View Fixed-Point Data

In Fixed-Point Designer™ software, the fipref object determines the display properties of fi objects. Code examples generally show fi objects as they appear with the following fipref object properties:

  • NumberDisplay'RealWorldValue'

  • NumericTypeDisplay'full'

  • FimathDisplay'full'

Setting 'FimathDisplay' to 'full' provides a quick and easy way to differentiate between fi objects with a local fimath and those that are associated with the default fimath. When 'FimathDisplay' is set to 'full', MATLAB® displays fimath object properties for fi objects with a local fimath. MATLAB never displays fimath object properties for fi objects that are associated with the default fimath. Because of this display difference, you can tell when a fi object is associated with the default fimath just by looking at the output.

Additionally, unless otherwise specified, examples throughout the Fixed-Point Designer documentation use the following default configuration of fimath:

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

For more information on display settings, refer to fi Object Display Preferences Using fipref.

Displaying the fimath Properties of fi Objects

To see the output as it appears in most Fixed-Point Designer code examples, set your fipref properties as follows and create two fi objects:

p = fipref('NumberDisplay', 'RealWorldValue',... 
'NumericTypeDisplay', 'full', 'FimathDisplay', 'full');
a = fi(pi,'RoundingMethod', 'Floor', 'OverflowAction', 'Wrap')
b = fi(pi)

MATLAB returns the following:

a =
    3.1415

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 13

        RoundingMethod: Floor
        OverflowAction: Wrap
           ProductMode: FullPrecision
               SumMode: FullPrecision

b =
    3.1416

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 13

MATLAB displays fimath object properties in the output of fi object a because a has a local fimath.

MATLAB does not display any fimath object properties in the output of fi object b because b associates itself with the default fimath.

Hiding the fimath Properties of fi Objects

If you are working with multiple fi objects that have local fimaths, you may want to turn off the fimath object display:

  • NumberDisplay'RealWorldValue'

  • NumericTypeDisplay'full'

  • FimathDisplay'none'

For example,

p = fipref('NumberDisplay','RealWorldValue',... 
'NumericTypeDisplay','full','FimathDisplay','none')
 
p =
 
         NumberDisplay: 'RealWorldValue'
    NumericTypeDisplay: 'full'
         FimathDisplay: 'none'
           LoggingMode: 'Off'
      DataTypeOverride: 'ForceOff'

F = fimath('RoundingMethod','Floor','OverflowAction','Wrap');
a = fi(pi, F)
 
a =
    3.1415

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 13

Although this setting helps decrease the amount of output produced, it also makes it impossible to tell from the output whether a fi object uses the default fimath. To do so, you can use the isfimathlocal function. For example,

isfimathlocal(a)

ans =
     1

When the isfimathlocal function returns 1, the fi object has a local fimath. If the function returns 0, the fi object uses the default fimath.

Shortening the numerictype Display of fi Objects

To reduce the amount of output even further, you can set the NumericTypeDisplay to 'short'. For example,

p = fipref('NumberDisplay','RealWorldValue',... 
'NumericTypeDisplay','short','FimathDisplay','full');

a = fi(pi)

a =
    3.1416
      s16,13
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