This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English version of the page.

Note: This page has been translated by MathWorks. Click here to see
To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

Fixed Point

Represent signals and parameter values with fixed-point numbers to improve performance of generated code

Within digital hardware, numbers are represented as either fixed-point or floating-point data types. For both of these data types, word sizes are fixed at a set number of bits. However, the dynamic range of fixed-point values is much less than floating-point values with equivalent word sizes. While floating-point processors can greatly simplify the real-time implementation of a system, and effectively approximate real-world numbers, fixed-point processors carry numerous other benefits. Fixed-point processors are generally smaller, consuming less power. They also require less memory and less processor time to perform.

To simulate a model that uses fixed-point numbers, you must install the Fixed-Point Designer™ product. You do not need the Fixed-Point Designer product to edit a model containing fixed-point blocks, or to specify fixed-point data types.


fxptdlgStart Fixed-Point Tool
fixdtCreate Simulink.NumericType object describing fixed-point or floating-point data type
fixpt_look1_func_approxOptimize fixed-point approximation of nonlinear function by interpolating lookup table data points
fixpt_evenspace_cleanupModify breakpoints of lookup table to have even spacing
fixpt_interp1Implement 1-D lookup table
fixpt_look1_func_plotPlot fixed-point approximation function for lookup table
fixpt_set_allSet property for each fixed-point block in subsystem
fixptbestexpExponent that gives best precision for fixed-point representation of value
fixptbestprecDetermine maximum precision available for fixed-point representation of value
floatCreate Simulink.NumericType object describing floating-point data type
num2fixptConvert number to nearest value representable by specified fixed-point data type
sfixCreate Simulink.NumericType object describing signed fixed-point data type


Specify Fixed-Point Data Types

If you do not have Fixed-Point Designer, you can still inspect and use fixed-point models that others share with you.

Specify Data Types Using Data Type Assistant

Interactively apply data types, such as integer, fixed-point, and enumerated types, to data items in a model.

Share Fixed-Point Models

Inspect and use an existing fixed-point model when you do not have Fixed-Point Designer.

Control Fixed-Point Instrumentation and Data Type Override

If you do not have Fixed-Point Designer, you can work with a model containing Simulink® blocks with fixed-point settings by turning off fixed-point instrumentation and setting data type override to scaled doubles.

Fixed-Point Numbers

In computer memory, an item of fixed-point data is stored as an integer. To interpret the data as a real-world number, the computer applies a mathematical scaling to the integer. The scaling is fixed, which means it cannot change during execution.

Benefits of Using Fixed-Point Hardware

Fixed-point designs can perform faster and consume fewer computing resources than floating-point designs.

Scaling, Precision, and Range

Examine the interaction between the scaling that you apply to fixed-point data, the precision with which the data can represent real-world values, and the range of real-world values that the data can represent.

Fixed-Point Data in MATLAB and Simulink

Apply fixed-point data types to data in Simulink models and to data in MATLAB® code.

Related Information