STAC9758 Datasheet, PDF (28/119 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
4.3.3.
CODEC ID Strapping
Audio CODECs in the 48-pin package use pins 45 and 46 (defined as ID0# and ID1#) as strapping
(i.e. configuration) pins to configure the CODEC ID. The ID0# and ID1# strapping bits adopt inverted
polarity and default to 00 = Primary (via a weak internal pullup) when left floating. This eliminates the
need for external resistors for CODECs configured as Primary, and maintains backward compatibil-
ity with existing layouts that treat pins 45 and 46 as “no connect” or cap to ground. Pulldowns are
typically 0-10 kΩ and connected to Digital (not Analog) Ground.
The STAC9758 is normally operated as Primary, which ID 00. Pin 46 is used as CID1. Pin 45 is used
as GPIO3.
Table 3. Recommended CODEC ID strapping
XTAL_OUT (pin 3)
short to gnd
XTAL
XTAL
Pin 46
NA (Freq Select)
NC
pulldown
Pin 45
NA (GPIO3)
NA (GPIO3)
NA (GPIO3)
Configuration
Primary ID 00
Primary ID 00
Secondary ID 01
4.4.
Clocking for Multiple CODEC Implementations
To keep the system synchronous, all Primary and Secondary CODEC clocking must be derived from
the same clock source, so they are operating on the same time base. In addition, all AC-Link proto-
col timing must be based on the BIT_CLK signal, to ensure that everything on the AC-Link will be
synchronous.
As a Secondary CODEC, the STAC9758 uses the Primary’s BIT_CLK output to derive 24.576 MHz.
See section 2.2.4: page19 for clock frequencies supported and configurations.
4.5.
STAC9758/9759 as a Primary CODEC
The following clocking options are supported as a primary:
• 24.576 MHz crystal attached to XTAL_IN and XTAL_OUT
• 24.576 MHz external oscillator provided to XTAL_IN
• 14.318 MHz external oscillator provided to XTAL_IN
• 48 MHz external oscillator provided to XTAL_IN
See section 2.2.4: page19 for clock frequencies supported and configurations.
4.5.1.
STAC9758/9759 as a Secondary CODEC
The following clocking option is supported as a secondary:
• BIT_CLK input provided by the Primary. In this mode, a clock at XTAL_IN (Pin 2) is ignored and
may be left unconnected.
See section 2.2.4: page19 for clock frequencies supported and configurations.
IDT™
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HIGH-PERFORMANCE 6-CHANNEL AC’97 2.3 CODEC WITH UNIVERSAL JACKS™
STAC9758/9759
V 1.2 1206