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What's Good About Eye Masks in PCB SI? You'll Need SPB16.2 to See!

Comments(3)Filed under: PCB design, SPB 16.2, Allegroro, Signal Intregrity, SigWave

Eye masks let you specify the acceptable parameters for what an eye should look like in order to extract clock transmissions and high-speed data to buffer models. The current method of creating and saving eye masks is tedious. SigWave  has been enhanced to allow you to create eye masks that you can save in .sim files and view/edit when you display the waveform in Eye Diagram mode.

One current use model for creating eye masks is to recreate an eye mask by redrawing it in an open waveform file. This is very repetitive and prone to errors, and it defeats the purpose of saving a .sww file.

Another use model is to import a waveform into an existing .sww file which contains a mask. This requires saving the waveform, exiting the current file, opening the mask file and importing the saved waveforms. This is both tedious and counterintuitive and requires many steps.

To support easier use of new or existing eye masks, the following features have been added:

  • Ability to import existing eye masks into open waveform files
  • A new GUI to facilitate eye mask creation and modification

Using Eye Masks

Eye masks that you create in a simulation file reside at the root of the waveform library. These “root-level” eye masks are linked to the waveforms they are attached to.



You can attach the same root-level eye mask to multiple waveforms. If you delete linked eye masks from a waveform, the root-level eye mask remains; however, if you delete the root-level eye mask, all iterations of the linked eye masks will also be deleted.

You can attach only a single eye mask to a waveform; if you attempt to attach a second eye mask to a waveform, the second eye mask replaces the first.

Creating and/or Loading an Eye Mask

You create a new eye mask or load an existing one into SigWave by way of the Eye Mask toolbar icon , or by selecting a waveform and clicking the right mouse button to display the context pop-up menu. 


When you launch the Load/Create Eye Mask dialog box from the toolbar icon, the mask you create attaches itself to the waveform library of your .sim file, not to an individual waveform. You can attach an eye mask residing in the waveform library to an individual waveform by highlighting a waveform and selecting the Attach Eye Mask option from the right-button popup menu. You can then choose an eye mask from a list of the eye masks in the .sim file. 



Eye mask configurations can be either hexagonal or octagonal. You select the appropriate configuration from the Load/Create Eye Mask dialog box.



The Create button allows you to save the eye mask. When this button is selected you will be prompted to enter an eye mask name.

When you load an existing eye mask from the eye mask library, you can edit all the parameter settings except the hexagon/octagon eye mask type. The control fields in the dialog box let you specify the eye mask point values in the vertical (time) and horizontal (voltage) dimensions. You can also offset the eye mask by specifying time and voltage values. Time measurement units are selectable in picoseconds (ps), nanoseconds, (ns) and unit intervals (UI). Voltage measurement units are selectable in volts (v) and millivolts (mv).

Note: The parameter settings in the dialog box are dynamic; that is, if you move the eye mask with your cursor to another point in the waveform, the settings in the dialog box will have changed to reflect the new position when you reopen it.  

Editing an Eye Mask

You can edit an existing eye mask through the use of the Edit Eye Mask toolbar icon or by right-clicking on a selected eye mask to display the context sensitive pop-up menu. 



Either operation opens the Edit Eye Mask dialog box.



You can change the display of the eye mask through the right-button pop-up menu. The options on the pop-up menu let you:

  • Change the color of the eye mask outline
  • Display/hide the eye mask
  • Re-name the eye mask
  • Export the eye mask data to a .sim file or a DML file
  • Delete the eye mask


As always, I welcome your suggestions and experience in using this new SPB16.2 feature!

Jerry "GenPart" Grzenia


By karthi on June 17, 2011
How to enter the values in eye mask page?

By Jerry GenPart on June 17, 2011
Hi Karthi,
I assume you mean where do the values for the eye mask come from, as opposed to actually entering them into the form.
The values for the eye masks would come from interface specifications and device datasheets.

By Jerry GenPart on June 17, 2011
Hi Karthi,
I assume you mean where do the values for the eye mask come from, as opposed to actually entering them into the form.
The values for the eye masks would come from interface specifications and device datasheets.

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