numerictype Object Properties - MATLAB & Simulink (original) (raw)

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Data Type and Scaling Properties

All properties of a numerictype object are writable. However, thenumerictype properties of a fi object become read only after the fi object has been created. Anynumerictype properties of a fi object that are unspecified at the time of fi object creation are automatically set to their default values. The properties of a numerictype object are:

Property	Description	Valid Values
Bias	Bias associated with the object.Along with the slope, the bias forms the scaling of a fixed-point number.	Any floating-point number
DataType	Data type category	Fixed (default) — Fixed-point or integer data typeboolean — Built-in MATLAB® boolean data typedouble — Built-in MATLABdouble data typeScaledDouble — Scaled double data typesingle — Built-in MATLABsingle data type
DataTypeMode	Data type and scaling associated with the object	Fixed-point: binary point scaling (default) — Fixed-point data type and scaling defined by the word length and fraction lengthBoolean — Built-inbooleanDouble — Built-indoubleFixed-point: slope and bias scaling — Fixed-point data type and scaling defined by the slope and biasFixed-point: unspecified scaling — Fixed-point data type with unspecified scalingScaled double: binary point scaling — Double data type with fixed-point word length and fraction length information retainedScaled double: slope and bias scaling — Double data type with fixed-point slope and bias information retainedScaled double: unspecified scaling — Double data type with unspecified fixed-point scalingSingle — Built-insingle
FixedExponent	Fixed-point exponent associated with the object	Any integer NoteThe FixedExponent property is the negative of theFractionLength. Changing one property changes the other.
FractionLength	Fraction length of the stored integer value, in bits	Best precision fraction length based on value of the object and the word length (default)Any integer NoteThe FractionLength property is the negative of theFixedExponent. Changing one property changes the other.
Scaling	Scaling mode of the object	BinaryPoint (default) — Scaling for thefi object is defined by the fraction length.SlopeBias — Scaling for thefi object is defined by the slope and bias.Unspecified — A temporary setting that is only allowed at fi object creation, to allow for the automatic assignment of a binary point best-precision scaling.
Signed	Whether the object is signedNoteAlthough the Signed property is still supported, theSignedness property always appears in thenumerictype object display. If you choose to change or set the signedness of your numerictype objects using theSigned property, MATLAB updates the corresponding value of theSignedness property.	true (default) — signedfalse — unsigned1 — signed0 — unsigned[] — auto
Signedness	Whether the object is signed, unsigned, or has an unspecified sign	Signed (default)Unsigned Auto — unspecified sign
Slope	Slope associated with the objectAlong with the bias, the slope forms the scaling of a fixed-point number.	Any finite floating-point number greater than zero Note slope=slope adjustment factor×2fixed exponentChanging one of these properties changes the other.
SlopeAdjustmentFactor	Slope adjustment associated with the objectThe slope adjustment is equivalent to the fractional slope of a fixed-point number.	Any number greater than or equal to 1 and less than 2 Note slope=slope adjustment factor×2fixed exponentChanging one of these properties changes the other.
WordLength	Word length of the stored integer value, in bits	16 (default)Any positive integer if Signedness isUnsigned or unspecifiedAny integer greater than one if Signedness is set toSigned

These properties are described in detail in the Set fi Object Properties. To learn how to specify properties fornumerictype objects in Fixed-Point Designer™ software, refer to Set numerictype Object Properties.

Properties that affect the slope

The Slope field of the numerictype object is related to the SlopeAdjustmentFactor andFixedExponent properties by

The FixedExponent and FractionLength properties are related by

If you set the SlopeAdjustmentFactor,FixedExponent, or FractionLength property, theSlope field is modified.

Stored integer value and real world value

In binary point scaling the numerictype StoredIntegerValue and RealWorldValue properties are related according to

In [Slope Bias] scaling the RealWorldValue can be represented by

which is equivalent to

If any of these properties are updated, the others are modified accordingly.

Set `numerictype` Object Properties

Setting `numerictype` Properties at Object Creation

You can set properties of numerictype objects at the time of object creation by including properties after the arguments of the numerictype constructor function.

For example, to set the word length to 32 bits and the fraction length to 30 bits,

T = numerictype('WordLength',32,'FractionLength',30)

T =

      DataTypeMode: Fixed-point: binary point scaling
        Signedness: Signed
        WordLength: 32
    FractionLength: 30

In addition to creating a numerictype object at the command line, you can also set numerictype properties using the Insert numerictype Constructor dialog box. For an example of this approach, seeExample: Build numerictype Object Constructors in a GUI.

Use Direct Property Referencing with numerictype Objects

You can reference directly into a property for setting or retrievingnumerictype object property values using MATLAB structure-like referencing. You do this by using a period to index into a property by name.

For example, to get the word length of T,

To set the fraction length of T,

T =

      DataTypeMode: Fixed-point: binary point scaling
        Signedness: Signed
        WordLength: 32
    FractionLength: 31