Intel PXA26X - Manual (Page 463)

Intel® PXA26x Processor Family Developer’s Manual 13-1
AC97 Controller Unit
13
13.1 Overview
The AC97 Controller Unit (ACUNIT) of the Intel® PXA26x Processor Family supports the AC97
revision 2.0 features listed in
Section 13.2, “Feature List” . The ACUNIT also supports audio
controller link (AC-link). AC-link is a serial interface for transferring digital audio, modem, Mic-
in, codec register control, and status information.
The AC97 codec sends the digitized audio samples that the ACUNIT stores in memory. For
playback or synthesized audio production, the processor retrieves stored audio samples and sends
them to the codec through the AC-link. The external digital-to-analog converter (DAC) in the
codec then converts the audio sample to an analog audio waveform.
This chapter describes the programming model for the ACUNIT. The information in this chapter
requires an understanding of the AC97 revision 2.0 specification.
Note: The ACUNIT, I
2
S Controller, and the ASSP may not be used at the same time.
13.2 Feature List
The processor ACUNIT supports the following AC97 features:
• Independent channels for stereo pulse code modulated (PCM) in, stereo PCM out, modem out,
modem-in and mono mic-in
All of the above channels support only 16-bit samples in hardware. Samples less than 16 bits
are supported through software.
• Multiple sample rate AC97 2.0 codecs (48 KHz and below). The ACUNIT depends on the
codec to control the varying rate.
• Read/write access to AC97 registers
• Secondary codec support
• Three receive FIFOs (32-bit, 16 entries)
• Two transmit FIFOs (32-bit, 16 entries)
The processor ACUNIT does not support these optional AC97 features:
• Double-rate sampling (n+1 sample for PCM L, R & C)
• 18- and 20-bit sample lengths