Rockwell Automation 1336T ControlNet Frn1.02 Rev 1.5 - Manual (Page 37)

Chapter
3
Publication 1336 FORCE–5.18 ––March, 1999
Using Scheduled Discrete
Data Transfer
This chapter provides information that can help you understand and
use ControlNet communications. This chapter covers the following
topics:
•
understanding communications
•
transferring data using scheduled discrete data transfer
When you use the ControlNet Adapter Board for ControlNet
communications, the drive looks like a remote I/O chassis to a PLC.
This allows you to use discrete message transfer.
With discrete message transfer, the PLC’s I/O image table is used to
transfer the data that the drive needs to have continuously updated.
ATTENTION: When configuring this drive on a ControlNet
network, you must request a NUT (Network Update Time) of 5ms or
greater. A NUT less than 5ms may cause data transfers to (and from)
the drive to become non–deterministic.
ControlNet has the option for redundancy. Redundancy for the entire
network is determined by the configuration tool (RS Networx
TM ).
The drive requires that some data be continuously updated. This
data is transferred using the PLC’s I/O image table. This data is
transferred between the drive and the PLC every Network Update
Interval (NUI).
Each group number reserves a single 16-bit word in both the input
and output image table of the PLC for the assigned rack number. In
the drive, these words are directly linked to internal drive parameters
using source and sink parameters.
In the following descriptions, each module group appears to have a
16-bit input and output module installed.
The following figure shows the ControlNet full rack configuration.
Module Group
0 1 2 3 4 5 6 7
Chapter Objectives
Understanding ControlNet
Communications
Transferring Data Using
Discrete Data Transfer
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