Toshiba DeviceNet nv Series, Инструкция по эксплуатации, Страница: 22 / 159

Chapter 1 DN611B Introduction
6F8C1686
6
Each drop line length: a
e
f + g
≤ 6[m], b ≤ 6[m], c ≤ 6[m], d ≤ 6m (short drop line configuration)
≤ 6[m] (multi-drop configuration)
≤ 6[m], f + h ≤ 6[m], f + i ≤ 6[m] (branch configuration)
Total extension of drop line: a + b + c + d + e + f + g + h + i
Figure 1-3 Drop line length calculation example-2 Formula
(3) Maximum cable length
The distance between two nodes on the network cannot exceed the "maximum cable length" of the DeviceNet
standard. In Figure 1-2, it is not possible to lay the cable so that the distance from node 0 to node 60 exceeds
the "maximum cable length".
"Maximum cable length" varies depending on the communication speed of the network and the type
of cable used for the trunk line.
(a) Table 1-2 shows the maximum cable length when the trunk line consists of only thick cables or thin cables
and no drop line is used (all nodes are connected on the trunk line) (Figure 1-4).
In this case, "Maximum length of trunk line between Node 0 and Node n" = "Maximum length of cable".
If "Maximum trunk length between Node 0 and Node n" = "Maximum cable length", new nodes cannot be
installed outside Node 0 and Node n.
Figure 1-4 Distance between two nodes in a network that does not use drop lines
Table 1-2 Maximum cable length (only thick cable / thin cable)
Rate Thick cable only Thin cable only
125 kbps 500 m 100 m
250 kbps 250 m 100 m
500 kbps 100 m 100 m
(b) Figure 1-5 shows the maximum distance between two nodes when the trunk line consists of only thick
cables or thin cables, and a drop line is used. The maximum cable length is shown in Table 1-2. In this case,
the "maximum trunk length between two nodes" is as follows.
Termination
Termination
Node 0 Node 2
Node 3
Node n
Distance between two nodes ≤ maximum cable length