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Five-Minute Tutorial: Fixing SI Victim Nets

Comments(9)Filed under: Digital Implementation, encounter, SI analysis, signal integrity, SI, EDI, five minute, NanoRoute, SI victim nets, victim nets

It's hard to believe there was a time when we didn't even run signal integrity analysis. It wasn't always a necessity at the larger nodes of several years ago, but it's absolutely essential in today's processes. So I'm sure every one of you out there has battled SI violations at some point. Today's tutorial will show you a quick and easy way to reroute some victim nets in EDI and get some of your SI issues under control.

Let's say you've run your SI analysis in EDI and you know that your violations are due to some victim nets that need to be rerouted away from aggressor nets. (How do you know this? You've either looked at the failing paths graphically and can see the long parallel runs of nets, or you've done a report_timing -net with the incremental delay column displayed, and you can see that the incremental delay is occurring on the net and not a cell.)

Once we know the names of the nets we want to fix, the rest is easy. For this example, imagine that nets named "net1" and "net2" are falling victim and contributing a large amount of incremental delay. So first we'll attach the "si_post_route_fix" attribute to these nets:

    setAttribute -net net1 -si_post_route_fix true
    setAttribute -net net2 -si_post_route_fix true

Next, we'll tell NanoRoute that we want to run in SIPostRouteFix mode:

    setNanoRouteMode -routeWithSiPostRouteFix true

If you have any other setNanoRouteMode variables that you always use, such as a max layer or double-cut via settings, go ahead and set those as well. Finally, we do the actual routing fix:

    globalDetailRoute

The nets in question (net1 and net2) will be rerouted so that they are not so parallel with other nets, thereby lessening the SI effect on them. You can re-extract and run timing again to see the improvement. I've had very good success with this method. It may not solve all of your SI problems, and there may be several issues causing any one path to fail SI timing, but this method should definitely be in your toolbox of SI fixes.

Bonus: I mentioned the "incremental delay" column in the timing report. How do you get that to show up? Add the incr_delay keyword to your report_timing format, as in this example:

    set_global report_timing_format {instance cell arc delay incr_delay arrival load slew fanout pin_location}

- Kari Summers

Comments(9)

By paramjeet on May 20, 2011
i ll be thank ful to u...

By raj7783 on May 26, 2011
Thank You Kari, i tried these options in my design and observed the change in routing of the victim net. It has done very good job, improved my slack. Thanks again :-)

By Kari on May 26, 2011
Hi Paramjeet and Raj7783 - I'm so glad you've found this post useful! Thank you for reading our blogs and joining the conversation.

By KarelH on January 5, 2012
But, don't forget to switch off setAttribute for already SI fixed nets.
Because, they could be rerouted in next eco or routing itteration.

By Kari on January 5, 2012
Hi KarelH, That's a great point! Thanks for commenting!

By ttran0671 on January 6, 2012
Hi Kari,

  I'm new to this forum, I'm a new user to EDI, I used Cadence SOCE 5 years ago in 2007 and have not used it since then, I worked with some Cadence AE in the past (Alex Kuo, etc) and I'm not sure if he's with the company or not.  Anyway, I'm trying to get some training material to learn EDI and it'd be great if you could send me some soft copy material in PDF.

As I said, I'm familiar with SOCE in the past but dont know how much difference between SOCE and EDI.


By Kari on January 9, 2012
Hi ttran, try the following Cadence Online Support solution, it should get you started: (you may need to cut and paste the URL into your browser, intead of clicking the link, which doesn't seem to be working for me)

http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:DocumentViewer;src=wp;q=Training/Digital_IC_Design/EDI101_Tutorial.html


By Jerin on February 1, 2012
after that should we do ecoRoute or globalDetailRoute


By Kari on February 2, 2012
Hi Jerin,
Take another look at the post - you'll see that I have a call to globalDetailRoute.

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