Honeywell AK3799, 1061, 3252, AK3798, AK3797 User Manual

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LONWORKS® Bus

TERMINATION

MODULE

TERMINATION

MODULE

DEVICE

DEVICE

DEVICE

TERMINATION

MODULE

TERMINATION

MODULE

DEVICE

DEVICE

DEVICE

MIXED

LOOP

DEVICE

DEVICE

DEVICE

DEVICE

DEVICE

DEVICE DEVICE

DEVICE

DEVICE

DEVICE

DEVICE DEVICE

DEVICE DEVICE

SINGLY TERMINATED

STAR

DEVICE DEVICE

DEVICE DEVICE

DEVICE

M12197

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.

USER’S GUIDE

A FTT network may comprise multiple segments (L
Bus sections containing from one to sixty devices, each
device having a Neuron® ID to validate) separated by

ONWORKS

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.

74-2865—04

LONWORKS® BUS WIRING GUIDELINES

209541B

TERMINATION

MODULE

209541B

TERMINATION

MODULE

209541B

TERMINATION

MODULE

Q7740A

REPEATER

Q7740A

REPEATER

Q7751A2002

ROUTER

DAISY-CHAIN

TOPOLOGY

DAISY-CHAIN

TOPOLOGY

DAISY-CHAIN

TOPOLOGY

DAISY-CHAIN

TOPOLOGY

209541B

TERMINATION

MODULE

M12369A

Q7740B

4-WAY

REPEATER

209541B

TERMINATION

MODULE

DAISY-CHAIN

TOPOLOGY

FREE
TOPOLOGY

FREE
TOPOLOGY

FREE
TOPOLOGY

M12368

Q7740A

2-WAY

REPEATER

FREE
TOPOLOGY

FREE
TOPOLOGY

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 L

ONWORKS 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). The repeaters will transfer data
between the two L

ONWORKS Bus segments, allowing the

number of devices to be spread out as well as increasing the
length of wire over which they c omm unicate.

NOTE: Do not exceed the maximum of 120 devices for a

Q7750A Zone Managers L
(up to 60 devices are allowed per L

ONWORKS Bus network

ONWORKS Bus

segment).

The repeater function permits an FTT network to grow as
system needs expand, without retrofitting existing controllers
or requiring the use of specialized bridges. The maximum
number of repeaters per L
(on either side of the router). A Q7751A L

ONWORKS Bus segment is one

ONWORKS Bus

router can also be used to effectively double the maximum
L

ONWORKS Bus length. The advantage of using the router is

that it will segregate traffic to a L

ONWORKS Bus segment.

When using the repeater all traffic is repeated on each
L

ONWORKS Bus segment. (see following NOTES).

NOTES:

— There can be no more than one repeater on either

side of a Q7751A router.

— An FTT network can have no more than one router

per Zone Manager. Systems requiring high levels
of network traffic may benefit from the use of a
Q7751A router , which forwards p ackets only when
necessary. Routers are not allowed within loops.

Fig. 2. Repeaters and router in a FTT network.

Fig. 3. Physical layer repeater (Q7740A 2-Way or Q7750B 4-Way).

NETWORK CABLING AND CONNECTIONS

This section provides information about cabling and FTT
network connections.

IMPORTANT

• For network terminal connections, twist the wires
together a minimum of three times.

• Only use approved wire and do not use different wire
types on the same bus.

• Follow the bus length limits for the cable type used.

• Properly install the 209541B FTT Termination

74-2865—04 2

Module, see Fig. 4 through 7.

System Performance and Cable Selection

Transmission Specifications

The free topology transmission specifications include two
rules that must both be met for proper system operation:

1. The distance from each device to all other devices and
to the termination must not exceed the (singly
terminated) maximum node-to-node (device-to-device)
distance. For example, if multiple paths exist using loop
topology, then use the longest path for the calculations.

2. The maximum total wire length is the total amount of
wire connected per L

NOTE: See Table 1 for daisy-chain doubly terminated FTT

network bus topology transmission specifications
and Echelon® cable parameters.

ONWORKS Bus segment.