AC’97 Controller Unit

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13.1Overview

The AC’97 Controller Unit (ACUNIT) of the PXA255 processor supports the AC’97 revision 2.0 features listed in Section 13.2. 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 AC’97 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 samples to an analog audio waveform.

This chapter describes the programming model for the ACUNIT. The information in this chapter requires an understanding of the AC’97 revision 2.0 specification.

Note: The ACUNIT and the I2S Controller cannot be used at the same time.

13.2Feature List

The processor ACUNIT supports the following AC’97 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 AC’97 2.0 CODECs (48 kHz and below). The ACUNIT depends on the CODEC to control the varying rate.

Read/write access to AC’97 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 AC’97 features:

Double-rate sampling (n+1 sample for PCM L, R & C)

18- and 20-bit sample lengths

Intel® PXA255 Processor Developer’s Manual

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Intel PXA255 manual AC’97 Controller Unit