Object Model - WAGO 750 Series Manual

7.3 Object model

7.3.1 General
For network communication, Ethernet/IP uses an object model, in which are
described all of the functions and data of a device.
Each node in the network is represented as a collection of objects.
A number of terms relating to object models are defined below:
• Object:
• Class:
• Instance:
• Variable (attribute):
• Service:
• Behaviour:
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
The object model consists of classes of objects. An object is an abstract
representation of individual related components within a device. It is
defined by its data or attributes, the functions or services it provides
externally and by its defined behaviour.
A class contains related components (objects) of a product, organized in
instances.
An instance consists of different variables (attributes) that describe the
properties of this instance. Different instances of a class have the same
services, the same behaviour and the same variables (attributes).
They can, however, have different variable values.
The variables (attributes) represent the data a device provides over
Ethernet/IP. These include the current values of, for example, a
configuration or an input. Typical attributes are configuration or status
information.
Services are used to access classes or the attributes of a class or to
generate specific events. These services execute defined actions such as
the reading of variables or the resetting of a class. For each class, there
exists a fixed set of services.
The behaviour defines how a device reacts as a result of external events
such as changed process data or internal events such as lapsing timers.
Ethernet/IP (Ethernet/Industrial Protocol) • 189
Object model