Default Parameters - Allen-Bradley ControlLogix User Manual

1-10 ControlNet Communication Basics

Default Parameters

1756-6.5.3 - December 1999
When a ControlNet network is powered on for the first time, it comes up
with a default set of ControlNet parameters capable of sending only
unscheduled data. The default set of network parameters in the 1756-CNB,
as well as all ControlNet devices, is:
Network Update Time (NUT) of 100ms
Scheduled Maximum Node Address (SMAX) of 0
The SMAX is the highest network address of a node that can use the
scheduled service.
Unscheduled Maximum Node Address (UMAX) of 99
The UMAX is the highest network address of a node that can
communicate on the 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 communicate between the
various devices on the network by using such packages as RSNetWorx for
ControlNet, RSLogix5000, and the ControlLogix Gateway Tool
(1756-GTWY).
If used in this default state, optimum performance may not be achieved.
However, the default network can be commissioned (tuned) for optimum
performance, as described later in this manual.
Important: The ControlNet network should be configured using
RSNetWorx for ControlNet to improve performance.
At a minimum, we recommend that the Unscheduled Maximum
Node Address (UMAX) be set equal to the highest node
address on the network. Leaving this parameter at the default
value of 99 will waste bandwidth and reduce system
performance.
We also recommend setting the Scheduled Maximum Node
Address (SMAX) to a value 3 or 4 above the highest scheduled
node address to allow for future expandability.