Rockwell Automation 1757-SWKIT5000 ProcessLogix R500.1 Installation and Upgrade Guide - Manual (Page 254)

Publication 1757-IN500A-EN-P - September 2002
11-14 Performance and Capacity Specifications
Processing power and memory are finite. CNB modules, for example, are
limited to 64 connections. The 1784-PCIC card is limited to 128 connections.
Node Processing Load Limits
Processing power of nodes of the network is finite. Usually the “highest” node
in the topology processes the most. A downlink CNB module in a Controller
Chassis can process I/O from 24 unscheduled or 64 scheduled IOMs,
requiring multiple CNBs when communicating with more than 24
unscheduled. The multiple CNBs can be configured in parallel to a single I/O
Net or to physically separate I/O Nets.
Communications Load Limits
Bandwidth of the network is finite. Some of this bandwidth must be used for
“housekeeping” functions. Message overhead also consumes bandwidth.
Limits expressed herein are largely derived from the above types of constraints.