Terminator - Toshiba 2000 V Series Manual

Chapter 1 Overview of the Devicenet Module
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1.2.3

Terminator

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(c) Figure 1-7 shows the maximum distance between two nodes in cases where the
trunk line consists of thick and thin Cables with drop lines. Use the formulas in
Table 1-3 for calculating maximum cable lengths.
Maximum trunk line length between two nodes = Maximum cable length (value in
Table 1-3) minus the total length of drop lines for the nodes at both ends of the
trunk line.
In the case of Figure 1-7, the maximum trunk line length between node 0 and
node n will be equal to the maximum cable length (value in Table 1-3) minus the
drop line length between node 0 and node n.
Distance between two nodes <= Maximum cable length
Terminator
Node 0
Figure 1-7 Distance between Two Nodes on a Network with Drop Lines
Table 1-3 Maximum Cable Length (Mixed Use of Thick and Thin Cables)
Communication Rate
125kbps
250kbps
500kbps
L-thin: Length of trunk line using thin cable (m)
L-thick: Length of trunk line using thick cable (m)
The DeviceNet needs a terminal resistor at both ends of a trunk line in order to reduce
signal reflections and stabilize communications. The specifications of the terminator are
as follows:
• 121Ω
• 1% of metal film
• 1/4 W
Terminators conforming with the above specifications are now commercially available.
See 3.6 Network Components.
Usage Recommendations
• Make sure that your network configuration does not consist simply of extended trunk and
drop cables without nodes connected.
• Don't attach terminators to the nodes. It could cause communication errors.
• Don't attach a terminator to the ends of drop lines. Attach a terminator to both ends of
the trunk line;
L-thin L-thick
Node 3
Calculation Formula
L-thick + 5 × L-thin <= 500m
L-thick + 2.5 × L-thin <= 250m
L-thick + L-thin <= 100m
model 2000 DeviceNet Module Manual (DN611/DN611A)
Terminator
Node n