Motorola M12 Oncore User's Guide download pdf (Page 48)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

Initialization

When powered up, the On cquisition and

tracking algorithms and will compute position when it acquires at least three

atellites. Fo eque ttery backed)

members t iously requested (continuous or onetime) and

te. If no me were requested uously the last time the receiver was

sed, it waits n input command b it outputs any other data, even though it

may have ac atellites and is p computing position fixes internally.

The Oncore receiver does not need to be initialized to its approximate user position

uire satellites and output position, nor does it require a current

satellite almanac. However, the TTFF will be considerably shorter if you help the

initially set the time or after it is obtained from the satellites. In addition, the receiver

retains the almanac and last used satellite ephemeris as long as the backup power is

applied. If you move the Oncore receiver a great distance before using it again, it will

find and acquire satellites, but the TTFF will be longer than normal the first time you

use the receiver. You can initialize the approximate position coordinates for faster

TTFF if desired.

Each message in the I/O format description in Chapter 6 shows the default value for

each parameter.

Shut Down

It is recommended that the receiver not be shut down within 35 s of computing an

initial 2D or 3D position fix. This allows for a full set of ephemerides to be downloaded

to RAM, which may shorten the next startup time.

Keep Alive Power

If you disconnect the keep alive power (BATT power), then the real-time clock (RTC)

and the battery backed RAM memory will be erased. In this scenario, date and time

are lost and the Oncore receiver will enter the cold powerup state when power is

reapplied. If the keep alive power is maintained during main power off, then the

receiver will retain the last known position and time as well as the almanac,

ephemeris, settings, and communications mode. If the receiver is turned on within

four hours of power down, then a hot start condition may apply. Otherwise, a warm

start condition will apply.

core receiver executes the satellite a

s r each of the user-r stable outputs, the receiver (if ba

re he prev message state

ra ssages contin

u for a efore

quired s ossibly

coordinates to acq

Oncore receiver find satellites by setting the approximate initial position coordinate

setting the time and date correctly, and installing a recent satellite almanac.

If backup power is available, the Oncore receiver retrieves its last known position

coordinates from RAM when main power is reapplied, and uses this information

the satellite acquisition algorithm. It also retrieves time and date information from the

internal real-time clock so you do not have to initialize this information after you

Revision 5.0 08/30/02

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Motorola M12 Oncore User's Guide Page 48

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