STAC9752A Datasheet, PDF (87/106 Pages) Integrated Device Technology – AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK

STAC9752A/9753A
AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK
PC AUDIO
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)”.
CID1 State
DVdd or floating
DVdd or floating
0V
0V
Table 29. CODEC ID Selection
CID0 State
DVdd or floating
0V
DVdd or floating
0V
CODEC ID
00
01
10
11
CODEC Status
Primary
Secondary
Secondary
Secondary
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, 10KΩ / 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).
IDT™
87
AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK
STAC9752A/9753A
V 1.5 1206