Clock Recovery (Mean Clock) VI

Owning Palette: Clock Recovery VIs

Requires: Jitter Analysis Toolkit

Constructs reference level crossings from a measured waveform. The reference level crossings are synchronized to a recovered internal clock using a method that finds a best fit of the reference to the waveform level crossings. Wire data to the waveform input to determine the polymorphic instance to use or manually select the instance.

Examples

Clock Recovery (Mean Clock) (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.
	level crossings contains information about the locations of level crossings in the original waveform. You can use the Level Crossing VI to generate this cluster. t0 specifies the time at which the first sample occurs in the original waveform. dt specifies the time interval in seconds between the individual samples in the original waveform. indexes contains the index numbers of the samples in the waveform 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 waveform at each of the samples in indexes.
	expected unit interval specifies the time interval you expect one bit period to last. The default is –1, which means this VI calculates an estimate of the clock period to use as the unit interval.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	data returns information about the data bit sequence between transitions in the waveform. bit count returns the number of bits between successive transitions. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope.
	waveform dup returns waveform unchanged.
	level crossings dup returns the level crossings unchanged. t0 returns the time at which the first sample occurred in the original waveform. dt returns the time interval in seconds between the individual samples in the original waveform. indexes contains the index numbers of waveform samples that fall on the crossing level and whose transition crosses both the high and low reference levels. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope. crossing level returns the input crossing level value at which the waveform falls at each sample in indexes.
	ref level crossings returns information about the locations of level crossings in the reference clock waveform. t0 returns the time at which the first sample occurred in the clock signal. dt returns the time interval in seconds between the individual samples in the clock signal. indexes returns the index numbers of samples in the clock signal that fall on the crossing level. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope. crossing level returns the crossing level value at which the clock signal falls at each sample in indexes.
	error out contains error information. This output provides standard error out functionality.
	unit interval returns the best fit duration of a single bit in the waveform.

Clock Recovery (Mean Clock) (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.
	level crossings contains information about the locations of level crossings in the original waveform. You can use the Level Crossing VI to generate this cluster. t0 specifies the time at which the first sample occurs in the original waveform. dt specifies the time interval in seconds between the individual samples in the original waveform. indexes contains the index numbers of the samples in the waveform 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 waveform at each of the samples in indexes.
	expected unit interval specifies the time interval you expect one bit period to last. The default is –1, which means this VI calculates an estimate of the clock period to use as the unit interval.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	data returns information about the data bit sequence between transitions in the waveform. bit count returns the number of bits between successive transitions. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope.
	waveform dup returns waveform unchanged.
	level crossings dup returns the level crossings unchanged. t0 returns the time at which the first sample occurred in the original waveform. dt returns the time interval in seconds between the individual samples in the original waveform. indexes contains the index numbers of waveform samples that fall on the crossing level and whose transition crosses both the high and low reference levels. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope. crossing level returns the input crossing level value at which the waveform falls at each sample in indexes.
	ref level crossings returns information about the locations of level crossings in the reference clock waveform. t0 returns the time at which the first sample occurred in the clock signal. dt returns the time interval in seconds between the individual samples in the clock signal. indexes returns the index numbers of samples in the clock signal that fall on the crossing level. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope. crossing level returns the crossing level value at which the clock signal falls at each sample in indexes.
	error out contains error information. This output provides standard error out functionality.
	unit interval returns the best fit duration of a single bit in the waveform.

Examples

Refer to the following VIs for examples of using the Clock Recovery (Mean Clock) VI:

• ISI Jitter Measurement VI: labview\examples\Jitter Analysis\Jitter Measurements
• Simulated Signal with Jitter VI: labview\examples\Jitter Analysis\Jitter Measurements