643
CAN Controller (CAN)
Chapter 19
Preliminary User’s Manual U17566EE1V2UM00
19.2 CAN Protocol
CAN (Controller Area Network) is a high-speed multiplex communication
protocol for real-time communication in automotive applications (class C). CAN
is prescribed by ISO 11898. For details, refer to the ISO 11898 specifications.
The CAN specification is generally divided into two layers: a physical layer and
a data link layer. In turn, the data link layer includes logical link and medium
access control. The composition of these layers is illustrated below.
Figure 19-2
Composition of layers
Note
CAN Controller specification
19.2.1
Frame format
(1)
Standard format frame
• The standard format frame uses 11-bit identifiers, which means that it can
handle up to 2,048 messages.
(2)
Extended format frame
• The extended format frame uses 29-bit (11 bits + 18 bits) identifiers, which
increases the number of messages that can be handled to 2,048
×
2
18
messages.
• An extended format frame is set when “recessive level” (CMOS level of “1”)
is set for both the SRR and IDE bits in the arbitration field.
Phy
s
ic
a
l l
a
yer
Pre
s
cription of
s
ign
a
l level
a
nd
b
it de
s
cription
D
a
t
a
link
l
a
yer
Note
·
Logic
a
l link control (LLC)
·
Medi
u
m
a
cce
ss
control (MAC)
·
Accept
a
nce filtering
·
Overlo
a
d report
·
Recovery m
a
n
a
gement
·
D
a
t
a
c
a
p
su
led/not c
a
p
su
led
·
Fr
a
me coding (
s
t
u
ffing/no
s
t
u
ffing)
·
Medi
u
m
a
cce
ss
m
a
n
a
gement
·
Error detection
·
Error report
·
Acknowledgement
·
S
eri
a
ted/not
s
eri
a
ted
Higher
Lower
electronic components distributor