Data Sheet

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PRELIMINARY

VS1063a Datasheet

9 FUNCTIONAL DESCRIPTION

9.8.4 SCI_CLOCKF (RW)

The operation of SCI_CLOCKF has changed slightly in VS1063a compared to VS1003 and

VS1033. Multiplier 1.5× and addition 0.5× have been removed to allow higher clocks to be

conﬁgured.

SCI_CLOCKF bits

Name Bits Description

SC_MULT 15:13 Clock multiplier

SC_ADD 12:11 Allowed multiplier addition

SC_FREQ 10: 0 Clock frequency

SC_MULT activates the built-in clock multiplier. This will multiply XTALI to create a higher CLKI.

When the multiplier is changed by more than 0.5×, the chip runs at 1.0× clock for a few hundres

clock cycles. The values are as follows:

SC_MULT MASK CLKI

0 0x0000 XTALI

1 0x2000 XTALI×2.0

2 0x4000 XTALI×2.5

3 0x6000 XTALI×3.0

4 0x8000 XTALI×3.5

5 0xa000 XTALI×4.0

6 0xc000 XTALI×4.5

7 0xe000 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 MASK Multiplier addition

0 0x0000 No modiﬁcation is allowed

1 0x0800 1.0×

2 0x1000 1.5×

3 0x1800 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 0x8BE8, SC_MULT = 4, SC_ADD = 1 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 + 1.0)×XTALI = 54 MHz.

Version: 0.42, 2011-11-24 44