Specifications

48
7.3 Digital Audio Interface (I
2
S)
The digital audio interface supports the industry standard formats for I
2
S, left-justified (LJ)
or right-justified(RJ). The interface shares the same pins as the PCM interface, which
means that each audio bus is mutually exclusive in its usage. Table 18 lists these
alternative functions. Figure 22 shows the timing diagram.
PCM Interface I2S Interface
PCM_OUT SD_OUT
PCM_IN SD_IN
PCM_SYNC WS
PCM_CLK SCK
Table 18: Alternative Functions of the Digital Audio Bus Interface on the PCM Interface
Table 19 describes the values for the PS Key (PSKEY_DIGITAL_AUDIO_CONFIG) that is
used to set-up the digital audio interface. For example, to configure an I
2
S interface with
16-bit SD data set PSKEY_DIGITAL_CONFIG to 0x0406.
Bit Mask Name Description
D[0] 0x0001 CONFIG_JUSTIFY_FORMAT 0 for left justified, 1 for right justified
D[1] 0x0002 CONFIG_LEFT_JUSTIFY_DELAY
For left justified formats: 0 is MSB of
SD data
occurs in the first SCLK period
following WS
transition. 1 is MSB of SD data occurs
in the
second SCLK period.
D[2] 0x0004 CONFIG_CHANNEL_POLARITY
For 0, SD data is left channel when WS
is
high. For 1 SD data is right channel.
D[3] 0x0008 CONFIG_AUDIO_ATTEN_EN
For 0, 17 bit SD data is rounded down
to 16
bits. For 1, the audio attenuation
defined in
CONFIG_AUDIO_ATTEN is applied over
24
bits with saturated rounding. Requires
CONFIG_16_BIT_CROP_EN to be 0.
D[7:4] 0x00F0 CONFIG_AUDIO_ATTEN Attenuation in 6 dB steps.
D[9:8] 0x0300 CONFIG_JUSTIFY_RESOLUTION
Resolution of data on SD_IN, 00=16
bit,
01=20 bit, 10=24 bit, 11=Reserved.
This is
required for right justified format and
with left
justified LSB first.
D[10] 0x0400 CONFIG_16_BIT_CROP_EN
For 0, 17 bit SD_IN data is rounded
down to
16 bits. For 1 only the most significant
16 bits
of data are received.
Table 19: PSKEY_DIGITAL_AUDIO_CONFIG