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| R2011b Documentation → Fixed-Point Toolbox | |
Learn more about Fixed-Point Toolbox |
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| Contents | Index |
The properties associated with fimath objects are described in the following sections in alphabetical order.
Whether both operands are cast to the sum data type before addition. Possible values of this property are 1 (cast before sum) and 0 (do not cast before sum).
The MATLAB factory default value of this property is 1 (true).
This property is hidden when the SumMode is set to FullPrecision.
Maximum allowable word length for the product data type.
The MATLAB factory default value of this property is 128.
Maximum allowable word length for the sum data type.
The MATLAB factory default value of this property is 128.
Overflow-handling mode. The value of the OverflowMode property can be one of the following strings:
saturate — Saturate to maximum or minimum value of the fixed-point range on overflow.
wrap — Wrap on overflow. This mode is also known as two's complement overflow.
The MATLAB factory default value of this property is saturate.
Bias of the product data type. This value can be any floating-point number. The product data type defines the data type of the result of a multiplication of two fi objects.
The MATLAB factory default value of this property is 0.
Fixed exponent of the product data type. This value can be any positive or negative integer. The product data type defines the data type of the result of a multiplication of two fi objects.
. Changing one
of these properties changes the others.
The ProductFixedExponent is the negative of the ProductFractionLength. Changing one property changes the other.
The MATLAB factory default value of this property is -30.
Fraction length, in bits, of the product data type. This value can be any positive or negative integer. The product data type defines the data type of the result of a multiplication of two fi objects.
The ProductFractionLength is the negative of the ProductFixedExponent. Changing one property changes the other.
The MATLAB factory default value of this property is 30.
Defines how the product data type is determined. In the following descriptions, let A and B be real operands, with [word length, fraction length] pairs [Wa Fa] and [Wb Fb], respectively. Wp is the product data type word length and Fp is the product data type fraction length.
FullPrecision — The full precision of the result is kept. An error is generated if the calculated word length is greater than MaxProductWordLength.
KeepLSB — Keep least significant bits. You specify the product data type word length, while the fraction length is set to maintain the least significant bits of the product. In this mode, full precision is kept, but overflow is possible. This behavior models the C language integer operations.
KeepMSB — Keep most significant bits. You specify the product data type word length, while the fraction length is set to maintain the most significant bits of the product. In this mode, overflow is prevented, but precision may be lost.
where
SpecifyPrecision — You specify both the word length and fraction length of the product data type.
For [Slope Bias] math, you specify both the slope and bias of the product data type.
[Slope Bias] math is only defined for products when ProductMode is set to SpecifyPrecision.
The MATLAB factory default value of this property is FullPrecision.
Slope of the product data type. This value can be any floating-point number. The product data type defines the data type of the result of a multiplication of two fi objects.
. Changing one
of these properties changes the others.
The MATLAB factory default value of this property is 9.3132e-010.
Slope adjustment factor of the product data type. This value can be any floating-point number greater than or equal to 1 and less than 2. The product data type defines the data type of the result of a multiplication of two fi objects.
. Changing one
of these properties changes the others.
The MATLAB factory default value of this property is 1.
Word length, in bits, of the product data type. This value must be a positive integer. The product data type defines the data type of the result of a multiplication of two fi objects.
The MATLAB factory default value of this property is 32.
The rounding mode. The value of the RoundMode property can be one of the following strings:
ceil — Round toward positive infinity.
convergent — Round toward nearest. Ties round to the nearest even stored integer. This is the least biased rounding method provided by Fixed-Point Toolbox software.
fix — Round toward zero.
floor — Round toward negative infinity.
nearest — Round toward nearest. Ties round toward positive infinity.
round — Round toward nearest. Ties round toward negative infinity for negative numbers, and toward positive infinity for positive numbers.
The MATLAB factory default value of this property is nearest.
See Rounding Methods in the Fixed-Point Toolbox User's Guide for more information.
The bias of the sum data type. This value can be any floating-point number. The sum data type defines the data type of the result of a sum of two fi objects.
The MATLAB factory default value of this property is 0.
The fixed exponent of the sum data type. This value can be any positive or negative integer. The sum data type defines the data type of the result of a sum of two fi objects
. Changing one
of these properties changes the others.
The SumFixedExponent is the negative of the SumFractionLength. Changing one property changes the other.
The MATLAB factory default value of this property is -30.
The fraction length, in bits, of the sum data type. This value can be any positive or negative integer. The sum data type defines the data type of the result of a sum of two fi objects.
The SumFractionLength is the negative of the SumFixedExponent. Changing one property changes the other.
The MATLAB factory default value of this property is 30 .
Defines how the sum data type is determined. In the following descriptions, let A and B be real operands, with [word length, fraction length] pairs [Wa Fa] and [Wb Fb], respectively. Ws is the sum data type word length and Fs is the sum data type fraction length.
Note In the case where there are two operands, as in A + B, NumberOfSummands is 2, and ceil(log2(NumberOfSummands)) = 1. In sum(A) where A is a matrix, the NumberOfSummands is size(A,1). In sum(A) where A is a vector, the NumberOfSummands is length(A). |
FullPrecision — The full precision of the result is kept. An error is generated if the calculated word length is greater than MaxSumWordLength.
where
KeepLSB — Keep least significant bits. You specify the sum data type word length, while the fraction length is set to maintain the least significant bits of the sum. In this mode, full precision is kept, but overflow is possible. This behavior models the C language integer operations.
KeepMSB — Keep most significant bits. You specify the sum data type word length, while the fraction length is set to maintain the most significant bits of the sum and no more fractional bits than necessary. In this mode, overflow is prevented, but precision may be lost.
where
SpecifyPrecision — You specify both the word length and fraction length of the sum data type.
For [Slope Bias] math, you specify both the slope and bias of the sum data type.
[Slope Bias] math is only defined for sums when SumMode is set to SpecifyPrecision.
The MATLAB factory default value of this property is FullPrecision.
The slope of the sum data type. This value can be any floating-point number. The sum data type defines the data type of the result of a sum of two fi objects.
. Changing one
of these properties changes the others.
The MATLAB factory default value of this property is 9.3132e-010.
The slope adjustment factor of the sum data type. This value can be any floating-point number greater than or equal to 1 and less than 2. The sum data type defines the data type of the result of a sum of two fi objects.
. Changing one
of these properties changes the others.
The MATLAB factory default value of this property is 1.
The word length, in bits, of the sum data type. This value must be a positive integer. The sum data type defines the data type of the result of a sum of two fi objects.
The MATLAB factory default value of this property is 32.
 | fi Object Properties | fipref Object Properties |  |
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