fimath
Set fixed-point math settings
Description
F = fimath
creates a fimath
object with the
default fimath
property settings.
F = fimath(
specifies the
properties of a Name,Value
)fimath
object by using one or more name-value pair
arguments. All properties not specified in the constructor use default values.
Examples
Create a Default fimath Object
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
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
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: F =
fimath('OverflowAction','Saturate','RoundingMethod','Floor')
CastBeforeSum
— Whether both operands are cast to the sum data type before addition
true
or 1
(default) | false
or 0
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| logical
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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
Changing one of these properties affects the others.
Example: F = fimath('ProductSlope',9.3132e-10)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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
Changing one of these properties affects the others.
Example: F =
fimath('ProductSlopeAdjustmentFactor',1)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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
Changing one of these properties affects the others.
Example: F = fimath('SumSlope',9.3132e-10)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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
Changing one of these properties affects the others.
Example: F = fimath('SumSlopeAdjustmentFactor',1)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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)
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
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 thefimath
object is set to anything other thanFullPrecision
, theProductWordLength
andProductFractionLength
properties must be constant.If the
SumMode
property of thefimath
object is set to anything other thanFullPrecision
, theSumWordLength
andSumFractionLength
properties must be constant.
HDL Code Generation
Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.
Version History
Introduced before R2006aR2021a: Inexact property names for fi
, fimath
, and
numerictype
objects not supported
In previous releases, inexact property names for fi
,
fimath
, and numerictype
objects would result in a
warning. In R2021a, support for inexact property names was removed. Use exact property names
instead.
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