Image Processing Reference
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multiple access (CSMA) approach. The peculiar aspect, however, was that CAN adopted a new
distributed nondestructive arbitration mechanism to solve contentions on the bus by means of prior-
ities implicitly assigned to the colliding messages. Moreover, the protocol specifications also included
anumberoferrordetectionandmanagementmechanismstoenhancethefaulttoleranceofthewhole
system.
In the following years both Intel and Philips started to produce controller chips for CAN following
two different philosophies. he Intel solution (often referred to as FullCAN in the literature) required
less host CPU power, since most of the communication and network management functions were
carried out directly by the network controller. Instead, the Philips solution (BasicCAN) was simpler
but imposed a higher load on the processor used to interface the CAN controller. Since the mid-s
more than semiconductor vendors including Siemens, Motorola, and NEC have been producing
and shipping millions of CAN chips mainly to car manufacturers such as Mercedes-Benz, Volvo,
Saab, Volkswagen, BMW, Renault, and Fiat.
The Bosch specification (CAN version .) was submitted for international standardization at the
beginningofthes.heproposalwasapprovedandpublishedastheISOstandardatthe
end of and contained the description of the medium access protocol and the physical layer archi-
tecture. In an addendum to ISO was approved to describe the extended format for message
identifiers.
The CAN specification has recently been revised and reorganized, and has been split into sev-
eral separate parts: part [ISO] defines the CAN data-link protocol, whereas part [ISO] and
part [ISO] specify the high-speed (nonfault-tolerant) and low-speed (fault-tolerant) physical lay-
ers, respectively. Part [ISO] specifies the protocol for time-triggered communication (TTCAN).
More recently, part [ISO] was added that deals with high-speed medium access units with
low-power mode.
15.1.1 CAN in Automotive Applications
hemainuseofCANhasbeen(andstillis)intheautomotiveindustry.Here,CANisadoptedasin-
vehicle network for engine management, comfort electronics (e.g., doors control, air conditioning,
lightning, and so on) as well as for some infotainment (information and entertainment) functions.
Currently, it is also being used as on-vehicle network for special-purpose cars, such as, for example,
police cars and taxis.
The different CAN networks in a vehicle are connected through gateways. In many cases, this
functionality is implemented in the dashboard, which may be equipped with a local CAN network
for connecting displays and instruments.
High-speed CAN networks (e.g., kbps), that comply with the ISO - physical layer, are
used by a vast majority of car makers in power-engine systems. In addition, most passenger cars
produced in Europe are equipped with CAN-based multiplex networks that connect doors and roof
control units as well as lighting and seat control units. hese networks are often based on either the
ISO - fault-tolerant physical layer or the ISO - high-speed physical layer with low-power
functionality.
Sometimes, also infotainment devices are interconnected by means of CAN. Besides proprietary
solutions, the Society of Automotive Engineers (SAE) defined the IDB-C application proile in the ITS
Data Bus series of specifications (SAE J), which is based on high-speed CAN ( bit identifiers)
with a bit-rate of kbps. Finally, a CAN-based diagnostic interface is provided by several passen-
ger cars for connecting diagnostics tools to in-vehicle networks. Several international standards are
available in this case, namely ISO (Diagnostics on CAN including Keyword over CAN),
ISO - (Unified Diagnostic Services), and ISO (on-board diagnostic standard).
Electronic control units (ECUs) for vehicles (e.g., passenger cars, trucks, and buses) are in
most cases original equipment manufacturer (OEM)-specific. This means they comply with the
