Installation guide

LMU Users Guide

V1.0.6 December 10 2009

- 53 - CalAmp Proprietary & Confidential

7.6

For the most part the data session of the LMU is controlled by PEG. The one exception to

this is the Power On or Wake-Up behavior. On a Power Up or a Wake-Up the LMU will

immediately

Controlling the Data Session

attempt to establish a data session. This behavior can actually be prevented

using bit 7 of S-Register 140. If you set this bit, then the data session will not be attempted

on Power Up or Wake Up. If it is cleared, then the LMU will behave as normal.

To prevent the data session on power up, you would use:

AT$APP PARAM 1024,20,128,128

To enable default behavior, you would use:

AT$APP PARAM 1024,20,128,0

7.7

CDMA devices (modems, phones, data-cards, etc.) use a feature called a Preferred Roaming

List (PRL) which defines what networks the devices is allowed to use. For most carriers it is

possible to update the PRL by dialing a special number. In the LMU, this number is known

as the PRL Dial String and is contained in Parameter 2318. The most common dial string

used to update the PRL is *228, so to set the dial string to this value, you would use:

Updating the PRL

AT$APP PARAM 2318,0,”*228”

Keep in mind that the LMU automatically defaults the PRL Dial String for the following

carriers, so you generally do not need to change this value.

• Verizon Wireless

• Sprint

• Telus Mobility

• Cricket

• Alltel

When the LMU does not have a known default, it will automatically use *228.

A PRL dial can be initiated in one of two ways, either via a PEG Action of Send Special with

an Action Modifier of 3 or via an AT Command:

AT$APP Modem Update

A PRL dial sequence lasts approximately 90s to 2 minutes. The LMU will attempt to re-

connect to a data session once the PRL dial is complete.

Immediate is a bit of a misnomer, the LMU powers up the modem, reads several identifiers, scans for a

network and THEN tries the data session.