:MEASure:JITTer:FOVer2

Meas. mode:

Jitter

Package License:

L-RND

Waveform type:

NRZ

PAM4

Flex Apps:

FlexDCA

Command Syntax

:MEASure:JITTer:FOVer2

Query Syntax

:MEASure:JITTer:FOVer2

Description

For NRZ measurements, returns the F/2 jitter (J_(F/2)) (also known as even-odd jitter (J_(even-odd)) measurement and moves the measurement to the top of the Jitter table. Displays the measurement if it is not already shown on the table. The query form of the command returns the measured value. To selects the eye in the PAM4 eye diagram on which to return the measurement, use the :MEASURE:JITTer:FOVer2:EYE command.

This command measures F/2 jitter which occurs as the result of timing data with a half-rate clock. If the clock is asymmetric then even symbols versus odd symbols will differ in length from nominal. F/2 jitter is measured as the absolute value of the difference between the even and odd symbols in seconds as a peak-to-peak value:

J_(F/2)) = | (bit_period_even − symbol_period_odd) / 2 |

The following figure shows an eye diagram in which blue and orange colors identify the portions of an eye that are created with the signal's even or odd symbols. This is one signal; the colors do not represent different scope channels. The eyes, formed by the even and odd symbol periods, are overlayed on top of each other with example symbol periods of 90 ps and 110 ps. In this example, the F/2 jitter measures 10 ps.

PAM4 Waveform?

For PAM4 waveforms, use this recommended (identical algorithm) command instead:

:MEASure:PEYE:FOVer2

This measurement is only available in Jitter Mode. When measuring a simulated waveform, the pattern length in pattern lock setup must be set to an even number by doubling the pattern length setting in the simulator. On real signals the user must be responsible for assuring that the pattern is consistent with any measurement standard requirements.

NRZ Waveform

This measurement can be made on PAM4 waveforms. See the sidebar in this topic. On PAM4 signals, Eye 0, Eye 1, or Eye 2 can be specified. The measurement results are moved to the top of the Jitter table.

PAM4 Waveform

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:FOVer2:STATus?')):
	measurement = Flex.query(':MEASure:JITTer:FOVer2?')

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:FOVer2:COUNt?). The technique uses the :COUNt? common measurement query. For example,

if (Flex.query(':MEASure:JITTer:FOVer2:COUNt?') >= Flex.query(':ACQuire:ECOUNt?')):
	measurement = Flex.query(':MEASure:JITTer:FOVer2?')

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?.

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:FOVer2:

flex.write(':MEASure:JITTer:FOVer2:SOURce CHAN1A')
if flex.query(':MEASure:JITTer:FOVer2:STATus?') == 'CORR';
    measurement = flex.query(':MEASure:JITTer:FOVer2?')
else:
	details = flex.query(':MEASure:JITTer:FOVer2:STATus:DETails?')
	reason = flex.query(':MEASure:JITTer:FOVer2:STATus:REASon?')

Child commands for measurement identification:

:MEASure:JITTer:FOVer2:SOURce

Requires FlexDCA revision A.04.50 and above.