VS1033 Datasheet, PDF (35/70 Pages) List of Unclassifed Manufacturers – MP3/AAC/WMA/MIDI AUDIO CODEC

VLSI
Solution ^y
VS1033a PRELIMINARY
VS1033A
8. FUNCTIONAL DESCRIPTION
8.6.4 SCI CLOCKF (RW)
The operation of SCI CLOCKF is different in VS1003 and VS1033 than in VS10x1 and VS1002. For
general applications with 12.288 MHz clock use 0x9000 for 3.0 × ..4.0×, or 0xa800 for 3.5 × ..4.0×.
Name
SC MULT
SC ADD
SC FREQ
SCI CLOCKF bits
Bits Description
15:13 Clock multiplier
12:11 Allowed multiplier addition
10: 0 Clock frequency
SC MULT activates the built-in clock multiplier. This will multiply XTALI to create a higher CLKI.
The values are as follows:
SC MULT
0
1
2
3
4
5
6
7
MASK
0x0000
0x2000
0x4000
0x6000
0x8000
0xa000
0xc000
0xe000
CLKI
XTALI
XTALI×1.5
XTALI×2.0
XTALI×2.5
XTALI×3.0
XTALI×3.5
XTALI×4.0
XTALI×4.5
SC ADD tells, how much the decoder firmware is allowed to add to the multiplier specified by SC MULT
if more cycles are temporarily needed to decode a WMA stream. The values are:
SC ADD
0
1
2
3
MASK
0x0000
0x0800
0x1000
0x1800
Multiplier addition
No modification is allowed
0.5×
1.0×
1.5×
SC FREQ is used to tell if the input clock XTALI is running at something else than 12.288 MHz. XTALI
is set
in
4
kHz steps.
The
formula
for
calculating
the
correct value
for this
register is
XT ALI−8000000
4000
(XTALI is in Hz).
Note: The default value 0 is assumed to mean XTALI=12.288 MHz.
Note:
because
maximum
sample
rate
is
X
T ALI
256
,
all
sample
rates
are
not
available
if
XTALI
<
12.288
MHz.
Note: Automatic clock change can only happen when decoding WMA files. Automatic clock change is
done one 0.5× at a time. This does not cause a drop to 1.0× clock and you can use the same SCI and
SDI clock throughout the WMA file.
Example: If SCI CLOCKF is 0x9BE8, SC MULT = 4, SC ADD = 3 and SC FREQ = 0x3E8 = 1000.
This means that XTALI = 1000×4000+8000000 = 12 MHz. The clock multiplier is set to 3.0×XTALI =
36 MHz, and the maximum allowed multiplier that the firmware may automatically choose to use is
(3.0 + 1.5)×XTALI = 54 MHz.
Version 0.6, 2005-01-05
35