The development
of CAN began when more and more electronic devices were implemented
into modern motor vehicles. Examples of such devices include engine
management systems, active suspension, ABS, gear control, lighting
control, air conditioning, airbags and central locking. All this
means more safety and more comforts for the driver and of course
a reduction of fuel consumption and exhaust emissions.
To improve
the behavior of the vehicle even further, it was necessary for
the different control systems to exchange information. This was
usually done by discrete interconnection of the different systems.
The requirement for information exchange has then grown to such
an extent that a cable network with a length of up to several
moles and many connectors was required. This produced throwing
problems concerning material cost, production time and reliability.
The solution to the problem was the connection of the control
systems through a serial bus system. This bus had to fulfill some
special requirements due to its usage in a vehicle.
With the use
of CAN, point-to-point wiring is replaced by one serial bus connecting
all control systems. This is accomplished by adding some CAN-specific
hardware to each control unit that provides the "rules"
or the protocol for transmitting and receiving information via
the bus. CAN or Controller Area Network is an advanced serial
bus system that efficiently supports distributed control systems,
It was initially developed for the use in motor vehicles by Robert
Bosch Gmbh, Germany, in the late 1980s, also holding the CAN license.
CAN is most widely used in the automotive and industrial market
segments. Typical applications for CAN are motor vehicles, utility
vehicles, and industrial automation. Other applications are trains,
medical equipment, building automation, household appliances,
and office automation.
FEATURES OF
CAN
" Multimaster
Concept
" No node addressing, Message identifier specifies contents
&priority
" Easy connection and disconnection of nodes
" Broadcast and Multicast capability
" Sophisticated Error detection
" NRZ Code + Bit Stuffing for Synchronization
" Bus access Via CSMA
MULTIMASTER
CONCEPT
CAN is a
multi-master bus with an open, linear structure with one logic
bus line and equal nodes. The number of nodes is not limited by
the protocol.
ADDRESSING
NODES
In CAN protocol,
the bus nodes do not have a specific address. Instead, the address
information is contained in the identifiers of the transmitted
messages, indicating the message content and the priority of the
message.