Datasheet

(1or0) 2 +´
1
(1or0) 2 +(1or0) 2 +.......(1or0) 2 +.......(1or0) 2´ ´ ´ ´
0 –1 –4 –23
2 Bit
1
2 Bit
0
2 Bit
–1
2 Bit
–4
2 Bit
–23
M0126-01
u
Coefficient
Digit8
u
u u u u
S
x
Coefficient
Digit7
x.
x x x
Coefficient
Digit6
x
x x x
Coefficient
Digit5
x
x x x
Coefficient
Digit4
x
x x x
Coefficient
Digit3
x
x x x
Coefficient
Digit2
x
x x x
Coefficient
Digit1
Fraction
Digit5
Fraction
Digit4
Fraction
Digit3
Fraction
Digit2
Fraction
Digit1
Integer
Digit1
Sign
Bit
Fraction
Digit6
u=unusedordon’tcarebits
Digit=hexadecimaldigit
M0127-01
0
TAS5715
www.ti.com SLOS645 –AUGUST 2010
The decimal value of a 3.23 format number can be found by following the weighting shown in Figure 52. If the
most significant bit is logic 0, the number is a positive number, and the weighting shown yields the correct
number. If the most significant bit is a logic 1, then the number is a negative number. In this case every bit must
be inverted, a 1 added to the result, and then the weighting shown in Figure 53 applied to obtain the magnitude
of the negative number.
Figure 53. Conversion Weighting Factors—3.23 Format to Floating Point
Gain coefficients, entered via the I
2
C bus, must be entered as 32-bit binary numbers. The format of the 32-bit
number (4-byte or 8-digit hexadecimal number) is shown in Figure 54
Figure 54. Alignment of 3.23 Coefficient in 32-Bit I
2
C Word
Table 1. Sample Calculation for 3.23 Format
db Linear Decimal Hex (3.23 Format)
0 1 8,388,608 80 0000
5 1.77 14,917,288 00E3 9EA8
–5 0.56 4,717,260 0047 FACC
X L = 10
(X/20)
D = 8388608 × L H = dec2hex (D, 8)
Table 2. Sample Calculation for 9.17 Format
db Linear Decimal Hex (9.17 Format)
0 1 131,072 20 000
5 1.77 231,997 38 A3D
–5 0.56 73,400 11 EB8
X L = 10
(X/20)
D = 131,072 × L H = dec2hex (D, 8)
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