CC2400-RTR1 datasheet(29/83 Pages) TI

29 / 83 page

CC2400

SWRS042A

Page 29 of 83

23 Packet Handling Hardware Support

The

CC2400 has built-in hardware support

for packet oriented radio protocols.

The buffered mode packet handling

support can in transmit mode be used to

construct the data packet:

•

Add a programmable number of

preamble bytes

•

Add a synchronization word

•

Compute

and

add

CRC

computed over the data field

In receive mode the packet handling

support can be used to de-construct the

data packet:

•

Synchronization word detection

•

Compute and check the received

CRC

The packet handling support can be

combined with the 8/10 line-encoding

scheme. The 8/10 coding will apply to the

data field (FIFO data) of the packet only

(and CRC).

In un-buffered mode the synchronization

word detection can be used to mute DCLK

until a valid sync word is received.

23.1 Data packet format

The format of the data packet can be

configured, and can consist of the

following items:

•

Preamble

•

Synchronization word

•

Data

•

CRC

See Table 16 and Figure 11 for details.

The preamble pattern is ‘(0)101010…’.

The first bit in the preamble is always the

same as the first bit in the synchronization

word. The length of the preamble is

programmable.

The

default

and

recommended length is 4 bytes.

When using GFSK modulation at 1 Mbps,

Chipcon recommends using a preamble

length of 32 bytes in order to avoid a high

level of bit errors. If low packet overhead

is required, Chipcon recommends that

FSK be used at 1 Mbps instead of GFSK.

GRMDM.

PRE_BYTES[2:0]

Number of bytes

(8 bits)

000

001

010

011

100

101

110

111

Infinitely until TX

GRMDM.PRE_BYTES

[2:0] is set to 000

* Should not be used if packet reception is to be

used. Use to terminate infinite transmission (111).

The length of the synchronization word is

programmable as shown below.

GRMDM.

SYNC_WORD_SIZE

[1:0]

Number of bits

The

synchronization

word

programmable in the SYNCL and SYNCH

registers. The default (and recommended)

synchronization word length is 32 bits,

which gives high immunity against false

synchronization word indication. If lower

immunity can be accepted, one can

reduce the length to 16 bits. (However,

using 8 bits will typically give too many

false synchronization word indications.)

A threshold on the number of bits in error

when receiving the synchronization word

can

programmed

GRMDM.SYNC_ERRBITS_ALLOWED[1:0]

in the range 0 – 3. (A threshold of 0 is

default.)

23.2 Error detection

When the CRC is enabled it will be

calculated based on the data field of the

packet, i.e. not including the preamble or

the

synchronization

word.

When

transmitting the packet the CRC is

appended after the last data byte in the

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