Overview; Signals - Intel PXA27 Series Design Manual

AC '97
This chapter describes guidelines to interface the AC '97 controller of Intel
Family (PXA27x processor) to an external CODEC device.
13.1

Overview

The AC '97 controller unit connects external audio integrated circuit devices and CODECs to the
PXA27x processor. The AC '97 controller supports the AC '97 (Audio CODEC '97) specification
revision 2.0 features and AC-link, a synchronous, fixed rate serial bus interface to the digital AC
'97 controller for transferring digital audio, modem, microphone input (MIC-in), CODEC register
control, and status information.
The AC '97 port is a bidirectional, serial, pulse code modulated (PCM) digital stream interface. For
recording, the AC '97 CODEC sends the digitized audio samples to the AC '97 controller which
stores them in memory. For playback or synthesized audio production, the PXA27x 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. A maximum of two CODECs can be connected to the AC '97 controller unit.
13.2

Signals

The AC '97 signals form the AC-link, which is a point-to-point synchronous serial interconnect
that supports full-duplex data transfers. All digital audio streams, modem line CODEC streams,
and command/status information are communicated over the AC-link. The AC-link uses general
purpose I/Os (GPIOs). Software must reconfigure the GPIOs to use them as the AC-link. See
Table 13-1
Table 13-1. External Interface to CODECs
Signal Name
AC97_RESET_n
AC97_BITCLK
AC97_SYNC
AC97_SDATA_OUT
AC97_SDATA_IN_0
AC97_SDATA_IN_1
AC97_SYSCLK
®
Intel PXA27x Processor Family Design Guide
for the list and description of the AC-link pins.
Direction
Active-low CODEC reset
Output
The CODEC's registers are reset when AC97_RESET_n is asserted.
Input 12.288-MHz bit-rate clock
Output 48-KHz frame indicator and synchronizer
Output Serial audio output data to CODEC for digital-to-analog conversion
Input Serial audio input data from primary CODEC
Input Serial audio input data from secondary CODEC
Output Optional 24.5-MHz clock output
®
PXA27x Processor
Description Summary
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