:CRECovery:JSANalysis:SPECtrum:FLOat:YDATa?
Query Syntax
:CRECoveryN:JSANalysis:SPECtrum:FLOat:YDATa?
Where N identifies the slot number and must be selected from {1:8}. The slot number is associated with the N1060A, N1076A/B, N1077A, N1078A, or 86108B module with Option JSA. When an 86108B module is used, the slot number is always 1.
Description
Returns the y-axis jitter-spectrum data as 32-bit floating-point values. The returned magnitude values are in seconds and do not require scaling. The data returned from this query has high resolution but can requires longer tranfer times than returning the data as ASCII. The data is sent in linear format starting from the graph's left side (lowest frequency) and progressing to the right side (highest frequency) . The frequency at any data point can be calculated as:
where,
- Xincrement is the frequency spacing between the data points and is returned with the
:CRECovery:JSANalysis:SPECtrum:XINCrement?query. - Xindex is the data point count, starting at zero and ending at the number of points minus one. Use the
:CRECovery:JSANalysis:SPECtrum:POINts?query to return the number of points. - Xorigin is the frequency value of the first data point and is returned using the
:CRECovery:JSANalysis:SPECtrum:XORigin?query.
Returned Data Type
The :CRECovery:JSANalysis:SPECtrum:FLOat:YDATa? 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(':CRECovery:JSANalysis:SPECtrum:FLOat:YDATa?',
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.
Command Compatibility
- N1060A Option JSA
- 86108A/B Option JSA
- N107X-series Option JSA
Requires FlexDCA revision A.01.70 and above.
Requires a clock-recovery module that has Option JSA (Jitter Spectrum Analysis and SW Clock Recovery Emulation).