CC2550-RTY1 datasheet(20/62 Pages) TI2

20 / 62 page

CC2550

SWRS039B

Page 20 of 58

.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)

Data field

Optional CRC-16 calculation

Optionally FEC encoded/decoded

8 x n bits

16/32 bits

bits

8 x n bits

16 bits

Optional data whitening

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

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