WM9710

Production Data

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PD Rev 4.0 December 2003

18

Figure 10 shows this function schematically. The output signal from the comparator is accessible

by reading bit HSCP in register 5Ch. Auto detect may be used by setting HSEN bit, or external

control by using the HSDT bit which is an over-ride that forces the headset tri-state and

microphone path switching function to occur.

This function would allow, for example, a stereo headphone to be used that had a microphone in

the connecting lead, and a switch. The switch changes the headphone into a mono headset with

microphone connected via the tip connection on the jack. If used in a product such as an MP3

capable phone it would allow the user to switch from headphone use to headset use by simply

switching a single switch in the headphone cable, so at the same time answering or initiating

telephone calls. It may also be possible to use the pull-up current to provide so called ‘phantom

power’ to dynamic microphones with appropriate choice of microphone.

DATA SLOT MAPPING

DAC data and SPDIF data sent to the device, ADC data sent from the device, can be optionally

mapped into alternative slots under control of slot mapping bits located as follows:

SLOT MAPPING DATA

TYPE

CONTROL

BITS

REGISTER LOCATION

DAC data

DSA[1,0]

28h

SPDIF data

SPSA[1,0]

2Ah

ADC data

ASS[1,0]

5Ch (non-AC’97 feature)

Table 4 Data Slot Mapping Control

Default values and functional behavior are further described in the Serial Interface Register Map

description. DAC slot mapping defaults are in Table 2.

AC-LINK DIGITAL SERIAL INTERFACE PROTOCOL

A digital interface has been provided to control the WM9710 and transfer data to and from it. This

serial interface is compatible with the Intel AC’97 specification.

The main control interface functions are:

•

Control of analogue gain and signal paths through the mixer

•

Bi-directional transfer of ADC and DAC words to and from AC’97 controller

•

Selection of power-down modes

The WM9710 incorporates a 5-pin digital serial interface that links it to the AC’97 controller. AC-

link is a bi-directional, fixed rate, serial PCM digital stream. It handles multiple input and output

audio streams, as well as control register accesses employing a time division multiplexed (TDM)

scheme. The AC-link architecture divides each audio frame into 12 outgoing and 12 incoming

data streams, each with 20-bit sample resolution. With a minimum required DAC and ADC

resolution of 16-bits, AC’97 may also be implemented with 18 or 20-bit DAC/ADC resolution,

given the headroom that the AC-link architecture provides. The WM9710 provides support for 18-

bit audio operation.