Rainbow Electronics MAX98088 - Manual (Page 74)

Stereo Audio Codec
with FLEXSOUND Technology
MAX98088
74
Table 8. Sidetone Register
Digital Audio Interfaces
The IC includes two separate playback signal paths and
one record signal path. Digital audio interface 1 (DAI1)
is used to transmit the recorded stereo audio signal and
receive a stereo audio signal for playback. Digital audio
interface 2 (DAI2) is used to receive a second stereo
audio signal. Use DAI1 for all full-duplex operations and
for all voice signals. Use DAI2 for music and to mix two
playback audio signals. The digital audio interfaces are
separate from the audio ports to enable either interface
to communicate with any external device connected to
the audio ports.
Each audio interface can be configured in a variety of
formats including left justified, I
2 S, PCM, and time divi-
sion multiplexed (TDM). TDM mode supports up to 4
mono audio slots in each frame. The IC can use up to
2 mono slots per interface, leaving the remaining two
slots available for another device. Table 9 shows how to
configure the device for common digital audio formats.
Figures 16 and 17 show examples of common audio
formats. By default, SDOUTS1 and SDOUTS2 are set
high impedance when the IC is not outputting data to
facilitate sharing the bus. Configure the interface in TDM
mode using only slot 1 to transmit and receive mono
PCM voice data.
The IC’s digital audio interfaces support both ADC to
DAC loop-through and digital loopback. Loop-through
allows the signal converted by the ADC to be routed
to the DAC for playback. The signal is routed from the
record path to the playback path in the digital audio
interface to allow the IC’s full complement of digital
signal processing to be used. Loopback allows digital
REGISTER BIT NAME DESCRIPTION
0x2E
7
DSTS
Sidetone Source
Selects which ADC output is fed back as sidetone. When mixing the left and right ADC
outputs, each is attenuated by 6dB to prevent full-scale signals from clipping.
00 = Sidetone disabled
01 = Left ADC
10 = Right ADC
11 = Left + Right ADC
6
4
DVST
Sidetone Level
Adjusts the sidetone signal level. All levels are referenced to the ADC’s full-scale output.
VALUE LEVEL (dB) VALUE LEVEL (dB)
3
0x00 Sidetone disabled 0x10 -30.5
0x01 -0.5 0x11 -32.5
0x02 -2.5 0x12 -34.5
0x03 -4.5 0x13 -36.5
2
0x04 -6.5 0x14 -38.5
0x05 -8.5 0x15 -40.5
0x06 -10.5 0x16 -42.5
0x07 -12.5 0x17 -44.5
1
0x08 -14.5 0x18 -46.5
0x09 -16.5 0x19 -48.5
0x0A -18.5 0x1A -50.5
0x0B -20.5 0x1B -52.5
0
0x0C -22.5 0x1C -54.5
0x0D -24.5 0x1D -56.6
0x0E -26.5 0x1E -58.5
0x0F -28.5 0x1F -60.5