User's Manual

905U-D Radio Modem Module User Manual
Page 28 © May 2000
Chapter Four CONFIGURATION
4.1 Before Configuring
Configuration comprises selecting parameter values for the operation of the 905U-D unit.
Before you start configuration, parameter settings must be decided.
The main parameters are :-
• Character type. You need to find out the character type of the host devices connected to
the 905U-D units. The most common character type is 8 data bits, no parity, 1 start bit
and 1 stop bit.
• Serial Data Rate. You need to find out the serial data rate used by the host devices. The
most common serial data rate is 9600 bits/sec.
• Radio Data Rate. You need to decide what radio data rate you wish to use. It does not
have to be the same as the serial data rate. Remember that the radio range for 9600
bits/sec will not be as good as that for lower data rates. Generally the data sent between
process control equipment is small, and 9600 bit/sec is not required. We recommend
that you use 4800 bits/sec unless your application requires the faster data rate.
• Operating mode . You need to decide which operating mode you wish to use. Modes are
transparent or controlled, error-checked or no-error-check, and autoconnect or host-
connect. These modes are discussed in more detail in following sections.
The other configuration parameters do not need to be selected, and are provided as a
means of "fine tuning" the operation of the 905U-D units.
Configuration may be performed from a terminal using Hayes commands, or by using the
miniature switches under the blue cover on the front of the unit.
The first step in configuration is to put the radio modem into Configuration Mode.
4.2 Configuration Mode
A 905U-D network comprises modules with the same "system" address. In controlled mode,
each module is also configured with a unit address between 0 and 127 - there can only be
127 modules in the one system. In transparent mode, modules are not configured with a unit
address, and there is no limit to the number of modules in a system (except for the capacity
of the radio channel).
4.3 Hayes Commands
The 905U-D unit may be configured by a host device using Hayes AT commands.
Configuration may be done by a user (with a PC terminal as the host device) or it can be
done automatically by a host device such as PLC or SCADA. The AT commands are ASCII
messages designed for use with conventional telephone modems.