STA323W datasheet(12/41 Pages) STMICROELECTRONICS

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STA323W

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7.1 CONFIGURATION REGISTER A (Address 00h)

7.1.1 Master Clock Select

The STA323W will support sample rates of 32kHz, 44.1kHz, 48Khz, 88.2kHz, and 96kHz. Therefore the

internal clock will be:

■ 32.768Mhz for 32kHz

■ 45.1584Mhz for 44.1khz, 88.2kHz, and 176.4kHz

■ 49.152Mhz for 48kHz, 96kHz, and 192kHz

The external clock frequency provided to the XTI pin must be a multiple of the input sample frequency (fs).

The correlation between the input clock and the input sample rate is determined by the status of the MCSx

bits and the IR (Input Rate) register bits. The MCSx bits determine the PLL factor generating the internal

clock and the IR bit determines the oversampling ratio used internally.

Table 7. IR and MCS Settings for Input Sample Rate and Clock Rate

7.1.2 Interpolation Ratio Select

The STA323W has variable interpolation (re-sampling) settings such that internal processing and DDX

output rates remain consistent. The first processing block interpolates by either 2 times or 1 time (pass-

through) or provides a down-sample by a factor of 2.

The IR bits determine the re-sampling ratio of this interpolation.

Table 8. IR bit settings as a function of Input Sample Rate

FDRB

TWAB

TFRB

IR1

IR0

MCS2

MCS1

MCS0

1000

BIT

R/W

RST

NAME

DESCRIPTION

R/W

MCS0

Master Clock Select: Selects the ratio between the input

I2S sample frequency and the input clock.

1R/W

MCS1

2R/W

MCS2

Input Sample Rate

fs (kHz)

MCS(2..0)

000

001

010

011

100

101

32, 44.1, 48

768fs

512fs

384fs

256fs

128fs

576fs

88.2, 96

384fs

256fs

192fs

128fs

64fs

176.4, 192

384fs

256fs

192fs

128fs

64fs

BIT

R/W

RST

NAME

DESCRIPTION

4...3

R/W

IR (1...0)

Interpolation Ratio Select: Selects internal interpolation ratio based

on input I2S sample frequency

Input Sample Rate Fs (kHz)

IR (1,0)

1st Stage Interpolation Ratio

2 times over-sampling

44.1

2 times over-sampling

88.2

Pass-Through

176.4

Down-sampling by 2

192

Down-sampling by 2

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