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Using an ftt-10a transceiver, Router user’s guide 65 – Echelon LonWorks Router User Manual

Page 75

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CP0

CP1

CP3

CP2

CP4

R

RE~

DE

D

A

B

VDD

GND

32 RX

34 TX

38

37 TXEN

39

Router 5000

EIA-485 Transceiver

+5 V

VDD3V3

+3.3 V

8

0.1 µF

10k

12V

12V

MUR115

(x4)

A

B

10k

+3.3 V

Figure 33. EIA-485 Twisted-Pair Interface (Uses Single-Ended Mode)

The EIA-485 specification requires a common ground reference for all

transceivers. This common ground reference can be provided by adding a third

conductor in the network cable or a separate connection to common ground at

each device.

Using an FTT-10A Transceiver

The FTT-10A Free Topology Twisted Pair Transceiver provides a simple, cost-

effective method of adding a L

ON

W

ORKS

transceiver to any Neuron Chip-based

control system. The FTT-10A transceiver supports polarity insensitive, free

topology wiring, freeing the system installer from the need to wire using a bus

topology. 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.
The FTT-10A transceiver consists of an isolation transformer that is integrated

with a 78 kbps differential Manchester coded communication transceiver. Pins

are provided for connections to the Router 5000 Communications Port (CP) and

clock lines, +5 V power, and the twisted pair network. The FTT-10A transceiver

provides automatic detection of the input clock frequency at 5, 10, and 20 MHz.

The pins are keyed to prevent accidental reversal during mounting. The FTT-

10A transceiver appears as a high impedance to the network when unpowered,

and does not interfere with network communications when powered down.
The transceiver is housed in an encapsulated plastic shell which contains the

transformer and signal processing electronics. The compact package is only 7.2

mm (0.28 inches) high, and is ideal for use in low profile applications such as DIN

packs. The sealed housing protects the transceiver should conformal coating or

other forms of environmental sealing be required on the printed circuit assembly.

L

ON

W

ORKS

Router User’s Guide

65