Serial Communication Converters & Adapters Instruction Manual
17
PDA8485 USB To RS-
422/485 Converter
Description
The PDA8485 converts USB to balanced, full or
half-duplex RS-422 or RS-485 signals.
The PDA8485 has a removable screw terminal
connector for the RS-422/485 terminals which
includes Transmit Data (DO) and (/DO), Receive
Data (DI) and (/DI), and Signal Ground.
Baud rates are automatic and handled by the
PDA8485.
The PDA8485 has three diagnostic LEDs: a
Power (P) LED to show when the converter is
powered properly, a Transmit Data (TX) LED to
show when the converter is sending data out
from the PC side, and a Receive Data (RX) LED
to show when the converter is receiving data
from the network side.
The DIP switch SW1 is located inside the case
and allows for system configurations.
Installation
The DIP switch SW1 allows for several different
options. Factory settings for the switch are
shown in Figure 24.
1 2 3 4 5
Figure 24. PDA8485 DIP Switch Location
The termination switch position adds an internal
120 ohm termination resistor when ON (up).
Termination should be used on both ends of the
network with high data rates and long wiring
runs.
To configure a two-wire network set both of the
2-wire switch positions to ON (up). For a four-
wire network set both of the 2-wire switches to
OFF (down).
When the RS-422 switch position is ON (up) and
the RS-485 switch position is OFF (down) it is
configured for an RS-422 network.
When the
RS-422 switch position is OFF (down) and the
RS-485 switch position is ON (up) it is
configured for an RS-485 network.
PDA8485 DIP Switch Settings
SW1 Switch
Position
ON Setting Function
1
Network Termination
Included (120 ohm)
2
2-Wire Network Mode
Connection (factory
setting)
3
2-Wire Network Mode
Connection (factory
setting)
4
RS-422 Mode
5
RS-485 Mode (factory
setting)
Figure 25. PDA8485 DIP Switch Settings
