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SIM548C Hardware Design
4.7 GPS operation modes
Table 29: GPS operation modes
Mode
Function
Normal
operation
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 receiver do not differ significantly under good visibility
conditions.
Power Down
mode
In this mode the user can cut off the GPS_VCC to save more power
consumption. But the VRTC must always be on. When the user resumes the
GPS_VCC, the receiver wakes up, a valid position can be computed in the
normal hot-start time.
Push-to-Fix
mode (Refer to
Note)
In this mode the receiver will turn on every a given minutes (this period can be
set form 10 minutes to 2 hours by software) to perform a system update
consisting of position, time, ephemeris data refreshing and RTC calibration.
When the PTF mode is enabled, upon power on or a new PTF cycle, the
receiver will stay on full power until the good navigation solution is computed.
The stand-by state will follow for the remainder of the period. For example, if it
took 36 seconds to fix position and refresh ephemeris on the default period of
30 minutes, the receiver will sleep for the 29 minutes and 24 seconds. When the
application needs a position report, it can toggle the GPS_M-RST pin to wake
up the receiver. When the receiver wakes up, a valid position can be computed
in the normal hot-start time.
4.8 Serial interface of the GPS part
The GPS part of the module offers two serial interfaces, Allows for different protocols to operate
on each port.
For example
:
Serial port A
z
2-wire serial interface
z
Includes the GPS_RXA (receive) and TXA (transmit) lines
z
Supported baud rate: 1200 -115200bps
,
but 4800 - 38400bps is a common rate range
z
Protocol: Default NMEA ,4800bps
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09.05.2008
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