WM8944BECSSLASHR datasheet(74/165 Pages) CIRRUS

74 / 165 page

WM8944B

Rev 4.3

DIGITAL PULL-UP AND PULL-DOWN

The WM8944B provides integrated pull-up and pull-down resistors on each of the DACDAT, LRCLK

and BCLK pins. This provides a flexible capability for interfacing with other devices. Each of the pull-

up and pull-down resistors can be configured independently using the register bits described in Table

50.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R4 (04h)

Audio

interface

15:14

DACDATA_PUL

L [1:0]

DACDAT pull-up / pull-down Enable

00 = no pull-up or pull-down

01 = pull-down

10 = pull-up

11 = reserved

13:12

FRAME_PULL

[1:0]

LRCLK pull-up / pull-down Enable

00 = no pull-up or pull-down

01 = pull-down

10 = pull-up

11 = reserved

11:10

BCLK_PULL

[1:0]

BCLK pull-up / pull-down Enable

00 = no pull-up or pull-down

01 = pull-down

10 = pull-up

11 = reserved

Table 50 Pull-Up and Pull-Down Control

CLOCKING AND SAMPLE RATES

The internal clocks for the CODEC and Digital Audio Interface are derived from a common internal

clock source, SYSCLK. This clock can either be derived directly from MCLK, or may be generated

using the Frequency Locked Loop (FLL) using MCLK as a reference. All commonly-used audio

sample rates can be derived directly from typical MCLK frequencies; the FLL provides additional

flexibility for a wider range of MCLK frequencies.

The WM8944B supports a wide range of standard audio sample rates from 8kHz to 48kHz. When the

ADC and DAC are both enabled, they operate at the same sample rate, fs.

Other functions such as the Interrupts and GPIO input de-bounce are clocked using a free-running

oscillator.

The control registers associated with Clocking and Sample Rates are described in Table 51.

The overall clocking scheme for the WM8944B is illustrated in Figure 31.

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