Delta DVP-SS2 User Manual

7 CANopen Function and Operation
7-9
7.3 The CANopen Protocol
7.3.1 The Introduction of the CANopen Protocol
The CAN (controller area network) fieldbus only defines the physical layer and the data link layer.
(See the ISO11898 standard.) It does not define the application layer. In the practical design, the
physical layer and the data link layer are realized by the hardware. The CAN fieldbus itself is not
complete. It needs the superior protocol to define the use of 11/29-bit identifier and that of 8-byte-
data.
The CANopen protocol is the superior protocol base on CAN. It is one of the protocols defined and
maintained by CiA (CAN-in-Automation). It is developed on the basis of the CAL (CAN application
layer) protocol, using a subset of the CAL communication and service protocols.
The CANopen protocol covers the application layer and the communication profile (CiA DS301). It
also covers a framework for programmable devices (CiA 302), the recommendations for cables
and connectors (CiA 303-1), and SI units and prefix representations (CiA 303-2).
In the OSI model, the relation between the CAN standard and the CANopen protocol is as follow.
 The object dictionary
CANopen uses an object-based way to define a standard device. Every device is represented
by a set of objects, and can be visited by the network. The model of the CANopen device is
illustrated below. As the figure below shows, the object dictionary is the interface between the
communication program and the superior application program.
The core concept of CANopen is the device object dictionary (OD). It is an orderly object set.
Every object adopts a 16-bit index for addressing. In order allow the visit to the single element
in the data structure, it also defines, an 8-bit subindex. Every node in the CANopen network
has an object dictionary. The object dictionary includes the parameters which describe the
device and the network behavior. The object dictionary of a node is described in the electronic
data sheet (EDS).
Device profile CiA
DSP
-401
Device profile CiA
DSP
-404
Device profile CiA
DSP
-xxx
OSI seventh layer
Application layer
Communication profile CiA DS-301
CAN controller
CAN 2.0A
ISO 11898
+
-
+
-
CAN network
OSI second layer
Data link layer
OSI first layer
Physical layer

Delta DVP-SS2 Specifications

General

Brand	Delta
Model	DVP-SS2
Category	Controller
Language	English