BU9409FV_12 Datasheet, PDF (25/58 Pages) Rohm – 32bit Audio DSP

BU9409FV
Technical Note
4-7. TREBLE
TREBLE of TONE Control can use Peaking filter or High-shelf filter.
The setting is converted, in the IC, into digital filter’s coefficients （b0, b1, b2, a1, a2）by selecting the F₀，Q and Gain, and
transmitted to coefficient RAM. The switching shock noise at the time of alteration of setting can be prevented by the smooth
transition function.
○TREBLE Control
Selection of filter types
Default = 0
Select Address
&h48 [ 7 ]
Value
0
1
Peaking filter
High-shelf filter
Operational explanation
Selection of smooth transition function
Default = 0
Select Address
&h48 [ 6 ]
Value
0
1
Operational explanation
Using smooth transition function
Not using smooth transition function
Selection of smooth transition time
Default = 0
Select Address
&h48 [ 5:4 ]
Value
0
1
2
3
21.4ms
10.7ms
5.4ms
2.7ms
Operational explanation
Setting of smooth transition start
In the case of using the smooth transition function, after being transmitted, by the &h48[0] command, to the coefficient RAM
for smooth transition, the alteration of TREBLE’s coefficients is completed by using this command.
Default = 0
Select Address
&h4C [ 2 ]
Value
0
1
Operational explanation
TREBLE smooth transition stop
TREBLE smooth transition start
What is necessary is the time of waiting, which is more than the time selected by the setting of TREBLE smooth
transition time, from the time the TREBLE smooth transition start（&h4C[2] = “1”）is executed until the following command is
sent. Please make sure to perform the TREBLE smooth transition stop（&h4C[2] = “0”） after the smooth transition is
completed.
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2012.03 - Rev.A