AC4830xC-C Data Book
Chapter 2. Functional Description
Revision 1.0
15
March 2000
2.2.2 PCM Clock Generator
A built-in PCM Clock Generator enables the sourcing of an external codec device, with
the PCM Clock and PCM Frame Sync from the AC4830xC-C. The operation of the
PCM Clock Generator is fully controlled by the PCM Command Sequence, using the
PCMCLK control.
The PCM Clock Generator can use a wide range of CLKIN-Crystal clock inputs,
providing the User with a cost-effective solution. See Table
2-1 for some examples of
external crystals. The internal circuitry derives the AC4830xC-C working clock
(CLKOUT) from the AC4830xC-C clock input, and also the PCM Clock and the Frame
Sync characteristics.
The setting of the AC4830xC-C working clock is made by modifying the PLLMUL
field of the last word of the Kernel File, which is the PLLMUL Register, as shown in
Figure
2-4. The PLLMUL range is $00 to $0E. The working clock is indicated by the
CLKOUT signal.
Figure
2-4
:
PLLMUL Register Contents
Bit Number
15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Contents
PLLMUL
$07
$FE
Special care must be taken while modifying the file to avoid damaging its content and to
follow up the required working clock. The working clock range must be in the limits
98.304 to 100.00 MHz. The following section shows some examples of the use of
external crystals, based on the formula:
CLKOUT
[98.304 to 100.00]
=
CLKIN
[MHz]
x (1)
Please refer to AC4830xC-C Designer’s Manual, Catalog Number LTRT-00066, for
details of the PCM Command sequence.
Содержание AC4830 C-C Series
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