Data Sheet

LJ1269HC
Rev1.0 Page 52 Web: www.ljelect.com
5.5.3. Tx Processing (without AES)
In Tx mode the packet handler dynamically builds the packet by performing the following operations on the payload available in
the FIFO:
 Add a programmable number of preamble bytes
 Add a programmable Sync word
 Optionally calculating CRC over complete payload field (optional length byte + optional address byte + message)
andappending the 2 bytes checksum.
 Optional DC-free encoding of the data (Manchester or whitening)
Only the payload (including optional address and length fields) is required to be provided by the user in the FIFO.
The transmission of packet data is initiated by the Packet Handler only if the Moduleis in Tx mode and the transmission
condition defined by TxStartCondition is fulfilled. If transmission condition is not fulfilled then the packet handler transmits a
preamble sequence until the condition is met. This happens only if the preamble length /= 0, otherwise it transmits a zero or one
until the condition is met to transmit the packet data.
The transmission condition itself is defined as:
 if TxStartCondition = 1, the packet handler waits until the first byte is written into the FIFO, then it starts sending the
preamble followed by the sync word and user payload
 If TxStartCondition = 0, the packet handler waits until the number of bytes written in the FIFO is equal to the number
defined in RegFifoThresh + 1
 If the condition for transmission was already fulfilled i.e. the FIFO was filled in Sleep/Stdby then the transmission of packet
starts immediately on enabling Tx
5.5.4. Rx Processing (without AES)
In Rx mode the packet handler extracts the user payload to the FIFO by performing the following operations:
 Receiving the preamble and stripping it off
 Detecting the Sync word and stripping it off
 Optional DC-free decoding of data
 Optionally checking the address byte
 Optionally checking CRC and reflecting the result on CrcOk.
Only the payload (including optional address and length fields) is made available in the FIFO.
W hen the Rx mode is enabled the demodulator receives the preamble followed by the detection of sync word. If fixed length
packet format is enabled then the number of bytes received as the payload is given by the PayloadLength parameter.
In variable length mode the first byte received after the sync word is interpreted as the length of the received packet. The
internal length counter is initialized to this received length. The PayloadLength register is set to a value which is greater than the
maximum expected length of the received packet. If the received length is greater than the maximum length stored in
PayloadLength register the packet is discarded otherwise the complete packet is received.
Sub GHz FSK/OOK Transceiver Module DATASHEET