Rockwell Automation 1756-LSC8XIB8I ControlLogix Low-speed Counter Module - Manual (Page 44)

44 Rockwell Automation Publication 1756-UM536A-EN-P - April 2012
Chapter 4 Configure the Module
Remote Chassis Operation
A remote chassis contains the module but not the module’s owner-controller. If a
module resides in a remote chassis, the role of the RPI changes slightly with
respect to getting data to the owner-controller. The RPI not only defines when
the module produces data within its own chassis, but also determines how often
the owner-controller receives it over the network.
When an RPI value is specified for a module in a remote chassis, in addition to
instructing the module to produce data within its own chassis, the RPI also
reserves a spot in the stream of data flowing across the network.
The timing of this reserved spot may not coincide with the exact value of the RPI,
but the control system guarantees that the owner-controller receives data at least
as often as the specified RPI. As shown in
Figure 15 , data from the remote chassis
is sent to the ControlNet communication module at a rate no slower than the
configured RPI.
Figure 15 - Data from Remote Chassis Sent to ControlNet Communication Module
IMPORTANT In a peer control operation where the counter module provides peer input data
directly to a 1756-OB16IEF module, both the counter module and
1756-OB16IEF module must reside in the same physical chassis. For more
information about peer control, refer to the Peer I/O Control Application
Technique, publication
1756-AT016 .
ControlNet Network
Data Sent at RPI
Counter Module
Local Chassis Remote Chassis
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