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1.2 Network Configuration of DeviceNet
1
(3) Maximum Cable Length
The distance between two nodes on a network cannot exceed the "maximum cable
lengths" of the DeviceNet specifications. In Figure 1-4, the distance from node 0 to
node 60 is not allowed to exceed the "maximum cable lengths."
The "maximum cable lengths" vary depending on the communication rate of the
network and the type of the cable used for the trunk line.
(a) Table 1-2 lists the maximum cable lengths in cases where the trunk line consists
of a thick Cable or a thin Cable alone without drop lines (that is, all nodes are
connected to the trunk line) as shown in Figure 1-5. In this case, the maximum
trunk line length between node 0 and node n will be the maximum cable length. If
the maximum trunk line length between node 0 and node n equals the maximum
cable length, no new node can be added outside node 0 and node n.
Figure 1-5 Distance between Two Nodes on a Network with No Drop Line
(b) Figure 1-6 shows the maximum distance between two nodes in cases where a
thick Cable or thin Cable alone is used for the trunk line with drop lines.Table 1-2
lists the maximum cable length between two nodes.
In this case, the maximum trunk line length between the two nodes will
be=Maximum cable length (value in Table 1-2) - Length of drop lines for the
nodes at both ends of the trunk line
In the case shown in Figure 1-6, the maximum trunk line length between node 0
and node n is equal to the maximum cable length (value in Table 1-2) minus the
total length of drop lines for node 0 and node n.
Figure 1-6 Distance between Two Nodes on a Network with Drop Lines
Table 1-2 Maximum Cable Length (Thick Cable or Thin Cable alone)
Communication Rate
Thick Cable alone
Thin Cable alone
125kbps
500m
100m
250kbps
250m
100m
500kbps
100m
100m
Node 0
Node 2
Node 3
Node n
Terminator
Terminator
Distance between two nodes <= Maximum cable length
Node 0
Node 2
Node 3
Node n
Terminator
Terminator
Distance between two nodes <= Maximum cable length
