SL869T3-I Product User Guide
1VV0301546 Rev. 3
Page 33 of 68
2021-03-31
8.7.2.
Antenna Enable (output)
The Antenna Enable output can be used to control an external power supply to an active
antenna (or external LNA, etc.). It will be high when the receiver is operating, or low when
it is in a low-power (standby) mode. It will also be set low when the Antenna Sense feature
detects a SHORT condition.
8.7.3.
Antenna Sense (input)
The Antenna Sense feature will measure the current consumed by the external LNA or
active antenna using two comparators with hysteresis. With 3.3 V supplied to an antenna
with a 30ma current draw, a 1
Ω
sense resistor yields input voltages to indicate the state
of the antenna. The FW reads these lines and provides an output message for antenna
NORMAL, OPEN, or SHORT.
This message can be configured to be output periodically or whenever the status
changes.
The Antenna Sense application note is available under a Non-Disclosure Agreement.
8.8.
I/O Port Operation
8.8.1.
UART Port Operation
The module provides three full-duplex UART ports which implement a standard
asynchronous 8-bit interface with configurable data rates. The signal input and output
levels are LVTTL compatible.
Warning: Care must be used to prevent back driving the RX line(s)
when the module is powered down or in a low-power state. If the RX
signal is used, it is important that it be either high impedance or logic
low whenever VCC has been removed from the device. Failure to
follow this requirement can lead to improper receiver operation upon
the next power-up.
8.8.1.1.
UART0 (TX & RX): Pins 20 & 21.
The UART can operate at rates from 4800 bps to 1.2288 Mbps.
This is the primary communications port which outputs data and accepts commands in
NMEA format.
