Danfoss CAN Controller User guide

CAN

Controller
Area
Network

Technical
Information

123,5

10,5

55,75

174

155

POWER

SYSTEM

MODE

STATUS

8,5

9

10

AMP Stecker
AMP Connector

60,25

8,5

10

1

15

29

14

28

42

55

CAN Controller Area Network

Technical Information

Overview

HISTORY

WHAT IS CAN

Forced by the increasing number of distributed control systems in cars and the
increasing wiring costs of electronics, the availability of a powerful and reliable data
communication system for the exchange of information between the different control
units was becoming urgent.
This was the starting point for BOSCH, a main provider of electronic car equipment to
develop the CAN protocol and standardize it as an international standard in ISO 11898.
1989 the fi rst protocol controller chip was provided by INTEL.

CAN is a serial bus system which is especially suited for connecting devices within a
system or sub-system. These devices (nodes) can be intelligent devices as well as sensors
and actuators.
CAN is a serial bus system with multi-master capabilities, that means that all CAN
nodes are able to transmit data and several CAN nodes can request access to the bus
simultaneously. A transmitter sends a message to all CAN nodes (broadcasting).
A CAN message can transmit from 0 up to 8 bytes of user information. Each CAN Message
starts with a so called identifi er followed by the data bytes. This identifi er can be 11
Bit or 29 Bit wide. If the identifi er is 11 bit wide, than it is a message in „standard
format“ (CAN specifi cation 2.0 Part A). Otherwise it is a message in the „extended format“
(CAN specifi cation 2.0 Part B). Please be aware that not all CAN controller supports the
extended format.
Each node decides on the basis of the identifi er received whether it should process the
message or not. The identifi er also determines the priority that the message have in
competition for bus access.
One of the outstanding features of the CAN bus is its high transmission reliability. The
CAN protocol controller detects a stations error and evaluates it statistically in order to
take appropriate actions. These may extend to disconnecting the CAN node producing
the errors.

BENEFITS

2

The use of a CAN system increases the fl exibility of a system. One of the most obvious
benefi ts is reduced wiring. A single two-wire bus is all that is needed to connect several
CAN devices. This reduces costs, simplifi es mechanical design, and makes it easier to
insert additional devices into a system.
The key benefi t of CAN, like any network, is that it makes it possible to share resources
and information between devices. This means that one sensor can easily be shared
between two or more controllers, or two controllers may share information about their
respective subsystems. Instead of using point to point communications, any device on a
CAN network can communicate with any other.
An additional benefi t of this is that system diagnostics can be centralized and simplifi ed.
As a single device can access all of the devices on the CAN, it is possible to centralize
diagnostic tools to a single access point.

© 2001, Sauer-Danfoss

Sauer-Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Sauer -Danfoss reserves the
right to alter its products without prior notice. This also applies to products already ordered provided that such alterations can be made without
subsequent changes being necessary in specifi cations already agreed. All trademarks in this material are properties of the respective companies.
Sauer-Danfoss and the Sauer-Danfoss logotype are trademarks of the Sauer-Danfoss Group. All rights reserved.

BLN-96-9916-E • Rev. A • 08/2001