Allen-Bradley ControlNet Compact GuardLogix 1769, User Manual, Page: 18 / 100

Chapter 1 ControlNet Overview
Understand the Effect of the NUT on the API
This example illustrates how the NUT affects the API. A module on the network
can produce data only at binary multiples of the NUT to a maximum of the
NUT multiplied by 128. These multiples are referred to as rates on a ControlNet
network. Therefore, with a NUT of 5 ms, the module can send data at these rates.
Table 5 - NUT Example Data Rates
NUT Multiple Rate at Which Module Can
Send Data
5 ms 1 5 ms
2 10 ms
4 20 ms
8 40 ms
16 80 ms
32 160 ms
64 320 ms
128 640 ms
In this example, if you specify an RPI of 25 ms, then the network produces an
API of 20 ms, which is the next fastest rate at which the module can send data.
The module places the data on the network at every fourth network update
interval to produce the 20 ms API. Similarly, if you specify an RPI of 150 ms, the
network produces an API of 80 ms.
Schedule the Network
Connections over a ControlNet network can be one of the following:
•
•
Scheduled—Data transferred at specific times.
Unscheduled—Data transferred when the network can accommodate the
transfer.
To use scheduled connections, you must schedule the ControlNet network via
RSNetWorx for ControlNet software. For more information on how to schedule
a ControlNet network with RSNetWorx for ControlNet software, see the section
Use R SNetWorx for ControlNet Software on page 44 .
You must use RSNetWorx for ControlNet software to enable any connection in a
remote chassis. In addition, RSNetWorx software transfers configuration
information for the remote modules, verifies and saves NUT and other user-
specified network parameters, and establishes a schedule that is compliant with
the RPI and other connection options specified for each module.
18 Rockwell Automation Publication CNET- UM001E-EN-P - June 2016