Data Sheet

CC1101
SWRS061B Page 31 of 93
15.1 Data Whitening
From a radio perspective, the ideal over the air
data are random and DC free. This results in
the smoothest power distribution over the
occupied bandwidth. This also gives the
regulation loops in the receiver uniform
operation conditions (no data dependencies).
Real world data often contain long sequences
of zeros and ones. Performance can then be
improved by whitening the data before
transmitting, and de-whitening the data in the
receiver. With
CC1101
, this can be done
automatically by setting
PKTCTRL0.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 10. 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 initialized to all 1’s.
Figure 10: Data Whitening in TX Mode
15.2 Packet Format
The format of the data packet can be
configured and consists of the following items
(see Figure 11):
Preamble
Synchronization word
Optional length byte
Optional address byte
Payload
Optional 2 byte CRC
Preamble bits
(1010...1010)
Sync word
Length field
Address field
Data field
CRC-16
Optional CRC-16 calculation
Optionally FEC encoded/decoded
8 x n bits 16/32 bits
8
bits
8
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 11: Packet Format