WM8728

Production Data

w

PD Rev 4.2 April 2004

17

The automute function detects a series of ZERO value audio samples of 1024 samples long

being applied to both channels. After such an event, a latch is set whose output (AUTOMUTED)

is wire OR’ed through a 10kohm resistor to the MUTEB pin. Thus if the MUTEB pin is not being

driven, the automute function will assert mute.

If MUTEB is tied high, AUTOMUTED is overridden and will not mute unless the IZD register bit is

set. If MUTEB is driven from a bi-directional source, then both MUTE and automute functions are

available. If MUTEB is not driven, AUTOMUTED appears as a weak output (10kOhm-source

impedance) so can be used to drive external mute circuits. AUTOMUTED will be removed as

soon as any channel receives a non-ZERO input.

A diagram showing how the various Mute modes interact is shown below Figure 12.

IZD (Register Bit)

AUTOMUTED

(Internal Signal)

10k

Ω

Ω

Ω

Ω

MUT (Register Bit)

SOFTMUTE

(Internal

Signal)

MUTEB

PIN

Figure 12 Selection Logic for MUTE Modes

INPUT FORMAT SELECTION

In hardware mode, LATI2S (pin 20) and CSBIWL (pin 15) become input controls for selection of

input data format type and input data word length.

LATI2S

CSBIWL

INPUT DATA MODE

0

0

24-bit right justified

0

1

20-bit right justified

1

0

16-bit I

1

1

24-bit I

Table 4 Input Format Selection

Note:

In 24 bit I

minimum of 24 BCKINs and low for a minimum of 24 BCKINs. If exactly 32 BCKINs occur in one

LRCIN (16 high, 16 low) the chip will auto detect and run a 16 bit data mode.

DE-EMPHASIS CONTROL

In hardware mode, SDIDEM (pin 18) becomes an input control for selection of de-emphasis

filtering to be applied.

SDIDEM

DE-EMPHASIS

0

Off

1

On

Table 5 De-emphasis Control