Understand the media 1
1-2
Get Started
Understand the Topology
1 Understand the
med ia
The DeviceNet cable system uses a trunk/drop line topology.
TR
TR
You must terminate the trunk line at both
ends with 121 Ohms, 1%, 1/4W terminating resistors.
trunk line
drop line
device or node
TR = terminating resistor
Use only DeviceNet™ media that meet
or exceed ODVA specifications.
Understand the Cable Options
You can connect components using five cable options:
Wir e
Color
Wir e
Identity
Usage
Round
Usage
Flat
white
CAN_H
signal
signal
blue
CAN_L
signal
signal
bare
drain
shield
n/a
black
V-
power
power
red
V+
power
power
Use this cable
For
Round (thick)
The trunk line on the DeviceNetTM
network with a nominal outside
diameter of 12.2 mm(0.48 in.). You can
also use this cable for drop lines.
Round (mid)
The trunk line on the DevicenetTM
network where smaller cable diameters
and smaller bend radii are required. Its
outside diameter is specified by the
vendor. This cable can also be used for
drop lines.
Round (thin)
The drop line connecting devices to the
main line with an outside diameter of 6.9
mm (0.27 in.). This cable has a smaller
diameter and is more flexible than thick
cable. You can also use this cable for
the trunk line.
Flat
The trunk line on the DeviceNetTM
network, with dimensions of 19.3 mm x
5.3 mm (0.76 in. x 0.21 in.). This cable
has no predetermined cord lengths, and
you are free to put connections
wherever you need them.
Unshielded drop cable
This is a non-shielded, 4 conductor,
drop cable for use only in flat cable
systems, with an outside diameter
specified by the vendor.
NOTE: These generic cable types are avialable in a variety of different
offerings such as FLEX, HAZ-DUTY, CLASS I (600V), UV RESISTANT,
etc.
ODVA 2002
Get Started
1-3
All Devi ceNetTM Cabl in g c omponents selected shal l be s uitable for the
env ironme nt in whi ch they are in sta lled and in particu lar; corrosion resistance,
IP rating and Ultra Violet stabilisation.
Note: DeviceNetTM cables are available in a variety of dif ferent types
including; High flexibil ity, Hazardous duty, Class 1 - 600 Volt, UV resista nt.
Consideration must also be gi ven to environmental protection of cable
compo nents when individual nodes are removed for maintenance and for
testing.
Excessive bending of DeviceNet TM cables can reduce their ability to meet
the Devi ceNetTM specification. Standar d Thick cables shall have a bendi ng
radi us of greater than 3" (75mm). Standard Thin cables shall have a bendi ng
radi us of greater than 2" (50mm).
Round shielded cable (thi ck, mid and thi n) contains five wires: One twisted
pai r (red and black) for 24V dc power; one twisted pair (blue and white) for
signal, and a drain wire (bare).
Flat cable contains four wires: One pair (red and black) for 24 dc power; one
pair (blue and white ) for signal.
Unshielded 4-wire drop cable is only designed for use with flat cable systems .
The max imum cable distance is not
necessarily the trunk length only. It is
the m aximum distance between any
two devices.
Determine the Maximum Trunk Line Distance
The d istance bet ween any two points must not exceed the maximum cable
distance allowed for the data rate used.
Data rate
Maximum
distance
(flat cable)
125k bi t/s
420m (1378 ft)
500m (1640 ft)
300m (984 ft)
100m (328 ft)
250k bi t/s
200m (656 ft)
250m (820 ft)
250m (8 20 ft)
100m (328 ft)
500k bi t/s
75m (246 ft)
100m (328 ft)
100m (328 ft)
100m (328 ft)
Maximum
dist ance
(thick cable)
Maximum
distance
(mid cable)
Maximum
distance
(thin cable)
ODVA 2002
1-4
Get Started
For most cases, the maximum distance should be the measurement between
terminating resistors. However, if the distance from a trunk line tap to the
farthest device connected to the trunk line is greater than the distance from
the tap to the nearest terminating resistor (TR), then you must include the
drop line length as part of the cable length.
Measure the distance between the terminating resistors.
TR
tap
tap
tap
tap
3m (9.8 ft)
TR
D
D
drop
1m (3.3 ft)
D
D
D
D
Always use the longest distance
between any 2 nodes of the network.
If the distance from the TR to
the last tap is greater than the
distance of the drop, then
measure from the TR.
Measure both drops and across the trunk.
3m (9.843 ft)
TR
3m (9.843
tap
tap
tap
tap
tap
D
drop
5m (16.405 ft)
D
D
D
TR
D
If the distance from
the TR to the last
tap is less than the
distance of the
drop, then measure
from the device.
drop
5m (16.405 ft)
D
D
Determine the Cumulative Drop Line Length
The data rate you choose determines
the maximum trunk line and the
cumulative drop line lengths.
The cumulative drop line length refers to the sum of all drop lines, thick,
thin, or mid cable, in the cable system. This sum cannot exceed the
maximum cumulative length allowed for the data rate used.
Data rate
The maximum cable distance from any
device on a branching drop line to the trunk
line is 6m (20 ft).
ODVA 2002
Cumulative drop line
length
125k bit/s
156m (512 ft)
250k bit/s
78m (256 ft)
500k bit/s
39m (128 ft)
1-5
Get Started
The following example uses four T-Port (single-port) taps and two
multi-port taps to attach 13 devices to the trunk line. The cumulative drop
line length is 42m (139 ft) and no single node is more than 6m (20 ft) from
the trunk line. This allows you to use a data rate of 250k bit/s or 125k bit/s. A
data rate of 500k bit/s cannot be used in this example because the
cumulative drop line length (42m) exceeds the total allowed (39m) for that
data rate.
TR
TR
2m (6.6 ft)
5m
(16 ft)
3m (10 ft)
4m(13 ft)
2m(6.6 ft)
1m
(3.3ft)
4m (13 ft)
Multiple-port
tap (4 ports)
= trunk line
4m
(13 ft)
3m (10)
3m(10 ft)
3m(10 ft)
2m(6.6 ft)
2m (6.6)
1m
(3.3 ft)
3m(10 ft)
= drop line
= device or node
Multiple Port tap
(8 ports)
TR = terminating resistor
device with
removable
open-style
connector
About the Direct Connection
Connect devices directly to the trunk line only if you can later remove
the devices without disturbing communications on the cable
system.This is called a “zero-length” drop, because it adds nothing
(zero) when calculating cumulative drop line length.
Important: If a device provides only fixed-terminal blocks for its
connection, you must connect it to the cable system by a
drop line. Doing this allows you to remove the device at
the tap without disturbing communications on the trunk
line of the cable system.
device with
fixed
open-style
connector
ODVA 2002
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