参数资料
型号: L64781
厂商: LSI CORP
元件分类: 消费家电
英文描述: SPECIALTY CONSUMER CIRCUIT, PQFP100
封装: PLASTIC, QFP-100
文件页数: 16/164页
文件大小: 2003K
代理商: L64781
5-42
Registers
5.5.17 Demod Parameters Registers 21, 22, and 23 (0x1B, 0x1C, 0x1D)
These are three 8-bit wide, read/write registers.
SPI_BIAS
SPI Bias Frequency
R/W
This register species the bias frequency for the SPI
block. The initial value of the SPI_BIAS is
0b10110111001011011100000 (0x5B96E0).
Equation 5.4 shows how this 23-bit value is determined.
Equation 5.4
where:
Bias = SPI_BIAS[22:0].
VCR = Viterbi code rate.
Log2 (QAMTYPE) = {2, 4, 6} = {QPSK, 16-QAM,
64-QAM}.
B is the channel bandwidth = {6, 7, 8 MHz}.
g is the guard interval = {1/32, 1/16, 1/8, 1/4}.
ε is the difference between the frequency of the XO
and the theoretical frequency in ppm.
Example:
If QAMTYPE = 64-QAM then log2 (QAMTYPE) = 6,
B = 6 MHz, g =1/32, VCR = 2/3, and the frequency of the
crystal is = 18.2912 = 128/7 + 300 ppm.
D7
D6
D0
SPI_BIAS_LSB
SPI_BIAS_CSB
SPI_CLK_AND
SPI_BIAS_MSB
Bias
1512
VC R
2
QAMTYPE
()
log
×
2
10
×
1
g
+
()
--------------------------------------------------------------------------------------------------------
B
810
6
1
ε
+
()
---------------------------------------
=
l64781.book Page 42 Friday, January 19, 2001 1:28 PM
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