Db9 Connector Pinouts; Rs485 Serial Port - ELPRO 245U-E User Manual

245U-E Wireless Ethernet

DB9 Connector Pinouts

Pin Name Direction
1 DCD Out
2 RD Out
3 TD
4 DTR
5 SG
6 DSR Out
7 RTS
8 CTS Out
9 RI

RS485 Serial Port

The RS485 port provides for communication between the 245U-E unit and its host device using a multi-drop cable. Up to
32 devices may be connected in each multi-drop network.
As the RS485 communication medium is shared, only one of the units on the RS485 cable may send data at any one
time. Thus, communication protocols based on the RS-485 standard require some type of arbitration.
RS485 is a balanced, differential standard but it is recommended that shielded, twisted pair cable be used to
interconnect modules to reduce potential RFI. It is important to maintain the polarity of the two RS485 wires. An
RS485 network should be wired as indicated in the diagram below and terminated at each end of the network with a
120-ohm resistor. On-board 120-ohm resistors are provided and may be engaged by operating the single DIP switch in
the end plate next to the RS485 terminals. The DIP switch should be in the "1" or "on" position to connect the resistor.
If the module is not at one end of the RS485 cable, the switch should be off.
Shorter runs of 485 cable may not require the termination resistors to be enabled.
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Function
Data carrier detect
Transmit Data – Serial Data Output (from DCE to DTE)
In Receive Data – Serial Data Input (from DTE to DCE)
Data Terminal Ready
In
Signal Ground
Data Set Ready - always high when unit is powered on.
In Request to Send
Clear to send
Ring indicator
HOST
RS485 CONNECTIONS
MODEM
User Manual
HOST
Dec 2009