Audio Codec '97 Revision 2.1

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AC ‘97 Component Specification Revision 2.1 1. Introduction 1.1 Feature List • Analog I/O component of two-chip PC audio solution • Two standard packages: 48-pins and 64-pins AC ’97 2.0 redefined the 64-pin to be entirely vendor specific • Split digital/analog architecture for improved S/N ratio (> 90 dB achievable) • 16-bit stereo full-duplex Codec with fixed 48K sampling rate, AC ’97 2.0 Appendix A defines variable sample rate support up to 96 kHz • Four analog line-level stereo inputs for connection from LINE IN, CD, VIDEO and AUX AC ’97 2.1 Appendix D defines optional VIDEO and AUX elimination • Two analog line-level mono inputs for speakerphone (or DLP 1 ) and PC BEEP AC ’97 2.1 Appendix D defines optional PHONE and PC_BEEP elimination • Mono mic input switchable from two external sources AC ’97 2.1 Appendix D defines optional MIC2 • High quality pseudo-differential CD input • Stereo line level output • Mono output for speakerphone (or DLP 1 ) AC ’97 2.1 Appendix D defines optional MONO_OUT elimination • Power management support • Optional tone control • Optional loudness control • Optional 3D stereo enhancement • Optional stereo headphone output with 32 Ohm drive AC ’97 2.1 Appendix D re-defines HP_OUT to support True Line Level out functionality • Optional 18 or 20-bit DAC and ADC resolution • Optional modem line Codec (ADC and DAC) AC ’97 2.0 Appendix B fully defines 2-line modem , handset, and GPIO • Optional 3rd ADC input channel for mic 1 Down Line Phone 12 May 22, 1998
AC ‘97 Component Specification Revision 2.1 1.2 Audio Codec ‘97 Architectural Overview AClink power management digital interface AC ‘97 Registers 64 x 16-bits 00h 02h 04h . . . 7Ch 7Eh PCM out DAC’s (2 channels, 48Kss) DAC DAC PCM in ADC’s (1, 2, or 3* channels, 48Kss) ADC ADC ADC modem line ADC & DAC* ADC DAC 13 stereo sources analog mixing and gain control (see AC ‘97 mixer) mono sources Figure 1. AC ‘97 1.0 Block Diagram Key analog options •tone control •3D stereo enhance •loudness mic boost 0/20dB * M U X mono analog stereo analog mono digital stereo digital optional LINE_OUT HP_OUT* MONO_OUT MIC1 MIC2 modem Rx* modem Hx* modem Tx* Figure 1 shows the functional blocks that make up the Audio Codec ‘97, which is the analog component of a twochip audio solution (fully described in the next section). The two fixed 48kHz or AC ’97 2.0 compliant variable rate DAC’s support a stereo PCM out channel which contains a mix generated in the AC ‘97 Controller of all software sources, including the internal synthesizer and any other digital sources. PCM out is mixed with additional analog sources, processed with optional 3D stereo enhancement and tone controls, and sent to independently controlled LINE_OUT and HP_OUT, or AC ’97 2.1 compliant True Line Level Out. For speakerphone telephony, the MONO_OUT delivers either mic only or a mono mix of sources to the telephony subsystem. The ADC path supports two channels of fixed 48kHz or AC ’97 2.0 compliant variable rate input, with an option to support a 3rd fixed 48kHz ADC input channel dedicated to the mic. The standard stereo PCM in channel supports record of any mono or stereo source, or a mix of sources 2 . The optional dedicated mic channel extends the range of acoustic echo cancellation capabilities by allowing the audio subsystem to record the MIC along with LINE_OUT (L and R) reference signals needed for robust stereo mic input filtering, either in the AC ‘97 Controller or on the host CPU. The independent mic channel also has the potential to be dedicated to voice input applications. The optional ADC and DAC pair supports integration of the line Codec portion of a modem AFE function into AC ’97, as defined in AC ’97 2.0 Appendix B. NAMING CONVENTION: Throughout this document signal names have been assigned to be consistent with the point of view of an application running on the PC. 2 For highest quality and greatest flexibility, the AC ‘97 controller should provide the capability to digitally record any or all of the contributing digital sources in the PCM out mix. May 22, 1998
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Audio Codec '97 Revision 2.1

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