Renesas M65881AFP - Manual (Page 15)

Rev.1.00 2003.05.08 page 15 of 23
M65881AFP
• Soft Mute
The Soft Mute function is executed by setting of Gain Data as 00000/00000000b
(" / " means dividing point between index part and mantissa part).
The release from Soft Mute Function must be executed by setting the gain data before soft mute.
The Soft mute Function and release from there don't have linear curve but
have characteristics of approximate exponential curve.
Output amplitude
16.0
T = xxxx/Fs (sec)
0
t
Characteristics of Soft Mute function
• Operating time of Soft Mute
Total steps from Maximum value(10100b/11111111b) to Minimum value(00000b/00000000b)
(128steps/1 index)
×
(20index (10100b-10000b)) +256steps = 2816steps.
The transition term of up and down depend on 2fso clock.
Therefore, in case of fso=48kHz, T=1/2fso=10.416µsec/step, transition term are following.
From Maximum value (10100b/11111111b) to Minimum value (00000b/00000000b) : 2816T=29.333msec.
From 0dB value (10000b/10000000b) to Minimum value (00000b/0000000b) : 2304T=24msec
6dB transition term (when over 00000b/10000000b (=-96dB) value ) : 128T=1.333msec.
• Soft Attenuate
Transition from older Gain Attenuation to newer Gain Attenuation always operates with Soft Mute function.
For example, in case of Gain1 > Gain3 > Gain2, transition process is shown below.
At first, GAIN1 is operated, then second, GAIN2 is operated.
In case that GAIN2 is operated faster than GAIN1 of transition completion (refer to "A" situation in figure)
GAIN1 is ignored and data approaches at GAIN2.
Further, GAIN3 is operated faster than GAIN2 of transition completion( Refer to "B" or "C" situation in figure),
GAIN2 is ignored and data approaches at GAIN3 .
Gain
Soft Attenuate
A
(GAIN1)
(GAIN3)
(GAIN2)
B
C
1.0
0
-1.0
t
//
T T
0.5
00000/00000000b setting 10000/10000000b setting