RF65 Datasheet, PDF (50/72 Pages) List of Unclassifed Manufacturers – Low Power Integrated UHF Receiver With -120dBm High Sensitivity

ADVANCED COMMUNICATIONS & SENSING
RF65
DATASHEET
data input
CRC Polynomial =X¹⁶ + X¹² + X⁵ + 1
X¹⁵
X¹⁴
X¹³
X¹²
X¹¹
***
X⁵
X⁴
***
X⁰
Figure 31. CRC Implementation
5.5.7. DC-Free Data Mechanisms
The received payload can be de-whitened or Manchester decoded automatically in the RF65 Packet Handler.
Note Only one of the two methods should be enabled at a time.
5.5.7.1. Manchester Decoding
Manchester decoding is enabled if DcFree = 01 and can only be used in Packet mode.
The Manchester data is decoded to NRZ code by decoding "10" as '1' and "01" as '0'.
In this case, the maximum chip rate is the maximum bit rate given in the specifications section and the actual bit rate is half
the chip rate.
Manchester 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 BitRate in RegBitRate (Chip Rate = Bit Rate
NRZ = 2 x Bit Rate Manchester).
Manchester decoding is thus made transparent for the user, who still retrieves NRZ data 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
01
1
0
1 0 ...
t
User/NRZ bits
Manchester ON
... 1 1 1 0 1 0 0
1
0
0
1
1
...
Figure 32. Manchester Decoding
5.5.7.2. Data De-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.
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