CC2430-RTR1-F32Z datasheet(174/234 Pages) TI

174 / 234 page

CC2430

CC2430 PRELIMINARY Data Sheet (rev. 1.03) SWRS036A

Page 174 of 232

compliant with [1]. Changing these values

will make the system non-compliant to

IEEE 802.15.4.

A synchronization header is always

transmitted first in all transmit modes.

The preamble sequence length can be set

with

bit

MDMCTRL0L.PREAMBLE_LENGTH,

while

the

SFD

programmed

the

SYNCWORDH:SYNCWORDL

registers.

SYNCWORDH:SYNCWORDL is two bytes

long, which gives the user some extra

flexibility as described below. Figure 46

shows how the

CC2430 synchronization

header relates to the IEEE 802.15.4

specification.

The programmable preamble length only

applies to transmission, it does not affect

receive mode. The preamble length should

not be set shorter than the default value.

Note that 2 of the 8 zero-symbols in the

preamble sequence required by [1] are

included in the SYNCWORDH:SYNCWORDL

registers so that the

CC2430 preamble

sequence is only 6 symbols long for

compliance with [1]. Two additional zero

symbols

SYNCWORDH:SYNCWORDL

make

CC2430 compliant with [1].

In reception,

CC2430 synchronizes to

received zero-symbols and searches for

the SFD sequence defined by the

SYNCWORDH:SYNCWORDL registers. The

least

significant

symbols

SYNCWORDH:SYNCWORDL set to 0xF will

be ignored, while symbols different from

0xF will be required for synchronization.

The default setting of 0xA70F thereby

requires one additional zero-symbol for

synchronization. This will reduce the

number of false frames detected due to

noise.

receive

mode

CC2430 uses the

preamble

sequence

for

symbol

synchronization

and

frequency

offset

adjustments. The SFD is used for byte

synchronization, and is not part of the data

stored in the receive buffer (RXFIFO).

IEEE 802.15.4

Preamble

SFD

CC2430

2·(PREAMBLE_LENGTH + 1) zero symbols

SW0

SW0 = SYNCWORD[3:0]

SW1 = SYNCWORD[7:4]

SW2 = SYNCWORD[11:8]

SW3 = SYNCWORD[15:12]

SW1

SW2

SW3

if different from 'F', else '0'

Synchronisation Header

Figure 46: Transmitted Synchronization Header

14.14 Length field

The frame length field shown in Figure 45

defines the number of bytes in the MPDU.

Note that the length field does not include

the length field itself. It does however

include

the

FCS

(Frame

Check

Sequence), even if this is inserted

automatically by

CC2430 hardware.

The length field is 7 bits and has a

maximum value of 127. The most

significant bit in the length field is reserved

[1], and should be set to zero.

CC2430 uses the length field both for

transmission and reception, so this field

must always be included. In transmit

mode, the length field is used for

underflow detection, as described in the

FIFO access section on page 169.

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