LLCC68 datasheet(43/111 Pages) SEMTECH

43 / 111 page

LLCC68

Data Sheet

Rev. 1.1

DS.LLCC68.W.APP

Dec 2024

43 of 111

Semtech

LLCC68

www.semtech.com

6.2.3.4 Whitening

The whitening process is built around a 9-bit LFSR which is used to generate a random sequence and the payload (including the payload

length, the Node or Broadcast address and CRC checksum when needed) is then XORed with this random sequence to generate the

whitened payload. The data is de-whitened on the receiver side by XORing with the same random sequence. This setup limits the number

of consecutive 1’s or 0’s to 9.

Note: Data whitening is only required when the user data has high correlation with long strings of 0’s and 1’s. If the data is already

random then the whitening is not required. For example a random source generating the Transmit data, when whitened, could

produce longer strings of 1’s and 0’s, thus it’s not required to randomize an already random sequence.

Figure 6-5: Data Whitening LFSR

The whitening is based around the 9-bit LFSR polynomial x^9+x^5+1. With this structure, the LSB at the output of the LFSR is XORed with

the MSB of the data.

At the initial stage, each flip-flop of the LFSR can be initialized through the registers at addresses 0x06B8 and 0x6B9.

Table 6-6: Whitening Initial Value

Whitening Initial Value

Default Value

Whitening initial value MSB

0x06B8

0x01

Whitening initial value LSB

0x06B9

0x00

X 7

X 6

X 5

X 4

X 3

X 2

X 1

X 0

X 8

LFS R P o ly nom ia l =X 9 + X 5 + 1

T ransm it data

W hitened data

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