Texas Instruments CC1101 User Manual

CC1101
SWRS061H Page 38 of 98
TX_OUT[7:0]
TX_DATA
8 7 6 5 4 3 2 1 0
7 6 5 4 3 2 1 0
The first TX_DATA byte is shifted in before doing the XOR-operation providing the first TX_OUT[7:0] byte. The
second TX_DATA byte is then shifted in before doing the XOR-operation providing the second TX_OUT[7:0] byte.
Figure 18: 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 19):
 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 19: Packet Format
The preamble pattern is an alternating
sequence of ones and zeros (10101010…).
The minimum length of the preamble is
programmable through the value of
MDMCFG1.NUM_PREAMBLE. 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 sync word and then the data
bytes.
The synchronization word is a two-byte value
set in the SYNC1 and SYNC0 registers. The
sync word provides byte synchronization of the
incoming packet. A one-byte sync word can be
emulated by setting the SYNC1 value to the
preamble pattern. It is also possible to emulate
a 32 bit sync word by setting
MDMCFG2.SYNC_MODE to 3 or 7. The sync
word will then be repeated twice.
CC1101 supports both constant packet length
protocols and variable length protocols.
Variable or fixed packet length mode can be
used for packets up to 255 bytes. For longer

Texas Instruments CC1101 Specifications

General

Brand	Texas Instruments
Model	CC1101
Category	Transceiver
Language	English