Echelon LonWorks Router - Manual (Page 75)

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