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<2. Overview of DeviceNet >
IM 34M6H28-01E
1st Edition : Feb.01,1999-00
• Cable
Five special purpose cables (2 signal lines, 2 power supply lines, and 1 SHIELD cable) are
used. There are 2 types of cables, namely, thick cables and thin cables .
• Trunk Line
Terminating resistors are attached at both ends of this cable. Both thick and thin cables can
be used. They can also be used together.
For a thin cable, the maximum network length is 100 m. In the case of thick cables, the
length limits depends on the data rate (see Table 2.1).
• Drop line
This is a branch cable from the trunk line and normally, thin cables are used for this pur-
pose.
The length (the distance from the point of branching from the trunk line to the end of the
drop line) of a drop-line cable should be 6 m or less. (There are no minimum distance
limits.) Generally, the total drop-line length depends on the data rate (see Table 2.1).
Table 2.1
Maximum Cable Length of DeviceNet
Data rate
Maximum cable length of trunk line
Length of drop line
Only thick cables used
Only thin cable
used
Maximum
Cumulative
125 kbps
500 m
100 m
6 m
156 m
250 kbps
250 m
78 m
500 kbps
100 m
39 m
T0201.EPS
• Connection Method
There are 2 methods of wire connection, the T-branching (using the T-branching tap) and
multiple-node daisy-chain methods. In a trunk line/ drop line, both methods can be com-
bined.
• Terminating Resistor
Terminating resistors (121
V
) are attached to both ends of a trunk line. This reduces the
reflection of signals and stabilizes communication.
In this module, there is a built-in terminating resistor. Therefore, when connecting the trunk
line using the daisychain method, you can turn on the terminating resistor setting switch
and use the built-in terminating resistor. In other connection methods, please turn the
switch off so that the built-in terminating resistor is not used.
• Network Power Supply
Out of the 5 special-purpose cables, two are for the 24 V DC network power supply. It is
necessary to supply power to each node of the network using the cables. If a single net-
work power supply source is used in a network, you can connect the power supply directly
to the trunk line. However, if multiple power supply sources are to be used in the network, it
is necessary to use special-purpose power supply taps.
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