ATR0621 Datasheet, PDF (13/20 Pages) ATMEL Corporation – GPS Baseband Processor

ATR0621 [Preliminary]
3.3.5
Active Antenna Supervisor
If GPSMODE configuration is enabled, the two pins P0/NANTSHORT and P15/ANTON, plus
one pin of P25/NAADET0/MISO or P14/NAADET1 are initialized as general purpose I/Os and
used as follows:
• P15/ANTON is an output which can be used to switch on and off the antenna power supply.
• Input P0/NANTSHORT will indicate an antenna short circuit, that is, zero DC voltage at the
antenna, to the firmware. If the antenna is switched off by output P15/ANTON, it is
assumed that also input P0/NANTSHORT will signal zero DC voltage, that is, switch to its
active low state.
• Input P25/NAADET0/MISO or P14/NAADET1 will indicate that a DC current is sunk into
the antenna. In case of short circuit, both P0 and P25/P14 will be active, that is, at low
level. If the antenna is switched off by output P15/ANTON, it is assumed that input
P25/NAADET0/MISO will also signal zero DC current, that is, switch to its active low state.
Which pin is used as NAADET (P14 or P25) depends on the settings of GPSMODE11 and
GPSMODE10 (Table 3-14).
Table 3-13. Pin Usage of Active Antenna Supervisor
Pin
Usage
Meaning
P0/NANTSHORT NANTSHORT
Active antenna short circuit detection
High = No antenna DC short circuit present
Low = Antenna DC short circuit present
P25/NAADET0/
MISO or
P14/NAADET1
NAADET
Active antenna detection input
High = No active antenna present
Low = Active antenna is present
P15/ANTON
ANTON
Active antenna power on output
High = Power supply to active antenna is switched on
Low = Power supply to active antenna is switched off
Table 3-14. Antenna Detection I/O Settings
GPSMODE11 GPSMODE10 GPSMODE9
(Reset = PU) (Reset = PU) (Reset = PU) Location of NAADET
Comment
0
0
0
P25/NAADET0/MISO
0
0
1
P25/NAADET0/MISO
0
1
0
P14/NAADET1
Reserved for further use. Do
not use this setting.
0
1
1
P14/NAADET1 (Default)
1
0
0
P14/NAADET1
Reserved for further use. Do
not use this setting.
1
0
1
P14/NAADET1
Reserved for further use. Do
not use this setting.
1
1
0
P25/NAADET0/MISO
1
1
1
P25/NAADET0/MISO
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4890AS–GPS–09/05