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Data Type Page (Properties Dialog Box)

LabVIEW 2013 Help

Edition Date: June 2013

Part Number: 371361K-01

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Requires: Base Development System

Use this page of the Properties dialog box to specify the representation of numeric objects or outputs and to configure fixed-point data types.

This page includes the following components:

Note  Some of the components in this list do not apply to all objects.
  • RepresentationSets the representation of numeric data.
  • Adapt to x—If x is source, this checkbox sets whether the configuration settings for the output value, such as Representation, adapt to the input values you wire to the function. If you wire fixed-point input values to the function, LabVIEW automatically sets the Fixed-Point Configuration settings to avoid data loss, if possible. If data loss cannot occur, the context help of the Output Configuration page of the function displays [Not Needed] next to the Rounding Mode and/or Overflow Mode to indicate that these modes are unused.

    If you remove the checkmark from this checkbox, you can specify the Fixed-Point Configuration settings manually. LabVIEW then displays a blue coercion dot on the function to indicate that data loss might occur.
    Note  The Adapt to Source checkbox does not appear for functions that cannot adapt the output value to the configuration settings of the input value. For example, this checkbox does not appear for the To Fixed-Point function.
  • Fixed-Point Configuration—Sets the configuration settings for fixed-point data. Set Representation to Fixed-point (FXP) to enable these options. These options are not available for enums, rings, knobs, slides, or waveforms.
    Note  LabVIEW calculates the Range of the fixed-point number according to the values you specify for the Encoding of the fixed-point number.
    • Rounding mode—Sets how the function handles rounding conditions. Set Representation to Fixed-point(FXP) to enable this option. You can select from the following options:
      • Truncate—LabVIEW rounds the value down to the nearest value that the output type can represent. LabVIEW discards the least significant bits of the value. This rounding mode has the lowest impact on performance, but also produces the least accurate values.

        For example, if s<x<t, LabVIEW sets x to equal s.
      • Round Half-Up—LabVIEW rounds the value to the nearest value that the output type can represent. If the value lies exactly between two such values, LabVIEW rounds the value up to the higher of the two by adding half a least significant bit to the value and then truncating the value. This rounding mode has a larger impact on performance than Truncate, but it produces more accurate output values.

        For example, if s<x<t, set x to equal the closer of s or t. If x is exactly between s and t, select t.
      • Round Half-Even—(Default) LabVIEW rounds the value to the nearest value that the output type can represent. If the value lies exactly between two such values, LabVIEW checks the bit of the value that becomes the least significant bit after rounding. If the bit is 0, LabVIEW rounds the value to the lower of the two values that the output type can represent. If the bit is not 0, LabVIEW rounds the value to the higher of the two values. This rounding mode has the largest impact on performance, but it produces more accurate output values than Truncate and neutralizes the bias towards higher values that can occur when you perform multiple Round Half-Up operations.

        For example, if s<x<t, LabVIEW sets x to equal the closer of s or t. If x is exactly between s and t, LabVIEW selects s if the least significant bit after rounding is 0. LabVIEW selects t if the least significant bit after rounding is not 0.
    • Overflow Mode—Sets how the function handles overflow conditions. Set Representation to Fixed-point(FXP) to enable this option. You can select from the following options:
      • Wrap—If the value is outside the specified Range, LabVIEW discards significant bits of the value until the value falls within the Range. If you select this option, LabVIEW recomputes the Range based on the Encoding settings you specify.
      • Saturate—If the value is greater than the Maximum value in the Range, LabVIEW coerces the value to the specified Maximum. If the value is less than the Minimum value in the Range, LabVIEW coerces the value to the specified Minimum.
    • Encoding—Sets the binary encoding settings for the fixed-point data. These options are not available for enums, rings, knobs, slides, or waveforms.
      • Signed—Sets whether the fixed-point data is signed. This option is not available for enums, rings, knobs, slides, or waveforms.
      • Unsigned—Sets whether the fixed-point data is unsigned. This option is not available for enums, rings, knobs, slides, or waveforms.
      • Word length—Sets the number of bits that LabVIEW uses to represent all the possible values of the fixed-point data. This option is not available for enums, rings, knobs, slides, or waveforms.
      • Integer word length—Sets the number of integer bits, or the number of bits to shift the binary point to the left to reach the most significant bit, for all the possible values of the fixed-point data. This option is not available for enums, rings, knobs, slides, or waveforms. Integer word length can be larger or smaller than the Word length and can be positive or negative.
    • Range—Displays the range LabVIEW calculates for the fixed-point data. These options are not available for enums, rings, knobs, slides, or waveforms.
      Note  These fields display the values in double-precision floating-point representation, so the precision of Maximum, Minimum, and Delta might not be exact in terms of fixed-point representation. However, the deviation is very small.
      • Minimum—Displays the minimum value for the fixed-point data range. This option is not available for enums, rings, knobs, slides, or waveforms.
      • Maximum—Displays the maximum value for the fixed-point data range. This option is not available for enums, rings, knobs, slides, or waveforms.
      • Delta—Displays the maximum distance between any two sequential numbers in the fixed-point data range. This option is not available for enums, rings, knobs, slides, or waveforms.
    • Include overflow status—Sets whether LabVIEW includes an overflow status with the fixed-point number. When you include an overflow status in a fixed-point number, LabVIEW allocates additional storage space to track whether the fixed-point number is the result of an operation that overflowed. If you place a checkmark in this checkbox, you can display an overflow status LED on fixed-point controls, constants, and indicators. This LED lights up when the overflow status of the fixed-point number is TRUE.

 

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