<s>
A	O
Controller	B-Protocol
Area	I-Protocol
Network	I-Protocol
(	O
CAN	B-Protocol
bus	I-Protocol
)	O
is	O
a	O
vehicle	B-Architecture
bus	I-Architecture
standard	O
designed	O
to	O
allow	O
microcontrollers	B-Architecture
and	O
devices	O
to	O
communicate	O
with	O
each	O
other	O
's	O
applications	O
without	O
a	O
host	B-Device
computer	I-Device
.	O
</s>
<s>
It	O
is	O
a	O
message-based	B-Architecture
protocol	I-Architecture
,	O
designed	O
originally	O
for	O
multiplex	B-Architecture
electrical	O
wiring	O
within	O
automobiles	O
to	O
save	O
on	O
copper	O
,	O
but	O
it	O
can	O
also	O
be	O
used	O
in	O
many	O
other	O
contexts	O
.	O
</s>
<s>
Development	O
of	O
the	O
CAN	B-Protocol
bus	I-Protocol
started	O
in	O
1983	O
at	O
Robert	O
Bosch	O
GmbH	O
.	O
</s>
<s>
The	O
protocol	O
was	O
officially	O
released	O
in	O
1986	O
at	O
the	O
Society	O
of	O
Automotive	O
Engineers	O
(	O
SAE	O
)	O
conference	O
in	O
Detroit	O
,	O
Michigan	B-Device
.	O
</s>
<s>
The	O
first	O
CAN	B-Protocol
controller	I-Protocol
chips	O
were	O
introduced	O
by	O
Intel	O
in	O
1987	O
,	O
and	O
shortly	O
thereafter	O
by	O
Philips	O
.	O
</s>
<s>
Released	O
in	O
1991	O
,	O
the	O
Mercedes-Benz	O
W140	O
was	O
the	O
first	O
production	O
vehicle	O
to	O
feature	O
a	O
CAN-based	O
multiplex	B-Architecture
wiring	O
system	O
.	O
</s>
<s>
In	O
1993	O
,	O
the	O
International	O
Organization	O
for	O
Standardization	O
(	O
ISO	O
)	O
released	O
CAN	O
standard	O
ISO	O
11898	O
,	O
which	O
was	O
later	O
restructured	O
into	O
two	O
parts	O
:	O
ISO	O
11898-1	O
which	O
covers	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
,	O
and	O
ISO	O
11898-2	O
which	O
covers	O
the	O
CAN	O
physical	B-Application
layer	I-Application
for	O
high-speed	O
CAN	O
.	O
</s>
<s>
ISO	O
11898-3	O
was	O
released	O
later	O
and	O
covers	O
the	O
CAN	O
physical	B-Application
layer	I-Application
for	O
low-speed	O
,	O
fault-tolerant	O
CAN	O
.	O
</s>
<s>
The	O
physical	B-Application
layer	I-Application
standards	O
ISO	O
11898-2	O
and	O
ISO	O
11898-3	O
are	O
not	O
part	O
of	O
the	O
Bosch	O
CAN	O
2.0	O
specification	O
.	O
</s>
<s>
The	O
CAN	B-Protocol
bus	I-Protocol
is	O
one	O
of	O
five	O
protocols	O
used	O
in	O
the	O
on-board	O
diagnostics	O
(	O
OBD	O
)	O
-II	O
vehicle	O
diagnostics	O
standard	O
.	O
</s>
<s>
The	O
modern	O
automobile	O
may	O
have	O
as	O
many	O
as	O
70	O
electronic	B-Device
control	I-Device
units	I-Device
(	O
ECU	O
)	O
for	O
various	O
subsystems	O
.	O
</s>
<s>
Traditionally	O
,	O
the	O
biggest	O
processor	O
is	O
the	O
engine	B-Device
control	I-Device
unit	I-Device
.	O
</s>
<s>
A	O
subsystem	O
may	O
need	O
to	O
control	O
actuators	B-Algorithm
,	O
or	O
receive	O
feedback	O
from	O
sensors	B-Application
.	O
</s>
<s>
Auto	O
start/stop	O
:	O
Various	O
sensor	O
inputs	O
from	O
around	O
the	O
vehicle	O
(	O
speed	O
sensors	B-Application
,	O
steering	O
angle	O
,	O
air	O
conditioning	O
on/off	O
,	O
engine	O
temperature	O
)	O
are	O
collated	O
via	O
the	O
CAN	B-Protocol
bus	I-Protocol
to	O
determine	O
whether	O
the	O
engine	O
can	O
be	O
shut	O
down	O
when	O
stationary	O
for	O
improved	O
fuel	O
economy	O
and	O
emissions	O
.	O
</s>
<s>
Electric	O
park	O
brakes	O
:	O
The	O
"	O
hill	O
hold	O
"	O
functionality	O
takes	O
input	O
from	O
the	O
vehicle	O
's	O
tilt	O
sensor	O
(	O
also	O
used	O
by	O
the	O
burglar	O
alarm	O
)	O
and	O
the	O
road	O
speed	O
sensors	B-Application
(	O
also	O
used	O
by	O
the	O
ABS	O
,	O
engine	O
control	O
and	O
traction	O
control	O
)	O
via	O
the	O
CAN	B-Protocol
bus	I-Protocol
to	O
determine	O
if	O
the	O
vehicle	O
is	O
stopped	O
on	O
an	O
incline	O
.	O
</s>
<s>
Similarly	O
,	O
inputs	O
from	O
seat	O
belt	O
sensors	B-Application
(	O
part	O
of	O
the	O
airbag	O
controls	O
)	O
are	O
fed	O
from	O
the	O
CAN	B-Protocol
bus	I-Protocol
to	O
determine	O
if	O
the	O
seat	O
belts	O
are	O
fastened	O
,	O
so	O
that	O
the	O
parking	O
brake	O
will	O
automatically	O
release	O
upon	O
moving	O
off	O
.	O
</s>
<s>
Parking	O
assist	O
systems	O
:	O
when	O
the	O
driver	O
engages	O
reverse	O
gear	O
,	O
the	O
transmission	O
control	O
unit	O
can	O
send	O
a	O
signal	O
via	O
the	O
CAN	B-Protocol
bus	I-Protocol
to	O
activate	O
both	O
the	O
parking	O
sensor	O
system	O
and	O
the	O
door	O
control	O
module	O
for	O
the	O
passenger	O
side	O
door	O
mirror	O
to	O
tilt	O
downward	O
to	O
show	O
the	O
position	O
of	O
the	O
curb	O
.	O
</s>
<s>
The	O
CAN	B-Protocol
bus	I-Protocol
also	O
takes	O
inputs	O
from	O
the	O
rain	O
sensor	O
to	O
trigger	O
the	O
rear	O
windscreen	O
wiper	O
when	O
reversing	O
.	O
</s>
<s>
Auto	O
lane	O
assist/collision	O
avoidance	O
systems	O
:	O
The	O
inputs	O
from	O
the	O
parking	O
sensors	B-Application
are	O
also	O
used	O
by	O
the	O
CAN	B-Protocol
bus	I-Protocol
to	O
feed	O
outside	O
proximity	O
data	O
to	O
driver	O
assist	O
systems	O
such	O
as	O
Lane	O
Departure	O
warning	O
,	O
and	O
more	O
recently	O
,	O
these	O
signals	O
travel	O
through	O
the	O
CAN	B-Protocol
bus	I-Protocol
to	O
actuate	O
brake	O
by	O
wire	O
in	O
active	O
collision	B-Protocol
avoidance	I-Protocol
systems	O
.	O
</s>
<s>
Auto	O
brake	O
wiping	O
:	O
Input	O
is	O
taken	O
from	O
the	O
rain	O
sensor	O
(	O
used	O
primarily	O
for	O
the	O
automatic	O
windscreen	O
wipers	O
)	O
via	O
the	O
CAN	B-Protocol
bus	I-Protocol
to	O
the	O
ABS	O
module	O
to	O
initiate	O
an	O
imperceptible	O
application	O
of	O
the	O
brakes	O
while	O
driving	O
to	O
clear	O
moisture	O
from	O
the	O
brake	O
rotors	O
.	O
</s>
<s>
Sensors	B-Application
can	O
be	O
placed	O
at	O
the	O
most	O
suitable	O
place	O
,	O
and	O
their	O
data	O
used	O
by	O
several	O
ECUs	O
.	O
</s>
<s>
For	O
example	O
,	O
outdoor	O
temperature	O
sensors	B-Application
(	O
traditionally	O
placed	O
in	O
the	O
front	O
)	O
can	O
be	O
placed	O
in	O
the	O
outside	O
mirrors	O
,	O
avoiding	O
heating	O
by	O
the	O
engine	O
,	O
and	O
data	O
used	O
by	O
the	O
engine	O
,	O
the	O
climate	O
control	O
,	O
and	O
the	O
driver	O
display	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
the	O
LIN	O
bus	B-General_Concept
(	O
Local	O
Interconnect	B-General_Concept
Network	O
)	O
standard	O
has	O
been	O
introduced	O
to	O
complement	O
CAN	O
for	O
non-critical	O
subsystems	O
such	O
as	O
air-conditioning	O
and	O
infotainment	O
,	O
where	O
data	O
transmission	O
speed	O
and	O
reliability	O
are	O
less	O
critical	O
.	O
</s>
<s>
The	O
CAN	B-Protocol
bus	I-Protocol
protocol	O
has	O
been	O
used	O
on	O
the	O
Shimano	O
DI2	O
electronic	O
gear	O
shift	O
system	O
for	O
road	O
bicycles	O
since	O
2009	O
,	O
and	O
is	O
also	O
used	O
by	O
the	O
Ansmann	O
and	O
BionX	O
systems	O
in	O
their	O
direct	O
drive	O
motor	O
.	O
</s>
<s>
The	O
CAN	B-Protocol
bus	I-Protocol
is	O
also	O
used	O
as	O
a	O
fieldbus	O
in	O
general	O
automation	B-Application
environments	O
,	O
primarily	O
due	O
to	O
the	O
low	O
cost	O
of	O
some	O
CAN	B-Protocol
controllers	I-Protocol
and	O
processors	O
.	O
</s>
<s>
Manufacturers	O
including	O
NISMO	O
aim	O
to	O
use	O
CAN	B-Protocol
bus	I-Protocol
data	O
to	O
recreate	O
real-life	O
racing	O
laps	O
in	O
the	O
videogame	O
Gran	B-Device
Turismo	I-Device
6	I-Device
using	O
the	O
game	O
's	O
GPS	O
Data	O
Logger	O
function	O
,	O
which	O
would	O
then	O
allow	O
players	O
to	O
race	O
against	O
real	O
laps	O
.	O
</s>
<s>
Johns	O
Hopkins	O
University	O
's	O
Applied	O
Physics	O
Laboratory	O
's	O
Modular	O
Prosthetic	O
Limb	O
(	O
MPL	O
)	O
uses	O
a	O
local	O
CAN	B-Protocol
bus	I-Protocol
to	O
facilitate	O
communication	O
between	O
servos	O
and	O
microcontrollers	B-Architecture
in	O
the	O
prosthetic	O
arm	O
.	O
</s>
<s>
Teams	O
in	O
the	O
FIRST	O
Robotics	O
Competition	O
widely	O
use	O
CAN	B-Protocol
bus	I-Protocol
to	O
communicate	O
between	O
the	O
roboRIO	O
and	O
other	O
robot	O
control	O
modules	O
.	O
</s>
<s>
The	O
CAN	B-Protocol
bus	I-Protocol
protocol	O
is	O
widely	O
implemented	O
due	O
to	O
its	O
fault	O
tolerance	O
in	O
electrically	O
noisy	O
environments	O
such	O
as	O
model	O
railroad	O
sensor	O
feedback	O
systems	O
by	O
major	O
commercial	O
Digital	O
Command	O
Control	O
system	O
manufacturers	O
and	O
various	O
open	O
source	O
digital	O
model	O
railroad	O
control	O
projects	O
.	O
</s>
<s>
CAN	O
is	O
a	O
multi-master	B-Architecture
serial	O
bus	B-General_Concept
standard	O
for	O
connecting	O
electronic	B-Device
control	I-Device
units	I-Device
(	O
ECUs	O
)	O
also	O
known	O
as	O
nodes	O
(	O
automotive	B-Device
electronics	I-Device
is	O
a	O
major	O
application	O
domain	O
)	O
.	O
</s>
<s>
PLD	O
,	O
via	O
FPGA	B-Architecture
up	O
to	O
an	O
embedded	O
computer	O
running	O
extensive	O
software	O
.	O
</s>
<s>
All	O
nodes	O
are	O
connected	O
to	O
each	O
other	O
through	O
a	O
physically	O
conventional	O
two	O
wire	O
bus	B-General_Concept
.	O
</s>
<s>
This	O
bus	B-General_Concept
uses	O
differential	O
wired-AND	O
signals	O
.	O
</s>
<s>
A	O
0	O
data	O
bit	O
encodes	O
a	O
dominant	O
state	O
,	O
while	O
a	O
1	O
data	O
bit	O
encodes	O
a	O
recessive	O
state	O
,	O
supporting	O
a	O
wired-AND	O
convention	O
,	O
which	O
gives	O
nodes	O
with	O
lower	O
ID	O
numbers	O
priority	O
on	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
ISO	O
11898-2	O
,	O
also	O
called	O
high-speed	O
CAN	O
(	O
bit	O
speeds	O
up	O
to	O
1	O
Mbit/s	O
on	O
CAN	O
,	O
5	O
Mbit/s	O
on	O
CAN-FD	O
)	O
,	O
uses	O
a	O
linear	O
bus	B-General_Concept
terminated	O
at	O
each	O
end	O
with	O
120	O
Ω	O
resistors	O
.	O
</s>
<s>
ISO	O
11898-3	O
,	O
also	O
called	O
low-speed	O
or	O
fault-tolerant	O
CAN	O
(	O
up	O
to	O
125	O
kbit/s	O
)	O
,	O
uses	O
a	O
linear	O
bus	B-General_Concept
,	O
star	O
bus	B-General_Concept
or	O
multiple	O
star	O
buses	O
connected	O
by	O
a	O
linear	O
bus	B-General_Concept
and	O
is	O
terminated	O
at	O
each	O
node	O
by	O
a	O
fraction	O
of	O
the	O
overall	O
termination	O
resistance	O
.	O
</s>
<s>
The	O
dominant	O
state	O
is	O
transmitted	O
by	O
driving	O
CANH	O
towards	O
the	O
device	O
power	O
supply	O
voltage	O
(	O
5V	O
or	O
3.3V	O
)	O
,	O
and	O
CANL	O
towards	O
0V	O
when	O
transmitting	O
a	O
dominant	O
(	O
0	O
)	O
,	O
while	O
the	O
termination	O
resistors	O
pull	O
the	O
bus	B-General_Concept
to	O
a	O
recessive	O
state	O
with	O
CANH	O
at	O
0V	O
and	O
CANL	O
at	O
5V	O
.	O
</s>
<s>
High-speed	O
CAN	O
is	O
usually	O
used	O
in	O
automotive	O
and	O
industrial	O
applications	O
where	O
the	O
bus	B-General_Concept
runs	O
from	O
one	O
end	O
of	O
the	O
environment	O
to	O
the	O
other	O
.	O
</s>
<s>
The	O
specifications	O
require	O
the	O
bus	B-General_Concept
be	O
kept	O
within	O
a	O
minimum	O
and	O
maximum	O
common	O
mode	O
bus	B-General_Concept
voltage	O
,	O
but	O
do	O
not	O
define	O
how	O
to	O
keep	O
the	O
bus	B-General_Concept
within	O
this	O
range	O
.	O
</s>
<s>
The	O
CAN	B-Protocol
bus	I-Protocol
must	O
be	O
terminated	O
.	O
</s>
<s>
The	O
termination	O
resistors	O
are	O
needed	O
to	O
suppress	O
reflections	O
as	O
well	O
as	O
return	O
the	O
bus	B-General_Concept
to	O
its	O
recessive	O
or	O
idle	O
state	O
.	O
</s>
<s>
High-speed	O
CAN	O
uses	O
a	O
120	O
Ω	O
resistor	O
at	O
each	O
end	O
of	O
a	O
linear	O
bus	B-General_Concept
.	O
</s>
<s>
Other	O
types	O
of	O
terminations	O
may	O
be	O
used	O
such	O
as	O
the	O
Terminating	O
Bias	O
Circuit	O
defined	O
in	O
ISO11783	B-Protocol
.	O
</s>
<s>
This	O
provides	O
automatic	O
electrical	O
bias	O
and	O
termination	O
at	O
each	O
end	O
of	O
each	O
bus	B-Protocol
segment	I-Protocol
.	O
</s>
<s>
An	O
ISO11783	B-Protocol
network	O
is	O
designed	O
for	O
hot	O
plug-in	O
and	O
removal	O
of	O
bus	B-General_Concept
segments	O
and	O
ECUs	O
.	O
</s>
<s>
The	O
host	B-General_Concept
processor	I-General_Concept
decides	O
what	O
the	O
received	O
messages	O
mean	O
and	O
what	O
messages	O
it	O
wants	O
to	O
transmit	O
.	O
</s>
<s>
Sensors	B-Application
,	O
actuators	B-Algorithm
and	O
control	O
devices	O
can	O
be	O
connected	O
to	O
the	O
host	B-General_Concept
processor	I-General_Concept
.	O
</s>
<s>
Receiving	O
:	O
the	O
CAN	B-Protocol
controller	I-Protocol
stores	O
the	O
received	O
serial	O
bits	O
from	O
the	O
bus	B-General_Concept
until	O
an	O
entire	O
message	O
is	O
available	O
,	O
which	O
can	O
then	O
be	O
fetched	O
by	O
the	O
host	B-General_Concept
processor	I-General_Concept
(	O
usually	O
by	O
the	O
CAN	B-Protocol
controller	I-Protocol
triggering	O
an	O
interrupt	O
)	O
.	O
</s>
<s>
Sending	O
:	O
the	O
host	B-General_Concept
processor	I-General_Concept
sends	O
the	O
transmit	O
message(s )	O
to	O
a	O
CAN	B-Protocol
controller	I-Protocol
,	O
which	O
transmits	O
the	O
bits	O
serially	O
onto	O
the	O
bus	B-General_Concept
when	O
the	O
bus	B-General_Concept
is	O
free	O
.	O
</s>
<s>
Receiving	O
:	O
it	O
converts	O
the	O
data	O
stream	O
from	O
CAN	B-Protocol
bus	I-Protocol
levels	O
to	O
levels	O
that	O
the	O
CAN	B-Protocol
controller	I-Protocol
uses	O
.	O
</s>
<s>
It	O
usually	O
has	O
protective	O
circuitry	O
to	O
protect	O
the	O
CAN	B-Protocol
controller	I-Protocol
.	O
</s>
<s>
Transmitting	O
:	O
it	O
converts	O
the	O
data	O
stream	O
from	O
the	O
CAN	B-Protocol
controller	I-Protocol
to	O
CAN	B-Protocol
bus	I-Protocol
levels	O
.	O
</s>
<s>
The	O
message	O
is	O
transmitted	O
serially	O
onto	O
the	O
bus	B-General_Concept
using	O
a	O
non-return-to-zero	B-Protocol
(	O
NRZ	O
)	O
format	O
and	O
may	O
be	O
received	O
by	O
all	O
nodes	O
.	O
</s>
<s>
The	O
devices	O
that	O
are	O
connected	O
by	O
a	O
CAN	O
network	O
are	O
typically	O
sensors	B-Application
,	O
actuators	B-Algorithm
,	O
and	O
other	O
control	O
devices	O
.	O
</s>
<s>
These	O
devices	O
are	O
connected	O
to	O
the	O
bus	B-General_Concept
through	O
a	O
host	B-General_Concept
processor	I-General_Concept
,	O
a	O
CAN	B-Protocol
controller	I-Protocol
,	O
and	O
a	O
CAN	B-Protocol
transceiver	I-Protocol
.	O
</s>
<s>
The	O
exact	O
voltages	O
for	O
a	O
logical	O
0	O
or	O
1	O
depend	O
on	O
the	O
physical	B-Application
layer	I-Application
used	O
,	O
but	O
the	O
basic	O
principle	O
of	O
CAN	O
requires	O
that	O
each	O
node	O
listen	O
to	O
the	O
data	O
on	O
the	O
CAN	O
network	O
including	O
the	O
transmitting	O
node(s )	O
itself	O
(	O
themselves	O
)	O
.	O
</s>
<s>
Message	O
IDs	O
must	O
be	O
unique	O
on	O
a	O
single	O
CAN	B-Protocol
bus	I-Protocol
,	O
otherwise	O
two	O
nodes	O
would	O
continue	O
transmission	O
beyond	O
the	O
end	O
of	O
the	O
arbitration	O
field	O
(	O
ID	O
)	O
causing	O
an	O
error	O
.	O
</s>
<s>
In	O
those	O
scenarios	O
,	O
a	O
low	O
CAN	B-Protocol
bus	I-Protocol
use	O
of	O
around	O
30%	O
was	O
commonly	O
required	O
to	O
ensure	O
that	O
all	O
messages	O
would	O
meet	O
their	O
deadlines	O
.	O
</s>
<s>
However	O
,	O
if	O
IDs	O
are	O
instead	O
determined	O
based	O
on	O
the	O
deadline	O
of	O
the	O
message	O
,	O
the	O
lower	O
the	O
numerical	O
ID	O
and	O
hence	O
the	O
higher	O
the	O
message	O
priority	O
,	O
then	O
bus	B-General_Concept
use	O
of	O
70	O
to	O
80%	O
can	O
typically	O
be	O
achieved	O
before	O
any	O
message	O
deadlines	O
are	O
missed	O
.	O
</s>
<s>
Synchronization	O
starts	O
with	O
a	O
hard	O
synchronization	O
on	O
the	O
first	O
recessive	O
to	O
dominant	O
transition	O
after	O
a	O
period	O
of	O
bus	B-General_Concept
idle	O
(	O
the	O
start	O
bit	O
)	O
.	O
</s>
<s>
The	O
CAN	B-Protocol
controller	I-Protocol
expects	O
the	O
transition	O
to	O
occur	O
at	O
a	O
multiple	O
of	O
the	O
nominal	O
bit	O
time	O
.	O
</s>
<s>
The	O
CAN	O
protocol	O
,	O
like	O
many	O
networking	O
protocols	O
,	O
can	O
be	O
decomposed	O
into	O
the	O
following	O
abstraction	B-Architecture
layers	I-Architecture
:	O
</s>
<s>
The	O
transfer	O
layer	O
receives	O
messages	O
from	O
the	O
physical	B-Application
layer	I-Application
and	O
transmits	O
those	O
messages	O
to	O
the	O
object	O
layer	O
.	O
</s>
<s>
CAN	B-Protocol
bus	I-Protocol
(	O
ISO	O
11898-1:2003	O
)	O
originally	O
specified	O
the	O
link	B-Protocol
layer	I-Protocol
protocol	O
with	O
only	O
abstract	O
requirements	O
for	O
the	O
physical	B-Application
layer	I-Application
,	O
e.g.	O
,	O
asserting	O
the	O
use	O
of	O
a	O
medium	O
with	O
multiple-access	O
at	O
the	O
bit	O
level	O
through	O
the	O
use	O
of	O
dominant	O
and	O
recessive	O
states	O
.	O
</s>
<s>
The	O
electrical	O
aspects	O
of	O
the	O
physical	B-Application
layer	I-Application
(	O
voltage	O
,	O
current	O
,	O
number	O
of	O
conductors	O
)	O
were	O
specified	O
in	O
ISO	O
11898-2:2003	O
,	O
which	O
is	O
now	O
widely	O
accepted	O
.	O
</s>
<s>
However	O
,	O
the	O
mechanical	O
aspects	O
of	O
the	O
physical	B-Application
layer	I-Application
(	O
connector	O
type	O
and	O
number	O
,	O
colors	O
,	O
labels	O
,	O
pin-outs	O
)	O
have	O
yet	O
to	O
be	O
formally	O
specified	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
an	O
automotive	O
ECU	O
will	O
typically	O
have	O
a	O
particular	O
—	O
often	O
custom	O
—	O
connector	O
with	O
various	O
sorts	O
of	O
cables	O
,	O
of	O
which	O
two	O
are	O
the	O
CAN	B-Protocol
bus	I-Protocol
lines	O
.	O
</s>
<s>
Nonetheless	O
,	O
several	O
de	O
facto	O
standards	O
for	O
mechanical	O
implementation	O
have	O
emerged	O
,	O
the	O
most	O
common	O
being	O
the	O
9-pin	B-Protocol
D-sub	I-Protocol
type	I-Protocol
male	I-Protocol
connector	I-Protocol
with	O
the	O
following	O
pin-out	O
:	O
</s>
<s>
This	O
de	O
facto	O
mechanical	O
standard	O
for	O
CAN	O
could	O
be	O
implemented	O
with	O
the	O
node	O
having	O
both	O
male	O
and	O
female	O
9-pin	B-Protocol
D-sub	I-Protocol
connectors	I-Protocol
electrically	O
wired	O
to	O
each	O
other	O
in	O
parallel	O
within	O
the	O
node	O
.	O
</s>
<s>
Bus	B-General_Concept
power	O
is	O
fed	O
to	O
a	O
node	O
's	O
male	O
connector	O
and	O
the	O
bus	B-General_Concept
draws	O
power	O
from	O
the	O
node	O
's	O
female	O
connector	O
.	O
</s>
<s>
Adoption	O
of	O
this	O
standard	O
avoids	O
the	O
need	O
to	O
fabricate	O
custom	O
splitters	O
to	O
connect	O
two	O
sets	O
of	O
bus	B-General_Concept
wires	O
to	O
a	O
single	O
D	B-Protocol
connector	I-Protocol
at	O
each	O
node	O
.	O
</s>
<s>
Such	O
nonstandard	O
(	O
custom	O
)	O
wire	O
harnesses	O
(	O
splitters	O
)	O
that	O
join	O
conductors	O
outside	O
the	O
node	O
reduce	O
bus	B-General_Concept
reliability	O
,	O
eliminate	O
cable	O
interchangeability	O
,	O
reduce	O
compatibility	O
of	O
wiring	O
harnesses	O
,	O
and	O
increase	O
cost	O
.	O
</s>
<s>
The	O
absence	O
of	O
a	O
complete	O
physical	B-Application
layer	I-Application
specification	O
(	O
mechanical	O
in	O
addition	O
to	O
electrical	O
)	O
freed	O
the	O
CAN	B-Protocol
bus	I-Protocol
specification	O
from	O
the	O
constraints	O
and	O
complexity	O
of	O
physical	O
implementation	O
.	O
</s>
<s>
However	O
it	O
left	O
CAN	B-Protocol
bus	I-Protocol
implementations	O
open	O
to	O
interoperability	O
issues	O
due	O
to	O
mechanical	O
incompatibility	O
.	O
</s>
<s>
In	O
order	O
to	O
improve	O
interoperability	O
,	O
many	O
vehicle	O
makers	O
have	O
generated	O
specifications	O
describing	O
a	O
set	O
of	O
allowed	O
CAN	B-Protocol
transceivers	I-Protocol
in	O
combination	O
with	O
requirements	O
on	O
the	O
parasitic	O
capacitance	O
on	O
the	O
line	O
.	O
</s>
<s>
Noise	O
immunity	O
on	O
ISO	O
11898-2:2003	O
is	O
achieved	O
by	O
maintaining	O
the	O
differential	O
impedance	O
of	O
the	O
bus	B-General_Concept
at	O
a	O
low	O
level	O
with	O
low-value	O
resistors	O
(	O
120	O
ohms	O
)	O
at	O
each	O
end	O
of	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
However	O
,	O
when	O
dormant	O
,	O
a	O
low-impedance	O
bus	B-General_Concept
such	O
as	O
CAN	O
draws	O
more	O
current	O
(	O
and	O
power	O
)	O
than	O
other	O
voltage-based	O
signaling	O
busses	O
.	O
</s>
<s>
On	O
CAN	B-Protocol
bus	I-Protocol
systems	O
,	O
balanced	O
line	O
operation	O
,	O
where	O
current	O
in	O
one	O
signal	O
line	O
is	O
exactly	O
balanced	O
by	O
current	O
in	O
the	O
opposite	O
direction	O
in	O
the	O
other	O
signal	O
provides	O
an	O
independent	O
,	O
stable	O
0V	O
reference	O
for	O
the	O
receivers	O
.	O
</s>
<s>
Best	O
practice	O
determines	O
that	O
CAN	B-Protocol
bus	I-Protocol
balanced	O
pair	O
signals	O
be	O
carried	O
in	O
twisted	O
pair	O
wires	O
in	O
a	O
shielded	O
cable	O
to	O
minimize	O
RF	O
emission	O
and	O
reduce	O
interference	O
susceptibility	O
in	O
the	O
already	O
noisy	O
RF	O
environment	O
of	O
an	O
automobile	O
.	O
</s>
<s>
ISO	O
11898-2	O
provides	O
some	O
immunity	O
to	O
common	O
mode	O
voltage	O
between	O
transmitter	O
and	O
receiver	O
by	O
having	O
a	O
0V	O
rail	O
running	O
along	O
the	O
bus	B-General_Concept
to	O
maintain	O
a	O
high	O
degree	O
of	O
voltage	O
association	O
between	O
the	O
nodes	O
.	O
</s>
<s>
The	O
actual	O
voltage	O
to	O
be	O
applied	O
by	O
the	O
bus	B-General_Concept
and	O
which	O
nodes	O
apply	O
to	O
it	O
are	O
application-specific	O
and	O
not	O
formally	O
specified	O
.	O
</s>
<s>
Common	O
practice	O
node	O
design	O
provides	O
each	O
node	O
with	O
transceivers	O
which	O
are	O
optically	O
isolated	O
from	O
their	O
node	O
host	O
and	O
derive	O
a	O
5V	O
linearly	O
regulated	O
supply	O
voltage	O
for	O
the	O
transceivers	O
from	O
the	O
universal	O
supply	O
rail	O
provided	O
by	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
ISO	O
11898-2	O
describes	O
the	O
electrical	O
implementation	O
formed	O
from	O
a	O
multi-dropped	O
single-ended	O
balanced	O
line	O
configuration	O
with	O
resistor	O
termination	O
at	O
each	O
end	O
of	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
In	O
this	O
configuration	O
a	O
dominant	O
state	O
is	O
asserted	O
by	O
one	O
or	O
more	O
transmitters	O
switching	O
the	O
CAN−	O
to	O
supply	O
0V	O
and	O
(	O
simultaneously	O
)	O
switching	O
CAN+	O
to	O
the	O
+5V	O
bus	B-General_Concept
voltage	O
thereby	O
forming	O
a	O
current	O
path	O
through	O
the	O
resistors	O
that	O
terminate	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
A	O
recessive	O
state	O
is	O
present	O
on	O
the	O
bus	B-General_Concept
only	O
when	O
none	O
of	O
the	O
transmitters	O
on	O
the	O
bus	B-General_Concept
is	O
asserting	O
a	O
dominant	O
state	O
.	O
</s>
<s>
Irrespective	O
of	O
signal	O
state	O
the	O
signal	O
lines	O
are	O
always	O
in	O
low	O
impedance	O
state	O
with	O
respect	O
to	O
one	O
another	O
by	O
virtue	O
of	O
the	O
terminating	O
resistors	O
at	O
the	O
end	O
of	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
Multiple	O
access	O
on	O
CAN	B-Protocol
bus	I-Protocol
is	O
achieved	O
by	O
the	O
electrical	O
logic	O
of	O
the	O
system	O
supporting	O
just	O
two	O
states	O
that	O
are	O
conceptually	O
analogous	O
to	O
a	O
‘	O
wired	O
AND’	O
network	O
.	O
</s>
<s>
CAN	B-Protocol
controllers	I-Protocol
that	O
support	O
extended	O
frame	O
format	O
messages	O
are	O
also	O
able	O
to	O
send	O
and	O
receive	O
messages	O
in	O
CAN	O
base	O
frame	O
format	O
.	O
</s>
<s>
Field	O
name	O
Length	O
(	O
bits	O
)	O
Purpose	O
Start-of-frame	O
1	O
Denotes	O
the	O
start	O
of	O
frame	O
transmission	O
Identifier	O
(	O
green	O
)	O
11	O
A	O
(	O
unique	O
)	O
identifier	O
which	O
also	O
represents	O
the	O
message	O
priority	O
Stuff	O
bit	O
1	O
A	O
bit	O
of	O
the	O
opposite	O
polarity	O
to	O
maintain	O
synchronisation	O
;	O
see	O
Bit	B-Protocol
stuffing	I-Protocol
,	O
below	O
Remote	O
transmission	O
request	O
(	O
RTR	O
)	O
(	O
blue	O
)	O
1	O
Must	O
be	O
dominant	O
(	O
0	O
)	O
for	O
data	O
frames	O
and	O
recessive	O
(	O
1	O
)	O
for	O
remote	O
request	O
frames	O
(	O
see	O
Remote	O
Frame	O
,	O
below	O
)	O
Identifier	O
extension	O
bit	O
(	O
IDE	O
)	O
1	O
Must	O
be	O
dominant	O
(	O
0	O
)	O
for	O
base	O
frame	O
format	O
with	O
11-bit	O
identifiers	O
Reserved	O
bit	O
(	O
r0	O
)	O
1	O
Reserved	O
bit	O
.	O
</s>
<s>
When	O
TEC	O
or	O
REC	O
is	O
greater	O
than	O
127	O
and	O
less	O
than	O
255	O
,	O
a	O
Passive	O
Error	O
frame	O
will	O
be	O
transmitted	O
on	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
When	O
TEC	O
and	O
REC	O
is	O
less	O
than	O
128	O
,	O
an	O
Active	O
Error	O
frame	O
will	O
be	O
transmitted	O
on	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
When	O
TEC	O
is	O
greater	O
than	O
255	O
,	O
then	O
the	O
node	O
enters	O
into	O
Bus	B-General_Concept
Off	O
state	O
,	O
where	O
no	O
frames	O
will	O
be	O
transmitted	O
.	O
</s>
<s>
Interframe	O
space	O
contains	O
the	O
bit	O
fields	O
intermission	O
and	O
bus	B-General_Concept
idle	O
,	O
and	O
suspend	O
transmission	O
for	O
error	O
passive	O
stations	O
,	O
which	O
have	O
been	O
transmitter	O
of	O
the	O
previous	O
message	O
.	O
</s>
<s>
This	O
practice	O
is	O
called	O
bit	B-Protocol
stuffing	I-Protocol
,	O
and	O
is	O
necessary	O
due	O
to	O
the	O
non-return-to-zero	B-Protocol
(	O
NRZ	O
)	O
coding	O
used	O
with	O
CAN	O
.	O
</s>
<s>
In	O
the	O
fields	O
where	O
bit	B-Protocol
stuffing	I-Protocol
is	O
used	O
,	O
six	O
consecutive	O
bits	O
of	O
the	O
same	O
polarity	O
(	O
111111	O
or	O
000000	O
)	O
are	O
considered	O
an	O
error	O
.	O
</s>
<s>
The	O
active	O
error	O
flag	O
consists	O
of	O
six	O
consecutive	O
dominant	O
bits	O
and	O
violates	O
the	O
rule	O
of	O
bit	B-Protocol
stuffing	I-Protocol
.	O
</s>
<s>
Bit	B-Protocol
stuffing	I-Protocol
means	O
that	O
data	O
frames	O
may	O
be	O
larger	O
than	O
one	O
would	O
expect	O
by	O
simply	O
enumerating	O
the	O
bits	O
shown	O
in	O
the	O
tables	O
above	O
.	O
</s>
<s>
Since	O
is	O
the	O
size	O
of	O
the	O
frame	O
before	O
stuffing	O
,	O
in	O
the	O
worst	O
case	O
one	O
bit	O
will	O
be	O
added	O
every	O
four	O
original	O
bits	O
after	O
the	O
first	O
one	O
(	O
hence	O
the	O
−1	O
at	O
the	O
numerator	O
)	O
and	O
,	O
because	O
of	O
the	O
layout	O
of	O
the	O
bits	O
of	O
the	O
header	O
,	O
only	O
34	O
out	O
of	O
44	O
of	O
them	O
can	O
be	O
subject	O
to	O
bit	B-Protocol
stuffing	I-Protocol
.	O
</s>
<s>
An	O
undesirable	O
side	O
effect	O
of	O
the	O
bit	B-Protocol
stuffing	I-Protocol
scheme	O
is	O
that	O
a	O
small	O
number	O
of	O
bit	O
errors	O
in	O
a	O
received	O
message	O
may	O
corrupt	O
the	O
destuffing	O
process	O
,	O
causing	O
a	O
larger	O
number	O
of	O
errors	O
to	O
propagate	O
through	O
the	O
destuffed	O
message	O
.	O
</s>
<s>
ISO	O
11898	O
series	O
specifies	O
physical	O
and	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
(	O
levels	O
1	O
and	O
2	O
of	O
the	O
ISO/OSI	O
model	O
)	O
of	O
serial	O
communication	O
category	O
called	O
Controller	B-Protocol
Area	I-Protocol
Network	I-Protocol
that	O
supports	O
distributed	O
real-time	O
control	O
and	O
multiplexing	B-Architecture
for	O
use	O
within	O
road	O
vehicles	O
.	O
</s>
<s>
There	O
are	O
several	O
CAN	O
physical	B-Application
layer	I-Application
and	O
other	O
standards	O
:	O
</s>
<s>
ISO	O
11898-1:2015	O
specifies	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
(	O
DLL	O
)	O
and	O
physical	O
signalling	O
of	O
the	O
controller	B-Protocol
area	I-Protocol
network	I-Protocol
(	O
CAN	O
)	O
.	O
</s>
<s>
This	O
document	O
describes	O
the	O
general	O
architecture	O
of	O
CAN	O
in	O
terms	O
of	O
hierarchical	O
layers	O
according	O
to	O
the	O
ISO	O
reference	O
model	O
for	O
open	O
systems	O
interconnection	O
(	O
OSI	O
)	O
established	O
in	O
ISO/IEC	O
7498-1	O
and	O
provides	O
the	O
characteristics	O
for	O
setting	O
up	O
an	O
interchange	O
of	O
digital	O
information	O
between	O
modules	O
implementing	O
the	O
CAN	O
DLL	O
with	O
detailed	O
specification	O
of	O
the	O
logical	O
link	O
control	O
(	O
LLC	O
)	O
sublayer	O
and	O
medium	B-Protocol
access	I-Protocol
control	I-Protocol
(	O
MAC	O
)	O
sublayer	O
.	O
</s>
<s>
ISO	O
11898-2:2016	O
specifies	O
the	O
high-speed	O
(	O
transmission	O
rates	O
of	O
up	O
to	O
1	O
Mbit/s	O
)	O
medium	O
access	O
unit	O
(	O
MAU	O
)	O
,	O
and	O
some	O
medium	O
dependent	O
interface	O
(	O
MDI	O
)	O
features	O
(	O
according	O
to	O
ISO	O
8802-3	O
)	O
,	O
which	O
comprise	O
the	O
physical	B-Application
layer	I-Application
of	O
the	O
controller	B-Protocol
area	I-Protocol
network	I-Protocol
.	O
</s>
<s>
It	O
is	O
the	O
most	O
used	O
physical	B-Application
layer	I-Application
in	O
vehicle	O
powertrain	O
applications	O
and	O
industrial	O
control	O
networks	O
.	O
</s>
<s>
ISO	O
11898-3:2006	O
specifies	O
low-speed	O
,	O
fault-tolerant	O
,	O
medium-dependent	O
interface	O
for	O
setting	O
up	O
an	O
interchange	O
of	O
digital	O
information	O
between	O
electronic	B-Device
control	I-Device
units	I-Device
of	O
road	O
vehicles	O
equipped	O
with	O
the	O
CAN	O
at	O
transmission	O
rates	O
above	O
40kbit/s	O
up	O
to	O
125kbit/s	O
.	O
</s>
<s>
ISO	O
11898-4:2004	O
specifies	O
time-triggered	O
communication	O
in	O
the	O
CAN	O
(	O
TTCAN	B-Protocol
)	O
.	O
</s>
<s>
It	O
is	O
applicable	O
to	O
setting	O
up	O
a	O
time-triggered	O
interchange	O
of	O
digital	O
information	O
between	O
electronic	B-Device
control	I-Device
units	I-Device
(	O
ECU	O
)	O
of	O
road	O
vehicles	O
equipped	O
with	O
CAN	O
,	O
and	O
specifies	O
the	O
frame	O
synchronisation	O
entity	O
that	O
coordinates	O
the	O
operation	O
of	O
both	O
logical	O
link	O
and	O
media	B-Protocol
access	I-Protocol
controls	I-Protocol
in	O
accordance	O
with	O
ISO	O
11898-1	O
,	O
to	O
provide	O
the	O
time-triggered	O
communication	O
schedule	O
.	O
</s>
<s>
ISO	O
11898-5:2007	O
specifies	O
the	O
CAN	O
physical	B-Application
layer	I-Application
for	O
transmission	O
rates	O
up	O
to	O
1Mbit/s	O
for	O
use	O
within	O
road	O
vehicles	O
.	O
</s>
<s>
This	O
represents	O
an	O
extension	O
of	O
ISO	O
11898-2	O
,	O
dealing	O
with	O
new	O
functionality	O
for	O
systems	O
requiring	O
low-power	O
consumption	O
features	O
while	O
there	O
is	O
no	O
active	O
bus	B-General_Concept
communication	O
.	O
</s>
<s>
ISO	O
11898-6:2013	O
specifies	O
the	O
CAN	O
physical	B-Application
layer	I-Application
for	O
transmission	O
rates	O
up	O
to	O
1Mbit/s	O
for	O
use	O
within	O
road	O
vehicles	O
.	O
</s>
<s>
ISO	O
16845-2:2018	O
establishes	O
test	O
cases	O
and	O
test	O
requirements	O
to	O
realize	O
a	O
test	O
plan	O
verifying	O
if	O
the	O
CAN	B-Protocol
transceiver	I-Protocol
with	O
implemented	O
selective	O
wake-up	O
functions	O
conform	O
to	O
the	O
specified	O
functionalities	O
.	O
</s>
<s>
CAN	O
in	O
Automation	B-Application
(	O
CiA	O
)	O
is	O
the	O
international	O
users	O
 '	O
and	O
manufacturers	O
 '	O
organization	O
that	O
develops	O
and	O
supports	O
CAN-based	O
higher-layer	O
protocols	O
and	O
their	O
international	O
standardization	O
.	O
</s>
<s>
Failure	O
to	O
implement	O
adequate	O
security	O
measures	O
may	O
result	O
in	O
various	O
sorts	O
of	O
attacks	O
if	O
the	O
opponent	O
manages	O
to	O
insert	O
messages	O
on	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
While	O
passwords	O
exist	O
for	O
some	O
safety-critical	O
functions	O
,	O
such	O
as	O
modifying	O
firmware	O
,	O
programming	O
keys	O
,	O
or	O
controlling	O
antilock	O
brake	O
actuators	B-Algorithm
,	O
these	O
systems	O
are	O
not	O
implemented	O
universally	O
and	O
have	O
a	O
limited	O
number	O
of	O
seed/key	O
pairs	O
.	O
</s>
<s>
When	O
developing	O
or	O
troubleshooting	O
the	O
CAN	B-Protocol
bus	I-Protocol
,	O
examination	O
of	O
hardware	B-Architecture
signals	O
can	O
be	O
very	O
important	O
.	O
</s>
<s>
Logic	O
analyzers	O
and	O
bus	B-General_Concept
analyzers	O
are	O
tools	O
which	O
collect	O
,	O
analyse	O
,	O
decode	O
and	O
store	O
signals	O
so	O
people	O
can	O
view	O
the	O
high-speed	O
waveforms	O
at	O
their	O
leisure	O
.	O
</s>
<s>
There	O
are	O
also	O
specialist	O
tools	O
as	O
well	O
as	O
CAN	B-Protocol
bus	I-Protocol
monitors	O
.	O
</s>
<s>
A	O
is	O
an	O
analysis	O
tool	O
,	O
often	O
a	O
combination	O
of	O
hardware	B-Architecture
and	O
software	O
,	O
used	O
during	O
development	O
of	O
hardware	B-Architecture
which	O
uses	O
the	O
CAN	B-Protocol
bus	I-Protocol
.	O
</s>
<s>
Typically	O
the	O
CAN	B-Protocol
bus	I-Protocol
monitor	O
will	O
listen	O
to	O
the	O
traffic	O
on	O
the	O
CAN	B-Protocol
bus	I-Protocol
in	O
order	O
to	O
display	O
it	O
in	O
a	O
user	O
interface	O
.	O
</s>
<s>
Often	O
the	O
CAN	B-Protocol
bus	I-Protocol
monitor	O
offers	O
the	O
possibility	O
to	O
simulate	O
CAN	B-Protocol
bus	I-Protocol
activity	O
by	O
sending	O
CAN	O
frames	O
to	O
the	O
bus	B-General_Concept
.	O
</s>
<s>
The	O
CAN	B-Protocol
bus	I-Protocol
monitor	O
can	O
therefore	O
be	O
used	O
to	O
validate	O
expected	O
CAN	O
traffic	O
from	O
a	O
given	O
device	O
or	O
to	O
simulate	O
CAN	O
traffic	O
in	O
order	O
to	O
validate	O
the	O
reaction	O
from	O
a	O
given	O
device	O
connected	O
to	O
the	O
CAN	B-Protocol
bus	I-Protocol
.	O
</s>
<s>
Manufacturers	O
of	O
products	O
with	O
custom	O
ASICs	O
or	O
FPGAs	B-Architecture
containing	O
CAN-compatible	O
modules	O
need	O
to	O
pay	O
a	O
fee	O
for	O
the	O
CAN	O
Protocol	O
License	O
if	O
they	O
wish	O
to	O
use	O
the	O
CAN	O
trademark	O
or	O
CAN	O
FD	O
capabilities	O
.	O
</s>
