Rockwell Automation 9220-WINTA ControlNet Traffic Analyzer Reference Manual - Manual (Page 13)

Publication 9220-052C-EN-P - August 2002
Introduction 1-3
The amount of time available for the unscheduled portion is
determined by the traffic load of the scheduled portion.
ControlNet guarantees at least one node will have the
opportunity to transmit unscheduled data every interval. The
starting node for each NUT rotates to guarantee each node will
have an unscheduled transmit time. The remaining bandwidth
supports non time-critical data transfers. Non time-critical data
transfers include:
•
connection establishment
•
peer to peer messaging
•
programming (uploads and downloads)
•
Moderator
The node with the lowest MAC ID (node address) assumes the
moderator role. The moderator frame is transmitted to keep the
other nodes synchronized. This moderator frame is sent in the
guardband.
ControlNet MAC Frame Structure
All transfers use the MAC frame format shown in the following
illustration.
Each node can send only one MAC Frame at each opportunity to
transmit. Each MAC Frame contains one or more LPackets
(Link-Packets). Each LPacket contains one piece of “application
information”.
Audience This interface software is written for network specialists. It will assist
network engineers in designing and debugging of ControlNet
products and will help maintenance personnel during installation or
troubleshooting of a ControlNet network.
0 - 510 Bytes Max Source
MAC
LPacket LPacket LPacket .........
41562
MAC Frame