SWRS046H – NOVEMBER 2006 – REVISED MARCH 2015
Table 5-31. MODEM Register (0Dh)
DEFAULT
REGISTER
NAME
ACTIVE
DESCRIPTION
VALUE
MODEM[7]
—
0
—
Reserved, write 0
MODEM[6:4]
ADC_DIV[2:0]
3
—
ADC clock divisor
(1)
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
—
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
1: PN9 scrambling is enabled (x
9
+ x
5
+ 1)
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[1:0]
DATA_FORMAT[1:0]
0
—
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
(1)
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.
Table 5-32. DEVIATION Register (0Eh)
DEFAULT
REGISTER
NAME
ACTIVE
DESCRIPTION
VALUE
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 to 470 MHz band:
F
REF
× XDEV_M × 2
(TXDEV_X
−
16)
Deviation in 804 to 960 MHz band:
F
REF
× 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)
/ F
REF
in 402 to 470 MHz band,
TXDEV_M = deviation × 2
(15
−
TXDEV_X)
/ F
REF
in 804 to 960 MHz band,
Decrease TXDEV_X and try again if TXDEV_M < 8.
Increase TXDEV_X and try again if TXDEV_M
≥
16.
68
Detailed Description
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