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When I Measure the length of net, the total measure consider the via lenght?

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Message 1 of 6
abraham94CTR
374 Views, 5 Replies

When I Measure the length of net, the total measure consider the via lenght?

Hello Everyone 😀

I routing a eMMC in Eagle so I need to make a length match for the interface, My question is, if the result of the measurement made by ULP length-freq-ri consider the via length.

Regards

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Message 2 of 6

This is something we should expect to find in the documentation for the software.

In the meantime. As long as you route with the same topology on all nets, use the same layer sets on all signals, it shouldn’t matter. Unless of course if you need the absolute length.

Message 3 of 6

Hi @abraham94CTR ,

 

I hope you're doing well. There's more to consider here, a via doesn't just add length it also changes the impedance so you have to be careful in using them with diff-pairs for example. The length-freq-ri.ulp was made by a user so I'm not sure if it take it into account or not but my guess would be no since a via introduce more complex behaviors in the signal path.

 

Rule of thumb, if you place a via on one member of a pair or bus you are better off doing it to all of them and then matching lengths from there. This is basically what @erik.buerV95QJ  said.

 

Hope this helps, let me know if there's anything else I can do for you.

 

Best Regards,

 

You can use the meander command to equalize lengths and that's what I would recommend to use in this scenario.

 

Best Regards,



Jorge Garcia
​Product Support Specialist for Fusion 360 and EAGLE

Kudos are much appreciated if the information I have shared is helpful to you and/or others.

Did this resolve your issue? Please accept it "As a Solution" so others may benefit from it.
Message 4 of 6

Hellow @erik.buerV95QJ 

 

Yeah I assumed the same, but I consider that the documentation isn't most clear and I think that meander doesn't work well without differencial pairs.

But I only have this like a good practice, because the eMMC doesn't work in HS mode.

Thanks for you comments!

Message 5 of 6

Thanks for your comments @jorge.garcia

I used the meander for the match length of eMMC signals, I use this post like a reference https://www.autodesk.com/products/eagle/blog/length-match-high-speed-nets/

However it isn't so clear for non differencial pairs and doesn't consider that the meander doesn't measure all the net length and I had to deal with it for a while without knowing.

And I hope that this tool improves in the next versions.

Best Regards!
Message 6 of 6

Hi @abraham94CTR ,

 

I hope you're doing well. The Meander command will measure the length of any trace between two pads, so you can use it to make a single ended trace. If you use it on net like GND, it will only measure the specific ground connection between the nearest two pads it connects. It won't measure the length of all of the GND traces.

 

Let me know if there's anything else I can do for you.

 

Best Regards,



Jorge Garcia
​Product Support Specialist for Fusion 360 and EAGLE

Kudos are much appreciated if the information I have shared is helpful to you and/or others.

Did this resolve your issue? Please accept it "As a Solution" so others may benefit from it.

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