SX1239IMLTRT Semtech, SX1239IMLTRT Datasheet - Page 50

• Manufacturer Part Number: SX1239IMLTRT
• Description: IC, RF RECEIVER, 1.02GHz, QFN-24
• Manufacturer: Semtech

Specifications of SX1239IMLTRT

• Applications: Wireless Sensor Networks, Automated Meter Reading, Home And Building Automation
• Receiving Current: 16mA
• Data Rate: 300Kbps
• Modulation Type: FSK, OOK
• Sensitivity Dbm: -120dBm
• Rohs Compliant: Yes
• Rf Ic Case Style: QFN
• No. Of Pins: 24
• Sensitivity (dbm): -120dBm
• Supply Voltage Range: 1.8V To 3.6V
• Operating Temperature Range: -40°C To +85°C
• Lead Free Status / Rohs Status: Supplier Unconfirmed

5.5.7. DC-Free Data Mechanisms
The received payload can be de-whitened or Manchester decoded automatically in the SX1239 Packet Handler.
Note
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.
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.
Rev 3 - Jan 2011
ADVANCED COMMUNICATIONS & SENSING
RF chips @ BR
User/NRZ bits
Manchester OFF
User/NRZ bits
Manchester ON
Only one of the two methods should be enabled at a time.
data input
X
15
...
...
...
X
14
1
1
1
1/BR
1
1
1
X
13
...Sync
1
1
1
Figure 32. Manchester Decoding
Figure 31. CRC Implementation
0
0
0
X
12
1
1
1
CRC Polynomial =X
0
0
0
0
0
0
Page 50
X
11
1
1
1
0
0
* * *
1/BR
0
0
16
+ X
0
1
1
12
X
5
+ X
0
0
Payload...
5
+ 1
0
1
1
1
1
X
1
4
0
0
* * *
1
1
1
DATASHEET
0
0
www.semtech.com
SX1239
X
0
...
...
...
t