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Lost and Found: Missing Filler Cells, Power Vias, and Highlighted Objects

Comments(2)Filed under: Digital Implementation, "SoC-Encounter", 8.1, filler cells, power vias, highlighted objects, checkFiller, F9, verifyPowerVia

Have you ever gotten to signoff DRC and found that there was a small area where a filler cell did not get placed for some reason? Well, now there's an easy way to check for that with the checkFiller command:
    
    checkFiller -highlight true

   

To get rid of the highlights, do this:

    checkFiller -clearHighlight true

Another thing that is often found near the end of the design flow is missing power vias. You may have an IR-drop issue that leads you to discover this, or you may find it by visual inspection. In the old days, before taping out a chip we would turn on just two layers at a time, and the via layer between them, and visually check the whole power grid to make sure there were vias at every intersection. Now, you can easily check this anytime with verifyPowerVia:

    verifyPowerVia

   

After running the command, you'll see the violation marker in your design, and you'll also get a report that looks like this:

###############################################################
#  Generated by:      Cadence First Encounter 08.10-s273_1
#  OS:                Linux x86_64(Host ID crvclo16)
#  Generated on:      Thu Aug 27 14:49:51 2009
#  Command:           verifyPowerVia
###############################################################
Verify Power Via report created on Thu Aug 27 14:49:51 2009

Net VDD: Missing via at (414.280, 621.190) (422.280, 629.190) between layers: M5 and  M6.

Begin Summary
    Missing 1 Via(s) between Layers: M5 and M6.
    1 total info(s) created.
End Summary


You can narrow down which layers you want to check with the -layerRange parameter.


Finally, sometimes in large designs, or when you have a lot of things displayed in the GUI, it can be hard to find one small thing that you've highlighted either in the design browser or with a script. You know it's highlighted, but you still can't see it! To make it easier to find, you can hit the F9 key to dim everything but the highlighted object. There are two levels of dimming, and the third press of F9 returns the GUI to normal. Here's an example of how it looks:

Much easier to spot!


I hope these things will help you find the missing pieces of your design.

Comments(2)

By Mani.G on October 5, 2009
Very helpful commands, indeed. We are going to update our signoff scripts with these commands.

By Kari on October 19, 2009
Hi Mani, Glad you found these useful! You're right, these commands are a great part of any signoff script. I would recommend running them at least once earlier in the flow as well, so if you do have to fix something, it doesn't hold up your tapeout.

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