HP dc7900 5.8.1 HD Audio Controller, 5.8.2HD Audio Link Bus, 5.8.3 Audio Multistreaming

Input/Output Interfaces

5.8.1 HD Audio Controller

The HD Audio Controller is a PCI Express device that is integrated into the 82801 ICH component and supports the following functions:

■Read/write access to audio codec registers

■Support for greater than 48-KHz sampling

■HD audio interface

5.8.2HD Audio Link Bus

The HD audio controller and the HD audio codec communicate over a five-signal HD Audio Link Bus (Figure 5-10). The HD Audio Interface includes two serial data lines; serial data out (SDO, from the controller) and serial data in (SDI, from the audio codec) that transfer control and PCM audio data serially to and from the audio codec using a time-division multiplexed (TDM) protocol. The data lines are qualified by the 24-MHz BCLK signal driven by the audio controller. Data is transferred in frames synchronized by the 48-KHz SYNC signal, which is derived from the clock signal and driven by the audio controller. When asserted (typically during a power cycle), the RESET- signal (not shown) will reset all audio registers to their default values.

Frame

BCLK

Frame

Frame

Start

Tag A

Tag B

Start

SYNC

SDO

Command Stream

Stream B

Stream A

SDI

Response Stream

Tag C

Stream C

RST#

NOTE: Clock not drawn to scale.

Figure 5-10. HD Audio Link Bus Protocol

5.8.3 Audio Multistreaming

The audio subsystem can be configured (through the ADI control panel) for processing audio for multiple applications. The Headphone Out jack can provide audio for one application while the Line Out jack can provide external speaker audio from another application.

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