CC1021-RTR1 datasheet(58/91 Pages) TI1

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Not Recommended for New Designs NRND

CC1021

SWRS045D – JANUARY 2006 – REVISED JANUARY 2015

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5.20.6 Frequency Hopping Spread Spectrum Systems (FHSS)

Due to the very fast locking properties of the PLL, the CC1021 is also very suitable for frequency hopping

systems. Hop rates of 1 to 100 hops/s are commonly used depending on the bit rate and the amount of

data to be sent during each transmission. The two frequency registers (FREQ_A and FREQ_B) are

designed such that the ‘next’ frequency can be programmed while the ‘present’ frequency is used. The

switching between the two frequencies is done through the MAIN register. Several features have been

included to do the hopping without a need to re-synchronize the receiver. For more details refer to

Application Note AN014 Frequency Hopping Systems (SWRA077).

In order to implement a frequency hopping system with CC1021 do the following:

1. Set the desired frequency, calibrate and store the following register settings in non-volatile memory:

STATUS1[3:0]: CHP_CURRENT[3:0]

STATUS2[4:0]: VCO_ARRAY[4:0]

STATUS3[5:0]:VCO_CAL_CURRENT[5:0]

2. Repeat the calibration for each desired frequency. VCO_CAL_CURRENT[5:0] is not dependent on the

RF frequency and the same value can be used for all frequencies. When performing frequency

hopping, write the stored values to the corresponding TEST1, TEST2 and TEST3 registers, and enable

override:

TEST1[3:0]: CHP_CO[3:0]

TEST2[4:0]: VCO_AO[4:0]

TEST2[5]: VCO_OVERRIDE

TEST2[6]: CHP_OVERRIDE

TEST3[5:0]:VCO_CO[5:0]

TEST3[6]:VCO_CAL_OVERRIDE

3. CHP_CO[3:0] is the register setting read from CHP_CURRENT[3:0], VCO_AO[4:0] is the register

setting read from VCO_ARRAY[4:0] and VCO_CO[5:0] is the register setting read from

VCO_CAL_CURRENT[5:0].

4. Assume channel 1 defined by register FREQ_A is currently being used and that CC1021 should

operate on channel 2 next (to change channel simply write to register MAIN[6]). The channel 2

frequency can be set by register FREQ_B which can be written to while operating on channel 1. The

calibration data must be written to the TEST1-3 registers after switching to the next frequency. That is,

when hopping to a new channel write to register MAIN[6] first and the test registers next. The PA

should be switched off between each hop and the PLL should be checked for lock before switching the

PA back on after a hop has been performed.

NOTE

The override bits VCO_OVERRIDE, CHP_OVERRIDE and VCO_CAL_OVERRIDE must be

disabled when performing a re-calibration.

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