Command Syntax

:MEASure:EYE:PAM:EWIDth

Query Syntax

:MEASure:EYE:PAM:EWIDth?

Description

The fastest and recommended method of performing an Eye Width measurement on PAM4 waveforms is to use Jitter Mode's :MEASures:PEYE:EWIDth command. Eye mode's :MEASure:EYE:PAM:EWIDth command can be used as a quick comparative check between signals. For example, when tuning pre-emphasis on a transmitter. In the following situations, you may want to use Eye Mode's measurement:

• For longer patterns, such as PRBS31Q, as Eye mode does not require pattern lock.
• When data is random or when measuring multiple waveforms at the same time.

Returns Eye/Mask mode's PAM4 Eye Width measurement. Eye Width measures the horizontal opening for the selected eye of a PAM4 signal. Select the eye measurement to be returned using the :EYE child command. To measure the eye width for all of the eyes on a PAM4 signal, you must send this command once for each eye as there is no command for simultaneously measuring all eyes.

For each eye, the eye width is derived from eye boundaries that are located based on zero data "hits" or at an eye opening probability (:DEFine:EOPening child command). The probability defines the ratio of total hits in a waveform database column that can occur in the eye's opening. The probablility can be set from 1 x 10^–1 to 1 x 10^–9 using the :DEFine:EOPening:PROBability child command. The default probability is 1 x 10^–2. No extrapolation is used to determine Eye Widths at a specified probability.

Specify the measurement units with the :MEASure:PAM:TIME:UNITs 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:EYE:PAM:EWIDth:

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

Child commands for measurement identification:

• :MEASure:EYE:PAM:EWIDth:SOURce
• :MEASure:EYE:PAM:EWIDth:DEFine:EOPening
• :MEASure:EYE:PAM:EWIDth:DEFine:EOPening:PROBability
• :MEASure:EYE:PAM:EWIDth:DEFine:EOPening:RJSTabilize
• :MEASure:EYE:PAM:EWIDth:DEFine:EOPening:RJSValue
• :MEASure:EYE:PAM:EWIDth:DEFine:EOPening:RNSTabilize
• :MEASure:EYE:PAM:EWIDth:DEFine:EOPening:RNSValue:LEVel1
• :MEASure:EYE:PAM:EWIDth:DEFine:EOPening:RNSValue:LEVel0

Related Commands

Command	Equivalent Setting in PAM-N Analysis Setup Dialog Box	Description
:MEASure:PAM:EYE:ESTiming	Receiver Sample Timing	Configures the timing for sampling the signal data for all PAM measurements in Eye/Mask mode.
:MEASure:PAM:EYE:ELMethod	Eye Center Location	Selects the basis for determining the location of an eye's center on the waveform: at maximum eye width or maximum eye height.
:MEASure:PAM:EYE:TIME:UNITs	Time Units	Sets the time units for measurement: seconds or unit intervals.

Example Command Sequence

:MEASure:EYE:PAM:EWIDth:SOURce CHAN1A
:MEASure:PAM:TIME:UNITs SECond
:MEASure:EYE:PAM:EWIDth:DEFine:EOPening ZHITs 
:MEASure:EYE:PAM:EWIDth:EYE EYE2
:MEASure:EYE:PAM:EWIDth
:MEASure:EYE:PAM:EWIDth?