adf7023-j Analog Devices, Inc., adf7023-j Datasheet - Page 43

• Manufacturer Part Number: adf7023-j
• Description: High Performance, Low Power, Ism Band Fsk/gfsk/msk/gmsk Transceiver Ic
• Manufacturer: Analog Devices, Inc.

DATA WHITENING
Data whitening can be employed to avoid long runs of 1s or
0s in the transmitted data stream. This ensures sufficient bit
transitions in the packet, which aids in receiver clock and data
recovery because the encoding breaks up long runs of 1s or 0s
in the transmit packet. The data, excluding the preamble and
sync word, is automatically whitened before transmission by
XOR’ing the data with an 8-bit pseudorandom sequence. At
the receiver, the data is XOR’ e d with the same pseudorandom
sequence, thereby reversing the whitening. The linear feedback
shift register polynomial used is x
dewhitening are enabled by setting DATA_WHITENING = 1 in
the SYMBOL_MODE register (Address 0x11C).
7
+ x
1
+ 1. Data whitening and
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MANCHESTER ENCODING
Manchester encoding can be used to ensure a dc-free (zero mean)
transmission. The encoded over-the-air bit rate (chip rate) is
double the rate set by the DATA_RATE variable (Address 0x10C
and Address 0x10D). A Binary 0 is mapped to 10, and a Binary 1 is
mapped to 01. Manchester encoding and decoding are applied
to the payload data and the CRC. Manchester encoding and
decoding are enabled by setting MANCHESTER_ENC = 1 in
the SYMBOL_MODE register (Address 0x11C).
8b/10b ENCODING
8b/10b encoding is a byte-orientated encoding scheme that
maps an 8-bit byte to a 10-bit data block. It ensures that the
maximum number of consecutive 1s or 0s (that is, run length)
in any 10-bit transmitted symbol is five. The advantage of this
encoding scheme is that dc balancing is employed without the
efficiency loss of Manchester encoding. The rate loss for 8b/10b
encoding is 0.8, whereas for Manchester encoding, it is 0.5.
Encoding and decoding are applied to the payload data and
the CRC. The 8b/10b encoding and decoding are enabled by
setting EIGHT_TEN_ENC =1 in the SYMBOL_MODE register
(Address 0x11C).
ADF7023-J