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Plotting disconnected marker lines (mask) on an eye diagram

Ivars

Hi,

Prior to Virtuoso 6.1.7, I was able to add disconnected lines to an eye diagram by creating a waveform which contained a special "invalid" y-value of -2e+37 at the point where I wanted to break the line. I found this trick in a post to this forum by Andrew Beckett.

An example of the X and Y vectors used to create a set of marker lines is (I've tried to uses spaces to align the x and y values) is:

X: (0.0       0.0             3.571429e-11 3.571429e-11 3.571429e-11 7.142857e-11 7.142857e-11 7.142857e-11 7.5e-11      1.071429e-10)

y:(-2e+37 4.810022 4.810022         -2e+37              1.738277        1.738277         -2e+37               2.870995         2.870995 -2e+37)

Each section between the -2e+37 values marks a separate line segment. This sequence creates 3 separate marker lines. Two that span the whole eye diagram to mark the high/low signal levels and one that is only a short stub on one side to mark the crossing point).

After moving to 6.1.7, the special invalid y-value no longer appears to work. The three lines are plotted but a vertical line appears along the plot edge that  descend to -2e37 (luckily the y axis range in unaffected by this value). The three line segments are no longer disconnected.


Version 6.1.7 does add a new eye mask function that could be used to replace some of my function's functionality (I use the same technique to create an eye mask) does not allow things such as marker lines to be added..


Any suggestions of how I can create a waveform with disconnected line segments that can be plotted using eyeDiagram?


An example of an (ugly) eye diagram with the marker lines (green) superimposed is shown below. (this is the 6.1.7 version). (As a side note, the "Dotted" lineStyle also appears broken in 6.1.7.8, at least for eye diagrams, causing Viva to hang.)


Thanks.

Ivars

  • After some more experimentation, I discovered that using a value of -2e999 (which evaluates to -Inf) will allow me to plot, in Version 6.1.7, disconnected line segments on an eyeDiagram. The same value also works in 6.1.6, so everything is good.

    An example eyediagram (plotted in 6.1.7) is shown below. I use the disconnected line segments to create the mask (dark blue), the mask margin (light blue), and the high/low/crossing point marker lines (green).

    Non-solid line styles still appears broken in 6.1.7, otherwise the mask margin line would have been plotted as a dashed line. Trying to set the line style to a non-solid option causes Viva to hang.



    Ivars

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