WM9704M

Production Data

WOLFSON MICROELECTRONICS LTD

PD Rev 3.2 January 2001

16

MODE

ID

SLOTS MAPPED TO

FRONT DACS

SLOTS MAPPED TO REAR

DACS

00 or 01

3 and 4

10

7 and 8

Rev 2.1

(00)

11

6 and 9

Not supported

in this mode

00 or 01

3 and 4

10

7 and 8

Modem (11)

11

6 and 9

5

(or 5 & 10 if DLM set)

Table 7 Slot to DAC Mapping Based on Mode and Codec ID

SLAVE CODEC REGISTER ACCESS DEFINITIONS

Master Codec access is exactly as defined for AC’97. For slave Codec access, the AC’97 Digital

Controller must invalidate the tag bits for Slot 1 and 2 Command Address and Data (Slot 0, bits 14

and 13) and place a non-zero value (01, 10, or 11) into the Codec ID field (Slot 0, bits 1 and 0).

Slave Codecs disregard the Command Address and Command Data (Slot 0, bits 14 and 13) tag bits

when they see a 2-bit Codec ID value (Slot 0, bits 1 and 0) that matches their configuration. In a

sense the Slave Codec ID field functions as an alternative Valid Command Address (for Slave reads

and writes) and Command Data (for Slave writes) tag indicator.

Slave Codecs must monitor the Frame Valid bit, and ignore the frame (regardless of the state of the

Slave Codec ID bits) if it is not valid. AC’97 Digital Controllers should set the frame valid bit for a

frame with a slave register access, even if no other bits in the output tag slot except the Slave Codec

ID bits are set.

OUTPUT TAG SLOT (16-BITS)

BIT

DESCRIPTION

15

Frame Valid

14

Slot 1 Valid Command Address Bit (Master Codec only)

13

Slot 2 Valid Command Data Bit (Master Codec only)

12-3

Slot 3-12 Valid Bits as defined by AC’97

2

Reserved (Set to 0)

1-0

2-bit Codec ID field (00 reserved for Master; 01, 10, 11 indicate Slave)

New definitions for Slave Codec Register Access

Table 8 Slave Codec Register Access Slot 0-Bit Definitions

CONTROL INTERFACE

A digital interface has been provided to control the WM9704M and transfer data to and from it. This

serial interface is compatible with the Intel AC’97 specification as illustrated in the System Diagram

(Figure 7).

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 modes