CC1020-RTR1 datasheet(38/95 Pages) TI1

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AFC

Baud rate

D =

[

]

xoscx

ADC

(ADC _ DIV 2 : 0

Power down

Crystal oscillator and bias off

Frequency synthesizer off

Receive chain off

Wait for PLL

lock or timeout,

127 filter clocks

Turn on crystal oscillator/bias

Frequency synthesizer off

Receive chain off

Crystal oscillator and bias on

Turn on frequency synthesizer

Receive chain off

Optional waiting time before

turning on receive chain

Programmable:

32-256 ADC clocks

Crystal oscillator and bias on

Frequency synthesizer on

Turn on receive chain

Receive mode

Crystal oscillator and bias on

Frequency synthesizer on

Receive chain on

Wait for

carrier sense or timeout

Programmable: 20-72

filter clocks

Set

SEQ_ERROR

flag in STATUS

Optional calibration

Programmable: each time,

once in 16, or once in 256

Receive chain off

PLL in lock

PLL timeout

Sequencing wake-up event

Carrier sense timeout

Carrier sense

(negative transition on

PSEL pin or DIO pin)

(Positive transition on SEQ_PD in MAIN register)

Sequencing power-down event

CC1020

SWRS046H – NOVEMBER 2006 – REVISED MARCH 2015

www.ti.com

(1)

Filter clock (FILTER_CLK): ffilter_clock = 2 × ChBW where ChBW is defined in Section 5.9.2.

(2)

ADC clock (ADC_CLK):

where ADC_DIV[2:0] is set in the MODEM register.

Figure 5-16. Automatic Power-up Sequencing Flow Chart

5.9.13 Automatic Frequency Control

CC1020 has a built-in feature called AFC (Automatic Frequency Control) that can be used to compensate

for frequency drift.

The average frequency offset of the received signal (from the nominal IF frequency) can be read in the

AFC register. The signed (2’s-complement) 8-bit value AFC[7:0] can be used to compensate for frequency

offset between transmitter and receiver.

The frequency offset is given by Equation 22.

(22)

The receiver can be calibrated against the transmitter by changing the operating frequency according to

the measured offset. The new frequency must be calculated and written to the FREQ register by the

microcontroller. The AFC can be used for an FSK/GFSK signal, but not for OOK. Application Note AN029

CC1020/1021 Automatic Frequency Control (AFC) (SWRA063) provides the procedure and equations

necessary to implement AFC.

The AFC feature reduces the crystal accuracy requirement.

Detailed Description

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