Communication Protocols and Cable Networks 8000-2573-19

Communication Protocols and Cable Networks 8000-2573-19
Usage Guidelines
Brief Description
Communication
Protocols and Cable
Networks
SensorNet, RS-422, and Manchester are
proprietary serial data communications protocols.
SensorNet
SensorNet, RS-422, and
Manchester
SensorNet uses two wires to provide half-duplex,
multi-drop, differential communications.
How they are Different and
When to Use Them.
Advantages: High speed, 2-wire non-polarized,
high noise/surge/static immunity, long cable length,
drives 32 devices, upload firmware to domes, ping
communications test utility.
Disadvantages: Proper termination required for
reliable communications.
About this Guide
Network Topologies: Daisy Chain, Star,
Backbone.
This guide explains the difference between
American Dynamics video system dome control
protocols (SensorNet, RS-422, and Manchester)
and cable networks and when to use each. You
should carefully plan the network layout before
beginning an installation.
RS-422
Duplex RS-422 uses four wires to provide duplex,
multi-drop, differential communications.
Advantages: No termination required, allows more
repeaters per line.
For additional information see Application Note
AN_0026.
Disadvantages: Slower speed, 4-wire polarized,
less noise immunity.
If you need assistance...
Simplex RS-422 uses two wires to provide
simplex, multi-drop, differential communications.
Contact your sales representative.
Advantages: Two wires, no termination required,
allows more repeaters per line.
Disadvantages: Slow speed, one-way
communications, polarized wiring, less noise
immunity.
Network Topologies: Daisy Chain, Backbone.
Manchester
Manchester uses two wires to provide simplex,
multi-drop, differential communications.
Advantages: Moderate speed, high noise/surge/
static immunity.
American Dynamics and the American Dynamics logo are
registered trademarks of Sensormatic Electronics Corporation.
Belden is a registered trademark of Belden Inc. Other product
names (if any) mentioned herein may be trademarks or
registered trademarks of Sensormatic or other companies.
Disadvantages: Polarized wiring, not high speed,
drives three devices. Proper termination required
for reliable communications.
Network Topologies: Daisy Chain, Backbone.
No part of this guide may be reproduced in any form without
written permission from Sensormatic Electronics Corporation.
© 2008 Tyco International Ltd. and its Respective Companies.
All Rights Reserved.
RP 03/2008
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Protocol Comparison
Table 1 shows the differences between the various protocols: SensorNet, RS-422, and Manchester. Note that
each protocol requires certain types of cable. For more information, refer to application note AN-0026.
Table 1. Differences between protocols
Duplex
RS-422
SensorNet
Simplex
RS-422
Manchester
1 Twisted Pair
Unshielded
1 Twisted Pair
Shielded
1 Twisted Pair
Unshielded
2 Twisted Pair
Shielded
1 Twisted Pair
Shielded
1 Twisted Pair
Shielded
(Belden 8442 /
88442 or
equivalent)
(Belden 8760 /
88760 or
equivalent)
(CAT-5)
(Belden 8102 /
88102 or
equivalent)
(Belden 8102 /
88102, 8760 /
88760 or
equivalent)
(Belden 8760 /
88760 or
equivalent)
0.326mm2
(22AWG)
0.823 mm2
(18AWG)
0.205 mm2
(
24AWG)
0.326 mm
(
22AWG)
1000m (3300ft)
with repeater
600m (2000ft)
with repeater
1000m (3300ft)
with repeater
1500m (5000ft)
without
repeater
900m (3000ft)
without
repeater
1500m (5000ft)
without
repeater
Connection
Non-Polarized
Non-Polarized
Termination
Yes
Data Rate
Cable Type
2
2
0.326 mm
22AWG)
(
1000m
(3300ft)
1000m (3300ft)
1500m (5000ft)
Non-Polarized
Polarized
Polarized
Polarized
Yes
Yes
No
No
Yes
230.4
kbits/second
230.4
kbits/second
230.4
kbits/second
4.8
kbits/second
4.8
kbits/second
31
kbits/second
Max. Devices
32 per line
32 per line
32 per line
10 per line
10 per line
3 per line
Max.
Address
254
254
254
99
99
64
Network
Topologies
Daisy Chain,
Backbone,
Star
Daisy Chain,
Backbone,
Star
Daisy Chain,
Backbone, Star
Daisy Chain,
Backbone
Daisy Chain,
Backbone
Daisy Chain,
Backbone
Max. Length
0.823 mm
18AWG)
2
(
Wire Gauge
Note: In some environments, high noise on the network may limit cable distances to less than the maximums
indicated in the table.
Notes:
For SDU-3 through SDU-7:
• If using the dome pig-tail connector, terminate as usual (see Table 2).
• If using the I/O board connectors, terminate the I/O board as usual (see Table 2), but you must always
terminate the pig-tail connector so that the dome does not incorrectly think the pig-tail connector is being
used. This pig-tail termination does not appear on the network.
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Cable Network Comparison
Cable networks such as Star, Daisy Chain, and Backbone provide the means through which a communications
source speaks to remote devices. Table 2 explains what each network is, when to use it, and lists examples.
Note: The maximum number of remote devices connected to a network depends on the protocol and the
electrical demands of each device. Refer to instructions supplied with the device.
Table 2. Network comparisons
Cable
Network
What It Is:
Examples:
Star
• Use with SensorNet only.
The communications source is the hub of the
star network. Terminate the devices but do
not terminate the communications source.
• Use if you anticipate that the customer will want
to relocate devices in the future.
• The Star network consists of a single driver as
the communications source connected to a
maximum of four cable segments. Note that the
SensorNet/Manchester Distribution Panel
(ADACSNETD) and the SensorNet J-Box
(RJ6SN) contain multiple drivers.
CS = Communications Source
T = Terminated devices
• The cable distance is cumulative, meaning that
when added together they should not exceed
the maximum cable distance of 1000 meters
(3300 feet) with unshielded cable or 600 meters
(2000 feet) with shielded cable.
• The Star network is not recommended for high
noise environments or long distances due to the
extra terminations, which lower the signal to
noise ratio.
DaisyChain
• Use with SensorNet, RS-422, or Manchester.
Backbone
Daisy Chain:
• RS-422 does not require termination.
• A separate cable connects each adjacent device
along the chain. Daisy chaining makes it easy to
add devices by extending the network from a
nearby device. The communications source can
connect anywhere along the cable.
The communications source is at one end of a
daisy chain or backbone network. Terminate
the communications source and the last
device on the cable.
CS = Communications Source
T = Terminated devices
• Use if the cable is to be short and extended in
the future, or when the central distribution point
and the remote devices are in the same room.
Backbone:
• A single cable connects all the devices along the
backbone. To add a device, the insulation is
stripped and connected to the device. The cable
is not cut. The communications source can
connect anywhere along the backbone.
The communications source is in the center of
the cable. Terminate the devices on both ends
of the cable. Do not terminate the
communications source.
• Use if the cable is to be long and not extended
in the future.
• The backbone operates the same as the daisy
chain, but uncut wires may be more conductive
and reliable.
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Combining Cable Networks
Wire Connection
Star, Daisy Chain, and Backbone networks can be
used in combination. The diagram below shows
the communications source as the hub of a
combination of a Star and Daisy Chain/Backbone
network. CS = Communications Source, T =
Terminated device. Note that the star network is
used with SensorNet only.
Star and Daisy Chain networks use standard wire
connections where the wire is cut and inserted into
a connector and tightened down.
A Backbone network uses a different technique
where the cable is not cut. A 2.5cm (1in) section of
the insulation is stripped away and the wire is bent
(not cut) and inserted into the connector. Each
device is connected in this fashion so there are no
cuts in the cable.
Standard (cut)
Daisy Chain (wire is cut)
Backbone (wire is not cut)
Segment Terminations
Each communications source or remote device has
a termination switch or jumper to prevent signals
from reflecting back along a cable. Only terminate
a device when it is at the end of a cable.
Only terminate the ends of the main (long) cables.
Short stubs (less then 3 meters (10 feet)) of the
main cable, while not desirable, have a minimal
effect and should not be terminated.
Note: Because a J-Box Aux Out contains a driver
to amplify the signal, it acts as a communications
source to the devices connected to it. It is at the
end of the cable when a daisy chain or backbone
network is used so the J-Box Aux Out should be
terminated. It is not at the end of the cable when a
star network is used (SensorNet only) so the J-Box
Aux Out should not be terminated.
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#6: Attach network devices in stages. Check that
their response is correct so you can correct the
problem before continuing with the installation.
Use ping tests to measure failure rate or operate
the dome to verify proper operation.
Installation Tips
SensorNet
#1: Only terminate a communications source or
#7: No more than 32 devices per cable segment.
With a daisy chain or backbone network, a cable
segment starts at the first network device on the
cable and ends at the last network device on the
cable. The network device at the start or end of the
cable may be a communications source. With a
star network, up to four branches can be
supported. All four branches are considered one
cable segment for the purpose of determining the
cable length. However, the network device at the
end of each of the four branches should be
terminated to ensure reliable communication.
network device if it is at the end of a cable or “endof-line”. Each SensorNet device has a termination
switch or jumper. Terminating the devices at the
ends of the cable prevent the signals from
reflecting back along a cable. Proper termination
makes communications more reliable. J-Box and
distribution panel outputs renew or amplify the
signals, so they are considered communications
sources. With daisy chain and backbone networks,
they are considered end-of-line and should be
terminated. With star networks, they are not
considered end-of-line and should not be
terminated. J-Box and distribution panel inputs are
considered network devices. Terminate them only
if they are end-of-line.
#8: SensorNet can be used with Star, Daisy
Chain, or Backbone networks.
#9: SensorNet connections are not polarized.
#2: If a repeater must be used, place the repeater
midway along the cable. This will ensure that there
is a reliable signal at the input to the repeater.
Advantages of SensorNet
#3: No more than four repeaters are allowed
1. The connections are not polarized and the two
wires can be connected in any order.
between any two devices on the network. Devices
include SensorNet Domes, TouchTrackers,
SensorNet I/O units, SensorNet to RS-422
converters, SensorNet Distribution Panels,
SensorNet links for American Dynamics MPCPU /
MP48 / VM96 / AD168 switches, SensorNet JBoxes, and fiber optic transceivers that contain
repeaters between their separate output ports.
2. Firmware can be uploaded to domes using a
PC with a USB-to-SensorNet module
(ADACSNET), an MP48 Plus system, or an
ADTT16E controller.
3. A ping test can be used to determine the
reliability of the network.
4. Remote manual dome reset command from
console.
This 4-repeater restriction includes devices that are
not on the same cable segment or leg of the
network. Network collisions resulting in loss of data
may occur between out-bound (from the
communications source) and in-bound (to the
communications source) communications.
5. SensorNet outputs are transformer coupled to
provide 2000V galvanic isolation, to prevent
ground loops, and to prevent conducted
discharge currents from flowing through the
system.
#4: Signal repeaters (J-Boxes, Distribution Panels)
should only be cascaded when cable distances
exceed the maximum allowed or when noise is an
issue. SensorNet devices can operate at signal
levels from 0.3 to 5V, but 1 to 5V is recommended.
6. SensorNet outputs incorporate TVS surge
protection diodes and drivers that can
withstand 2000V ESD level surges.
7. SensorNet outputs are protected with PTC
self-resetting fuses to guard against
inadvertent wiring connection to up to 30Vac
class 2 LPS power.
#5: If shielded cable is used, signals may rapidly
decline as more devices are connected or as the
cable length increases. As a result, the maximum
length allowed for shielded cable is reduced. The
shield should be connected at the communications
source end only.
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RS-422
Manchester
#1: RS-422 does not require terminations.
#1: Only terminate a communications source or
network device if it is at the end of a cable or “endof-line”. Each device has a termination switch or
jumper. Terminating the devices at the ends of the
cable prevent the signals from reflecting back
along a cable. Proper termination makes
communications more reliable. J-Box and
distribution panel outputs renew or amplify the
signals, so they are considered communications
sources. With daisy chain and backbone networks,
they are considered end-of-line and should be
terminated. Distribution panel inputs are
considered network devices. Terminate them only
if they are end-of-line.
#2: If a repeater must be used, place the repeater
midwayt along the cable. This will ensure that there
is a reliable signal at the input to the repeater.
#3: More than four repeaters are allowed between
any two devices on the network. Devices include
Domes, RS-422 converters (RCSN422), RS-422
Distribution Panels, RS-422 links for American
Dynamics MPCPU / MP48 / VM96 / AD168
switches, and RS-422 J-Boxes.
#4: Signal repeaters (J-Boxes, Distribution Panels)
should only be cascaded when cable distances
exceed the maximum allowed or when noise is an
issue.
#2: If a repeater must be used, place the repeater
midwayt along the cable. This will ensure that there
is a reliable signal at the input to the repeater.
#5: Ground the shield wire at the source device
only. This will prevent ground loops.
#3: No more than three repeaters are allowed
#6: Attach network devices in stages. Check that
between any two devices on the network. Devices
include Domes, code converters, Manchester
Distribution Panels, and Manchester links for
American Dynamics MPCPU / MP48 / AD168 /
AD2150 switches.
their response is correct so you can correct the
problem before continuing with the installation.
#7: No more than 10 devices per cable segment.
With a daisy chain or backbone network, a cable
segment starts at the first network device on the
cable and ends at the last network device on the
cable. The network device at the start or end of the
cable may be a communications source.
#4: Signal repeaters (Distribution Panels) should
only be cascaded when cable distances exceed
the maximum allowed or when noise is an issue.
#5: Ground the shield wire at the source device
#8: RS-422 can be used with Daisy Chain or
only. This will prevent ground loops.
Backbone networks only.
#6: Attach network devices in stages. Check that
their response is correct so you can correct the
problem before continuing with the installation.
#9: RS-422 connections are polarized. Care must
be taken to connect the correct wires to the
appropriate device terminals.
#7: No more than 3 devices per cable segment.
With a daisy chain or backbone network, a cable
segment starts at the first network device on the
cable and ends at the last network device on the
cable. The network device at the start or end of the
cable may be a communications source.
#8: Manchester can be used with Daisy Chain or
Backbone networks only.
#9: Manchester connections are polarized. Care
must be taken to connect the correct wires to the
appropriate device terminals.
COMMUNICATIONS PROTOCOLS AND CABLE NETWORKS
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