SWRS046H – NOVEMBER 2006 – REVISED MARCH 2015
Table 5-33. AFC_CONTROL Register (0Fh)
(1)
DEFAULT
REGISTER
NAME
ACTIVE
DESCRIPTION
VALUE
AFC_CONTROL[7:6]
SETTLING[1:0]
2
—
Controls AFC settling time versus accuracy
0: AFC off; zero average frequency is used in demodulator
1: Fastest settling; frequency averaged over 1 0/1 bit pair
2: Medium settling; frequency averaged over 2 0/1 bit pairs
3: Slowest settling; frequency averaged over 4 0/1 bit pairs
Recommended setting:
AFC_CONTROL=3 for higher accuracy unless it is essential to
have the fastest settling time when transmission starts after RX
is activated.
AFC_CONTROL[5:4]
RXDEV_X[1:0]
1
—
RX frequency deviation exponent
AFC_CONTROL[3:0]
RXDEV_M[3:0]
12
—
RX frequency deviation mantissa
Expected RX deviation should be:
Baud rate × RXDEV_M × 2
(RXDEV_X
−
3)
/ 3
To find RXDEV_M given the deviation and RXDEV_X:
RXDEV_M = 3 × deviation × 2
(3
−
RXDEV_X)
/ Baud rate
Decrease RXDEV_X and try again if RXDEV_M < 8.
Increase RXDEV_X and try again if RXDEV_M
≥
16.
(1)
The RX frequency deviation should be close to half the TX frequency deviation for GFSK at 100 kBaud data rate and below. The RX
frequency deviation should be close to the TX frequency deviation for FSK and for GFSK at 100 kBaud data rate and above.
Table 5-34. FILTER Register (10h)
DEFAULT
REGISTER
NAME
ACTIVE
DESCRIPTION
VALUE
FILTER[7]
FILTER_BYPASS
0
H
Bypass analog image rejection / anti-alias filter. Set to 1 for increased
dynamic range at high Baud rates.
Recommended setting:
FILTER_BYPASS=0 below 76.8 kBaud,
FILTER_BYPASS=1 for 76.8 kBaud and up.
FILTER[6:5]
DEC_SHIFT[1:0]
0
—
Number of extra bits to shift decimator input (may improve filter
accuracy and lower power consumption).
Recommended settings:
DEC_SHIFT=0 when DEC_DIV
≤
1
(receiver channel bandwidth
≥
153.6 kHz),
DEC_SHIFT=1 when optimized sensitivity and 1< DEC_DIV <
24
(12.29 kHz < receiver channel bandwidth < 153.6 kHz),
DEC_SHIFT=2 when optimized selectivity and DEC_DIV
≥
24
(receiver channel bandwidth
≤
12.29 kHz)
FILTER[4:0]
DEC_DIV[4:0]
0
—
Decimation clock divisor
0: Decimation clock divisor = 1, 307.2 kHz channel filter BW.
1: Decimation clock divisor = 2, 153.6 kHz channel filter BW.
…
30: Decimation clock divisor = 31, 9.91 kHz channel filter BW.
31: Decimation clock divisor = 32, 9.6 kHz channel filter BW.
Channel filter bandwidth is 307.2 kHz divided by the decimation clock
divisor.
Copyright © 2006–2015, Texas Instruments Incorporated
Detailed Description
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