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1.2.2 Trunk Line/Drop Line and Maximum Cable Length
The DeviceNet specification stipulates the Thick Cable and the Thin Cable. For detail, see
DeviceNet Volume I. Currently, cables conforming with the standards of the Thick Cable and Thin
Cable are available in the commercial market. Buy ones which meet the configuration of your
network (Details are explained in "3.6 The Network Components").
(1) The Trunk Line
The trunk line of a DeviceNet consists of a Thick Cable or a Thin Cable (their mixture is also
possible). Since the Thin Cable is flexible compared with the Thick Cable, wiring the cable is easy.
Conversely, the Thick Cable allows longer network cabling than the Thin Cable. A maximum of the
trunk line length varies depending on the type of cable used and the communication rate on the
network. For details, see "3 The Maximum Network Length."
(2) The Drop Line
The drop lines of a DeviceNet consists of Thin Cables. Table 1.1 lists the length of drop lines and
the total length. A node on a drop line can be configured in a short drop line configuration/multi-
drops configuration/short brunch configuration. Figure 1.4 shows how to calculate the drop line
length and the total length by different configurations.
Table 1.1 Maximum Drop Line Length
Communication
Rate
Drop Line Total Extension by Network
125 kbps 156 meters
250 kbps 6 meters 78 meters
500 kbps 39 meters
Node 45
Node 5
Node 0
Node 60
Node 55
Node 50
Node 40
Node 30
Node 35
Node
25
Node
20
Node
15
Node
10
Tap
Terminal
resistor
Tap
Multiport tap
Branch configuration
Short drop line configuration
Multidrop
configuration
Terminal
resistor
i
h
g
f
e
d
c
b
a
Tap Multiport tap
Individual drop line length: a ≤ 6 m, b ≤ 6 m, c ≤ 6 m, and d ≤ 6 m (short drop line configuration)
e ≤ 6 m (multi-drops configuration)
f + g ≤ 6 m, f + h ≤ 6 m, f + i ≤ 6 m (branch configuration)
Total of drop lines extended : a + b + c + d + e + f + g + h + i
Figure 1.4 Example of Calculating the Drop Line Length