> 3 | Digital Audio Interface (DAI)

> The DAI can be used to connect audio devices capable of PCM (Pulse Code Modulation) or for type approval. The following sections describe the PCM interface functionality.
> The PCM functionality allows the use of a codec like for example the MC145483. This codec replaces the analog audio inputs and outputs during a call, if digital audio is selected by AT^SAIC.
> The PCM interface is configurable with the AT^SAIC command (see [2]) and supports the following features:

> • | Master and slave mode

> • | Short frame and long frame synchronization

> • | 256 kHz or 512 kHz bit clock frequency

> For the PCM interface configuration the parameters <clock>, <mode> and <framemode> of the AT^SAIC command are used. The following table lists possible combinations:

> Table 2: | Configuration combinations for the PCM interface

> Configuration | <clock> | <mode> | <framemode>
> Master, 256kHz, short frame | 0 | 0 | 0
> Master, 256kHz, long frame | 0 | 0 | 1
> Master, 512kHz, short frame | 1 | 0 | 0
> Master, 512kHz, long frame | 1 | 0 | 1
> Slave, 256kHz, short frame | 0 or 11 | 1 | 0
> Slave, 256kHz, long frame | 0 or 1 | 1 | 1
> Slave, 512kHz, short frame | 0 or 1 | 1 | 0
> Slave, 512kHz, long frame | 0 or 1 | 1 | 1

> 1
> In slave mode the BCLKIN signal is directly used for data shifting. Therefore, the clock frequency setting is not evaluated and may be either 0 or 1.
> In all configurations the PCM interface has the following common features:

> • | 16 Bit linear

> • | 8 kHz sample rate

> • | the most significant bit MSB is transferred first

> • | 125 µs frame duration

> • | common frame sync signal for transmit and receive

> Table 3 shows the assignment of the DAI0…6 pins to the PCM interface signals. To avoid hardware conflicts different pins are used as inputs and outputs for frame sync and clock signals in master or slave operation. The table shows also which pin is used for master or slave. The data pins (TXDAI and RXDAI) however are used in both modes. Unused inputs have to be tied to GND, unused outputs must be left open.

> Table 3: | Overview of DAI pin functions

> Signal name on B2B connector | Function for PCM Interface | Input/Output
> DAI0 | TXDAI | Master/Slave | O
> DAI1 | RXDAI | Master/Slave | I
> DAI2 | FS (Frame sync) | Master | O
> DAI3 | BITCLK | Master | O
> DAI4 | FSIN | Slave | I
> DAI5 | BCLKIN | Slave | I
> DAI6 | nc |  | I