User's Manual Part 1

MC75 Hardware Interface Description

Strictly confidential / Draft

MC75_V00.190a Page 54 of 91 15.02.2005

3.12.4 Digital Audio Interface DAI

The DAI can be used to connect audio devices capable of PCM (Pulse Code Modulation), for

example a codec.

Table 9: Overview of USC pin functions

Signal name on

B2B connector

Function for PCM Interface Input/Output

USC0 (DAI0) REF_CLK_13M O

USC1 (DAI1) Reserved for future use I

USC2 (DAI2) REF_CLK_8K (Bit clock slave) O

USC3 (DAI3) BITCLK I

USC4 (DAI4) FS_IN (Frame sync slave) I

USC5 (DAI5) RXDAI I

USC6 (DAI6) TXDAI O

To clock input and output PCM samples the PCM interface requires a clock (BITCLK) which

is synchronous to the 26 MHz system clock. The customer application must be designed to

generate this bit clock by a PLL circuit or a divider controlled by one of the two following

reference clock signals:

• REF_CLK_13M that is equal to the system clock of 13 MHz.

• REF_CLK_8K that is an 8 kHz signal divided from the system clock.

The frequency of the bit clock can vary from 256 kHz to 2048 kHz. The PCM interface is

slave for the bit clock and the frame sync signals generated by the external codec.

PCM interface

of the GSM

module

BITCLK

FS_IN

REF_CLK8

TXDAI

bitclk

RXDAI

REF_CLK13

PLL or divider

frame sync logic

Codec

frame sync

RX_data

TX_data

e.g. 256kHz

Figure 24: PCM interface application