13

4890AS–GPS–09/05

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

(Reset = PU)

GPSMODE10

(Reset = PU)

GPSMODE9

(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