Start-Up Procedure; Coldstart; Warmstart - SimCom SIM548C HD V1.01 Hardware Design

SIM548C Hardware Design
Default output message: GGA,GSA, GSV,RMC,VTG
Update rate: Default 1Hz
Datum WGS84 default (User configurable)
Serial port B
2-wire serial interface
Includes the GPS_RXB(receive) and GPS_TXB (transmit) lines
Supported baud rate: 1200－115200 bps
Protocol: Default none
Notes:
1. Both interfaces are configured as 8 data bits, no parity and 1 stop bit..
2. The serial ports also can be configured to adapt to customer specific applications, such as for
DGPS, and so on. More detail please contact with SIMCom ltd.
3. We can also help the user to change the protocol and baud rate of the two serial ports by
different firmware. For more detail please contact SIMCom Ltd.

4.9 Start-up procedure

The start-up strategy of the module's GPS part depends on the last position, current time and
ephemeris data, that the receiver has stored the external SRAM memory. There are three different
start-up procedures:

4.9.1 Coldstart

The coldstart takes place when the receiver has no knowledge of its last position or time. In this
case the GPS RTC has not been running and no valid ephemeris data or almanac data is available
(The receiver has never been navigating or no battery backup memory available).

4.9.2 Warmstart

This start-up procedure is performed whenever the receiver is able to use the valid almanac data,
and has not in an important manner moved since the last valid position calculation. This procedure
starts if the receiver has been shut off for more than 2 hours, but the last position, time and
almanac are still acknowledged. This procedure is able to announce the current visible satellites in
advance. However, since ephemeris data are not available or cannot longer be used, the receiver
has to wait for the ephemeris broadcast to complete.
SIM548C_HD_V1.01
70
09.05.2008