Hardware Interface Description - KORE Telematics

XT55/56 Hardware Interface Description
Confidential / Released
s
4.3 GPS operating modes
Mode
Normal operation
Trickle Power
mode
Push-to-Fix mode
Function
The receiver is continuously running in Normal mode, as long as the operating
voltage Vcc is supplied. Position fixes are generated at the maximum update
rate. This enables the receiver a warm- and hotstart. However, the cold- and
warmstart times of the receiver do not differ significantly under good visibility
conditions.
Vcc is continuously supplied to the receiver in Trickle Power mode. By using a
especially configurable software, the user can force the receiver to acquire a
position fix periodically. Between two fixes, the receiver will be in a low power
mode.
The power-on scenario in Trickle Power mode on the XT55/56 GPS part differs
from one in continuous mode. If the receiver fails to acquire satellites within a
given period of time (approx. 150 sec), the receiver enters an extended sleep
phase. The duration of this sleep phase is approx. 30 sec. After that, the
receiver wakes up, starts a reset and tries to acquire satellites. This procedure
will be repeated until the GPS receiver can detect satellites. For further details
refer to [1].
In this mode the receiver will turn on every 30 minutes to perform a system
update consisting of a GPS RTC calibration and satellite ephemeris data
collection if required (i.e. a new satellite has become visible) as well as all
software tasks to support SnapSart in the event of an NMI. Ephemeris
collection time in general takes 18 to 30 seconds. If ephemeris data is not
required the system will recalibrate and shut down. In either case, the amount
of time the receiver remains off will be in proportion to how long it stayed on:
Off period = On Period*(1-Duty Cycle)
Duty Cycle
The off period has a possible range between 10 and 7200 seconds. The default
is 1800 seconds.
XT55/56_hd_v02.06a Page 72 of 125 17.12.2004