Advanced Information

WM8722

WOLFSON MICROELECTRONICS LTD

AI Rev 1.5 May 2000

21

SQR

The WM8722 can generate three different tone types. The default setting is a sinusoidal tone.

Square waves are generated by setting the SQR bit.

F2F

A two-tone output that generates one cycle at the chosen frequency, followed by two cycles at twice

that frequency can be selected by setting the F2F bit. This facility may be used in sine or square

wave modes.

SYSTEM DIAGRAM

STORAGE

(HDD)

VIDEO

DAC

DIGITAL

DECODER

MEDIA

FRONT END

HOME

CONNECTIVITY

SYSTEM

CLOCKS

WM8722

AUDIO

DAC

AMPLIFIER

VIDEO OUT

TONE

GENERATOR

OUTPUT

MONO AUDIO

OUTPUT

(OPTIONAL)

L

R

L

R

VARIABLE LEVEL

AUDIO OUTPUT (TV)

LINE LEVEL AUDIO

OUTPUT (VCR)

HEADPHONE

OUT

MIC OR

ANALOGUE

INPUT

Figure 10. Digital Set Top Box Application

The WM8722 is a complete audio sub-system designed for digital set top box applications. A typical

application might require audio outputs to be routed to a VCR and television. The WM8722 allows

the user to control the output audio level being sent to the television whilst maintaining a constant

volume level to the VCR. The on-board tone generator can be programmed to provide a audible

warning signal from the set top box to the television outputs without appearing on the line level

outputs. The WM8722 can also directly generate a mono signal for UHF outputs.

The WM8722 contains a stereo analogue input. This signal can be routed or mixed together onto the

line and variable outputs. It can be used to control the volume level of an audio output from another

audio source such as a games machine or additional set top box. Alternatively, it could be used to

provide a karaoke input from a digital effects processor.