APRILIA RSV 1000 R, Workshop Manual

Page: 302 / 308

ELECTRICAL SYSTEM
7 - 14
RSV 1000 R - RSV 1000 R FACTORY
7.1.3. CAN LINE
A CAN (Controller Area Network) line is a connection be-
tween the vehicle’s various electronic components that oper-
ates like a computer (Internet) network.
The use of CAN lines greatly simplifies the electrical system
and its overall weight.
With this type of network, duplicating the sensors around the
vehicle is unnecessary, inasmuch as both electronic control
systems (dashboard and ECU) share the sensors’ signals.
ADVANTAGES OF THE CAN SYSTEM
• Reduction of the number of cables: the CAN line runs
on a double cable between its nodes.
• The nodes are also capable of isolating errors without
causing the system to breakdown (Fault Confinement).
• Robustness: the signal is transmitted over two cables
and the reading is differential (voltage difference be-
tween the two signals on separate cables). If the two
signals are perturbed by external factors, their differ-
ence is not affected.
• Speed of communications: bandwidth is around 250
kbps (data is transmitted to the nodes every 20 ms =
50 times a second).
THE CAN (CONTROLLER AREA NETWORK) PROTOCOL
The CAN comms protocol is a CSMA/CD (Carrier Sense
Multiple Access /w Collision Detection) protocol.
In order to transmit, each node must first check that the BUS
connecting it to all the other nodes is free (Carrier Sense);
only then can it transmit on the BUS. If there is no activity on
the BUS, all nodes are able to transmit over it (Multiple Ac-
cess). If two nodes start transmitting at the same time, they
detect the collision (Collision Detection) and judge the situa-
tion based on a set priority ranking (the messages are unal-
tered during the mediating and the higher priority message is
not delayed).
The CAN protocol is message-oriented, not address-
oriented. The message itself is composed of a number of
component frames, each of which has a set significance:
message priority, data, error checking, reception confirma-
tion, and so on. All nodes receive all messages on the BUS
(with reception confirmation or error) and each node decides
whether the message is to be handled or discarded. Each
node can also request information from other nodes (RTR =
Remote Transmit Request).