STAC9758 Datasheet, PDF (107/119 Pages) Integrated Device Technology – HIGH-PERFORMANCE 6-CHANNEL AC’97 2.3 CODEC WITH UNIVERSAL JACKS

STAC9758/9759
HIGH-PERFORMANCE 6-CHANNEL AC’97 2.3 CODEC WITH UNIVERSAL JACKS™
PC AUDIO
10.MULTIPLE CODEC SUPPORT
The STAC9758/9759 provides support for the multi-CODEC option according to the Intel AC'97, rev
2.3 specification. The CODEC ID functions as a chip select. Secondary devices therefore have com-
pletely orthogonal register sets; each is individually accessible and they do not share registers. The
STAC9758/9759 supports only the CODEC ID 10 in secondary mode (IDs 01 and 11 are NOT sup-
ported).
10.1. Primary/Secondary CODEC Selection
In a multi-CODEC environment the CODEC ID is provided by external programming of pin46
(CID1). The CID pin electrical function is logically inverted from the CODEC ID designation. The cor-
responding 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)”.
Table 24. CODEC ID Selection
XTAL Out Pin State
GND
XTL / FLOAT
CID1 Pin State
DVdd or floating
0V
CID0 Pin State
NA
NA
CODEC ID
00
10
CODEC Status
Primary
Secondary
10.1.1.
Primary CODEC Operation
As a Primary device the STAC9758/9759 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 STAC9758/9759 operates as Primary by default, and the
external ID pin (46), has an internal pull-up so that this pin may be left as no-connect for primary
operation.
When used as the Primary CODEC, the STAC9758/9759 generates the master AC-Link BIT_CLK
for both the AC'97 Digital Controller and any Secondary CODECs. The STAC9758/9759 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.
10.1.2.
Secondary CODEC Operation
When the STAC9758/9759 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 10 in the
two-bit field(s) of the Extended Audio and/or Extended Modem ID Register(s).
The STAC9758/9759 supports only the CODEC ID 10 in secondary mode (IDs 01 and 11 are NOT
supported).
IDT™
107
HIGH-PERFORMANCE 6-CHANNEL AC’97 2.3 CODEC WITH UNIVERSAL JACKS™
STAC9758/9759
V 1.2 1206