STAC9766 Datasheet, PDF (20/97 Pages) Integrated Device Technology – TWO-CHANNEL, 20-BIT, AC’97 2.3 CODECS WITH STEREO MICROPHONE AND MIC/JACK SENSING

STAC9766/9767
TWO-CHANNEL, 20-BIT, AC’97 2.3 CODECS WITH STEREO MICROPHONE AND MIC/JACK SENSING
PC AUDIO
4. CONTROLLER, CODEC AND AC-LINK
This section describes the physical and high-level functional aspects of the AC‘97-Controller to
CODEC interface, referred to as AC-link.
4.1. AC-link Physical interface
The STAC9766/9767 communicates with its companion Digital Controller via the AC-link digital
serial interface. AC-link has been defined to support connections between a single Controller and up
to four CODECs. All digital audio, modem, and handset data streams, as well as all control (com-
mand/status) information are communicated over this serial interconnect, which consists of a clock
(BIT_CLK), frame synchronization (SYNC), serial data in (SDATA_IN), serial data out
(SDATA_OUT), and a reset (RESET#).
4.2. Controller to Single CODEC
The simplest and most common AC‘97 system configuration is a point-to-point AC-link connection
between Controller and the STAC9766/9767, as illustrated in Figure 11.
Figure 11. AC-Link to its Companion Controller
SYNC
XTAL_IN
D i g i t a l AD C ' 9 7
Controller
BIT_CLK
SDATA_OUT
AC'97 Codec
SDATA_IN
RESET#
XTAL_OUT
A primary CODEC may act as either a source or a consumer of BIT_CLK, depending on the config-
uration.
While RESET# is asserted, if a clock is present at the BIT_CLK pin for at least five cycles before
RESET# is de-asserted, then the CODEC is a consumer of BIT_CLK, and must not drive BIT_CLK
when RESET# is de-asserted. The clock is being provided by other than the primary CODEC, for
instance by the controller or an independent clock chip. In this case the primary CODEC must act as
a consumer of the BIT_CLK signal as if it were a secondary CODEC.
This clock source detection must be done each time the RESET# line is asserted. In the case of a
warm reset, where the clock is halted but RESET# is not asserted, the CODEC must remember the
clock source, and not begin generating the clock on the assertion of SYNC if the CODEC had previ-
ously determined that it was a consumer of BIT_CLK.
IDT™
20
TWO-CHANNEL, 20-BIT, AC’97 2.3 CODECS WITH STEREO MICROPHONE AND MIC/JACK SENSING
STAC9766/9767
V 7.4 12/06