User's Manual

455U-D Radio Modem Module User Manual
Page 26 © Jan 2008
2.4.2 RS232 Configuration Port
The serial port is a 9 pin DB9 female and provides configuration and diagnostics of both the
local module and of other modules in the system wile the primary RS232 port is active. This
port is wired as a DCE according to EIA-561. The following table describes the connections
required to connect to a PC serial port. The highlighted entries in this table are those essential
for operation of the Configuration port.
RJ-45
Pin
E455U-D
Modem Function
EIA-561 Signal Name
1 None Ring Indicator
2 None Data Carrier Detect
3 Input Data Terminal Ready
4 Common Signal Common
5 Output Receive Data (from
Modem)
6 Input Transmit Data (to
Modem)
7 None Clear to Send
8 None Request to Send
2.4.3 RS485 Serial Port
The RS485 port provides for communication between the 455U-D 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
HOST 455U-D HOST
RS485 CONNECTIONS