Rockwell Automation 1403-NDNET DeviceNet Communications Card Installation Instructions - Manual (Page 138)

Publication 1403-IN054B-EN-P - August 2001
Glossary 2
Explicit (Client or Server) Messages
Explicit Messages provide multi-purpose, point-to-point
communication paths between two devices. They provide the typical
request/responsoriented network communications used to perform
node configuration and problem diagnosis. Explicit messages typically
use low priority identifiers and contain the specific meaning of the
message right in the data field. This includes the service to be
performed and the specific object attribute address.
Instance
An instance is the actual representation of a particular object within a
class. Each instance is assigned an integer value (Instance ID) that
identifies it from all of the other instances of the same class. This value
is unique within the Node Address/Class in which the instance
resides.
I/O Slave Messages
I/O messages are for time-critical, control-oriented data. They provide
a dedicated, special-purpose communication path between a
producing application and one or more consuming applications. They
are exchanged across single or multi-cast connections and typically
use high priority identifiers. I/O messsages contain no protocol in the
8-byte data field.
Node Address
A node address is an integer value that identifies each node on a
DeviceNet network. Also referred to as the Media Access Control
Identifier (MAC ID).
Object
A DeviceNet node is modeled as a collection of objects. An object
provides an abstract representation of a particular component within a
product. Each product internally maps objects specfic to its
implementation.
Server
The server is a device that reacts to a transmission. The server’s
reaction may cause it to return a message to the client. This applies to
both Explicit Meassaging and I/O connections. See Client.
UCMM
UCMM is an acronmy for Unconnected Message Manager. The UCMM
provides for the dynamic establishment of Explicit Messaging
Connections. The UCMM processes two services which manage the
allocation and de-allocation of Explicit Messaging Connections:
•
Open Explicit Messaging Connection. Establishes an Explicit
Message Connection.