CC2430-RTR1-F64Z datasheet(173/234 Pages) TI

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CC2430

CC2430 PRELIMINARY Data Sheet (rev. 1.03) SWRS036A

Page 173 of 232

significant degradation of the receiver

performance.

Soft decision is used at the chip level, i.e.

the demodulator does not make a decision

for each chip, only for each received

symbol. De-spreading is performed using

over-sampling symbol correlators. Symbol

synchronization

achieved

continuous start of frame delimiter (SFD)

search.

When an SFD is detected, data is written

to the RXFIFO and may be read out by the

CPU at a lower bit rate than the 250 kbps

generated by the receiver.

The

CC2430 demodulator also handles

symbol rate errors in excess of 120 ppm

without

performance

degradation.

Resynchronization

performed

continuously to adjust for error in the

incoming symbol rate.

The RF register MDMCTRL1H.CORR_THR

control bits should be written to 20 to set

the threshold for detecting IEEE 802.15.4

start of frame delimiters.

Digital

IF Channel

Filtering

ADC

Digital

Data

Filtering

Frequency

Offset

Compensation

Symbol

Correlators and

Synchronisation

RSSI

Generator

I / Q Analog

IF signal

Data

Symbol

Output

RSSI

Average

Correlation

Value (may be

used for LQI)

Figure 44: Demodulator Simplified Block Diagram

14.12 Frame Format

CC2430 has hardware support for parts of

the IEEE 802.15.4 frame format. This

section gives a brief summary to the IEEE

802.15.4 frame format, and describes how

CC2430 is set up to comply with this.

Figure 45 [1] shows a schematic view of

the IEEE 802.15.4 frame format. Similar

figures describing specific frame formats

(data

frames,

beacon

frames,

acknowledgment

frames

and

MAC

command frames) are included in [1].

Figure 45: Schematic view of the IEEE 802.15.4 Frame Format [1]

14.13 Synchronization header

The

synchronization

header

(SHR)

consists

the

preamble

sequence

followed by the start of frame delimiter

(SFD). In [1], the preamble sequence is

defined to be four bytes of 0x00. The SFD

is one byte, set to 0xA7.

CC2430, the preamble length and SFD is

configurable. The default values are

PHY

Layer

Frame

Control Field

(FCF)

Data

Sequence

Number

Bytes:

Address

Information

0 to 20

Frame payload

Frame Check

Sequence

(FCS)

MAC Header (MHR)

MAC Payload

MAC Footer

(MFR)

Frame

Length

MAC Protocol

Data Unit

(MPDU)

Start of frame

Delimiter

(SFD)

Bytes:

5 + (0 to 20) + n

Preamble

Sequence

Synchronisation Header

(SHR)

PHY Header

(PHR)

PHY Service Data Unit

(PSDU)

PHY Protocol Data Unit

(PPDU)

11 + (0 to 20) + n

MAC

Layer

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