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DISTRIBUTED I/O
in a different cabinet, or allow a minimum distance of
18 inches (50 cm) between frequency converters
and their respective cabling, and Distributed I/0
Modules.
FTT devices can be wired in daisy chain, star, loop or any
combination thereof as long as the maximum wire length re-
quirements given below are met. The recommended con-
figuration is a daisy chain with two bus terminations. This
layout allows for maximum bus length, and its simple struc-
ture presents the least number of possible problems, par-
ticularly when adding on to an existing bus.
NOTE: A doubly-terminated bus may have stubs of up to
10 ft (3 m) from the bus to each node.
Table 13. Doubly-terminated bus specifications
Cable type
Belden 85102
Belden 8471
Level IV, 22 AWG
JY (St) Y 2x2x0.8
TIA568A Categ. 5 24AWG, twisted pair
NOTE: The cable types listed above are as recommended
by Echelon® in their FTT-10A User Guide. The
cable recommended by Honeywell is the level IV, 22
AWG, solid core, non-shielded cable. Belden part
numbers are 9H2201504 (plenum) and 9D220150
(non-plenum).
device
termination
device
module
Fig. 29. Doubly-terminated bus configuration
(recommended)
Free topology requires only one bus termination and allows a
variety of bus configurations (see Fig. 30):
device
termination
device
module
singly-terminated
device
termination
module
device
Fig. 30. Possible bus configurations
EN0B-0090GE51 R0802
Max. bus length
8,900 ft (2,700m)
8,900 ft (2,700m)
4,600 ft (1,400m)
3,000 ft (900m)
3,000 ft (900m)
device
termination
device
device
module
device
device
device
device
device
star
device
termination
module
device
The FTT specification includes two components that must be
met for proper system operation. The distance from each
transceiver to all other transceivers and to the termination
must not exceed the maximum node-to-node distance. If
multiple paths exist, the maximum total wire length is the total
amount of wire used.
Table 14. Free topology (singly-terminated)
Cable type
Belden 85102
Belden 8471
Level IV, 22AWG
JY (St) Y 2x2x0.8
TIA568A Category 5
24AWG, twisted pair
IMPORTANT
device
Do not use different wire types or gauges on the
same L
change in line impedance characteristics would
cause unpredictable reflections on the bus.
Examples of allowed and not-allowed free topology layouts
for cable JY (St) Y 2x2x0.8 are shown in Fig. 32.
22
device
device
device
loop
device
device
termination
module
mixed
Fig. 31. Free topology examples
specifications
Maximum node-
to-node distance
1,650 ft (500 m)
1,300 ft (400 m)
1,300 ft (400 m)
1,050 ft (320 m)
825 ft (250 m)
W
network segment. The step
ON
ORKS
device
device
device
device
device
device
device
device
Maximum total
wire length
1,650 ft (500 m)
1,650 ft (500 m)
1,650 ft (500 m)
1,650 ft (500 m)
1,500 ft (450 m)
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