82801FB Datasheet, PDF (234/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

Functional Description
5.23 Intel^® High Definition Audio (D27:F0)
5.23.1 Link Protocol Overview
The Intel High Definition Audio Link is the digital serial interface that connects HD audio codecs
to the ICH6 HD audio controller. The HD audio link protocol is synchronous with the controller
based on a fixed 24.000 MHz clock (ACZ_BIT_CLK), and is purely isochronous (no flow control),
with a 48 KHz framing period. Separate input and output serial digital signals support multiple
inbound and outbound streams, as well as fixed command and response channels.
Figure 5-16. Intel^® High Definition Audio Link Protocol Example
Previous Frame
ACZ_BIT_CLK
(24.00 MHz)
ACZ_SYNC
ACZ_SDOUT
ACZ_SDIN
ACZ_RST#
Frame SYNC
Command Stream
Response Stream
T_{frame_sync}= 20.833µs (48kHz)
Stream 1 Data
Tag
Tag
Stream 5 Data
Stream ‘b’ Data
Next Frame
5.23.1.1
5.23.1.1.1
5.23.1.1.2
Since the HD Audio link is purely an isochronous transport mechanism, all link data transmission
occurs within periodic time frames. A frame is defined as a 20.833 ms window of time marked by
the falling edge of the Frame Sync marker, identifying the start of each frame. The HD Audio
controller is responsible for generating the Frame Sync marker, which is a high-going pulse on the
ACZ_SYNC signal, exactly 4 ACZ_BIT_CLK cycles in width.
Frame Composition
Basic inbound and outbound frames are made up of three major components: Command/Response
field, Stream Packets, and Null fields.
Command/Response field
This field is used for link and codec management. One of these fields appears exactly once per
frame, most significant bit first, and is always the first field in the frame. It is composed of a 40-bit
Command Field on each outbound frame and a 36-bit Response Field on each inbound frame.
Stream Packet
A stream packet is the logical “envelop” in which data is transferred on the link. Since all data is
associated with a given stream, each stream packet is delineated with an associated stream tag,
which provides the stream ID or stream number of the packet data. The stream packet is made up
with zero or more sample blocks each of which has the same length (or sample size) and same time
reference (or sample point). A sample block contains one or more samples, the number of which is
specified by a control register. As an example, a monaural stream has one sample per sample block;
a stereo stream has two samples per sample block; a 5.1multi-channel stream has 6 samples per
sample block, and so forth.
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Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet