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Owning Palette: Jitter VIs
Requires: Jitter Analysis Toolkit
Computes the worstcase amounts of different types of datadependent jitter (DDJ) from time interval error values measured in a waveform. Datadependent jitter is a form of deterministic jitter caused by level crossing time deviations correlated to the sequence of bits. You must manually select the polymorphic instance to use.
Use the pulldown menu to select an instance of this VI.
Use this polymorphic instance when the TIE sequence was computed from a waveform that contains a sequence of bits whose period is known, or periodic. When you know the length and pattern of the bit sequence, this polymorphic instance requires less processor resources to measure the datadependent jitter than the Arbitrary instance.
This VI divides the TIE sequence into segments that are # bits long and then averages the segments to remove the uncorrelated jitter components.
TIE sequence specifies the time interval error measurements from which to calculate datadependent jitter values. You can use the Time Interval Error VI to generate these measurements.  
# bits specifies the length, in bits, of the repeating sequence of time interval error values in TIE sequence.  
data contains information about the data bit sequence between transitions in a waveform. You can use the Clock Recovery (Mean Clock) VI to generate this cluster.
 
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.  
TIE (less DDJ) sequence returns the time interval error measurements with all forms of datadependent jitter removed. Any remaining jitter in the sequence is uncorrelated deterministic jitter or random jitter.  
data dependent jitter (s pp) returns the peaktopeak value of the averaged time interval error values in the TIE sequence.  
intersymbol interference (s pp) returns the peaktopeak value of intersymbol interference values. This output returns the greater of the peaktopeak value of averaged time interval error in rising edges and the corresponding value for falling edges.  
duty cycle distortion (s pp) returns the peaktopeak value of duty cycle distortion values. This VI subtracts the mean time interval error average for falling edges from the mean time interval error average for rising edges to measure the duty cycle distortion.  
error out contains error information. This output provides standard error out functionality. 
Use this polymorphic instance when the TIE sequence was computed from a waveform that contains a sequence of bits that does not repeat and whose period is unknown, or arbitrary.
TIE sequence specifies the time interval error measurements from which to calculate datadependent jitter values. You can use the Time Interval Error VI to generate these measurements.  
# bits specifies the length, in bits, of the repeating sequence of time interval error values in TIE sequence.  
data contains information about the data bit sequence between transitions in a waveform. You can use the Clock Recovery (Mean Clock) VI to generate this cluster.
 
minimum population specifies a threshold for the number of instances a particular bit pattern must repeat for this VI to include jitter at those bits in measurements of datadependent jitter.  
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.  
data dependent jitter (s pp) returns the peaktopeak value of the averaged time interval error values in the TIE sequence.  
intersymbol interference (s pp) returns the peaktopeak value of intersymbol interference values. This output returns the greater of the peaktopeak value of averaged time interval error in rising edges and the corresponding value for falling edges.  
duty cycle distortion (s pp) returns the peaktopeak value of duty cycle distortion values. This VI subtracts the mean time interval error average for falling edges from the mean time interval error average for rising edges to measure the duty cycle distortion.  
error out contains error information. This output provides standard error out functionality.  
DDJ collector is an array of clusters that describe repeated bit patterns in the TIE sequence.

The following pseudocode illustrates the algorithm this VI uses.
TIE_{avg} = ensemble average TIE[k, k+1, .. K + Nb –1], yielding M waveforms M = floor(N / Nb)
TIE_{+avg} = average of rising edges
TIE_{–avg} = average of falling edges
data dependent jitter = PP of TIE_{avg}
intersymbol interference = max [ (PP(TIE_{+avg}), PP(TIE_{–avg}) ]
duty cycle distortion = mean(TIE_{+avg}) – mean(TIE_{–avg})
Refer to the ISI Jitter Measurement VI in the labview\examples\Jitter Analysis\Jitter Measurements directory for an example of using the Data Dependent Jitter VI.