STA321 datasheet(42/157 Pages) STMICROELECTRONICS

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Digital processing stage

STA321

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Doc ID 15351 Rev 3

6.9.1

Configuration example

This is an example of the tone control register setup. It is assumed that every peripheral is

already configured and working correctly.

Table 21 gives the register values to obtain +12 dB of bass on all channels and -10 dB of

treble on channels 0 and 1.

6.10

Programmable delay

Every channel, just after the biquads stage, is connected to a dedicated delay block.

The length of the delay is stored in RAM at location 0x128 and can vary from 0 to 35

samples. The corresponding time delay depends on the processing sampling frequency.

6.10.1

Presets

The delay of every channel is set to 0.

6.11

Volume and mute control

The STA321 provides a flexible volume and mute control stage. Using the registers VOLCH0

to VOLCH3 on page 122 it is possible to set the volume for each channel individually from

+36 dB to -105 dB with 0.5-dB steps.

There is a master volume control, register MVOL on page 120, as well. The master volume

adds an offset to all the individual volume settings.

The mute function offers the possibility to turn off the sound by reducing the volume setting

to -127.5 dB. It could be activated in two ways:

pin MUTE, driven by an external signal, puts all four channels into mute mode.

change procedures are applied. If bit SVOL_ONx is activated the volume of channel x is

changed gradually (soft volume or soft mute); using a ramp it starts from the current value

and goes down to the target value or to -127.5 dB for mute. The slope of the ramp is set with

with the value TIM_SVOL which represents how many samples are needed to achieve a

0.5-dB step.

tSTEP = 2

TIM_SVOL / f

Table 21.

Selecting EQ curves

Programmed value

Description

BASS_SEL0_R

0x38

CH0 +12 dB bass

BASS_SEL1_R

0x38

CH1 +12 dB bass

BASS_SEL2_R

0x38

CH2 +12 dB bass

BASS_SEL3_R

0x38

CH3 +12 dB bass

TREB_SEL0_R

0x22

CH0 -10 dB treble

TREB_SEL1_R

0xx22

CH1 - 10 dB treble

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