CC2550_13 Datasheet, PDF (20/61 Pages) Texas Instruments – Low-Cost Low-Power 2.4 GHz RF Transmitter

CC2550
.WHITE_DATA=1. All data, except the
preamble and the sync word, are then XOR-ed
with a 9-bit pseudo-random (PN9) sequence
before being transmitted as shown in Figure 9.
At the receiver end, the data are XOR-ed with
the same pseudo-random sequence. This way,
the whitening is reversed, and the original data
appear in the receiver. The PN9 sequence is
reset to all 1’s.
Data whitening can only be used when
PKTCTRL0.CC2400_EN=0 (default).
Figure 9: Data Whitening in TX Mode
13.2 Packet Format
The format of the data packet can be
configured and consists of the following items
(see Figure 10):
• Preamble
• Synchronization word
• Optional length byte
• Optional address byte
• Payload
• Optional 2 byte CRC
Preamble bits
(1010...1010)
Optional data whitening
Optionally FEC encoded/decoded
Optional CRC-16 calculation
Data field
8 x n bits
16/32 bits
8
bits
8
bits
8 x n bits
16 bits
Legend:
Inserted automatically in TX,
processed and removed in RX.
Optional user-provided fields processed in TX,
processed but not removed in RX.
Unprocessed user data (apart from FEC
and/or whitening)
Figure 10: Packet Format
The preamble pattern is an alternating
sequence of ones and zeros (101010101…).
The minimum length of the preamble is
programmable. When enabling TX, the
modulator will start transmitting the preamble.
When the programmed number of preamble
bytes has been transmitted, the modulator will
send the sync word and then data from the TX
FIFO if data is available. If the TX FIFO is
empty, the modulator will continue to send
preamble bytes until the first byte is written to
the TX FIFO. The modulator will then send the
SWRS039B
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