STA680 datasheet(28/43 Pages) STMICROELECTRONICS

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Digital I/O and memory interfaces

STA680

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5.3

Audio interface (AIF)

The AIF (Audio Interface) is used for the communication with external digital signal sources

and receivers. The main AIF features are:

●

1 Input SAI interface.

●

3 Output SAI interface.

●

1 S/PDIF transmitter.

●

Audio Sample Rate Converter (ASRC).

●

I/O sample rates: 44.1 kHz, 45.6 kHz, 48 kHz.

The AIF includes 1 Input SAI interface, 3 Output SAI interface and 1 S/PDIF (industry

standard) transmitter. The receivers and transmitters can be used either in master-mode,

running with the STA680 internal audio frequency of 44.1 kHz or in slave mode running with

a frequency determined by the external device. In slave mode, in order to adapt the external

data rate to the internal audio data rate, it is possible to use an internal Audio Sample Rate

Converter (ASRC, see Chapter 5.3.4).

5.3.1

Output serial audio interface (SAI)

The output serial audio interface is used to send decoded audio samples from the HD Radio

Decoder to an external IC for audio processing, or directly to a digital power amplifier.

The output SAI is an I2S interface which provides audio samples in stereo at a 44,1 kS/s

sample rate. Other sample rates may be provided by means of the internal ASRC (see

Chapter 5.3.4).

The output SAI interface shares the word strobe and the bit clock signal with three data

output signals in order to support up to a total of 3 stereo channels of audio output. For

interfacing the STA680 to an external DAC an oversampling clock whose frequency is 256

times the sampling frequency is provided. For pin description refers to Table 8.

The output SAI supports a 32x or 64x bit clock. The 32x clock mode shifts out serial data

with no padding. The 64x clock mode shifts out the 16-bit audio data first followed by 16 bits

of zero padding. Figure 10 shows timing diagrams for the supported modes.

Table 8.

AIF pin list

Pin name

Designation

Type

Drive

AUDIO_IN_AWS

Digital audio input word strobe

AUDIO_IN_ABCK

Digital audio input bit clock

AUDIO_IN_ADAT

Digital audio input serial data

AWS

Digital audio output word strobe

I/O

4mA

ABCK

Digital audio output clock

I/O

4mA

ADAT

Digital audio output serial data

4mA

ADAT2

Digital audio output serial data channel 2

4mA

ADAT3

Digital audio output serial data channel 3

4mA

DAC256X

Digital audio output oversampling clock (256 x Fs)

4mA

SPDIF

Digital audio output in SPDIF format

4mA

BLEND

Digital audio output blend output

4mA

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