Serial Communication Converters & Adapters Instruction Manual
18
Connections
The PDA8485 is powered by the USB port.
The PDA8485 can be configured for either a
four-wire or two-wire network. Figure 26 details
the wiring connections from the PDA8485 to an
RS-422/485 serial device in a four-wire network.
PDA8485 to RS-422/485 Serial Device Four-
Wire Connections
PDA8485 Serial
Converter
RS-422/485 Serial
Device
DO
DI
DO
DI
DI
DO
DI
DO
Figure 26. Connections for PDA8485 in a
Four-Wire Network
Figure 27 details the wiring connections from the
PDA8485 to an RS-422/485 serial device in a
two-wire network when the DIP switches on the
PDA8485 have been set to the “2-Wire Mode”.
PDA8485 to RS-422/485 Serial Device Two-
Wire Connections
PDA8485 Serial
Converter
RS-422/485 Serial
Device
DO
DATA
DO
DATA
Figure 27. Connections for PDA8485 in a
Two-Wire Network
The PDA8485 internally connects the /DI to the
/DO and the DI to the DO when the DIP
switches are set to “2-Wire Mode”. Either the /DI
or /DO could be used to connect to /DATA and
either the DI or DO could be used to connect to
DATA.
Figure 28 shows an example configuration of a
two-wire network. Each device (e.g. Trident
PD765 meter) connected to the same network
must have a unique address.
Figure 28. RS-485 Two-Wire Multi-Drop
Wiring
Notes:
1. Termination resistors are optional and
values depend on the cable length and
characteristic impedance. Consult the
cable manufacturer for
recommendations.
2. Refer to PDA7422 documentation for
further details.
3. Use shielded cable, twisted-pair plus
ground. Connect ground shield only at
one location.
