5-28 www.hp.com Technical Reference Guide
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
5.8.2 HD Audio Interface
The HD audio controller and the HD audio codec communicate over a five-signal HD Audio
Interface (Figure 5-11). 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.
Figure 5-11. HD Audio Interface Protocol
BCLK
SYNC
SDO
SDI
RST#
Command Stream
Response Stream
Tag C
Stream C
Tag A
Tag B
Frame
Start
Start
Frame
Frame
Stream A
Stream B
NOTE: Clock not drawn to scale.
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