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j

Jean

11/29/2020, 10:18 PM
[WARNING] FastRoute cannot handle net user_clock2 due to large number of pins [WARNING] Net user_clock2 has 37130 pins It's a clock... It goes everywhere! Should I be concerned with this warning?
a

Anish

11/29/2020, 10:19 PM
you might need to mark the clock as a clock in the config so that it's properly treated as a clock tree
t

tnt

11/29/2020, 10:20 PM
The fact it can't distribute your clock ? Yeah, I'd be concerned.
j

Jean

11/29/2020, 10:20 PM
It is already marked as a clock!
t

tnt

11/29/2020, 10:20 PM
Apparently not. But as I told you I'm not sure multi clock works ...
at least not without custom script.
j

Jean

11/29/2020, 10:24 PM
Hmm.. The caravel SOC provides 2 clocks to for the user project.
t

tnt

11/29/2020, 10:25 PM
yeah, for you to pick one ...
j

Jean

11/29/2020, 10:25 PM
You'd need two clock tree generations.
t

tnt

11/29/2020, 10:25 PM
I mean, you can also work out how to support multiple, but from what I've seen here, it's not "out of the box" ATM so if you want that ,you need to work it out.
yes exactly you need two clock tree which isn't supported (AFAIK) by the default flow script so you need to write your own.
j

Jean

11/29/2020, 10:28 PM
Also, would STA handle asynchronous clocks?
t

tnt

11/29/2020, 10:30 PM
you'd need custom constraint files to define relationships between clock or maximum delays, etc etc ... AFAIK OpenSTA supports analyzing those path but it's all up to you to call it correctly, I don't thin kanything in OpenLANE supports that.
j

Jean

11/29/2020, 10:36 PM
Ok, I can handle the custom .sdc if I ever get to a 2 clock flow.
By switching CLOCK_NET to clock_user2 I can get to detailed routing.