CC1110-RTR1 datasheet(161/203 Pages) TI

161 / 203 page

CC1110

CC1110 PRELIMINARY Datasheet (Rev. 1.01) SWRS033A

Page 161 of 202

FREQEST.FREQOFF_EST,

can

automatically be used to adjust the

frequency offset programming in the

frequency synthesizer. This will add the

current RX frequency offset estimate to

the value in FSCTRL0.FREQOFF, which

adjust the synthesizer frequency. Thus,

the frequency offset will be compensated

in both RX and TX when the SAFC

command strobe is used.

To avoid compensating for frequency

offsets measured without a valid signal in

the RF channel, FREQEST.FREQOFF_EST

is copied to an internal register when

issuing the SAFC strobe in RX, and when a

synch word is detected. If SAFC was

issued in RX, this internal value is added

to FSCTRL0.FREQOFF after exiting RX.

Issuing SAFC when not in RX will

immediately add the internal register value

to FSCTRL0.FREQOFF. Thus, the SAFC

strobe should be issued when currently

receiving a packet, or outside the RX

state.

Note that frequency offset compensation is

not supported for ASK or OOK modulation.

15.7.2 Bit Synchronization

The bit synchronization algorithm extracts

the clock from the incoming symbols. The

algorithm requires that the expected data

rate is programmed as described in

Section

15.5

page

159.

Re-

synchronization is performed continuously

to adjust for error in the incoming symbol

rate.

15.7.3 Byte synchronization

Byte synchronization is achieved by a

continuous sync word search. The sync

word is a 16 or 32 bit configurable field

that is automatically inserted at the start of

the packet by the modulator in transmit

mode. The demodulator uses this field to

find the byte boundaries in the stream of

bits. The sync word will also function as a

system identifier, since only packets with

the correct predefined sync word will be

received.

The

sync

word

detector

correlates against the user-configured 16-

bit sync word. The correlation threshold

can be set to 15/16 bits match or 16/16

bits match. The sync word can be further

qualified using the preamble quality

indicator mechanism described below

and/or a carrier sense condition. The sync

word is programmed with SYNC1 and

SYNC0.

In order to make false detections of sync

words less likely, a mechanism called

preamble quality indication (PQI) can be

used to qualify the sync word. A threshold

value for the preamble quality must be

exceeded in order for a detected sync

word to be accepted. See section 15.10.1

on page 165 for more details.

15.8 Packet Handling Hardware Support

The

CC1110 has built-in hardware support

for packet oriented radio protocols.

In transmit mode, the packet handler will

add the following elements to the packet

stored to be transmitted:

•

A programmable number of preamble

bytes.

Four

preamble

bytes

recommended.

•

A two byte Synchronization Word. Can

be duplicated to give a 4-byte sync

word. (Recommended).

•

Optionally whiten the data with a PN9

sequence.

•

Optionally Interleave and Forward

Error Code the data.

•

Optionally compute and add a CRC

checksum over the data field.

In receive mode, the packet handling

support will de-construct the data packet:

•

Preamble detection.

•

Sync word detection.

•

Optional one byte address check.

•

Optionally compute and check CRC.

•

Optionally append two status bytes

(see Table 45 and Table 46) with

RSSI value, Link Quality Indication

and CRC status.

CC1110-RTR1 데이터시트(PDF) 161 Page - Texas Instruments

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