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L5-SD3 signal length n/a

milos.stankovic , 06-07-2019, 05:31 AM

I am about to finish my L5 activities and I have a problem. I opened activity for Module and I see that signal length for some SD3 signal is n/a. These signals are SD3_CD, SD3_WP and SD3_CMD. I wonder why signal length is n/a for these signals since they all belong to SD_CARD Class. In my project these signals also have n/a for signal length. I would also like to know why none of the SD3 signals is length matched in file for this activity. I was expecting that all of them will have same length.

Best regards,
robertferanec , 06-09-2019, 12:51 PM
- n/a .... it depends, but usually it means, that the signal is not fully routed (sometimes it may show n/a when you need to re-run DRC).
- do you mean activity "Length match the signals of SD3 Interface."? Length matching the signals is your activity, that is why they are not length matched.

PS: I do not have access to Altium right now, but if you can not figure it out, let me know the exact name of the file what you are using and I will have a look.
milos.stankovic , 06-10-2019, 12:57 AM
In Fedevel's activity file is the same situation. All nets are fully routed and there is no DRC errors other than two which have nothing to do with SD3 Interface. Again these three signals are n/a for Signal Length. I used file from following folder: L5 - 01 - Improving Layout - Module.
robertferanec , 06-11-2019, 04:14 AM
I believe, it may be because Altium doesn't know how to calculate length of signals with more than 2 pins. Notice, how node count influences signal length (anything about node count 2 will have signal length n/a)

milos.stankovic , 06-11-2019, 07:40 AM
In that case I will measure signal bit by bit. I will see later whether to length match parts of the track on each layer with one another (that is how I routed one of my boards). I can see that SD3 interface on your activity L5 - 01 - Module is not length matched. Am I right?


robertferanec , 06-12-2019, 12:17 AM
In that case I will measure signal bit by bit.
- if you like, you can also use xSignals: https://www.fedevel.com/welldoneblog...useful-things/

I can see that SD3 interface on your activity L5 - 01 - Module is not length matched. Am I right?
- yes, the activity is to length match the signals
milos.stankovic , 06-12-2019, 08:01 AM
Hi Robert,

Thanks for the answers. I went through your files and I thought that you length matched SD3 interface. In L5-01 SD3 signals are not length matched. Before I start length matching SD3 interface I tried to see how Fedevel did it. I suppose that SD3 signals should be latched in L6-02 activity.

Here is what I measured using Reports-> Measure Selected Objects (table in attachment):

SD3_DATA0..3 and SD3_CMD + SD3_CMD_R have almost same length (2014 mils).
Here are my questions:
1. Why length of series resistors for SD3_CMD (R1) and SD3_CLK (R50) were not taken into account?
2. I noticed that total length of SD3_CLK + SD3_CLK_R is a little bit longer (2112 mils)
3. SD3_CD length is around 1831 mils and SD3_WP length is 1997 mils. Why?
I did not calculate length of stubs leading to pullup resistors R38, R39 and R40.

Now I will try to use xSignals as you suggested.

Best regards,
milos.stankovic , 06-12-2019, 03:39 PM
Hi Robert,

I tried xSignals and it looks really useful. I just need to find a way how to create 45 degrees corners. When I go to Route->Interactive Length Tuning and press tab, I fill the same values that you filled in your video, but I get 90 degrees corners instead of 45 degrees.

milos.stankovic , 06-13-2019, 02:21 PM
One more thing - I cannot edit track after using Route -> Interactive Length Tuning. The only way to do the length matching is to use xSignals to make rectangular wave, then erase it and to it by hand. xSignals in that case serves to show approximate size of wave. I use AD17.
milos.stankovic , 06-13-2019, 03:05 PM
I found it! I just need a little practice. I think I will find the way

This video explains how to setup a Length Matching Rule and do Interactive Length Tuning in Altium Designer.
robertferanec , 06-14-2019, 09:24 AM
Oki, perfect. If you still have any questions, let me know.
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