PCM2900

PCM2902

SLES035B − MARCH 2002 − REVISED JUNE 2004

www.ti.com

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End-Points

The PCM2900/2902 has the following four end-points.

The control end-point is a default end-point. The control end-point is used to control all functions of the

PCM2900/2902 by the standard USB request and USB audio class specific request from the host. The

isochronous-out audio data stream end-point is an audio sink end-point, which receives the PCM audio data.

The isochronous-out audio data stream end-point accepts the adaptive transfer mode. The isochronous-in

audio data stream end-point is an audio source end-point, which transmits the PCM audio data. The

isochronous-in audio data stream end-point uses asynchronous transfer mode. The HID end-point is an

interrupt-in end-point. HID end-point reports HID0, HID1, and HID2 pin status every 32 ms.

The human interface device (HID) pins are defined as consumer control devices. The HID function is designed

as an independent end-point from both isochronous-in and -out end-points. This means that the result of

affection for the HID operation depends on the host software. Typically, the HID function is affected for the

primary audio-out device.

Clock and Reset

The PCM2900/2902 requires a 12-MHz (

±500 ppm) clock for the USB and audio function, which can be

generated by a built-in crystal oscillator with a 12-MHz crystal resonator. The 12-MHz crystal resonator must

be connected to XTI (pin 21) and XTO (pin 20) with one high (1-M

Ω) resistor and two small capacitors, the

capacitance of which depends on the load capacitance of the crystal resonator. The external clock can be

supplied from XTI (pin 21). If the external clock is supplied, XTO (pin 20) must be left open. Because of no

clock-disabling signal, it is not recommended to use the external clock supply. SSPND (pin 28) is unable to use

clock disabling.

exceeds 2.5 V typical (2.7 V–2.2 V), and about 700

µs is required until internal reset release.

Digital Audio Interface (PCM2902)

The PCM2902 employs both S/PDIF input and output. Isochronous-out data from the host is encoded to the

S/PDIF output and the DAC analog output. Input data is selected as either S/PDIF or ADC analog input. When

the device detects an S/PDIF input and successfully locks the received data, the isochronous-in transfer data

source is automatically selected from S/PDIF itself; otherwise, the data source is selected to ADC analog input.

Supported Input Data (PCM2902)

The following data formats are accepted by the S/PDIF input and output. All other data formats are unable to

use S/PDIF.

Mismatch between input data format and host command may cause unexpected results except in the following

conditions.

A combination between the above conditions is not accepted.

For the playback, all possible data rate source is converted to 16-bit stereo format at the same source data rate.

Channel Status Information (PCM2902)

The channel status information is fixed as consumer application, PCM mode, copyright, and digital/digital

converter. All other bits are fixed as 0s except for the sample frequency, which is set automatically according

to the data received through the USB.