Oscilloscope Reference Serial mask testing with mask testing
Segments and mask hits
Each mask can have a maximum of 16 s egments. Segments can overlap. The number of mask hits is the
sum o f all hits in all segments, regardless of whether or not segments overlap. For example, if a waveform
crosses over an area where two segments overlap, both segments will count the waveform hit.
Vertices
Each segment ca n have a maximum of 50 vertice s. Vertices are numbered counterclockwise, with vertex
one generally located at the bottom left of each segment.Theactive(selected)vertexisindicatedbyanX.
The instrument automatically assigns numbers to vertices during mask creation or editing.
Mask margin tolerance
Mask margin tolerance moves the mask segment boundaries by the specified percentage. Negative margins
reduce the size of the segment, making it easier to pass a mask test. Positive numbers make it harder to
pass and allow you to perform margin testing on your design. If a user definedmaskhasmorethanthree
segments, turning on mask margins generates an error mes sage. Turning mas k margin tolerance off
redraws the mask segment margins to their default values, but leaves the nume ric value as i t is, allowing
you to quickly toggle between d efault and user-set margin values.
Standards and bandwidth
When the instrument system bandwidth (which includes the instrument, attached probes, and/or cabling)
falls into the range of 1.5 to 1.8 (0.8 for optical signals) times the data signal bit rate, the third harmonic
of the data signal is significantly attenuated. The instrument displays useful qualitative information, but
quantitative rise-time measurements under these conditions may not be accurate.
For example, a FC531E Elec mask has a bit rate of 531.25 Mb/s; 1.5 to 1.8 times this value is a range
of 796.5 MHzBW to 955.8 MHzBW. Therefore, you should not use an instrument with less than 1 GHz
measurement system for making quantitative rise-time measurements of this standard.
When just the instrument bandwidth falls within 1.5–1.8 (0.8 for optical signals) times the bit rate of a
selected mask standard, the instrument displays the message "Consider system bandwidth when testing at
this bit rate." in the status area above the graticule.
What do you want to do next?
Learn more about eye measurements. (see page 784)
Le
arn a bout communication triggering.
(see page 704)
Go to mask testing setup overview. (see page 209)
Serial mask testing with mask testing
The Serial Mask Testing option (see page 209) provides electrical mask testing on communication
standards and communication triggering.
782 DSA/DPO70000D, MSO/DPO/DSA70000C, DPO7000C, and MSO/DPO5000 Series
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