STAC9721 Datasheet, PDF(31/48 Page) List of Unclassifed Manufacturers – Stereo AC 97 Codec With Multi-Codec Option

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

STAC9721 Datasheet, PDF (31/48 Pages) List of Unclassifed Manufacturers – Stereo AC 97 Codec With Multi-Codec Option

◁

SigmaTel, Inc.

Data Sheet

STAC9721

6. MULTIPLE CODEC SUPPORT

The STAC9721/23 provides support for the multi-codec option according to the Intel AC'97, rev 2.1

specification. By definition there can be only one Primary Codec (Codec ID 00) and up to three

Secondary Codecs (Codec IDs 01,10, and 11). The Codec ID functions as a chip select. Secondary

devices therefore have completely orthogonal register sets; each is individually accessible and they do not

share registers.

6.1 Primary/Secondary Codec Selection

In a multi-codec environment the codec ID is provided by external programming of pins 45 and 46 (CID0

and CID1). The CID pin electrical function is logically inverted from the codec ID designation. The

corresponding pin state and its associated codec ID are listed in the "Codec ID Selection" table. Also see

slot assignment discussion, âMulti-Channel Programming Register (Index 74)â.

CID1 State

+5V or floating

Table 21. Codec ID Selection

CID0 State

Codec ID Codec Status

+5V or floating

Primary

Secondary

EXTENDED AUDIO

ID, 28h

ID1, ID0

0, 0

0, 1

1, 0

1, 1

6.1.1

Primary Codec Operation

As a Primary device the STAC9721/23 is completely compatible with existing AC'97

definitions and extensions. Primary Codec registers are accessed exactly as defined in

the AC'97 Component Specification and AC'97 Extensions. The STAC9721/23 operates

as Primary by default, and the external ID pins (47 and 48) have internal pull-ups so that

these pins may be left as no-connects for primary operation.

When used as the Primary Codec, the STAC9721/23 generates the master AC-Link

BIT_CLK for both the AC'97 Digital Controller and any Secondary Codecs. The

STAC9721/23 can support up to 4, 10 Kâ¦ 50 pF loads on the BIT_CLK. This is to

insure that up to 4 Codec implementations will not load down the clock output.

6.1.2

Secondary Codec Operation

When the STAC9721/23 is configured as a Secondary device the BIT_CLK pin is

configured as an input at power up. Using the BIT_CLK provided by the Primary Codec

insures that everything on the AC-Link will be synchronous. As a Secondary device it

can be defined as Codec ID 01, 10, or 11 in the two-bit field(s) of the Extended Audio

and/or Extended Modem ID Register(s).

04/07/00

▷