NXP Semiconductors MKW01Z128, Reference Manual, Page: 84 / 884

Transceiver Operating Modes
MKW01xxRM Reference Manual, Rev. 3, 04/2016
Freescale Semiconductor, Inc. 6-5
6.3 Listen Mode
The receiver can be set to Listen mode, by setting ListenOn in RegOpMode to 1 while in Standby mode.
In this mode, transceiver spends most of the time in Idle mode, during which only the RC oscillator runs.
Periodically the receiver is awakened 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 the transceiver it
is handled locally by the Listen mode block without using the MCU resources.
The simplified timing diagram of this procedure is illustrated in Figure 6-5 .
Figure 6-5. Listen Mode Sequence (no wanted signal is received)
NOTE
In Idle mode (a phase of Listen mode), the 32 MHz crystal oscillator of the
transceiver is disabled. If this signal, or a derivative thereof, is used as the
MCU clock via CLKOUT to EXTAL0, care should be taken in firmware to
configure the MCU clock to an internal low-power clock immediately prior
to asserting Listen mode to prevent loss of clock affecting MCU
performance.
6.3.1 Timing
The duration of the Idle phase is given by t
ListenIdle
. The time during which the receiver is on and waits for
a signal is given by t
ListenRx
.
t
ListenRx
includes the the wake-up time of the receiver, described in Section 6.2.3, “Receiver Startup
Time” . This duration can be programmed in the configuration registers via the SPI.
Both time periods t
ListenRx
and t
ListenIdle
(denoted t
ListenX
in the following text) are fixed by two
parameters from the configuration register and are calculated as follows:
time
t
ListenIdle
t
ListenRx
t
ListenRx
Idle
Rx
Rx