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RT Timestamp Analysis (RT Module)

LabVIEW Real-Time Module 8.2 Help
August 2006

NI Part Number:
370622D-01

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Analyzes the array of timestamps returned by the RT Get Timestamp VI. Details  

timestamp array specifies the array of 64-bit timestamps returned from the RT Get Timestamp VI that you want to analyze.
calibration array is an array used to remove the overhead associated with the RT Get Timestamp VI. The RT Timestamp Analysis VI subtracts the mean value of all elements in calibration array from each element in timestamp array to remove the overhead incurred when the RT Get Timestamp VI adds the element to the timestamp array in memory on the RT target.
Warmup iterations specifies the number of timestamps to ignore from the beginning of timestamp array. Use Warmup iterations to remove initial timestamps from the beginning of timestamp array that might have been affected during the initial execution of the application on an RT target.
error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE.
code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
mean time returns the average execution time for the values in the execution times array.
standard deviation returns the standard deviation for the values in the execution times array.
execution times returns the execution time, in microseconds, between each element of timestamp array.
execution histogram returns histogram values for the elements of execution times.
max jitter returns the maximum deviation between elements of execution time and the value of mean time. The value can represent a positive or negative deviation.
error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.
status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.
code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

RT Timestamp Analysis Details

The RT Get Timestamp VI returns a timestamp array that you can use to benchmark code. The timestamps returned in the array contain an added overhead incurred when the RT Get Timestamp VI adds timestamp values to the array in memory on an RT target. You can use the calibration array input of the RT Timestamp Analysis VI to remove the overhead from the timestamp values.

The example in the following figure uses the RT Get Timestamp VI to return an array of timestamps. The timestamps indicate the overhead incurred when the RT Get Timestamp VI adds a timestamp value to the timestamp array on the RT target.

Generating Calibration Array

You then can wire the array to the calibration array input of the RT Timestamp Analysis VI. The RT Timestamp Analysis VI subtracts the mean value of the calibration array from all timestamps provided in timestamp array to calculate the actual execution times for the code that you benchmark.


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