LMX9820ASM datasheet(16/44 Pages) NSC

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Revision 1.0

7.0 Functional Description (Continued)

7.5 AUDIO PORT

Advanced Audio Interface

The Advanced Audio Interface (AAI) is an advanced ver-

sion of the Synchronous Serial Interface (SSI) that pro-

vides a full-duplex communications port to a variety of

industry-standard 13/14/15/16-bit linear or 8-bit log PCM

codecs, DSPs, and other serial audio devices.

The LMX9820A allows the support for one codec. The

firmware selects the desired audio path and interface con-

figuration by a parameter stored in NVS. The audio path

options include the Motorola MC145483 codec, the OKI

MSM7717 codec through the AAI, or no audio.

Table 20 summarizes the audio path selection and the con-

figuration of the audio interface at the specific mode.

Table 20. Audio Path Configuration

Audio Path

Format

AAI Bit Clock

AAI Frame Clock

AAI Frame Sync

Pulse Length

Motorola MC1454831

13-bit linear

480 kHz

8 kHz

13 bits

OKI MSM7717

8-bit log PCM

(A-law only)

120 kHz

8 kHz

14 bits

Due to internal clock divider limitations, the optimum of 512 kHz, 8 kHz cannot be reached. The values are set to the

best possible values. The clock mismatch does not result in any discernible loss in audio quality.

LMX9820ASM Datasheet(PDF) 16 Page - National Semiconductor (TI)