STA321 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STA321' PDF : 157 Pages View PDF
STA321
Digital processing stage
6.3.1
Presets
By default, each mixer output is connected to its corresponding input without any attenuation
and without any mixing with the other channels:
ch0_out = ch0_in, ch1_out = ch1_in, ch2_out = ch2_in, ch3_out = ch3_in.
6.4
6.4.1
Pre scaler
The pre scale block, which precedes the first biquad, could be used to attenuate the input
signal when the filters of the processing chain have a gain that could reach the clamping
value.
Each channel has a dedicated 24-bit signed multiplier in the range -1 (0x800000) to almost
+1 (0x7FFFFF).
Presets
By default, all pre-scale factors are set to 0x7FFFFF
6.5
Equalization, tone control and effects
Figure 18. EQ/tone block diagram
From
prescaler
Biquad
00
Biquad
07
Biquad
08
Biquad
09
Biquad
10
Reserved
Reserved
effects_en[0]
effects_en[1]
Reserved
RAM Reserved RAM Reserved RAM High RAM
pass
Deemph. RAM Reserved
RAM Treble RAM Bass
treb_sel
bass_sel
To
delay stage
Biquad
12
Biquad
11
Four channels of input data are fed to the EQ processing block which provides 13
user-programmable biquad filters per channel as shown in Figure 18 above.
A description of the biquad programming is given in Section 6.14 on page 44.
Some filter coefficients are pre-programmed and stored in the non-volatile memory in order
to supply particular EQ effects (see Figure 19 and Table 20 on page 38).
The selection of RAM, ROM bass/treble or ROM effects is made using registers
EFFS_EN_CHn on page 109 for the effects and BASS_SELn_R on page 111 and
TREB_SELn_R on page 113 for the bass/treble. Each biquad can be configured
independently.
Doc ID 15351 Rev 3
37/157
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