BU9409FV_12 Datasheet, PDF (14/58 Pages) Rohm – 32bit Audio DSP

BU9409FV
Technical Note
4. Digital sound processing（DSP）
BU9409FV’s Digital Sound Processing（DSP） consists of special hardware most suitable to Thin TV.
BU9409FV uses this special DSP to perform the following processing.
Prescaler, DC Cut HPF, Channel Mixer, P²Volume（Perfect Pure Volume）, BASS, MIDDLE, TREBLE,
Pseudo Stereo, Surround, P²Bass, P²Treble, 7 Band・Parametric Equalizer, Master Volume, L/R Balance,
Output Clipper、 Sub-woofer output Processing.
PostScaler,
DSP Outline and Signal Flow
Data width：
Machine cycle：
Multiplier：
Adder：
Data RAM：
Coefficient RAM：
Sampling frequency：
Master clock：
32 bit （DATA RAM）
40.7ns （512fs, fs=48kHz）
32×24 → 56 bit
32＋32 → 32 bit
256×32 bit
128×24 bit
fs=48kHz
512fs （24.576MHz, fs=48kHz）
Data
RAM
Input
0
MUX
MUX
M
U
X
Coefficient
operation
Circuit
Coefficient
RAM
Decoder
circuit
ADD
Acc
Digital signal from 16bit to 24bit is inputted to DSP,
and it is extended by +8bit（+42dB） as overflow margin on the upper side.
The clip process is performed in DSP when the process exceeding this range is performed.
Output
Input1
Input2
Pre
scaler
HPF
Channel
mixer
P²Volume
BASS
MIDDLE
TREBLE
Scaler
1
Pseude
stereo
＆
surround
P²Bass
Digital Audio Processing Signal Flow
Channel
mCixheanr nel
mixer
P²Treble
Scaler
2
LPF
7Band
P-EQ
3band
P-EQ
EVR
＆
Blance
EVR
＆
Balance
Post
scaler
＆
Clipper
Post
scaler
＆
Clipper
Main output
Sub output
4-1. Prescaler
When digital signal is inputted to audio DSP, if the level is full scale input and the process of surround or equalizer is
performed, then it overflows, therefore the input gain is adjusted by prescaler.
Adjustable range is +24dB to -103dB and can be set by the step of 0.5dB.
Prescaler does not incorporate the smooth transition function.
Default = 30h
Select Address
&h20 [ 7：0 ]
Operational explanation
command
00
01
gain
+24dB
+23.5dB
30
0dB
31
-0.5dB
32
-1dB
FE
-103dB
FF
-∞
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14/54
2012.03 - Rev.A