WI-MOD-E-100 & WI-MOD-E-300 Wireless Ethernet
User Manual
WI-MOD-E Manual v1.10
Page
16
DB9 Connector Pinouts
Pin Name
Direction
Function
1
DCD
Out
Data carrier detect
–
2
RD
Out
Transmit Data
– Serial Data Output
3
TD
In
Receive Data
– Serial Data Input
4
DTR
In
Data Terminal Ready
-
5
SG
Signal Ground
6
DSR
Out
Data Set Ready
- always high when unit is powered on.
7
RTS
In
Request to Send -
8
CTS
Out
Clear to send -
9
RI
Ring indicator
-
2.4.2 RS485 Serial Port
The RS485 port provides for communication between the WI-MOD-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.
