WM9701A

Production Data

WOLFSON MICROELECTRONICS LTD.

PD Rev 3.2 January 2001

16

The ID decodes the capabilities of WM9701A based on the following:

BIT

FUNCTION

VALUE ON WM9701A

ID0

Dedicated Mic PCM in channel

0

ID1

Modem line Codec support

0

ID2

Bass and treble control

0

ID3

Simulated stereo (mono to stereo)

0

ID4

Headphone out support

0

ID5

Loudness (bass boost) support

0

ID6

18-bit DAC resolution

1

ID7

20-bit DAC resolution

0

ID8

18-bit ADC resolution

1

ID9

20-bit ADC resolution

0

SE4....SE

0

No stereo enhancement

00000

Table 1 Reset Register Function

Note that WM9701A defaults to indicate 18-bit compatibility. However, a control bit may be set in the

vendor - specific registers that changes bits ID6 and ID8 to be ‘0’, indicating a 16-bit device. It is

unlikely that this function will be required, however, as the MSB justification of the ADC and DAC

data means that a nominally 18-bit device should be fully compatible with controllers that only

provide 16-bit support. (Most PC type applications will only require 16-bit operation).

PLAY MASTER VOLUME REGISTERS (INDEX 02h, 04h AND 06h)

These registers manage the output signal volumes. Register 02h controls the stereo master volume

(both right and left channels), Register 04h controls the optional stereo headphone out, and

Register 06h controls the mono volume output. Each step corresponds to 1.5dB. The MSB of the

register is the mute bit. When this bit is set to 1 the level for that channel is set at -

ML5 to ML0 is for left channel level, MR5 through MR0 is for the right channel and MM5 to MM0 is

for the mono out channel.

Support for the MSB of the level is not provided by WM9701A. If the MSB is written to then

WM9701A detects when that bit is set and sets all 4 LSBs to 1s. Example: If the driver writes a

1xxxxx WM9701A interprets that as x11111. It will also respond when read with x11111 rather than

1xxxxx, the value written to it. The driver can use this feature to detect if support for the 6th bit is

there or not.

The default value of both the mono and the stereo registers is 8000h (1000 0000 0000 0000), which

corresponds to 0dB gain with mute on.

MUTE

MX4...MX0

FUNCTION

0

0 0000

0dB attenuation

0

0 0001

1.5dB attenuation

0

1 1111

46.5dB attenuation

1

x xxxx

Table 2 Volume Register Function

MASTER TONE CONTROL REGISTERS (INDEX 08h)

Optional register for support of tone controls (bass and treble). WM9701A does not support bass

and treble and writing to this register will have no effect, reading will result in all don’t care values.

PC BEEP REGISTER (INDEX 0Ah)

This controls the level for the PC-beep input. Each step corresponds to approximately 3dB of

attenuation. The MSB of the register is the mute bit. When this bit is set to 1 the level for that

channel is set at -

WM9701A defaults to the PC-beep path being muted, so an external speaker should be provided

within the PC to alert the user to power on self-test problems.