Installation guide

LMU Users Guide

V1.0.6 December 10 2009

- 31 - CalAmp Proprietary & Confidential

5.1.4 MDT Mode

MDT Mode allows a dumb serial device to pass messages through the LMU-4100™ or the

LMU-2500™ to the back-end system using LM Direct User Messages. The backend system

may also send a User Message to the LMU, the contents of which should be forwarded to

the serial device.

MDT mode can be enabled on either the Serial Adapter peripheral or on the ioPOD

peripheral by means of a jumper.

The Host Port’s MDT mode settings are controlled by S-Registers 130 thru 138 and S-

5.1.4.1 MDT Sub-Modes – LMU-4100™

The Host Port’s MDT mode supports two sub-modes, Generic Serial Device Mode and

Long Message Mode.

In Generic Serial Device mode, the LMU-4100™ will accept only single messages from the

generic serial device that are 804 bytes in length or less. Any excess data received will be

truncated. The LMU will package all 804 bytes in a single user message.

In Long Message Mode, the LMU-4100™ will break-up messages longer than 804 into

multiple User Messages. Each User Message will contain up to 804 bytes of data. It is up to

the receiving application (i.e. the backend) to re-assemble the original message from each of

the user messages.

In either mode, the backend system can only send messages to the LMU of 848 bytes or less.

Which mode is in use is controlled by S-Register 130. A value of 1 enables Generic-Serial

Device Mode and a value of 2 enables Long Message Mode. All other values are undefined

and should not be used. That is, to enable Generic Serial Device mode you would use:

ATS130=1

To enable long message mode you would use:

ATS130=2

5.1.4.2 MDT Modes – LMU-2500™

The LMU-2500™ only supports the Generic Serial Device mode. This mode is enabled by

setting S-Register 130 to 129. In this mode the LMU-2500™ will be in Host Port mode for

the first 30s after power up. After that, the LMU-2500™ switches to Generic Serial Device

mode. After a wake-up, the LMU-2500™ immediately enters Generic Serial Device mode.

To enable Generic Serial Device mode on the LMU-2500™, you would use:

ATS130=129