Renesas M65881AFP User Manual
Page 14
Rev.1.00 2003.05.08 page 14 of 23
M65881AFP
The index and Mantissa part of Gain Data (bit12-bit24 :GAIN0-GAIN12)
The gain value is set from bit12-bit24.
Index part: bit12(MSB) to bit16(LSB)
Mantissa part: bit17(MSB) to bit24(LSB)
The gain data is assigned 13bits, composed of Index part 5bits and of Mantissa part 8bits.
The range of Index parts is following statements.
Index part: 10100b(16.0) to 10000b(1.0) to 00000b(2
-16
)
The range of Mantissa parts is following statements.
Mantissa part:Index part; 10100b to 00001b: Mantissa part; 11111111b to 10000000b (128 step/ Index).
Index part; 00000b:
Mantissa part; 11111111b to 00000000b (256 step).
Initial value: Index part: 10000b Mantissa part: 10000000b
Infinity zero: Index part: 00000b Mantissa part: 00000000b
# Notice of GAIN value setting continuously
In case of Gain value setting continuously, for example of setting L/Rch independently, please take
the interval time (pulse interval time of SCLATCH signal) more than 1/fso. For example, in the case of
fso=48kHz, please take the interval time more than 21µsec.
• The Gain Data and Audio Output Level.
Gain data consists of 13bits (Index part: 5bit, Mantissa part: 8bit ).
e.g. 10000b(1.0)/10000000b(0.5) means 0.5(0dB).
Table 1-2 Gain data and output level
• Calculation method of Gain Value
The way to calculation of Gain value from Gain Data is following equation.
Output absolute
maximum value
Polarity
Gain Data
10100/11111111 (b)
~
10001/10000000 (b)
10000/10000000 (b)
01111/11111111 (b)
00000/10000000 (b)
00000/00000001 (b)
00000/00000000 (b)
15.9375
1.0
0.5
0.498046875
0.5
∗
2
-16
0.00390625
∗
2
-16
infinity zero
+
Output Level
+30.069dB
+6.021dB
0dB
-0.0340dB
-96.330dB
-138.474dB
Gain value = 20log Mantissa Data (decimal value)
128
dB
2
<Index data (decimal value)-16>
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