STAC9721 datasheet(27/48 Pages) ETC1

27 / 48 page

SigmaTel, Inc.

Data Sheet

STAC9721

04/07/00

4.4.12 Analog Current Adjust (Index 70h and 72h)

The Analog Current Adjust register (index 72h) is a locked register and can only be

properly written and read from when ABBAh has been written into register 70h. The

BIASx bits allow the analog current to be adjusted with minimal reduction in

performance. The –50% analog current setting is not recommended when a 5V analog

supply is used. The –50% setting for 3.3V supplies is recommended to reduce power

consumption for notebook computers to its lowest level.

Table 18: Analog Current Adjust

BIAS1

BIAS0

Analog Current

Normal Current

-50% Analog

Current

-25% Analog

Current

+25% Analog

Current

4.4.13 Multi-Channel Programming Register (Index 74h)

This read/write register is used to program the various options for multi-channel

configurations. Only the two LSBs are used (MC0 and MC1), and they define which

AC-Link slot data is supplied to the two PCM output channels on the STAC9721/23.

The purpose of using slot 10 and 11 in the final configuration is to allow for the

possibility of an eight-channel architecture using several STAC9721/23 or STAC9708

devices in the multi-codec configuration. Also see “Multiple Codec Support” discussion

for information on the use of external pins CID1 and CID0.

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