Rockwell Automation Publication CNET-UM001F-EN-P - February 2018  19 
NUT  Multiple  Rate at Which Module Can Send Data 
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. 
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 RSNetWorx for ControlNet Software on page 46 on 
page 
44 on page 46. 
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. 
Important: 
RSNetWorx for ControlNet software must be run whenever a scheduled connection is added to, removed 
from, or changed in your system. 
 
Scheduled connections let you send and receive data repeatedly at a 
predetermined rate. You can use the 1756-CNB or the 1756-CN2 module to 
control scheduled I/O when you use it in conjunction with a ControlLogix 
controller. When you place the module in the I/O configuration list of a 
ControlLogix controller and configure a second ControlLogix chassis with a 
remote 1756-CNB or 1756-CN2 module on the same ControlNet network, 
you can perform remote control operations on the I/O, or to a second 
controller in the second chassis.