VS1053B Datasheet, PDF (42/79 Pages) List of Unclassifed Manufacturers – Ogg Vorbis/MP3/AAC/WMA/MIDI AUDIO CODEC

VLSI
Solution ^y
VS1053b preliminary
VS1053B
8. FUNCTIONAL DESCRIPTION
8.7.4 SCI CLOCKF (RW)
The operation of SCI CLOCKF has changed slightly in VS1053b compared to VS1003 and VS1033.
Multiplier 1.5× and addition 0.5× have been removed to allow higher clocks to be configured.
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×2.0
XTALI×2.5
XTALI×3.0
XTALI×3.5
XTALI×4.0
XTALI×4.5
XTALI×5.0
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 or AAC stream. The values are:
SC ADD
0
1
2
3
MASK
0x0000
0x0800
0x1000
0x1800
Multiplier addition
No modification is allowed
1.0×
1.5×
2.0×
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
samplerate
is
XT ALI
256
,
all
samplerates
are
not
available
if
XTALI
<
12.288
MHz.
Note: Automatic clock change can only happen when decoding WMA and AAC 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 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 3.5×XTALI =
42 MHz, and the maximum allowed multiplier that the firmware may automatically choose to use is
(3.5 + 2.0)×XTALI = 66 MHz.
Version 0.5, 2007-12-03
42