Omron OMNUC W Series Manual page 51

4 Connectors
4.5.3 DeviceNet Network Configuration Restrictions
4
Communications Line Length Calculation Example
An example of calculating the maximum network length, drop line length, and total drop
line length is given below for the following DeviceNet network.
With
Trunk line
Trunk line
terminating
10 m
resistor
2 m 3 m
2 m 1 m
Node Node Node
Drop line length Drop line length
2 m 5 m
Maximum Network Length
The line length between two nodes that are farthest apart is 48 m. The line length between
the terminating resistors is 40 m. The maximum network length is thus 48 m.
Drop Line Length
There are four branches from the trunk line. The drop line length is given in the above dia-
gram for each. The longest drop line length is 6 m.
Total Drop Line Length
The total length of all drop lines is 41 m.
Connection of the Terminating Resistors
Be sure to connect the Terminating Resistors at both ends of the trunk line to reduce signal
reflection and stabilize communications.
• When there is a T-branch Tap 6 m or less from the end of the trunk line (or the node):
A Terminating Resistor attached to a T-branch Tap can easily be mounted without taking
up much space.
• When there is not a T-branch Tap 6 m or less from the end of the trunk line (or the node):
Use one of the following methods.
• Connect a T-branch Tap to which a Terminating Resistor has been mounted.
• Connect a Terminal-block Terminating Resistor.
Trunk line
10 m
6 m 1 m
Node
3 m
2 m
1 m
Node Node Node
Node
Drop line length
6 m
4-20
With
terminating
20 m
resistor
6 m 6 m
2 m
Node
Node
Node
Drop line length
6 m
6 m