Rockwell Automation 1403-NDNET DeviceNet Communications Card Installation Instructions - Manual (Page 137)

1 Publication 1403-IN054B-EN-P - August 2001
Glossary
Assembly Object
DeviceNet products usually have one or more Assembly Objects. The
purpose of the Assembly Object is to group different attributes (data)
from different applications into a single attribute which can be moved
by a single message.
Attribute
An attribgute is a characteristic of an Object and/o9r an Object Class.
Attributes provide status information or govern the operation of an
object. Each attributeis assigned an integer value (Attribute ID) as an
identifier.
Class
A class is a set of objects that represent the same kind of system
component. Each object class is assigned an integer value called the
Class ID.
Client
The client is the device that originates a transmission. This applies to
both Explicit Messaging and I/O connections. See Server.
COS/Cyclic
A Change of State (COS) device produces its data only when it
changes. To be sure the consuming device knows that the producer is
still alive and active, DeviceNet provides an adjustable, background
heartbeat rate. COS connections send data whenever the data changes
or the heartbeat timer expires. Cyclic connections send data only
when the heartbeat timer expires. The scanner determines whether or
not the I/O has changed and how much data is sent on each
COS/heartbeat.
DeviceNet
DeviceNet is an open network standard. The specification and
protocol are open. Vendors are not required to purchase hardware,
software or licensing rights to connect to a device to a system. Anyone
may obtain the DeviceNet Specifications form the Open DeviceNet
Vendor Association, Inc (ODVA).
EDS
EDS is an acronym for the Electronic Data Sheet, specially formatted
ASCII file that provides information about a device’s configuration
data context, content, and format. The information in an EDS allows
configuration tools to provide information screens that guide a user
through the steps necessary to configure a device.