Allwinner A20 - AC97 Interface Clock Tree; AC Link Frame Format

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6.10.3. AC97 Interface Clock Tree

The beginning of all audio sample packets, or Audio Frames, transferred over AC-link is synchronized to

the rising edge of the SYNC signal. SYNC is driven by the Controller. The Controller generates SYNC by

dividing BIT_CLK by 256 and applying some condition to tailor its duty cycle. This yields a 48 KHz SYNC

signal whose period defines an audio frame. Data is transitioned on AC-link on every rising edge of

BIT_CLK, and subsequently sampled by the receiving device on the receiving side of AC-link on each

immediately following falling edge of BIT_CLK.

6.10.4. AC Link Frame Format

Bi-directional AC-link Frame with slot assignments