CC1150-RTY1 datasheet(25/67 Pages) TI

25 / 67 page

CC1150

SWRS037A

Page 25 of 60

13.2

Packet Format

The format of the data packet can be

configured and consists of the following items:

•

Preamble

•

Synchronization word

•

Optional length byte

•

Optional Address byte

•

Payload

•

Optional 2 byte CRC

Preamble bits

(1010...1010)

Data field

Optional CRC-16 calculation

Optionally FEC encoded/decoded

8 x n bits

16/32 bits

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 13: Packet Format

The preamble pattern is an alternating

sequence of ones and zeros (01010101…).

The number of preamble bytes is programmed

with the MDMCFG1.NUM_PREAMBLE value.

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 synch word can

be emulated by setting the SYNC1 value to the

preamble pattern. It is also possible to emulate

bit

sync

word

using

MDMCFG2.SYNC_MODE

set to 3 or 7. The sync

word will then be repeated twice.

CC1150 supports both fixed packet length

protocols and variable packet length protocols.

Variable or fixed packet length mode can be

used for packets up to 255 bytes. For longer

packets, infinite packet length mode must be

used.

Fixed packet length mode is selected by

setting PKTCTRL0.LENGTH_CONFIG=0. The

desired packet length is set by the PKTLEN

PKTCTRL0.LENGTH_CONFIG=1,

the packet

length is configured by the first byte after the

sync word. The packet length is defined as the

payload data, excluding the length byte and

the optional automatic CRC.

With

PKTCTRL0.LENGTH_CONFIG=2

the

packet length is set to infinite and transmission

will continue until turned off manually. The

infinite mode can be turned off while a packet

is being transmitted. As described in the next

section, this can be used to support packet

formats with different length configuration than

natively supported by

CC1150. One should

make sure that TX mode is not turned off

during the transmission of the first half of any

byte. Refer to the

CC1150 Errata Notes [8] for

more details.

Note

that

the

minimum

packet

length

supported (excluding the optional length byte

and CRC) is one byte of payload data.

13.2.1

Arbitrary Length Field Configuration

The

packet

automation

control

PKTCTRL0,

can be reprogrammed during TX.

This opens the possibility to transmit packets

that are longer than 256 bytes and still be able

to use the packet handling hardware support.

At the start of the packet, the infinite mode

(PKTCTRL0.LENGTH_CONFIG=2)

must

active. The PKTLEN

mod(length,

256).

When less than 256

bytes remains of the packet, the MCU disables

infinite packet length and activates fixed length

packets. When the internal byte counter

reaches the PKTLEN value, the transmission

ends (the radio enters the state determined by

TXOFF_MODE)

. Automatic CRC appending

can

used

(by

setting

PKTCTRL0.CRC_EN=1

CC1150-RTY1 Datasheet(PDF) 25 Page - Texas Instruments

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