:MEASure:AMPLitude:ISISymbol:SYMBols?

Meas. mode:

Jitter

Package License:

L-RND

Waveform type:

NRZ

PAM4

Flex Apps:

FlexDCA

Query Syntax

:MEASure:AMPLitude:ISISymbol:SYMBols?

Description

Returns a list of symbols for which :MEASure:AMPLitude:ISISymbol? has returned values. The list is returned as definite-length block data.

This command moves the measurement to the top of the table. Displays the measurement if it is not already shown on the table. The query form of the command returns the measured value.

The ISI vs BIT graph does not need to be displayed before data can be returned from this query.

Amplitude analysis must be turned on before the first interference measurement can be made. Use the :MEASure:AMPLitude:DEFine:ANALysis command.

Requires FlexDCA revision A.05.60 and above.

This command replaces deprecated command :MEASure:AMPLitude:ISIVsbit:BITS?.

Returned Data Type

The :MEASure:AMPLitude:ISISymbol:SYMBols? 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:AMPLitude:ISISymbol:SYMBols?',
	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.