Echelon SmartServer 2.2 Hardware - Manual (Page 22)

The following table lists the enclosure markings for the L ON W ORKS network screw terminals on the
SmartServer and their connection type.
Screw Terminal Enclosure Marking L ON W ORKS Network Connection
17 LON ® B/PLT + TP/FT-10 twisted pair
18 LON ® A/PLT - TP/FT-10 twisted pair
RS-232/RS-485 Serial Ports
The SmartServer includes one RS-232 serial port and one isolated RS-485 multi-drop bus port. The
RS-232 serial connection is implemented on screw terminals 21–25. These connections are
polarity-sensitive. You can connect an external GSM modem, M-Bus devices, Modbus devices, or
legacy/nonnative devices (requires a custom driver) to the RS-232 serial port. The RS-232 serial port
supports only one device at a time.
The RS-485 bus connection is implemented on screw terminals 25–28. These connections are
polarity-sensitive: terminal 28 is marked positive (RT+), and terminal 27 is marked negative (RT-).
Do not reverse the polarity of the RS-485 port will because it will cause improper bus operation. The
RS-485 port picks up ground at terminal 25. The RS-485 connection is not susceptible to common
mode ground differential voltage swings, but you must use a suitable shielded cable when connecting
devices in noisy environments. You can connect Modbus devices or legacy/nonnative devices (requires
a custom driver) to the RS-485 port.
The following figure illustrates the location of the RS-232 and RS-485 screw terminals on the
SmartServer.
10 Assembling the SmartServer Hardware