAN-H   and CAN-L   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   occurs. Although the noise changes the voltage, the poten-
tial difference   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.

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 
control unit.

7

End of frame (7 bit)

End of message.

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