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Intel® PXA26x Processor Family Developer’s Manual 13-3
AC97 Controller Unit
13.4 AC-link Digital Serial Interface Protocol
Each AC97 codec incorporates a five-pin digital serial interface that links it to the ACUNIT.
AC-link is a full-duplex, fixed-clock, PCM digital stream. It employs a time division multiplexed
(TDM) scheme to handle control register accesses and multiple input and output audio streams.
The AC-link architecture divides each audio frame into 12 outgoing and 12 incoming data streams.
Each stream has 20-bit sample resolution and requires a DAC and an analog-to-digital converter
(ADC) with a minimum 16-bit resolution. The ACUNIT supports the data streams shown in
Table 13-2.
Figure 13-1. Data Transfer Through the AC-link
nACRESET
SDATA_OUT
SYNC (48 KHz)
SDATA_IN_0
BITCLK (12.288 MHz)
AC97 Controller Unit
AC97 Primary Codec
AC97 Secondary Codec
SDATA_IN_1
(ACUNIT)
AC-link
Table 13-2. Supported Data Stream Formats (Sheet 1 of 2)
Channel Slots Comments
PCM playback Two output slots Two-channel composite PCM output stream
PCM record data Two input slots Two-channel composite PCM input stream
Codec control Two output slots Control register write port
Codec status Two input slots Control register read port
Modem line codec
output
One output slot Modem line codec DAC input stream
Modem line codec
input
One input slot Modem line codec ADC output stream