Allen-Bradley ControlNet Compact GuardLogix 1769, User Manual, Page: 21 / 100

ControlNet Overview Chapter 1
Default Parameters
When a ControlNet network is first established, it relies on a default set of
parameters capable of sending only unscheduled data. Default parameters in all
ControlNet devices include the following:
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Network Update Time (NUT) = 100 ms
Scheduled Maximum Node Address (SMAX) = 1
The SMAX is the highest network address of a node that can use the
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scheduled service.
Unscheduled Maximum Node Address (UMAX) = 99
The UMAX is the highest network address of a node that can
communicate on a ControlNet network. The UMAX must be set equal to
•
or higher than the SMAX.
Assumed maximum cable lengths and maximum number of repeaters
With this default ControlNet network, you can have unscheduled
communication between the various devices on the network by using
RSLogix 5000 software and RSLinx software.
IMPORTANT
To improve performance, configure a ControlNet network with
RSNetWorx for ControlNet software. We recommend these settings:
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Set the Unscheduled Maximum Node Address (UMAX) equal to
the highest node address on the network. Leaving this parameter
at the default value of 99 wastes bandwidth and reduces system
•
performance.
Set the Scheduled Maximum Node Address (SMAX) to a value
three or four above the highest scheduled node address, so you
can expand the network in the future.
Also, be aware that each skipped node will subtract a small amount
of bandwidth from the network.
ControlNet Network
Capacity and Topology
When planning a ControlNet network, consider these factors:
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Topology
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Number of nodes
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Distances
Connections
Topology
A ControlNet network supports a variety of topologies, including trunkline/
dropline, star, tree, and ring redundancy. In its simplest form, a ControlNet
network is a trunkline to which you connect nodes with a tap and a one-meter
dropline.
Rockwell Automation Publication CNET- UM001E-EN-P - June 2016 21