fixdt

Create Simulink.NumericType object describing a fixed-point or floating-point data type

Syntax

a = fixdt(Signed,WordLength)

a = fixdt(Signed,WordLength,FractionLength)

a = fixdt(Signed,WordLength,TotalSlope,Bias)

a = fixdt(Signed,WordLength,SlopeAdjustmentFactor,FixedExponent,Bias)

a = fixdt(DataTypeNameString)

a = fixdt(___,'DataTypeOverride','Off')

[a,IsScaledDouble] = fixdt(___)

Description

a = fixdt(Signed,WordLength) returns a Simulink.NumericType object that describes a fixed-point data type with the specified signedness and word length, and unspecified scaling.

a = fixdt(Signed,WordLength,FractionLength) returns a Simulink.NumericType object that describes a fixed-point data type with binary point scaling.

a = fixdt(Signed,WordLength,TotalSlope,Bias) returns a Simulink.NumericType object that describes a fixed-point data type with slope and bias scaling.

a = fixdt(Signed,WordLength,SlopeAdjustmentFactor,FixedExponent,Bias) returns a Simulink.NumericType object that describes a fixed-point data type with slope and bias scaling.

a = fixdt(DataTypeNameString) returns a Simulink.NumericType object that describes an integer, fixed-point, or floating-point data type specified by the name of a data type.

a = fixdt(___,'DataTypeOverride','Off') returns a Simulink.NumericType object with its DataTypeOverride parameter set to Off. The default value for this property is Inherit. You can specify the DataTypeOverride parameter after any combination of other input parameters.

[a,IsScaledDouble] = fixdt(___) returns a Simulink.NumericType object that describes a fixed-point or floating-point data type and a flag that indicates whether the specified data type is of a scaled double data type.

Examples

Create a Simulink.NumericType Object with Unspecified Scaling

Create a signed Simulink.NumericType object with a word length of 16 bits and unspecified scaling.

a = fixdt(1,16)

a = 
  NumericType with properties:

    DataTypeMode: 'Fixed-point: unspecified scaling'
      Signedness: 'Signed'
      WordLength: 16
         IsAlias: 0
       DataScope: 'Auto'
      HeaderFile: ''
     Description: ''

Create a Simulink.NumericType Object with Binary Point Scaling

Create a Simulink.NumericType object that describes a signed fixed-point data type with a word length of 16 bits and fraction length of 2 bits.

a = fixdt(1,16,2)

a = 
  NumericType with properties:

      DataTypeMode: 'Fixed-point: binary point scaling'
        Signedness: 'Signed'
        WordLength: 16
    FractionLength: 2
           IsAlias: 0
         DataScope: 'Auto'
        HeaderFile: ''
       Description: ''

Create a Simulink.NumericType Object with Slope and Bias Scaling

The real-world value of a slope bias scaled number is represented by:

$$\mathrm{real}\mathrm{world}\mathrm{value}=\left(\mathrm{slope}\times \mathrm{integer}\right)+\mathrm{bias}$$

Create a Simulink.NumericType object that describes a signed fixed-point data type with a word length of 16 bits, slope of 2^-2, and bias of 4.

a = fixdt(1,16,2^-2,4)

a = 
  NumericType with properties:

    DataTypeMode: 'Fixed-point: slope and bias scaling'
      Signedness: 'Signed'
      WordLength: 16
           Slope: 0.2500
            Bias: 4
         IsAlias: 0
       DataScope: 'Auto'
      HeaderFile: ''
     Description: ''

Alternatively, the slope can by represented by:

$$\mathrm{slope}=\mathrm{slopeadjustmentfactor}\times 2^{\mathrm{fixedexponent}}$$

a = fixdt(1,16,1,-2,4)

a = 
  NumericType with properties:

    DataTypeMode: 'Fixed-point: slope and bias scaling'
      Signedness: 'Signed'
      WordLength: 16
           Slope: 0.2500
            Bias: 4
         IsAlias: 0
       DataScope: 'Auto'
      HeaderFile: ''
     Description: ''

The DataTypeMode property of the Simulink.NumericType object, a, is slope and bias scaling.

Create a Simulink.NumericType Object Using a Data Type Name

Use a data type name to create a Simulink.NumericType object that describes an 8-bit, unsigned, fixed-point data type and return a flag that indicates whether the object is of a scaled double data type.

[a,IsScaledDouble] = fixdt('ufix8')

a = 
  NumericType with properties:

      DataTypeMode: 'Fixed-point: binary point scaling'
        Signedness: 'Unsigned'
        WordLength: 8
    FractionLength: 0
           IsAlias: 0
         DataScope: 'Auto'
        HeaderFile: ''
       Description: ''

IsScaledDouble = logical
   0

The IsScaledDouble output returns 0, which indicates that the data type of a is not a scaled double data type.

Create a Simulink.NumericType Object with DataTypeOverride Set to Off

Create a Simulink.NumericType object with its DataTypeOverride property set to Off.

a = fixdt(0,8,2,'DataTypeOverride','Off')

a = 
  NumericType with properties:

        DataTypeMode: 'Fixed-point: binary point scaling'
          Signedness: 'Unsigned'
          WordLength: 8
      FractionLength: 2
    DataTypeOverride: 'Off'
             IsAlias: 0
           DataScope: 'Auto'
          HeaderFile: ''
         Description: ''

Input Arguments

Signed — Signedness

true or 1 | false or 0

Signedness of the Simulink.NumericType object, specified as a numeric or logical 1 (true) or 0 (false). A value of 1, or true, indicates a signed data type. A value of 0, or false, indicates an unsigned data type.

Data Types: logical

WordLength — Word length

positive scalar

Word length, in bits, of the Simulink.NumericType object, specified as a positive scalar.

Data Types: half | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

FractionLength — Fraction length

0 (default) | scalar

Fraction length, in bits, of the Simulink.NumericType object, specified as a scalar.

FractionLength can be greater than WordLength. For more information, see Binary Point Interpretation (Fixed-Point Designer).

Data Types: half | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

TotalSlope — Slope of the scaling

1 (default) | scalar

Slope of the scaling, specified as a scalar.

The following equation represents the real-world value of a slope bias scaled number:

$$realworldvalue=(slope\times integer)+bias$$

Data Types: half | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Bias — Bias of the scaling

0 (default) | scalar

Bias of the scaling, specified as a scalar.

The following equation represents the real-world value of a slope bias scaled number:

$$realworldvalue=(slope\times integer)+bias$$

Data Types: half | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

SlopeAdjustmentFactor — Slope adjustment factor of slope and bias scaled number

1 (default) | positive scalar

Slope adjustment factor of a slope bias scaled number, specified as a positive scalar.

The slope adjustment factor must be greater than or equal to 1 and less than 2. If you input a SlopeAdjustmentFactor outside this range, fixdt automatically applies a scaling normalization to the values of SlopeAdjustmentFactor and FixedExponent so that the revised slope adjustment factor is greater than or equal to 1 and less than 2, and maintains the value of the slope.

The following equation demonstrates the relationship between the slope, fixed exponent, and slope adjustment factor:

$$slope=slopeadjustmentfactor\times 2^{fixedexponent}$$

Data Types: half | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

FixedExponent — Fixed exponent of slope and bias scaled number

0 (default) | scalar

Fixed exponent of a slope bias scaled number, specified as a scalar.

The following equation demonstrates the relationship between the slope, fixed exponent, and slope adjustment factor:

$$slope=slopeadjustmentfactor\times 2^{fixedexponent}$$

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

DataTypeNameString — Data type name

character vector

Data type name, specified as a character vector.

The data type name can be either the name of a built-in Simulink^® data type or the name of a fixed-point data type that conforms to the naming convention for fixed-point names established by the Fixed-Point Designer™ product. For more information, see Fixed-Point Data Type and Scaling Notation (Fixed-Point Designer).

Data Types: char

Output Arguments

a — Data type

Simulink.NumericType object

Data type, returned as a Simulink.NumericType object.

IsScaledDouble — Scaled double flag

logical

Scaled double flag, returned as a logical that indicates whether the specified data type name is the name of a scaled double data type.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

For the fixdt function, code is generated via the embedded.numerictype object. The Simulink.NumericType object is not supported for code generation.

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

Version History

Introduced before R2006a