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Chapter 2
Configurable Flowmeter Operation in the ControlLogix System
Configurable Flowmeter
Modules in a Remote Chassis
20
If a module resides in a networked chassis, the role of the RPI changes slightly
with respect to getting data to the owner.
The RPI not only defines when the module multicasts data within its own
chassis (as described in the previous section), but also determines how often
the owner-controller will receive it over the network.
When an RPI value is specified for a module in a remote chassis, in addition to
instructing the module to multicast data within its own chassis, the RPI also
"reserves" a spot in the stream of data flowing across the ControlNet network.
The timing of this "reserved" spot may or 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.
See
Figure 2
remote chassis.
Figure 2 - Module in Remote Chassis with RPI Reserving a Spot in Flow of Data
Owner controller
ControlNet Bridge module
Rockwell Automation Publication 1756-UM010C-EN-P - June 2021
for a better understanding of the data flow with a module in a
CFM data at least as often as RPI
ControlNet Bridge module
CFM module
Data in remote chassis
at the RPI rates
ControlNet
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