| FORUM

FEDEVEL
Platform forum

Advanced PCB Layout Course - Lesson 4 - Max Uncoupled Length

milos.stankovic , 10-07-2018, 11:02 AM
Hi,
I am not sure should I post questions on this Forum regarding Advanced PCB Layout Course, Lesson 4 or not. Anyway, my question is:
When setting up Rules for DIFF90 and DIFF100 differential pairs, we set up Max Uncoupled length to 0 mils. Also, in Preferences we set up that this be reported as en error.
My problem is that it doesn't happen. I made on purpose distance between DRAM_CLK0_P and DRAM_CLK0_N to be 0.14 mm instead of 0.16 mm and DRC reports nothing (this is activity shown around 33th minute of Lesson 4). I use AD17.

Best regards,
Milos
robertferanec , 10-08-2018, 06:54 AM
It is sometimes stuck. Try run DRC again, or switch OFF and ON Altium. It should work. Let me know then.
milos.stankovic , 10-08-2018, 07:37 AM
I tried same file iMX6_Rex in AD16, AD17 and AD18. It works only in AD18. I tried one of my designs in AD17 and AD18 and it works only in AD18. I attached settings in AD17. In AD18 if I check only Violation Details it still works.

Regards,
Milos
robertferanec , 10-08-2018, 07:53 AM
Hmm, I know, that it has happened to me couple of times (the uncoupled length error was not visible), but I always tried to change something and then it worked. But I do not really remember what made it work
milos.stankovic , 10-08-2018, 07:57 AM
Ok

Regards,
Milos
milos.stankovic , 01-13-2019, 04:06 AM
Hi Robert,
I think I found out what is the reason for AD17 not reporting max uncoupled length when routing differential pairs.
On the pictures are shown Design Rules for diff pairs. When I make a distance between P an N wire bigger on purpose and then run DRC, no mistake is reported. I then open Design Rules and just change the priority order of DIFF100 and DIFF90 routing rules. When I close Design Rules on-line DRC is being run again (I guess because I made a change in DR) and white color is then present on the place of uncoupled length.
In AD18 everything worked ok.

Best regards,
Milos
robertferanec , 01-14-2019, 01:49 AM
Thank you @milos.stankovic for sharing this
Comments:
milos.stankovic, 01-14-2019, 04:58 AM
Priority of rules DIFF100 and DIFF90 is not important. It is important to swap them, to make a change in Design Rules so that online DRC is run again. Only than max uncoupled length works in AD17. In AD18 there is no problem with this feature.Regards,Milos
Use our interactive Discord forum to reply or ask new questions.
Discord invite
Discord forum link (after invitation)

Didn't find what you were looking for?