Allen-Bradley 1794-IE8H, User Manual, Page: 64 / 146

Publication 1794-UM063A-EN-P - 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 nondiscrete 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 nondeterministic. Your
application and your configuration (for example, number of nodes, application
program, NUT, and 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.
I/O Structure
Output data is received by the adapter in the order of the installed I/O
modules. The output data for slot 0 is received first, followed by the output
data for slot 1, and so on up to slot 7.
Input data is sent by the adapter. The first word is the Adapter status word.
This is followed by the input data from each slot, in the order of the installed
I/O modules. The input data from slot 0 is first after the status word, followed
by input data from slot 1, and so on up to slot 7.