AD1816AJS datasheet(15/52 Pages) AD

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AD1816A

–15–

REV. A

HOST INTERFACE

The AD1816A contains all necessary ISA bus interface logic on

chip. This logic includes address decoding for all onboard

resources, control and signal interpretation, DMA selection and

control logic, IRQ selection and control logic, and all interface

configuration logic.

The AD1816A supports a Type “F” DMA request/grant archi-

tecture for transferring data with the ISA bus through the 8-bit

interface. The AD1816A also supports DACK preemption. Pro-

grammed I/O (PIO) mode is also supported for control register

accesses and for applications lacking DMA control. The

AD1816A includes dual DMA count registers for full-duplex

operation enabling simultaneous capture and playback on sepa-

rate DMA channels.

Codec Functional Description

The AD1816A’s full-duplex stereo codec supports business audio

and multimedia applications. The codec includes stereo audio

converters, complete on-chip filtering, MPC Level-2 and

Level-3 compliant analog mixing, programmable gain and at-

tenuation, variable sample rate converters, extensive digital mixing

and FIFOs buffering the Plug and Play ISA bus interface.

Analog Inputs

The codec contains a stereo pair of

∑∆ analog-to-digital con-

verters (ADC). Inputs to the ADC can be selected from the fol-

lowing analog signals: mono (PHONE_IN), mono microphone

(MIC), stereo line (LINE), external stereo synthesizer

(SYNTH), stereo CD ROM (CD), stereo audio from a video

source (VID) and post-mixed stereo or mono line output (OUT).

Analog Mixing

PHONE_IN, MIC, LINE, SYNTH, CD and VID can be mixed

in the analog domain with the stereo line OUT from the

Σ∆

digital-to-analog converters (DAC). Each channel of the stereo

analog inputs can be independently gained or attenuated from

+12 dB to –34.5 dB in 1.5 dB steps, except for PHONE_IN,

which has a range of 0 dB to –45 dB steps. The summing path

for the mono inputs (MIC, and PHONE_IN to line OUT) du-

plicates mono channel data on both the left and right line OUT,

which can also be gained or attenuated from +12 dB to –34.5 dB

in 1.5 dB steps for MIC, and +0 dB to –45.0 dB in 3 dB steps

for PHONE_IN. The left and right mono summing signals are

always identical being gained or attenuated equally.

Analog-to-Digital Datapath

The selector sends left and right channel information to the pro-

grammable gain amplifier (PGA). The PGA following the selec-

tor allows independent gain for each channel entering the ADC

from 0 dB to 22.5 dB in 1.5 dB steps.

For supporting time correlated I/O echo cancellation, the ADC

is capable of sampling microphone data on the left channel and

the mono summation of left and right OUT on the right channel.

The codec can operate in either a global stereo mode or a global

mono mode with left channel inputs appearing at both channels of

the 16-bit

Σ∆ converters. Data can be sampled at the programmed

sampling frequency (from 4 kHz to 55.2 kHz with 1 Hz resolution).

Digital Mixing and Sample Rates

The audio ADC sample rate and the audio DAC sample rates

are completely independent. The AD1816A includes a variable

sample rate converter that lets the codec instantaneously change

and process sample rates from 4 kHz to 55.2 kHz with a reso-

lution of 1 Hz. The in-band integrated noise and distortion

artifacts introduced by rate conversions are below –90 dB.

Up to four channels of digital data can be summed together and

presented to the stereo DAC for conversion. Each digital chan-

nel pair can contain information encoded at a different sample

rate. For example, 8 kHz .wav data received from the ISA inter-

face, 48 kHz MPEG audio data received from I

2S(0), digital

44.1 kHz CD data received from I

2S(1) and internally generated

22.05 kHz music data may be summed together and converted

by the DACs.

Digital-to-Analog Datapath

The internally generated music synthesizer data, PCM data

received from the ISA interface, data received from the I

2S(0)

port and data received from the I

2S(1) port, and the DSP serial

port passes through an attenuation mute stage. The attenuator

allows independent control over each digital channel, which can

be attenuated from 0 dB to –94.5 dB in 1.5 dB steps before be-

ing summed together and passed to the DAC, or the channel

may be muted entirely.

Analog Outputs and Phat Stereo

The analog output of the DAC can be summed with any of the

analog input signals. The summed analog signal enters the

Master Volume stage where each channel L_OUT, R_OUT and

PHONE_OUT may be attenuated from 0 dB to –46.5 dB in

1.5 dB steps or muted.

Analog Outputs and Phat Stereo

The AD1816A includes ADI’s proprietary Phat Stereo 3D

phase enhancement technology, which creates an increased

sense of spaciousness using two speakers. Our unique patented

feedback technology enables superior control over the width and

depth of the acoustic signals arriving at the human ear. The

AD1816A employs an electrical model of the speaker-to-ear

path allowing precise control over a signal’s phase at the ear. The

Phat Stereo circuitry expands apparent sound images beyond the

angle of the speakers by exploiting phase information in the audio

signal and creating a more immersive listening experience.

Digital Data Types

The codec can process 16-bit twos complement PCM linear

digital data, 8-bit unsigned magnitude PCM linear data and

8-bit

µ-law or A-law companded digital data as specified in the

control registers. The AD1816A also supports ADPCM en-

coded in the Creative SoundBlaster ADPCM formats.

Host-Based Echo Cancellation Support

The AD1816A supports time correlated I/O data format by pre-

senting MIC data on the left channel of the ADC and the mono

summation of left and right OUT on the right channel. The

ADC sample rates are independent of the DAC sample rate allow-

ing the AD1816A to support ADC time correlated I/O data at

8 kHz and DAC data at any other sample rate in the range of

4 kHz to 55.2 kHz simultaneously.

Telephony Support

The AD1816A contains a PHONE_IN input and a

PHONE_OUT output. These pins are supplied so the AD1816A

may be connected to a modem chip set, a telephone handset or

down-line phone.

WSS and SoundBlaster Compatibility

Windows Sound System software audio compatibility is built

into the AD1816A.

SoundBlaster emulation is provided through the SoundBlaster

version 3.02 functions are supported, including record and Cre-

ative SoundBlaster ADPCM.

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