Installation guide

LMU Users Guide
V1.0.6 December 10 2009
Copyright ©CalAmp DataCom Inc 2009
- 33 - CalAmp Proprietary & Confidential
5.1.4.4 MDT Mode – Termination Character
The LMU-4100™ and LMU-2500™ can optionally detect a ‘Termination Character’ in the
data sent from the serial device over the MDT port. This character is meant to denote the
end of the message and that LMU should send the contents to the back-end system.
The Termination Character is meant for use when the serial device is sending ASCII
encoded text. When using serial devices that produce binary messages, it is best not to use a
Termination Character.
Two S-Registers control the Termination Character, one to enable it (S-133) and one to
define it (S-134).
To enable use of a Termination Character, you would need to set bit 2 of S-133. This is done
as follows:
AT$APP PARAM 1024,13,4,4
To disable the Termination Character, you would clear bit 2 using:
AT$APP PARAM 1024,13,4,0
The Termination Character to use is defined in S-134. S-134 is set to the decimal ASCII
value of the desired character. For instance, to use a Carriage Return, you would set S-134 to
13. That is:
ATS134=13
An ASCII chart can be found in Appendix C of this document.
5.1.4.5 MDT Mode – Message Termination Length
As an alternative to using a Termination Character, the LMU can be configured to send User
Messages based on the amount of data it receives from the serial device. That is, the LMU
will buffer a certain number of bytes and once it reaches the limit it will package the entire
buffer into a User Message and send it to the back-end system. The size limit of the buffer is
defined by S-Register 135. The value of S-135 is scaled in 4 byte increments up to a
maximum 804 bytes. The range of S-135 is therefore 1-201. For instance, to package 200
byte User Messages you would use:
ATS135=50
By setting the value of S-135 to 0 disables the termination length feature.
5.1.4.6 MDT Mode – Message Termination Timeout
The last option to define when to build a User Message is the Termination Timeout. In this
case, the LMU will collect data from the serial device for a specific period of time. When
that time has elapsed, the LMU will package the data into a User Message and send it to the