LJelect Sub GHz FSK/OOK Transceiver Module : Data Sheet : Page 37

LJ1269HC

Rev1.0 Page 37 Web: www.ljelect.com

4.2.4. Rx Start Procedure

As described in the former sections, the RxReady interrupt warns the uC that the receiver is ready.

 In Continuous mode with Bit Synchronizer, the receiver will start locking its Bit Synchronizer on a minimum or 12 bits of

received preamble (see section 3.4.13 for details), before the reception of correct Data, or Sync W ord (if enabled) can

occur.

 In Continuous mode without Bit Synchronizer, valid data will be available on DIO2/DATA right after the RxReady interrupt.

 In Packet mode, the receiver will start locking its Bit Synchronizer on a minimum or 12 bits of received preamble (see

section 3.4.13 for details), before the reception of correct Data, or Sync W ord (if enabled) can occur.

4.2.5. Optimized Frequency Hopping Sequences

In a frequency hopping-like application, it is required to turn off the transmitter when hopping from one channel to another, to

avoid spectral splatter and obtain the best spectral purity.

 Transmitter hop from Ch A to Ch B: it is advised to step through the Rx mode:

（0）LJ1269HC is in Tx mode in Ch A

（1）Program the LJ1269HC in Rx mode

（2）Change the carrier frequency in the RegFrf register

（3）Turn the transceiver back to Tx mode

（4）Respect the Tx start procedure, described in section 4.2.2

 Receiver hop from Ch A to Ch B:

（0）LJ1269HC is in Rx mode in Ch A

（1）Change the carrier frequency in the RegFrf registers

（2）Program the LJ1269HC in FS mode

（3）Turn the transceiver back to Rx mode

（4）Respect the Rx start procedure, described in section 4.2.4

Note all sequences described above are assuming that the sequencer is turned on (SequencerOff=0 in RegOpMode).

4.3 Listen Mode

The circuit can be set to Listen mode, by setting ListenOn in RegOpMode to 1 while in Standby mode. In this mode, LJ1269HC

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 LJ1269HC 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 21.