Serial Communication Converters & Adapters Instruction Manual
14
Figure 15. 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.
Connections
To power the PDA7485, connect 12 VDC to the
+12VDC and ground to the GND screw
terminals from the supplied 115 VAC/12 VDC
adapter.
The PDA7485 may be configured for either a
four-wire or two-wire network. Figure 16 details
the wiring connections from the PDA7485 to an
RS-422/485 serial device in a four-wire network.
PDA7485 to RS-422/485 Serial Device Four-
Wire Connections
PDA7485 Serial
Converter
RS-422/485 Serial
Device
DO
DI
DO
DI
DI
DO
DI
DO
Figure 16. Connections for PDA7485 in a
Four-Wire Network
Figure 17 details the wiring connections from the
PDA7485 to an RS-422/485 serial device in a
two-wire network when the DIP switches on the
PDA7485 have been set to the “2-Wire Mode”.
PDA7485 to RS-422/485 Serial Device Two-
Wire Connections
PDA7485 Serial
Converter
RS-422/485 Serial
Device
DO
DATA
DO
DATA
Figure 17. Connections for PDA7485 in a Two-
Wire Network
The PDA7485 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.
Two PDA7485 RS-232 to RS-422/485 Serial
Converters could be used as a serial extender to
allow RS-232 serial devices to communicate
over long distances. This would allow an RS-
232 device to operate up to 3,937’ (1,200 m).
