3-2
Section
Limitations on the Network Configuration
24
3-2
Limitations on the Network Configuration
3-2-1 Baud Rate and Communications Distance
The communications distance in a DeviceNet network is also restricted by the
baud rate, as shown in the following table.
Baud rate
Maximum network length
Drop line
Total drop
Thick cable
Thin cable
length
line length
500 kbps
100 m max.
100 m max.
6 m max.
39 m max.
250 kbps
250 m max.
78 m max.
125 kbps
500 m max.
156 m max.
Note Always keep the communications distance within the limits shown in this table.
3-2-2 Maximum Network Length
The length of the network is longest at either the distance between the two most
distant nodes or at the distance between the Terminating Resistors.
Node
Length of
drop line
Node
Communications
power supply
Node
Terminal-block
Terminating Resistor
T-branch Tap with
Terminating Resistor
Longest distance is the maximum network length
Length of
drop line
Node
There are two types of cables: Thick cables and thin cables. The thick cables are
relatively hard and inflexible, but they protect against signal attenuation and can
be used for relatively long communications distances. The thin cables are soft
and flexible, but they do not protect as well against signal attenuation and are not
suited to long communications distances.
The maximum length of a network thus depends on the type of cable that is used,
as shown in the following table.
Cable type
Maximum network length
Thick cables (5-wire)
500 m
Thin cables (5-wire)
100 m
Reference a) If the length of the network is 100 meters or less, the thin cables
can be used for the trunk line. When using thin cables for the trunk
line, be sure that communications power supply conditions are
met. Refer to 3-3 Sharing the Communications Power Supply.
b) The length of the network is also restricted by the baud rate used.
Even with thick cables, the length of the network will be restricted if
the baud rate is set to anything but 125 kbps. Refer to 3-2-1 Baud
Rate and Communications Distance above.
