Single-Chip Low Power RF Transceiver for Narrowband Systems ...

CC1021
MODEM Register (0Dh)
REGISTER NAME Default
value
Active Description
MODEM[7] - 0 - Reserved, write 0
MODEM[6:4] ADC_DIV[2:0] 3 - ADC clock divisor
0: Not supported
1: ADC frequency = XOSC frequency / 4
2: ADC frequency = XOSC frequency / 6
3: ADC frequency = XOSC frequency / 8
4: ADC frequency = XOSC frequency / 10
5: ADC frequency = XOSC frequency / 12
6: ADC frequency = XOSC frequency / 14
7: ADC frequency = XOSC frequency / 16
MODEM[3] - 0 -
Note that the intermediate frequency should be as close
to 307.2 kHz as possible. ADC clock frequency is always
4 times the intermediate frequency and should therefore
be as close to 1.2288 MHz as possible.
Reserved, write 0
MODEM[2] PN9_ENABLE 0 H Enable scrambling of TX and RX with PN9 pseudo-
random bit sequence
0: PN9 scrambling is disabled
9 5
1: PN9 scrambling is enabled (x +x +1)
MODEM[1:0] DATA_FORMAT[1:0] 0 -
The PN9 pseudo-random bit sequence can be used
for
BER testing by only transmitting zeros, and then
counting the number of received ones.
Modem data format
0 (00): NRZ operation
1 (01): Manchester operation
2 (10): Transparent asynchronous UART operation,
set
DCLK=0
3 (11): Transparent asynchronous UART operation,
set
DCLK=1
DEVIATION Register (0Eh)
REGISTER NAME Default
value
Active Description
DEVIATION[7] TX_SHAPING 1 H Enable Gaussian shaping of transmitted data
Recommended setting: TX_SHAPING=1
DEVIATION[6:4] TXDEV_X[2:0] 6 - Transmit frequency deviation exponent
DEVIATION [3:0] TXDEV_M[3:0] 8 - Transmit frequency deviation mantissa
Deviation in 402-470 MHz band:
FREF ·TXDEV_M ·2 (TXDEV_X−16)
Deviation in 804-940 MHz band:
FREF ·TXDEV_M ·2 (TXDEV_X−15)
On-off-keying (OOK) is used in RX/TX if TXDEV_M[3:0]=0
To find TXDEV_M given the deviation and TXDEV_X:
TXDEV_M = deviation·2 (16−TXDEV_X) /FREF
in 402-470 MHz band,
TXDEV_M = deviation·2 (15−TXDEV_X) /FREF
in 804-940 MHz band.
Decrease TXDEV_X and try again if TXDEV_M < 8.
Increase TXDEV_X and try again if TXDEV_M ≥ 16.
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