sta323wqs STMicroelectronics, sta323wqs Datasheet - Page 61

• Manufacturer Part Number: sta323wqs
• Description: 2.1-channel High-efficiency Digital Audio System With Qsound Qhd??
• Manufacturer: STMicroelectronics

STA323WQS
8.5
8.6
8.6.1
8.6.2
8.6.3
8.6.4
Calculating 24-bit signed fractional numbers from a dB value
The pre-scale, mixing, and post-scale functions of the STA323WQS use 24-bit signed
fractional multipliers to attenuate signals. These attenuations can also invert the phase and
therefore range in value from -1 to +1.
It is possible to calculate the coefficient to use for a given negative dB value (attenuation)
using the equations following.
●
●
As can be seen by the preceding equations, the value for positive phase 0dB is 0x7FFFFF
and the value for negative phase 0dB is 0x800000.
User defined coefficient RAM
Coefficient address register 1 (address 0x16)
Coefficient b1data register bits 23...16 (address 0x17)
Coefficient b1data register bits 15...8 (address 0x18)
Coefficient b1data register bits 7...0 (address 0x19)
C1B23
C1B15
C1B7
CFA7
D7
D7
D7
D7
non-inverting phase numbers 0 to +1:
–
inverting phase numbers 0 to -1:
–
0
0
0
0
coefficient = round(8388607 * 10 ^ (dB/20))
coefficient = 16777216 - round(8388607 * 10^(dB/20))
C1B22
C1B14
CFA6
C1B6
D6
D6
D6
D6
0
0
0
0
C1B21
C1B13
C1B5
CFA5
D5
D5
D5
D5
0
0
0
0
C1B20
C1B4
CFA4
C1B12
D4
D4
D4
0
0
0
D4
0
C1B19
C1B3
CFA3
C1B11
D3
D3
D3
0
0
0
D3
0
C1B18
C1B2
CFA2
User-programmable settings
C1B10
D2
D2
D2
0
0
0
D2
0
C1B17
C1B1
CFA1
D1
C1B9
D1
D1
0
0
0
D1
0
C1B16
C1B0
CFA0
C1B8
D0
D0
D0
D0
0
0
0
0
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