WM9707

Production Data

w

PD Rev 4.1 June 2006

17

MASTER/SLAVE ID SUPPORT

WM9707 supports operation as either a master or a slave CODEC. Configuration of the device as

either a master or as a slave, is selected by tying the CID pin 45 on the package.

Fundamentally, a device identified as a master (ID = 0) produces BITCLK as an output, whereas a

slave (any other ID) must be provided with BITCLK as an input. This has the obvious implication that

if the master device on an AC link is disabled, the slave devices cannot function.

The AC’97 Revision 2.1 specification defines that the CID pin has inverting sense, and are provided

with internal weak pull ups. Therefore, if no connections are made to the CID pin, then the pin pulls hi

and an ID = 0 is selected, i.e. master. External connects to ground will select other IDs.

PIN 45 CID

ID

SELECTED

MASTER OR

SLAVE

BITCLK

NC

0

Master

Output

Ground

1

Slave

Input

Table 3 ID Selection

CONTROL INTERFACE

A digital interface has been provided to control the WM9707 and transfer data to and from it. This

serial interface is compatible with the Intel AC’97.

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 Powerdown down modes.

AC-LINK DIGITAL SERIAL INTERFACE PROTOCOL

The WM9707 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 WM9707 provides support for 18-bit operation.

SLOT

NUMBER

SYNC

SDATAOUT

SDATAIN

TAG PHASE

TAG

CMD

ADR

CMD

DATA

PCM

LEFT

PCM

RIGHT

RSRVD

RSRVD

RSRVD

TAG

STATUS

ADDR

STATUS

DATA

PCM

LEFT

PCM

RIGHT

RSRVD

RSRVD

RSRVD

RSRVD

RSRVD

RSRVD

RSRVD

DATA PHASE

01

23

4567

89

10

11

12

PCM C

(n+1)

PCM R

(n+1)

PCM L

(n+1)

CODEC ID

SLOTREQ 3-12

PCM

CENTRE

RSRVD

PCM

L SURR

PCM

R SURR

PCM

LFE

RSRVD

Figure 11 AC’97 Standard Bi-Directional Audio Frame