Ac-Link Digital Serial Interface Protocol; Data Transfer Through The Ac-Link; Supported Data Stream Formats - Intel PXA255 Developer's Manual

Figure 13-1. Data Transfer Through the AC-link
AC'97 Controller Unit
(ACUNIT)
13.4

AC-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. Supported Data Stream Formats (Sheet 1 of 2)
Channel
PCM Playback
PCM Record data
CODEC control
CODEC status
Modem Line
CODEC Output
Modem Line
CODEC Input
Intel® PXA255 Processor Developer's Manual
AC-link
nACRESET
SDATA_OUT
SYNC (48 kHz)
SDATA_IN_0
SDATA_IN_1
BITCLK (12.288 MHz)
Slots Comments
Two output slots Two-channel composite PCM output stream
Two input slots Two-channel composite PCM input stream
Two output slots Control register write port
Two input slots Control register read port
One output slot Modem line CODEC DAC input stream
One input slot Modem line CODEC ADC output stream
AC'97 Controller Unit
AC'97 Primary CODEC
AC'97 Secondary CODEC
Table 13-2.
13-3