Technical information

Audio Interface

36 G30 - Module Hardware Description December 15, 2009

Digital Audio Interface

The G30 digital audio interface is a serial Pulse Code Modulation (PCM) bus, which uses linear

2's compliment coding. G30 is the PCM bus master, supplying the clock and sync signals to the

application.

The G30 digital interface is a 4 signal PCM bus, which includes a bit clock output signal for the

bus timing, a frame sync output signal for audio sampling timing, and serial data input and output

signals.

Important: The PCM bus signals are shared internally by the analog audio interface and the

digital audio interface. Therefore, when using the analog audio interface the PCM

bus signals must be tri-stated or disconnected at the interface connector.

The digital audio interface supports 2 types of audio data formats, which define the PCM bus

configuration and data rates:

• Normal I

S mode.

• PCM mode.

The PCM bus configuration is defined by the audio data format that is sounded through the digital

audio path, as described in Table 2-13.

Note: Switching between Audio Modes is done using AT+MAI2SY command. For detailed

information, refer to G30 AT Commands Reference Manual (P/N 6802986C33).

Voiceband Audio

This digital voice audio format is used for speech during voice calls and for mono rings and

alerts.

The I

S bus signal's configuration for voiceband audio is:

• I

S_CLK - 512 kHz serial clock

• I

S_FS - 8 kHz bit-wide frame-sync

• I

S_DOUT - 16-bit linear audio data output

• I

S_DIN - 16-bit linear audio data input

Table 2-13:

Digital Audio modes

Audio Mode

Frame Sync

Sampling

Bit Clock

PCM 8 kHz 144 kHz

8 kHz 512 kHz