Specifications

13
AC’97 Controller Unit Overview
The AC’97 Controller Unit (ACUNIT) of the PXA270 processor supports AC’97 revision
2.0 features. The ACUNIT also supports the audio controller link (AC-link). The 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.
WM9715L
The WM9715L is a highly integrated device supporting audio and touchscreen functions.
The device can connect directly to a 4-wire touch panel, mono or stereo microphones,
stereo headphones and a mono speaker. Additionally, phone input and output pins are
provided for seamless integration with wireless communication devices.
The WM9715L contains a universal touch screen interface for a 4-wire resistive touch
screen, capable of performing position, pressure and plate resistance measurements. The
touch screen interface is connected to the system’s LCD panel connector.
Audio Interconnection
The following block diagram describes the EM-X270’s audio interconnection path.
RECORD
SELECT
RECORD
VOLUME
MIC IN
LINE IN L
LINE IN R
PHONE IN
ADC
L
ADC
R
ALC
BASS
BOOST
3D
DAC
L
DAC
R
AC`97
INTERFACE
HEADPHONE
MIXER
SPEAKER
MIXER
PHONE
MIXER
DIFF. SPK OUT
HP OUT L
PHONE OUT
HP OUT R
PXA270
AC`97 UNIT
 The headphone stereo output connects to the on-board audio jack (P6). This output is
designed to drive a 16Ω or 32Ω headphone or a line output.
 The audio mic input is directly connected to the on-board ECM microphone.
 The phone output and input are internally connected to the cellular module audio
signals.