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Chapter One
Introduction
Page
7
Chapter One INTRODUCTION
1.1
General
The WI-MOD-9-D radio modem module has been designed to provide flexible and reliable radio
modem functions, at an economical price.
Radio modems
transmit serial data over a long
distance via radio. The serial data is not changed - the output data is the same as the input data.
Although the WI-MOD-9-D is intended to be simple in its application, it also provides many
sophisticated features. This manual should be read carefully to ensure that the modules are
configured and installed to give reliable performance.
Each WI-MOD-9-D module will connect to a host device by RS232 or RS485 serial connection.
Examples of host devices are PLC’s, data loggers, intelligent transducers and computers. The
WI-MOD-9-D unit can receive data from the host device and transmit this data by radio to
another (or several) WI-MOD-9-D module. The other module will recreate the serial data and
output it as either a RS232 or RS485 serial signal. The WI-MOD-9-D unit provides two-way
communications - each module can accept serial data and also output serial data.
The WI-MOD-9-D module includes power supply, microprocessor controller, serial input/output
circuits and a 900MHz frequency-hopping spread-spectrum radio transceiver - no external
electronics are required. The WI-MOD-9-D radio frequency has been selected to meet the
requirements of unlicensed operation for remote monitoring and control of equipment. That is, a
radio licence is not required for the WI-MOD-9-D modules in many countries. See Chapter Five
Specifications
for details. The units are configured from a PC using a “free-ware” configuration
package, or from a PC terminal using Hayes commands.
RS232 is an electrical standard format for a full
duplex point-to-point serial connection. RS485
is an electrical standard format for a half-duplex
multidrop serial connection. Up to 32 devices
can communicate on a common RS485 serial
bus. Each WI-MOD-9-D unit can only connect
to one serial signal - either RS232
or
RS485.
However different modules in the same system
can connect to different types of serial signals. For example, RS232 data from one host device
can be transmitted to a remote WI-MOD-9-D unit and output as RS485 data to another host
device.
The WI-MOD-9-D has been designed to be flexible enough to cover a wide range of
applications. The user is able to configure many different parameters such that the WI-MOD-9-
D unit will connect reliably to different types of host devices. Before the radio modem can be
used, these parameters must be configured. Some of these parameters are :-
•
Character type - the WI-MOD-9-D will accept a variety of 7 or 8 data bit characters
•
Serial Data Rate - between 1200 and 115200 bits/sec
•
Radio Data Rate - 19200, 57600 or 115200 bits/sec
HOST
WI-MOD-9-D
RS232
HOST
WI-MOD-9-D
RS485