LJelect Sub GHz FSK/OOK Transceiver Module : Data Sheet : Page 49

LJ1269HC

Rev1.0 Page 49 Web: www.ljelect.com

5.5. Packet Mode

5.5.1. General Description

In Packet mode the NRZ data to (from) the (de)modulator is not directly accessed by the uC but stored in the FIFO and

accessed via the SPI interface.

In addition, the LJ1269HC packet handler performs several packet oriented tasks such as Preamble and Sync word generation,

CRC calculation/check, whitening/dewhitening of data, Manchester encoding/decoding, address filtering, AES

encryption/decryption, etc. This simplifies software and reduces uC overhead by performing these repetitive tasks within the RF

Moduleitself.

Another important feature is ability to fill and empty the FIFO in Sleep/Stdby mode, ensuring optimum power consumption and

adding more flexibility for the software.

Figure 31. Packet Mode Conceptual View

Note The Bit Synchronizer is automatically enabled in Packet mode.

5.5.2. Packet Format

Fixed Length Packet Format

Fixed length packet format is selected when bit PacketFormat is set to 0 and PayloadLength is set to any value greater than 0.

In applications where the packet length is fixed in advance, this mode of operation may be of interest to minimize RF overhead

(no length byte field is required). All nodes, whether Tx only, Rx only, or Tx/Rx should be programmed with the same packet

length value.