Specifications

Page 59
WT1231H
ADVANCED COMMUNICATIONS & SENSING DATASHEET
5.5.8.2
. 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.
Th
e wh
itening/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/d
e-whitening is thus made transparent for the user, who still provides/retrieves NRZ data to/from the
FIFO.
LFS R P o ly nom ia l =X
9
+ X
5
+ 1
X
8
X
7
X
6
X
5
X
4
X
3
X
2
X
1
X
0
Tra n s m it d a ta
W
h iten ed da ta
Figure 38. Data Whitening