fimath

Set fixed-point math settings

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Syntax

F = fimath

F = fimath(Name,Value)

Description

example

F = fimath creates a fimath object with the default fimath property settings.

example

F = fimath(Name,Value) specifies the properties of a fimath object by using one or more name-value pair arguments. All properties not specified in the constructor use default values.

Examples

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Create a Default fimath Object

Open Live Script

This example shows how to create a fimath object with the default property settings.

F = fimath

F = 
        RoundingMethod: Nearest
        OverflowAction: Saturate
           ProductMode: FullPrecision
               SumMode: FullPrecision

Set Properties of a fimath Object

Open Live Script

Set the properties of a fimath object at the time of object creation by using name-value pairs. For example, set the overflow action to saturate and the rounding method to convergent.

F = fimath('OverflowAction','Saturate','RoundingMethod','Convergent')

F = 
        RoundingMethod: Convergent
        OverflowAction: Saturate
           ProductMode: FullPrecision
               SumMode: FullPrecision

Input Arguments

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Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example:

F =
          fimath('OverflowAction','Saturate','RoundingMethod','Floor')

`'CastBeforeSum'` — Whether both operands are cast to the sum data type before addition
`false` or `0` (default) | `true` or `1`

Whether both operands are cast to the sum data type before addition, specified as a numeric or logical 1 (true) or 0 (false).

Note

This property is hidden when the SumMode is set to FullPrecision.

Example: F = fimath('CastBeforeSum',true)

`'MaxProductWordLength'` — Maximum allowable word length for the product data type
`65535` (default) | positive integer

Maximum allowable word length for the product data type, specified as a positive integer.

Example: F = fimath('MaxProductWordLength',16)

`'MaxSumWordLength'` — Maximum allowable word length for sum data type
65535 (default) | positive integer

Maximum allowable word length for the sum data type, specified as a positive integer.

Example: F = fimath('MaxSumWordLength',16)

`'OverflowAction'` — Action to take on overflow
`'Saturate'` (default) | `'Wrap'`

Action to take on overflow, specified as one of these values:

'Saturate' – Saturate to the 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.

Example: F = fimath('OverflowAction','Wrap')

Data Types: char

`'ProductBias'` — Bias of product data type
`0` (default) | floating-point number

Bias of the product data type, specified as a floating-point number.

Example: F = fimath('ProductBias',1)

`'ProductFixedExponent'` — Fixed exponent of product data type
`-30` (default) | nonzero integer

Fixed exponent of the product data type, specified as a nonzero integer.

Note

The ProductFractionLength is the negative of the ProductFixedExponent. Changing one property changes the other.

Example: F = fimath('ProductFixedExponent',-20)

`'ProductFractionLength'` — Fraction length of product data type
`30` (default) | nonzero integer

Fraction length, in bits, of the product data type, specified as a nonzero integer.

Note

The ProductFractionLength is the negative of the ProductFixedExponent. Changing one property changes the other.

Example: F = fimath('ProductFractionLength',20)

`'ProductMode'` — How product data type is determined
`'FullPrecision'` (default) | `'KeepLSB'` | `'KeepMSB'` | `'SpecifyPrecision'`

How the product data type is determined, specified as one of these values:

'FullPrecision' – The full precision of the result is kept.
'KeepLSB' – Keep the least significant bits. Specify the product word length. The fraction length is set to maintain the least significant bits of the product.
'KeepMSB' – Keep the most significant bits. Specify the product word length. The fraction length is set to maintain the most significant bits of the product.
'SpecifyPrecision' – Specify the word and fraction lengths or slope and bias of the product.

Example: F = fimath('ProductMode','KeepLSB')

Data Types: char

`'ProductSlope'` — Slope of product data type
`9.3132e-10` (default) | finite, positive floating-point number

Slope of the product data type, specified as a finite, positive floating-point number.

Note

$P r o d u c t S l o p e = P r o d u c t S l o p e A d j u s t m e n t F a c t o r \times 2^{P r o d u c t F i x e d E x p o n e n t}$

Changing one of these properties affects the others.

Example: F = fimath('ProductSlope',9.3132e-10)

`'ProductSlopeAdjustmentFactor'` — Slope adjustment factor of the product data type
`1` (default) | floating-point number greater than or equal to 1 and less than 2

Slope adjustment factor of the product data type, specified as a floating-point number greater than or equal to 1 and less than 2.

Note

$P r o d u c t S l o p e = P r o d u c t S l o p e A d j u s t m e n t F a c t o r \times 2^{P r o d u c t F i x e d E x p o n e n t}$

Changing one of these properties affects the others.

Example: F = fimath('ProductSlopeAdjustmentFactor',1)

`'ProductWordLength'` — Word length of product data type
`32` (default) | positive integer

Word length, in bits, of the product data type, specified as a positive integer.

Example: F = fimath('ProductWordLength',64)

`'RoundingMethod'` — Rounding method to use
`'Nearest'` (default) | `'Ceiling'` | `'Convergent'` | `'Zero'` | `'Floor'` | `'Round'`

Rounding method to use, specified as one of these values:

'Nearest' – Round toward nearest. Ties round toward positive infinity.
'Ceiling' – Round toward positive infinity.
'Convergent' – Round toward nearest. Ties round to the nearest even stored integer (least biased).
'Zero' – Round toward zero.
'Floor' – Round toward negative infinity.
'Round' – Round toward nearest. Ties round toward negative infinity for negative numbers, and toward positive infinity for positive numbers.

Example: F = fimath('RoundingMethod','Convergent')

Data Types: char

`'SumBias'` — Bias of sum data type
`0` (default) | floating-point number

Bias of the sum data type, specified as a floating-point number.

Example: F = fimath('SumBias',0)

`'SumFixedExponent'` — Fixed exponent of sum data type
`-30` (default) | nonzero integer

Fixed exponent of the sum data type, specified as a nonzero integer.

Note

The SumFractionLength is the negative of the SumFixedExponent. Changing one property changes the other.

Example: F = fimath('SumFixedExponent',-20)

`'SumFractionLength'` — Fraction length of sum data type
`30` (default) | nonzero integer

Fraction length, in bits, of the sum data type, specified as a nonzero integer.

Note

The SumFractionLength is the negative of the SumFixedExponent. Changing one property changes the other.

Example: F = fimath('SumFractionLength',20)

`'SumMode'` — How the sum data type is determined
`'FullPrecision'` (default) | `'KeepLSB'` | `'KeepMSB'` | `'SpecifyPrecision'`

How the sum data type is determined, specified as one of these values:

'FullPrecision' – The full precision of the result is kept.
'KeepLSB' – Keep least significant bits. Specify the sum data type word length. The fraction length is set to maintain the least significant bits of the sum.
'KeepMSB' – Keep most significant bits. Specify the sum data type word length. The fraction length is set to maintain the most significant bits of the sum and no more fractional bits than necessary.
'SpecifyPrecision' – Specify the word and fraction lengths or slope and bias of the sum data type.

Example: F = fimath('SumMode','KeepLSB')

Data Types: char

`'SumSlope'` — Slope of sum data type
`9.3132e-10` (default) | floating-point number

Slope of the sum data type, specified as a floating-point number.

Note

$S u m S l o p e = S u m S l o p e A d j u s t m e n t F a c t o r \times 2^{S u m F i x e d E x p o n e n t}$

Changing one of these properties affects the others.

Example: F = fimath('SumSlope',9.3132e-10)

`'SumSlopeAdjustmentFactor'` — Slope adjustment factor of the sum data type
`1` (default) | floating-point number greater than or equal to 1 and less than 2

Slope adjustment factor of the sum data type, specified as a floating-point number greater than or equal to 1 and less than 2.

Note

$S u m S l o p e = S u m S l o p e A d j u s t m e n t F a c t o r \times 2^{S u m F i x e d E x p o n e n t}$

Changing one of these properties affects the others.

Example: F = fimath('SumSlopeAdjustmentFactor',1)

`'SumWordLength'` — Word length of sum data type
`32` (default) | positive integer

Word length, in bits, of the sum data type, specified as a positive integer.

Example: F = fimath('SumWordLength',64)

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

Fixed-point signals coming in to a MATLAB^® Function block from Simulink^® are assigned a fimath object. You define this object in the MATLAB Function block dialog in the Model Explorer.
Use to create fimath objects in the generated code.
If the ProductMode property of the fimath object is set to anything other than FullPrecision, the ProductWordLength and ProductFractionLength properties must be constant.
If the SumMode property of the fimath object is set to anything other than FullPrecision, the SumWordLength and SumFractionLength properties must be constant.

Documentation

fimath

Syntax

Description

Examples

Create a Default fimath Object

Set Properties of a fimath Object

Input Arguments

Name-Value Pair Arguments

`'CastBeforeSum'` — Whether both operands are cast to the sum data type before addition
`false` or `0` (default) | `true` or `1`

`'MaxProductWordLength'` — Maximum allowable word length for the product data type
`65535` (default) | positive integer

`'MaxSumWordLength'` — Maximum allowable word length for sum data type
65535 (default) | positive integer

`'OverflowAction'` — Action to take on overflow
`'Saturate'` (default) | `'Wrap'`

`'ProductBias'` — Bias of product data type
`0` (default) | floating-point number

`'ProductFixedExponent'` — Fixed exponent of product data type
`-30` (default) | nonzero integer

`'ProductFractionLength'` — Fraction length of product data type
`30` (default) | nonzero integer

`'ProductMode'` — How product data type is determined
`'FullPrecision'` (default) | `'KeepLSB'` | `'KeepMSB'` | `'SpecifyPrecision'`

`'ProductSlope'` — Slope of product data type
`9.3132e-10` (default) | finite, positive floating-point number

`'ProductSlopeAdjustmentFactor'` — Slope adjustment factor of the product data type
`1` (default) | floating-point number greater than or equal to 1 and less than 2

`'ProductWordLength'` — Word length of product data type
`32` (default) | positive integer

`'RoundingMethod'` — Rounding method to use
`'Nearest'` (default) | `'Ceiling'` | `'Convergent'` | `'Zero'` | `'Floor'` | `'Round'`

`'SumBias'` — Bias of sum data type
`0` (default) | floating-point number

`'SumFixedExponent'` — Fixed exponent of sum data type
`-30` (default) | nonzero integer

`'SumFractionLength'` — Fraction length of sum data type
`30` (default) | nonzero integer

`'SumMode'` — How the sum data type is determined
`'FullPrecision'` (default) | `'KeepLSB'` | `'KeepMSB'` | `'SpecifyPrecision'`

`'SumSlope'` — Slope of sum data type
`9.3132e-10` (default) | floating-point number

`'SumSlopeAdjustmentFactor'` — Slope adjustment factor of the sum data type
`1` (default) | floating-point number greater than or equal to 1 and less than 2

`'SumWordLength'` — Word length of sum data type
`32` (default) | positive integer

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

See Also

Topics

Fixed-Point Designer Documentation

Support

Documentation

fimath

Syntax

Description

Examples

Create a Default fimath Object

Set Properties of a fimath Object

Input Arguments

Name-Value Pair Arguments

'CastBeforeSum' — Whether both operands are cast to the sum data type before addition false or 0 (default) | true or 1

'MaxProductWordLength' — Maximum allowable word length for the product data type 65535 (default) | positive integer

'MaxSumWordLength' — Maximum allowable word length for sum data type 65535 (default) | positive integer

'OverflowAction' — Action to take on overflow 'Saturate' (default) | 'Wrap'

'ProductBias' — Bias of product data type 0 (default) | floating-point number

'ProductFixedExponent' — Fixed exponent of product data type -30 (default) | nonzero integer

'ProductFractionLength' — Fraction length of product data type 30 (default) | nonzero integer

'ProductMode' — How product data type is determined 'FullPrecision' (default) | 'KeepLSB' | 'KeepMSB' | 'SpecifyPrecision'

'ProductSlope' — Slope of product data type 9.3132e-10 (default) | finite, positive floating-point number

'ProductSlopeAdjustmentFactor' — Slope adjustment factor of the product data type 1 (default) | floating-point number greater than or equal to 1 and less than 2

'ProductWordLength' — Word length of product data type 32 (default) | positive integer

'RoundingMethod' — Rounding method to use 'Nearest' (default) | 'Ceiling' | 'Convergent' | 'Zero' | 'Floor' | 'Round'

'SumBias' — Bias of sum data type 0 (default) | floating-point number

'SumFixedExponent' — Fixed exponent of sum data type -30 (default) | nonzero integer

'SumFractionLength' — Fraction length of sum data type 30 (default) | nonzero integer

'SumMode' — How the sum data type is determined 'FullPrecision' (default) | 'KeepLSB' | 'KeepMSB' | 'SpecifyPrecision'

'SumSlope' — Slope of sum data type 9.3132e-10 (default) | floating-point number

'SumSlopeAdjustmentFactor' — Slope adjustment factor of the sum data type 1 (default) | floating-point number greater than or equal to 1 and less than 2

'SumWordLength' — Word length of sum data type 32 (default) | positive integer

Extended Capabilities

C/C++ Code Generation Generate C and C++ code using MATLAB® Coder™.

HDL Code Generation Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

See Also

Topics

Fixed-Point Designer Documentation

Support

`'CastBeforeSum'` — Whether both operands are cast to the sum data type before addition
`false` or `0` (default) | `true` or `1`

`'MaxProductWordLength'` — Maximum allowable word length for the product data type
`65535` (default) | positive integer

`'MaxSumWordLength'` — Maximum allowable word length for sum data type
65535 (default) | positive integer

`'OverflowAction'` — Action to take on overflow
`'Saturate'` (default) | `'Wrap'`

`'ProductBias'` — Bias of product data type
`0` (default) | floating-point number

`'ProductFixedExponent'` — Fixed exponent of product data type
`-30` (default) | nonzero integer

`'ProductFractionLength'` — Fraction length of product data type
`30` (default) | nonzero integer

`'ProductMode'` — How product data type is determined
`'FullPrecision'` (default) | `'KeepLSB'` | `'KeepMSB'` | `'SpecifyPrecision'`

`'ProductSlope'` — Slope of product data type
`9.3132e-10` (default) | finite, positive floating-point number

`'ProductSlopeAdjustmentFactor'` — Slope adjustment factor of the product data type
`1` (default) | floating-point number greater than or equal to 1 and less than 2

`'ProductWordLength'` — Word length of product data type
`32` (default) | positive integer

`'RoundingMethod'` — Rounding method to use
`'Nearest'` (default) | `'Ceiling'` | `'Convergent'` | `'Zero'` | `'Floor'` | `'Round'`

`'SumBias'` — Bias of sum data type
`0` (default) | floating-point number

`'SumFixedExponent'` — Fixed exponent of sum data type
`-30` (default) | nonzero integer

`'SumFractionLength'` — Fraction length of sum data type
`30` (default) | nonzero integer

`'SumMode'` — How the sum data type is determined
`'FullPrecision'` (default) | `'KeepLSB'` | `'KeepMSB'` | `'SpecifyPrecision'`

`'SumSlope'` — Slope of sum data type
`9.3132e-10` (default) | floating-point number

`'SumSlopeAdjustmentFactor'` — Slope adjustment factor of the sum data type
`1` (default) | floating-point number greater than or equal to 1 and less than 2

`'SumWordLength'` — Word length of sum data type
`32` (default) | positive integer

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.