Rockwell Automation 1797-OE8H FLEX Ex HART Analog Modules User Manual - Manual (Page 72)

Publication 1797-6.5.3 - March 2006
4-4 Input, Output and Configuration Files for the Analog I/O Modules on the ControlNet Network
Unscheduled Data Transfer
Unscheduled operations include:
• Unscheduled non-discrete I/O data transfers–through ControlNet I/O
Transfer (CIO) instructions
• Peer-to-peer messaging–through message (MSG) instructions
• Messaging from programming devices
Unscheduled messaging on a ControlNet network is non-deterministic. Your
application and your configuration, that is, the number of nodes, application
program, NUT, amount of scheduled bandwidth used, determine how much
time there is for unscheduled messaging.
Module I/O Mapping
The I/O map for a module is divided into read words and write words. Read
words consist of input and status words, and write words consist of output and
configuration words. The number of read words or write words can be 0 or
more.
The length of each I/O module’s read words and write words vary in size
depending on module complexity. Each I/O module will support at least 1
input word or 1 output word. Status and configuration are optional, depending
on the module.