:MEASure:JITTer:DDJSymbol?
Query Syntax
:MEASure:JITTer:DDJSymbol?
Description
Returns the DDJ values for each measured edge as definite-length block data. DDJ values are returned for only the edge types specified by the command :MEASure:JITTer:DEFine:EDGE. Use the query :MEASure:JITTer:PATTern? to return the edge type values. Use the :MEASure:JITTer:DDJSymbol:SYMBols query to return a list of symbols corresponding to the returned values. Use the :DISPlay:JITTer:SGRaph:RANGe command to specify the number of symbols included in the data. Use the :DISPlay:JITTer:SGRaph:STARt command to specify the starting symbol for the data. The DDJ value has units of time or unit interval as specified by :MEASure:JITTer:DEFine:UNITs.
The DDJ-versus-Bit graph does not need to be displayed to return the data using this command.
Measurement Identification
Avoid subtle programming errors! To ensure that the correct measurement is installed or queried, always explicitly identify a measurement when installing a measurement or querying a measured value, status, or detail. To identify a measurement, specify the measurement's source waveform (:SOURce child command). With some measurements, you may also need to specify other identifying values. Generally, when selecting a measurement using FlexDCA's GUI, if a dialog appears prompting you to select values, you should explicitly specify these values when remotely identifying the measurement. More information.
For example, to return the status of the measurement, :MEASure:JITTer:DDJSymbol?:
flex.write(':MEASure:JITTer:DDJSymbol?:SOURce CHAN1A')
if flex.query(':MEASure:JITTer:DDJSymbol?:STATus?') == 'CORR';
measurement = flex.query(':MEASure:JITTer:DDJSymbol??')
else:
details = flex.query(':MEASure:JITTer:DDJSymbol?:STATus:DETails?')
reason = flex.query(':MEASure:JITTer:DDJSymbol?:STATus:REASon?')
Child commands for measurement identification:
:MEASure:JITTer:DDJSymbol?:SOURce
Requires FlexDCA revision A.05.60 and above.
This command replaces deprecated command :MEASure:JITTer:DDJVsbit.
Returned Data Type
The :MEASure:JITTer:DDJSymbol? query returns float (4 bytes) values as binary definite-length block data queries binary definite-length block data queries binary definite-length block data queries. You must specify this data type in your program language's command that you use to query the data. The specifier for this data type in your programming language will likely be "f" and it is identified in this example with red text. Confirm this with your programming language's documentation. The following is an example of the command used in Python using pyvisa.
Flex.read_termination = ''
Flex.write_termination = ''
endianness = Flex.query(':SYSTem:BORDER?')
Flex.write(':SYSTem:BORDER LENDian')
data = Flex.query_binary_values(':MEASure:JITTer:DDJSymbol?',
datatype='f',
container=list,
is_big_endian=False,
header_fmt='ieee')
Flex.write(':SYSTem:BORDER ' + endianness)
Endianness of Returned Definite-Length Block Data
To correctly interpret definite-length block data, you must know the endianness (byte order) of the returned data (integers or real) from FlexDCA and you will must likely need specify this same endianness in your program language's command that is used to query the data. Endianness can be set to "little endian" order in which the least significant byte is sent first and the most significant byte sent last. Or, the endianness can be set to "big endian" order in which the most significant byte is sent first and the least significant byte sent last.
To specify or query the endianness setting for binary block data, use the :SYSTem:BORDer command. The endiannes setting applies to all binary queries except for :DISK:FILE:READ? query.
If you plan to change FlexDCA's current endian setting, it is a good practice to query FlexDCA's current endian setting and restore the setting when your program completes. This will avoid other programs having errors due to assuming a particular endianness setting.
After a factory preset (:SYSTem:FACTory), sets little endian. A default setup (:SYSTem:DEFault) does not affect endianness.
Be aware that VXI plug-and-play drivers can change the endianness setting. As a result always explicitly set the endianness in your program before transferring any binary data.
The ability to specify endianness requires FlexDCA revision A.04.00 and above. Prior to revision A.04.00, the endianness of returned block data was always LSB (Least Significant Byte) first.
Example Command Sequence
:SYSTem:MODE JITTer :MEASure:JITTer:DDJ:SOURce CHAN1A :MEASure:JITTer:DDJSymbol?
Measurement Ready?
To confirm that the measurement is ready to read, you can query the measurement's status:
if ('CORR' in Flex.query(':MEASure:JITTer:DDJSymbol?:STATus?')):
measurement = Flex.query(':MEASure:JITTer:DDJSymbol??')
If averaging is turned on (:ACQuire:AVERaging), you can also confirm if the measurement result is ready by comparing the number of specified averages (:ACQuire:ECOunt?) versus the number of measurement sweeps that have occurred (:MEASure:JITTer:DDJSymbol?:COUNt?). The technique uses the :COUNt? common measurement query. For example,
if (Flex.query(':MEASure:JITTer:DDJSymbol?:COUNt?') >= Flex.query(':ACQuire:ECOUNt?')):
measurement = Flex.query(':MEASure:JITTer:DDJSymbol??')
You can also use an acquisition limit lest to test that a number of waveform samples, or pattern acquisitions have completed before returning a measurement. Refer to the :LTESt:ACQuire:CTYPe command.
Common Measurement Child Queries
This command supports the use of the following common measurement queries: :LOCation?, :COUNt?, :MAXimum?, :MINimum?, :MEAN?, and :SDEViation?.