SX1231 SEMTECH [Semtech Corporation], SX1231 Datasheet - Page 37

• Manufacturer Part Number: SX1231
• Description: Low Power Integrated UHF Transceiver
• Manufacturer: SEMTECH [Semtech Corporation]

4.3. Listen mode
The circuit can be set to Listen mode, by setting ListenOn in RegOpMode to 1. In this mode, SX1231 spends most of the
time in Idle mode, during which only the RC oscillator runs. Periodically the receiver is woken up and listens for an RF
signal. If a wanted signal is detected, the receiver is kept on and the data is demodulated.
Otherwise, if a wanted signal hasn't been detected after a pre-defined period of time, the receiver is disabled until the next
time period.
This periodical Rx wake-up requirement is very common in low power applications. On SX1231 it is handled locally by the
Listen mode block without using uC resources or energy.
The simplified timing diagram of this procedure is illustrated in Figure 18.
The duration of the idle phase is given by t
by t
programmed in the configuration registers via the serial interface.
Both time periods t
configuration register and are calculated as follows:
where ListenResol gives the Rx/Idle common resolution and is programmable on three values (1, 2 and 3), whereas
ListenCoefX is an integer between 1 and 255. All parameters are located in RegListen registers.
The timing ranges are tabulated in Table 15 below.
Table 15 Range of Durations in Listen Mode
Rev 2 - Nov 2009
ADVANCED COMMUNICATIONS & SENSING
ListenRx
. t
ListenRx
ListenRx
includes the wake-up time of the receiver, described in section 4.2.3. This duration can be
Figure 18. Listen Mode Sequence (no wanted signal is received)
and t
t
ListenRx
ListenResol
Rx
0101
1010
1111
ListenIdle
t
(denoted t
ListenIdle
ListenX
t
ListenIdle
( ListenCoef = 1 )
=
Min duration
. The time during which the receiver is on and waits for a signal is given
ListenCoef
4.1 ms
0.26 s
64 us
ListenX
Page 37
Idle
in the following text) are fixed by two parameters from the
X
⋅
Listen
( ListenCoef = 255 )
Re
Max duration
sol
16 ms
1.04 s
67 s
t
ListenRx
Rx
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SX1231
time