U-Net cabling of SCP panels to
the SC-3 controller
Field Bulletin
Date: 9/28/99
Products: SC-3, SCP Panels
Subject: U-Net cabling of SCP panels to the SC-3 controller
Author: Greg Campbell
Communications
The SCP control panels communicate with SC-3 over
a proprietary network called U-Net. The U-Net cabling
link between the SC-3 and the SCP panels can be configured
in several different ways as detailed in this document.
Certain specifications must be followed to ensure
that reliable communications exist. Failure to adhere
to the guidelines specified in the manuals and this
document may result in intermittent or faulty communications
between the SCP panels and the SC-3.
SC-3 to SCP Panel Cabling (U-Net)
The SCP panels are connected to SC-3 U-Net ports
using a standard four pair straight-through Ethernet
cable. U-Net is a proprietary protocol used by the
SC-3 to communicate to the SCP Control Panels. Even
though the cable for Ethernet and U-Net are the same,
the actual pairs that are utilized for communications
are different. When referring to figure 2, the U-Net
cable utilizes pairs 1 and 2. This pin out is also
shown below in figure 3. Care must be taken to utilize
the twisted pairs as shown in figure 2. Failure to
adhere to this guideline will result in poor communications
especially over long distances.
Figure 1 - RJ-45
Jack
Figure 2 - Standard
Ethernet Cable Pairs
Figure 3 - U-Net
Cabling
U-Net Specifications
- Eight total U-Net ports on the SC-3
- Standard 10 Base T or 100 Base T cables should
be used for all connections
- Maximum total cable length per U-Net port is 1000
feet
- Maximum panels per U-Net port is 32 panels (not
to exceed 250 panels for the SC-3)
- Panels may be of any combination of SCP models
- The end of each U-Net line must be terminated
using a U-Net terminator.
Basic Configurations
Most applications will fit into one of two basic
configurations, star and daisy chain. These two configurations
are depicted in figures 4 and 6. Figure 5 depicts
a modification to the Daisy Chain configuration as
explained below. Combinations of these three configurations
may be used as long as the U-Net specifications mentioned
above are followed.
Daisy Chain
The Daisy Chain is a simple configuration as shown
in figure 4. The SCP panels are connected to the SC-3
through a chain of cables and panels with the loop-through
port of the last panel being terminated. This type
of configuration provides for a simple installation
but does not lend itself well to troubleshooting.
In this configuration the removal of a panel in the
middle of the chain will break communications with
any panels past that point.
Figure 4 - Daisy
Chain Configuration
Daisy Chain with RJ-45 "T's"
To improve the trouble shooting capabilities of the
Daisy Chain, a RJ-45 "T" connector can be used to
connect each panel instead of the panel's loop-through
port as shown in figure 10. This will allow each panel
to be removed from the chain without affecting other
panels. The loop-through ports of the panels do not
need to be terminated when the RJ-54 "T" is used but
the last panel or "T" in the chain must be terminated
as shown in figure 5.
Figure 5 - Daisy
Chain with "T" Configuration
Star
The Star configuration provides for very easy troubleshooting
and maintenance since each panel is connected to its
own U-Net port, as shown in figure 6, and can be removed
without affecting any other panels on the SC-3. The
loop-through port on each panel would require termination
in this configuration.
Figure 6 - Star
Configuration
U-Net Hub Applications
For applications that require distances beyond that
of the U-Net specifications listed above, a U-Net
Hub may be used. The U-Net Hub is designed specifically
for use with Utah Scientific's U-Net protocol and
can not be replaced
with an Ethernet hub.
U-Net Hub Specifications:
- Maximum of two hubs per U-Net line
- One input and eight output U-Net ports on each
U-Net Hub
- Standard 10 Base T or 100 Base T cabling should
be used for all connections
- Maximum total cable length per U-Net Hub port
is 1000 feet (with two hubs in series this provides
an overall maximum cable length of 3000 feet).
- Maximum panels per U-Net Hub port is 32 panels
(not to exceed 250 panels for the SC-3)
- Panels may be of any combination of SCP models
- The end of each U-Net line must be terminated
using a U-Net terminator.
- Unused U-Net ports are internally terminated but
may be terminated as well.
Figures 7 and 8 below show applicable uses for the
U-Net Hub to extend the overall length of a U-Net
line or increase the number of panels on one U-Net
line. Both figures show an advanced version of the
Star configuration shown in figure 6.
Figure 7 - U-Net
Hub Application
With the addition of the U-Net Hubs in the configuration
shown in figure 8, up to 64 panels can be connected
and disconnected without affecting each others communication
link to the SC-3. The Hubs also allow for each of
these 64 panels to be up to 2000 feet away from the
SC-3. Combinations of all of the U-Net configurations
depicted in this document may be used to fit a particular
requirement or application as long as the U-Net and
U-Net Hub specifications are followed as a guideline.
Figure 8 - Star
Configuration with U-Net Hubs
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