90
Fieldbus Communication
WAGO-I/O-SYSTEM 750
750-306 DeviceNet
TM
Fieldbus Coupler
Manual
Version 2.0.0
10.1.2
Network Communication
10.1.2.1 Objects, Classes, Instances and Attributes
Protocol processing of DeviceNet
TM
is object oriented. Each node in the network
is depicted as a collection of objects. Some related terms are defined below:
•
Object
An object is an abstract representation of individual, related components
within a device. It is determined by its data or attributes, its outwardly
applied functions or services and by its defined behavior.
•
Class
A class contains related components (objects) of a product organized in
instances, e.g., Identity Class, DeviceNet Class.
•
Instance
An instance is composed of various variables (attributes). Different
instances of a class have the same services, the same behavior and the same
variables (attributes).
However, they can have different variable values, e.g., different
“Connection Instances”: “Explicit Message”, “Poll I/O” or “Bit-Strobe
Connection Instance”.
•
Attributes
The attributes represent data provided by a device via DeviceNet
TM
. They
contain the current values of e.g., a configuration or input, such as “Vendor
ID”, “Device Type” or “Product Name”.
•
Service
Services can be applied to classes and attributes and perform defined
actions, e.g., reading attributes or resetting a class.
•
Behavior
The behavior defines how a device responds to external events, e.g.,
changed process data or as a consequence of internal events, e.g., elapsed
timers.
