Eye Data Generation VI

Owning Palette: Eye Diagram Measurements VIs

Requires: Jitter Analysis Toolkit

Divides a waveform into segments and returns data you can use to create an eye diagram. Wire data to the waveform input to determine the polymorphic instance to use or manually select the instance.

Refer to the Details section of this topic for information about using this VI to plot a waveform in an eye diagram.

Details  Examples

Eye Data Generation (DBL)

This instance operates on the waveform data type when the Y data values are double-precision, floating-point numeric values. Use the I8 instance of this VI with integer data to reduce the size of the data and the memory usage.

	waveform is the waveform to measure. t0 specifies the start time of the waveform. dt specifies the time interval in seconds between data points in the waveform. Y specifies the data values of the waveform.
	eye diagram resolution contains controls you can use to set the resolution of the eye diagram data. bins on time specifies the number of intervals into which you want to group time values on the x-axis. bins on voltage specifies the number of intervals into which you want to group voltage values on the y-axis.
	ref level crossings specifies information about the locations of level crossings in the reference clock waveform. You can use the Clock Recovery VIs to generate this cluster from a measured waveform. t0 specifies the time at which the first sample occurs in the clock signal. dt specifies the time interval in seconds between the individual samples in the clock signal. indexes contains the index numbers of the samples in the clock signal with values that fall at the crossing level. slope identifies the direction of the first transition in the waveform. -1 Falling Edge—Specifies the transition is a falling edge, or one with a negative slope. 1 Rising Edge (default)—Specifies the transition is a rising edge, or one with a positive slope. crossing level specifies the value of the clock signal at each of the samples in indexes.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	unit interval is the best fit duration of a single bit in the waveform. You can use the Clock Recovery (Mean Clock) VI to generate this value.
	percent overlap specifies the amount of previous and subsequent unit intervals to include in each segment to be plotted. The default is 50 percent.
	waveform dup returns waveform unchanged.
	eye diagram data is a cluster of data that defines the eye diagram you want to plot. Note  Height- and width-related cluster elements contain default data because this VI does not measure those values. Use this cluster with the Eye Height and Width VI to calculates those values. segments is an array of values that define portions of the waveform to plot in the eye diagram. Each segment contains one unit interval that is preceded and followed by portions of adjacent unit intervals. start idx is the index number within the original waveform of the first sample in the waveform segment. The start idx of the segment that contains a particular unit interval is the sample in the previous unit interval that corresponds to the percent overlap you specify. For example, if percent overlap is 50, this VI sets the start idx as the sample halfway into the previous unit interval. end idx is the index number within the original waveform of the last sample in the waveform segment. The end idx of the segment that contains a particular unit interval is the sample in the following unit interval that corresponds to the percent overlap you specify. For example, if percent overlap is 50, this VI sets the end idx as the sample halfway into the next unit interval. ref crossing returns the index number of the sample between start index and end index whose value falls at the crossing level. t min is the initial time in the eye diagram. t max is the final time in the eye diagram. v min is the minimum voltage value in the eye diagram. v max is the maximum voltage value in the eye diagram. unit interval returns the unit interval unchanged. height is TRUE if this cluster contains values that define the height of the eye opening. If height is FALSE, height time, top, and base contain default data. height time is the time at which the height measurement occurs. top is the upper voltage level of the eye opening. base is the lower voltage level of the eye opening. width is TRUE if this cluster contains values that define the width of the eye opening. If width is FALSE, crossing level, left, and right contain default data. crossing level returns the voltage at which the eye width measurement occurs. left is the lower time value of the eye opening. right is the upper time value of the eye opening. 2D histogram is a 2D array of values that represent the magnitude at locations in the eye diagram.
	error out contains error information. This output provides standard error out functionality.

Eye Data Generation (I8)

This instance operates on the waveform data type when the Y data values are 8-bit signed integers.

	waveform is the waveform to measure. t0 specifies the start time of the waveform. dt specifies the time interval in seconds between data points in the waveform. Y specifies the data values of the waveform.
	eye diagram resolution contains controls you can use to set the resolution of the eye diagram data. bins on time specifies the number of intervals into which you want to group time values on the x-axis. bins on voltage specifies the number of intervals into which you want to group voltage values on the y-axis.
	ref level crossings specifies information about the locations of level crossings in the reference clock waveform. You can use the Clock Recovery VIs to generate this cluster from a measured waveform. t0 specifies the time at which the first sample occurs in the clock signal. dt specifies the time interval in seconds between the individual samples in the clock signal. indexes contains the index numbers of the samples in the clock signal with values that fall at the crossing level. slope identifies the direction of the first transition in the waveform. -1 Falling Edge—Specifies the transition is a falling edge, or one with a negative slope. 1 Rising Edge (default)—Specifies the transition is a rising edge, or one with a positive slope. crossing level specifies the value of the clock signal at each of the samples in indexes.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	unit interval is the best fit duration of a single bit in the waveform. You can use the Clock Recovery (Mean Clock) VI to generate this value.
	percent overlap specifies the amount of previous and subsequent unit intervals to include in each segment to be plotted. The default is 50 percent.
	waveform dup returns waveform unchanged.
	eye diagram data is a cluster of data that defines the eye diagram you want to plot. Note  Height- and width-related cluster elements contain default data because this VI does not measure those values. Use this cluster with the Eye Height and Width VI to calculates those values. segments is an array of values that define portions of the waveform to plot in the eye diagram. Each segment contains one unit interval that is preceded and followed by portions of adjacent unit intervals. start idx is the index number within the original waveform of the first sample in the waveform segment. The start idx of the segment that contains a particular unit interval is the sample in the previous unit interval that corresponds to the percent overlap you specify. For example, if percent overlap is 50, this VI sets the start idx as the sample halfway into the previous unit interval. end idx is the index number within the original waveform of the last sample in the waveform segment. The end idx of the segment that contains a particular unit interval is the sample in the following unit interval that corresponds to the percent overlap you specify. For example, if percent overlap is 50, this VI sets the end idx as the sample halfway into the next unit interval. ref crossing returns the index number of the sample between start index and end index whose value falls at the crossing level. t min is the initial time in the eye diagram. t max is the final time in the eye diagram. v min is the minimum voltage value in the eye diagram. v max is the maximum voltage value in the eye diagram. unit interval returns the unit interval unchanged. height is TRUE if this cluster contains values that define the height of the eye opening. If height is FALSE, height time, top, and base contain default data. height time is the time at which the height measurement occurs. top is the upper voltage level of the eye opening. base is the lower voltage level of the eye opening. width is TRUE if this cluster contains values that define the width of the eye opening. If width is FALSE, crossing level, left, and right contain default data. crossing level returns the voltage at which the eye width measurement occurs. left is the lower time value of the eye opening. right is the upper time value of the eye opening. 2D histogram is a 2D array of values that represent the magnitude at locations in the eye diagram.
	error out contains error information. This output provides standard error out functionality.

Eye Data Generation Details

Use this VI with the Eye Diagram Support VI to graph the eye diagram. The following block diagram illustrates a common workflow for the Eye Diagram Measurements VIs.

Examples

Refer to the following VIs for examples of using the Eye Data Generation VI:

• Basic Eye Diagram VI: labview\examples\Jitter Analysis\Eye Diagram Measurements
• Mask and Limit Test VI: labview\examples\Jitter Analysis\Eye Diagram Measurements