Advanced Information

WM9707

WOLFSON MICROELECTRONICS LTD

AI Rev 2.2 January 2001

13

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

SDATA_OUT

SDATA_IN

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

0

123

45

6789

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 10 AC’97 Standard Bi-directional Audio Frame