STAC9750XXTAEC1X IDT, Integrated Device Technology Inc, STAC9750XXTAEC1X Datasheet - Page 58

• Manufacturer Part Number: STAC9750XXTAEC1X
• Manufacturer: IDT, Integrated Device Technology Inc

Specifications of STAC9750XXTAEC1X

• Single Supply Voltage (typ): 3.3/5V
• Single Supply Voltage (min): 3.135V
• Single Supply Voltage (max): 3.465/5.25V
• Package Type: TQFP
• Lead Free Status / RoHS Status: Compliant

8. MULTIPLE CODEC SUPPORT
IDT™
VALUE-LINE TWO-CHANNEL AC’97 CODECS
STAC9750/9751
VALUE-LINE TWO-CHANNEL AC’97 CODECS
8.1.
8.1.1.
8.1.2.
Primary/Secondary CODEC Selection
The STAC9750/9751 provides support for the multi-CODEC option according to the Intel AC'97, rev
2.2 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.
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)”.
Primary CODEC Operation
As a Primary device the STAC9750/9751 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 STAC9750/9751 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 STAC9750/9751 generates the master AC-Link BIT_CLK
for both the AC'97 Digital Controller and any Secondary CODECs. The STAC9750/9751 can support
up to four loads of 10 KΩ and 50 pF on the BIT_CLK line. This is to ensure that implementations of
up to four CODECs will not load down the clock output.
Secondary CODEC Operation
When the STAC9750/9751 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).
DVdd or floating
DVdd or floating
CID1 State
0 V
0 V
DVdd or floating
DVdd or floating
CID0 State
Table 41. CODEC ID Selection
0 V
0 V
58
CODEC ID
00
01
10
11
STAC9750/9751
CODEC Status
Secondary
Secondary
Secondary
Primary
PC AUDIO
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