STAC9752A datasheet(87/106 Pages) IDT

87 / 106 page

STAC9752A/9753A

AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK

PC AUDIO

IDT™

STAC9752A/9753A

V 1.5 1206

AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK

9. MULTIPLE CODEC SUPPORT

The STAC9752A/9753A provides support for the multi-CODEC option according to the Intel AC'97,

rev 2.3 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 accessi-

ble and they do not share registers.

9.1.

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 desig-

nation. The corresponding pin state and its associated CODEC ID are listed in the "CODEC ID

Selection" table. Also see slot assignment discussion, “Multi-Channel Programming Register (Index

74)”.

9.1.1.

Primary CODEC Operation

As a Primary device the STAC9752A/9753A 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 STAC9752A/9753A operates as Primary by default, and

the external ID pins (45 and 46), have internal pull-ups so that these pins may be left as no-connects

for primary operation.

When used as the Primary CODEC, the STAC9752A/9753A generates the master AC-Link

BIT_CLK for both the AC'97 Digital Controller and any Secondary CODECs. The STAC9752A/

9753A can support up to four, 10K

Ω / 50pF loads on the BIT_CLK output. This is to ensure that up

to four CODEC implementations will not load down the clock output.

9.1.2.

Secondary CODEC Operation

When the STAC9752A/9753A 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).

Table 29. CODEC ID Selection

CID1 State

CID0 State

CODEC ID

CODEC Status

DVdd or floating

Primary

DVdd or floating

Secondary

DVdd or floating

Secondary

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