參數(shù)資料
型號: L64777
英文描述: L64777 DVB QAM Modulator technical manual 6/00
中文描述: L64777的DVB QAM調(diào)制器技術手冊6 / 00
文件頁數(shù): 51/124頁
文件大?。?/td> 988K
代理商: L64777
Global Control and PLL Module
2-37
The host computes the following formulae to get the initial step for
phase 2, where indicates the average n value.
Equation 2.3
and from this:
Equation 2.4
In the above formulae:
C1 is the reading from NM_COUNT register.
C2 is the reading from N_COUNT register.
C3 is the reading from NP_COUNT register.
n is the reading from N_PCLK register.
Sync length is the number of ICLK cycles between sync bytes (for
example, 204).
Valid bytes are the number of valid bytes during the sync interval (for
example, 188).
ld(QAMmode) is the number of bits per QAM symbol.
If the RS encoder is enabled in DVB mode and the SPI interface of
L64724 is programmed to Mode 2, the factor of sync length by valid
bytes becomes one.
In order to get an accurate initial step, the measurement must run for a
long duration. A recommended duration is 250 ms.
In general the OCLK frequency is calculated as
.
Above, 0 < step < 2
23
1.
Start measurement by toggling the “start measurement” bit (bit 6) in the
NCO control register 14. If the NCO control register is enabled for
interrupt (through bit 2 of Register 14), an interrupt indicates completion.
n
-----------------–
)
C2 n
C2
+
C3 n
C3
)
1
+
)
+
+
(
)
+
=
initial step
24
n
--
ld QAMmode
)
-----------------------------------------
valid bytes
------------------------------
=
f
OCLK
f
PCLK
step
2
24
=
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L64777 Digital Video Broadcasting(DVB)-Compliant,quadrature amplitude modulation (QAM)Modulator(數(shù)字視頻廣播系統(tǒng)適配的積分調(diào)幅調(diào)制器)
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