9XTend‐PKG‐R™RS‐232/485RFModem–ProductManualv1.2.4
©2005MaxStream,Inc.ConfidentialandProprietary 11
RS-422
Figure2‐14.XTendRFModeminanRS‐485(4‐wire)environment
2.3.3. 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 XTend 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.
Figure2‐15.MaleDB‐9toRJ‐45Adapter(yellow)
Figure2‐16.FemaleDB‐9toRJ‐45Adapter(green)
An XTend RF Modem Accessories Kit is available that includes connectors that facilitate RS-485/422
and other serial communications. Refer to the Development Guide in Appendix B for information
concerning the connectors and tools included in the kit.
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