Page
14
RS
‐
232/485
RF
Modem
Product
Manual
–
MAN0782
‐
02
Wiring Diagram: RS-422
Figure
2.14.
RS
‐
232/485
RF
Modem
in
an
RS
‐
485
(4
‐
wire)
environment
RS-485/422 Connection Guidelines
The RS-485/422 protocol provides a solution for wired communications that can tolerate high
noise and push signals over long cable lengths. RS-485/422 signals can communicate as far as
4000 feet (1200 m). RS-232 signals are suitable for cable distances up to 100 feet (30.5 m).
RS-485 offers multi-drop capability in which up to 32 nodes can be connected. The RS-422
protocol is used for point-to-point communications.
Suggestions for integrating the RS-232/485 Modem with the RS-485/422 protocol:
1. When using Ethernet twisted pair cabling: Select wires so that T+ and T- are connected to
each wire in a twisted pair. Likewise, select wires so that R+ and R- are connected to a
twisted pair. (For example, tie the green and white/green wires to T+ and T-.)
2. For straight-through Ethernet cable (not cross-over cable) – The following wiring pattern
works well: Pin3 to T+, Pin4 to R+, Pin5 to R-, Pin6 to T-
3. Note that the connecting cable only requires 4 wires (even though there are 8 wires).
4. When using phone cabling (RJ-11) – Pin2 in the cable maps to Pin3 on opposite end of cable
and Pin1 maps to Pin4 respectively.
Figure
2.15.
Male
DB
‐
9
to
RJ
‐
45
Adapter
(yellow)
Figure
2.16.
Female
DB
‐
9
to
RJ
‐
45
Adapter
(green)
