Echelon LonWorks Router - Manual (Page 74)

Designator Value
R7, R8 499 Ω, 1%
R9, R11 2.15 kΩ, 1%
R10, R12 10 kΩ, 1%
U103 LT1016CN8
U104 AD826AN
Using an EIA-485 Transceiver
You can use the Router 5000 with commercially available EIA-485 transceivers.
A number of wire types can be supported, along with multiple data rates (up to
1.25 Mbps), as listed in the Series 5000 Chip Data Book.
With an EIA-485 transceiver, the common-mode network voltage can range
between –7 V to +12 V. To implement an EIA-485 device, the Router 5000’s
communications port runs in single-ended mode.
Available industry standards that describe EIA-485 specifications provide details
on unit loads, data rate, wire size, and wire distances. To ensure interoperability
between devices, the L
ON
M
ARK ® interoperability guidelines require a data rate of
39 kbps for devices that use EIA-485 transceivers. In addition, the EIA-485
transceiver must have TTL-compatible inputs for the connection to the 3.3 V
Router 5000 chip. A typical circuit configuration, shown in Figure 33, can
support up to 32 loads.
An EIA-485 network works best with a common power source. Individual device
power sources can create problems when the network common-mode voltage
exceeds –7 V to + 12 V, or when ground faults cause damage to devices.
64 Developing a LONWORKS Router