RFM66W Datasheet, PDF (62/87 Pages) List of Unclassifed Manufacturers – 868 & 915MHz Ultra Low Power High Link Budget Integrated UHF Transceiver

WIRELESS & SENSING
RFM66W
DATASHEET
5.5.7.2. Data Whitening
Another technique called whitening or scrambling is widely used for randomizing the user data before radio transmission.
The data is whitened using a random sequence on the Tx side and de-whitened on the Rx side using the same sequence.
Comparing to Manchester technique it has the advantage of keeping NRZ data rate i.e. actual bit rate is not halved.
The whitening/de-whitening process is enabled if DcFree = 10. A 9-bit LFSR is used to generate a random sequence. The
payload and 2-byte CRC checksum is then XORed with this random sequence as shown below. The data is de-whitened
on the receiver side by XORing with the same random sequence.
Payload whitening/de-whitening is thus made transparent for the user, who still provides/retrieves NRZ data to/from the
FIFO.
LFSR Polynom ial =X⁹ + X⁵ + 1
X⁸
X⁷
X⁶
X⁵
X⁴
X³
X²
X¹
X⁰
T ransm it data
W hitened data
Figure 36. Data Whitening Polynomial
5.5.8. Beacon Tx Mode
In some short range wireless network topologies a repetitive message, also known as beacon, is transmitted periodically
by a transmitter. The Beacon Tx mode allows for the re-transmission of the same packet without having to fill the FIFO
multiple times with the same data.
When BeaconOn in RegPacketConfig2 is set to 1, the FIFO can be filled only once in Sleep or Stdby mode with the
required payload.
After a first transmission, FifoEmpty will go high as usual, but the FIFO content will be restored when the chip exits
Transmit mode. FifoEmpty, FifoFull and FifoLevel flags are also restored.
This feature is only available in Fixed packet format, with the Payload Length smaller than the FIFO size.
The Beacon Tx mode is exited by setting BeaconOn to 0, and clearing the FIFO by setting FifoOverrun to 1.
5.6. io-homecontrol^® Compatibility Mode
The RFM66W features a io-homecontrol^® compatibility mode. Please contact your local Semtech representative for
details on its implementation.
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