Interface #0

Interface #1

PCM2900B

PCM2902B

Interface #0 is defined as the control interface. Alternative setting #0 is the only possible setting for interface #0.

Alternative setting #0 describes the standard audio control interface. The audio control interface consists of a

single terminal. The PCM2900B/2902B has the following five terminals:

• Input terminal (IT #1) for isochronous-out stream

• Output terminal (OT #2) for audio analog output

• Feature unit (FU #3) for DAC digital attenuator

• Input terminal (IT #4) for audio analog input

• Output terminal (OT #5) for isochronous-in stream

Input terminal #1 is defined as a USB stream (terminal type 0x0101). Input terminal #1 can accept two-channel

audio streams consisting of left and right channels. Output terminal #2 is defined as a speaker (terminal type

0x0301). Input terminal #4 is defined as a microphone (terminal type 0x0201). Output terminal #5 is defined as a

USB stream (terminal type 0x0101). Output terminal #5 can generate two-channel audio streams composed of

left and right channel data. Feature unit #3 supports the following sound control features:

• Volume control

• Mute control

The built-in digital volume controller can be manipulated by an audio class specific request from 0 dB to –64 dB

until the volume level has reached the requested value. Each channel can be set for different values. The master

volume control is not supported. A request to the master volume is stalled and ignored. The built-in digital mute

controller can be manipulated by an audio class specific request. A master mute control request is acceptable. A

request to an individual channel is stalled and ignored.

Interface #1 is the audio streaming data-out interface. Interface #1 has five alternative settings listed in Table 6.

Alternative setting #0 is the zero bandwidth setting. All other alternative settings are operational settings.

Table 6. Interface #1 Alternative Settings

ALTERNATIVE

TRANSFER

SAMPLING RATE

SETTING

DATA FORMAT

MODE

(kHz)

00

Zero Bandwidth

01

16-bit

Stereo

Twos complement (PCM)

Adaptive

32, 44.1, 48

02

16-bit

Mono

Twos complement (PCM)

Adaptive

32, 44.1, 48

03

8-bit

Stereo

Twos complement (PCM)

Adaptive

32, 44.1, 48

04

8-bit

Mono

Twos complement (PCM)

Adaptive

32, 44.1, 48

Copyright © 2008, Texas Instruments Incorporated

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Product Folder Link(s): PCM2900B PCM2902B

Not Recommended For New Designs