Nissan Versa Note. Manual — part 544
LAN-24
< SYSTEM DESCRIPTION >
[CAN]
SYSTEM
SYSTEM
CAN COMMUNICATION SYSTEM
CAN COMMUNICATION SYSTEM : System Description
INFOID:0000000008968387
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.
JSMIA1430GB
JSMIA0450GB
LAN
SYSTEM
LAN-25
< SYSTEM DESCRIPTION >
[CAN]
C
D
E
F
G
H
I
J
K
L
B
A
O
P
N
• 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
JSMIA0543GB
JSMIA0544ZZ
JSMIA0545ZZ
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.
LAN-26
< SYSTEM DESCRIPTION >
[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
JSMIA0382ZZ
JSMIA0383ZZ
JSMIA0576GB
LAN
SYSTEM
LAN-27
< SYSTEM DESCRIPTION >
[CAN]
C
D
E
F
G
H
I
J
K
L
B
A
O
P
N
• 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
.
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.
JSMIA0577GB
JSMIA0453GB
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.
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