3-1
Section
Network Configuration
22
3-1
Network Configuration
The following diagram shows the configuration of a DeviceNet network.
DeviceNet
cables are used.
T:
T-branch connection
M: Multi-drop connection
DeviceNet cables (5-wire cables) are
used for the trunk lines and drop lines.
Node
Drop line
Drop line
Drop line
T-branch
Tap
Drop line
Drop line
Trunk line
Trunk line
Trunk line
Trunk
line
Trunk line
Trunk line
Node
Node
Node
Node
Node
Node
Node
Node
Node
T
T
T
T
M
M
T
M
M
M
T
Terminating Resistors
are connected at each
end of the trunk line.
Power Supply Tap
or T-branch Tap
24 VDC
Communications
power supply
DeviceNet
Cables are used.
T-branch
Tap
T-branch
Tap
T-branch
Tap
Drop line
Drop line
T-branch
Tap
T-branch Tap
Terminating Resistors
are connected at each
end of the trunk line.
3-1-1 Network Components
There are two kinds of nodes in a DeviceNet network. The Slaves connect to
external I/O and the Master administers the Network and manages the external
I/O of the Slaves. (There are also Slaves that exchange data with devices such
as the CPU Unit and PTs.) The Master and Slaves can be connected at any loca-
tion in the Network, as shown in the preceding diagram.
The trunk line refers to the cable that has Terminating Resistors on both ends.
Cables branching from the trunk line are known as drop lines. The trunk line
length does not necessarily coincide with the maximum length of the Network.
DeviceNet communications are transmitted through 5-wire cables. The cables
come in thick or thin versions.
Two methods can be used to connect DeviceNet nodes: The T-branch method
and the multi-drop method. With the T-branch method, the node is connected to
a drop line created with a T-branch Tap. With the multi-drop method, the node is
directly connected to the trunk line or the drop line. Secondary branches can be
made from a drop line. Both of these connection methods can be used in the
same Network, as shown in the example.
Terminating Resistors are connected at each end of the trunk line to reduce sig-
nal reflection and stabilize communications. There are two kinds of Terminating
Resistors available, one for a T-branch Tap and one for a Terminating-block Ter-
minating Resistor. Use a DeviceNet cable when connecting a Terminating-block
Terminating Resistor.
To use DeviceNet, connect a communications power supply to the communica-
tions connector of each node with a 5-wire cable. Basically, a communications
power supply, internal circuit power supply, and I/O power supply must be pro-
vided separately. (Refer to 3-7 Sharing the Same Power Supply for details.)
Note
1. Always use 5-wire DeviceNet cables.
2. Connect Terminating Resistors to both ends of the trunk line. When using a
Terminating-block Terminating Resistor, use a DeviceNet cable to connect
the Terminating Resistor. When connecting the Terminating Resistor, insu-
late the power supply lines that are not being used with vinyl electrical tape
to avoid a short-circuit in the cables.
3. Do not use products other than DeviceNet products (for example, a lightning
arrester) in the communications path. Using other products can interfere
with normal communications by causing signal reflections and other prob-
lems.
Nodes
Trunk/Drop Lines
Connection Methods
Terminating Resistors
Communications Power
Supplies
