AC’97 Controller Unit

Figure 13-1. Data Transfer Through the AC-link

AC’97 Controller Unit (ACUNIT)

AC-link

nACRESET

SDATA_OUT

SYNC (48 kHz)

SDATA_IN_0

SDATA_IN_1

BITCLK (12.288 MHz)

AC’97 Primary CODEC

AC’97 Secondary CODEC

13.4AC-link Digital Serial Interface Protocol

Each AC’97 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, but only 16-bit samples are supported in hardware. Each stream requires a DAC or an analog-to-digital converter (ADC), both having a minimum 16-bit resolution. The ACUNIT supports the data streams shown in Table 13-2.

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

One output slot

Modem line CODEC DAC input stream

CODEC Output

 

 

 

 

 

Modem Line

One input slot

Modem line CODEC ADC output stream

CODEC Input

 

 

 

 

 

Intel® PXA255 Processor Developer’s Manual

13-3

Page 455
Image 455
Intel PXA255 manual AC-link Digital Serial Interface Protocol, Supported Data Stream Formats Sheet 1, SDATAIN0 SDATAIN1