Rockwell Automation 1794-OB16D FLEX I/O Diagnostic Modules User Manual - Manual (Page 44)

Publication 1794-UM061A-EN-P - July 2006
42 Configuring Modules for Communication on a Remote I/O Network
Create a Block Transfer
(Read or Write) Message
Instruction
Analog and specialty I/O modules are block transfer I/O modules. The size of
the data that is transferred from the modules to the controller is larger than the
space that RSLogix 5000 software has allocated in the controller memory. As a
result, you must create message instructions in the Ladder Logic program of
the ControlLogix controller to initiate the block transfer request and generate
tags (for example, space in the controller’s memory) for the data transferred.
This section explains how to configure a block transfer application.
To monitor or control an I/O device, assign the tag name of the device to an
instruction in your ladder logic:
• For step-by-step instructions on how to enter logic and tag names, refer
to the Logix5000 Controllers Common Procedures, publication number
1756-PM001.
• Data for I/O modules is stored at the controller scope. Controller scope
data tags can be used by all programs. In other words, the data in a
controller tag is available to every task or program within the controller
application. Controller tags can be viewed as global variables. When you
assign addresses, be sure the scope selection is at the Controller to view
the I/O tags.
1. Access the project’s Main Routine of ladder logic in the controller
organizer.
A. Right-click on Main Routine.
B. Click Open in the pull-down menu.