RF64 Datasheet, PDF (54/76 Pages) List of Unclassifed Manufacturers – ADVANCED COMMUNICATIONS & SENSING

RF64
ADVANCED COMMUNICATIONS & SENSING
Manchester encoding and decoding is only applied to the payload and CRC checksum while preamble and Sync
word are kept NRZ. However, the chip rate from preamble to CRC is the same and defined by MCParam_BR (Chip
Rate = Bit Rate NRZ = 2 x Bit Rate Manchester).
Manchester encoding/decoding is thus made transparent for the user, who still provides/retrieves NRZ data to/from
the FIFO.
1/BR ...Sync
1/BR
Payload...
RF chips @ BR ... 1 1 1 0 1 0 0 1 0 0 1 0 1 1 0 1 0 ...
User/NRZ bits
Manchester OFF
... 1 1 1 0 1 0 0 1
0
0
1
0
1
1
0
1
0 ...
t
User/NRZ bits
Manchester ON
... 1 1 1 0 1 0 0
1
0
0
1
1
...
Figure 46: Manchester Encoding/Decoding
5.5.6.2. 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 datarate i.e. actual
bit rate is not halved.
The whitening/de-whitening process is enabled by setting bit PKTParam_Whitening_on. 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 in Figure 47. 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
Figure 47: Data Whitening
5.5.7. Interrupt Signal Mapping
Tables below give the description of the interrupts available in Packet mode.
W hitened data
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