Rockwell Automation 1757-SWKIT4000 ProcessLogix R400.0 Installation and Upgrade Guide - Manual (Page 265)

Publication 1757-IN040B-EN-P - March 2002
Performance and Capacity Specifications 11-13
Figure 11.1 System Communications Architecture
The server is the head of a “pyramid” of controllers. Each controller,
in turn, is a head of a pyramid of IO chassis. Each IO chassis is in
turn, a head of a pyramid of field devices nodes.
System communication is most effective and efficient if minimum
networks and nodes are involved between communicating devices
within a pyramid. For example, if a transmitter and a valve form a ¼
second control loop, and they are on the same H1 network, latency of
communications will be minimal and traffic in other nodes and
networks will be minimal.
There are tradeoffs, however. A better algorithm set in the
ProcessLogix controller, the need for sequencing logic, or mixture
with conventional or other bus I/O are examples where controller
interaction is required. Further, interlocks with equipment in other
areas of the plant under other ProcessLogix controllers is not
uncommon.
Operator and
Applications Nodes
Server Node
Controller
Nodes
IO Nodes
Device Nodes