Network Cables User Manual

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USER’S GUIDE

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74-2865—04

LONWORKS® Bus

Wiring Guidelines

HONEYWELL CABLE 3252, 3253, 1061,

AK3797, AK3798, AK3799

INTRODUCTION

The Free Topology Transceiver (FTT) supports polarity

insensitive, free topology wiring. This frees the system

installer from wiring using a specific bus topology. T-tap, star,

loop, and mixed wiring topologies are all supported by this

architecture. Free topology wiring reduces the time and

expense of system installation by allowing the wiring to be

installed in the most expeditious manner. It also simplifies

network expansion by eliminating restrictions on wire routing,

splicing, and device placement.

A FTT network may comprise multiple segments (L

ONWORKS

Bus sections containing from one to sixty devices, each

device having a Neuron® ID to validate) separated by

physical layer repeaters or routers.

FTT networks are very flexible and convenient to install and

maintain, but it is imperative to carefully plan the network

layout and create and maintain accurate documentation. This

will aid in compliance verification and future expansion of the

FTT network. This will also minimize unknown or inaccurate

wire run lengths, node-to-node (device-to-device) distances,

node counts, total wire length, inaccurate repeater/router

locations, and misplaced or missing terminations.

APPLICATIONS

Free topology architecture allows the user to wire the control

devices with virtually no topology restrictions.

Unlike bus wiring designs, the FTT system uses a free

topology wiring scheme that supports T-tap, star, loop, mixed,

and/or daisy-chain (see Fig. 1). This design has many

advantages. First, the installer is free to select the method of

wiring that best suits the installation, reducing the need for

advanced planning and allowing last minute changes at the

installation site. Second, if installers have been trained to use

one style of wiring for all installations, free topology

technology can be introduced without requiring retraining.

Third, retrofit installations with existing wiring plans can be

accommodated with minimal, if any, rewiring. This capability

ensures that FTT technology can be adapted to both old and

new projects, widening the potential market for FTT based

products. Finally, free topology allows FTT systems easy

future expansion by tapping into the existing wiring where it is

most convenient to do so. This reduces the time and expense

of system expansion, and from the customers’ perspective,

keeps down the life cycle cost of the free topology network.

Fig. 1. Typical wiring topologies

supported by the FTT System.

TERMINATION

MODULE

TERMINATION

MODULE

DEVICE

TERMINATION

MODULE

TERMINATION

MODULE

DEVICE

MIXED

LOOP

DEVICE

DEVICE DEVICE

DEVICE

DEVICE DEVICE

SINGLY TERMINATED

STAR

DEVICE DEVICE

DEVICE

M12197

Summary of content (4 pages)

PAGE 1
LONWORKS® Bus Wiring Guidelines HONEYWELL CABLE 3252, 3253, 1061, AK3797, AK3798, AK3799 USER’S GUIDE INTRODUCTION DEVICE The Free Topology Transceiver (FTT) supports polarity insensitive, free topology wiring. This frees the system installer from wiring using a specific bus topology. T-tap, star, loop, and mixed wiring topologies are all supported by this architecture.
PAGE 2
LONWORKS® BUS WIRING GUIDELINES System expansion is simplified by the use of physical layer repeaters and routers. The Q7740A 2-Way or Q7740B 4-Way devices perform a repeater function, and the Q7751A operates as a router. See Fig. 2. If a LONWORKS Bus segment grows beyond the maximum number of devices or total wire distance, additional FTT segments can be added. This is done by connecting a Q7740A 2-Way or a Q7740B 4-Way physical layer repeater (see Fig. 3).
PAGE 3
LONWORKS® BUS WIRING GUIDELINES Table 1. Daisy-chain FTT Network Bus Topology Transmission Specifications (Doubly Terminated). Cable Parameters Wire/Cable Type (Unshielded) C nF/km Vprop% of c AWG/Dia. RloopW/km Maximum FTT Network Bus Length for Segment(s) Honeywell Cable 1125 (stranded non-plenum) 79 67 16/1.5 mm2 17.9 4600 feet (1400 m) Belden 85102 (stranded non-plenum) 56 62 16/1.
PAGE 4
LONWORKS® BUS WIRING GUIDELINES Table 5. Echelon Generic Cable Specification For Belden 85102 Equivalent, Stranded Twisted Pair 16 AWG (1.5 mm2). Minimum Typical Maximum Units 14.0 14.7 15.5 Ohms/km DC Resistance, each conductor DC Resistance Unbalance Mutual Capacitance Characteristic Impedance Attenuation 20 khz 64 khz 78 khz 156 khz 256 khz 512 khz 772 khz 1000 khz Propagation Delay 92 100 Cable Termination The FTT network segment requires termination for proper data transmission performance.