Compaq W4000 Manual De Usuario

Technical Reference Guide 

 

 
The audio codec provides pulse code modulation (PCM) coding and decoding of audio 
information as well as the selection and/or mixing of analog channels. As shown in Figure 5-13, 
analog audio from a microphone, tape, or CD can be selected and, if to be recorded (saved) onto a 
disk drive, routed through an analog-to-digital converter (ADC). The resulting left and right PCM 
record data are muxed into a time-division-multiplexed (TDM) data stream (SD IN signal) that is 
routed to the audio controller. Playback (PB) audio takes the reverse path from the audio 
controller to the audio codec as SD OUT data and is decoded and processed by the digital-to-
analog converter (DAC).  The codec supports simultaneous record and playback of stereo (left 
and right) audio. The Sample Rate Generator may be set for sampling frequencies up to 48 KHz. 
 
Analog audio may then be routed through 3D stereo enhancement processor or bypassed to the 
output selector (SEL). The integrated analog mixer provides the computer control-console 
functionality handling multiple audio inputs.  
 
 

Audio 

Format 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

ADC 

PB 
Data (R)

 

PB 
Data (L)

 

DAC 

DAC 

Rec 
Data (R) 

ADC 

Rec 
Data (L) 

S 
E 
L

 

(R) 

(L) 

(R) 

(R) 

(L) 

(L) 

3D Proc. 

3D Proc. 

SW 

PB 

Gain 

PB 

Gain 

Rec 

Gain 

Σ/Mixer 

CD In (R) 

CD In (L) 

Line In (R) 

Line In (L) 

Mic In 

S 

e 

l 

e 
c 

t 

o 

r 

SD Out 

SD IN 

AC97 

Link 

I/F 

Sample 

Rate 
Gen. 

Right 
Audio

 

Rec 

Gain 

Analog 

Output 

Circuits 

Left 
Audio

 

Audio 
Controller 

 
Figure 5-12.   AD1885 Audio Codec Functional Block Diagram 

 

All inputs and outputs are two-channel stereo except for the microphone input, which is inputted 
as a single-channel but mixed internally onto both left and right channels.  The microphone input 
is the default active input. All block functions are controlled through index-addressed registers of 
the codec.  

 
 
 
 
 
 

 

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