Forum Discussion
Occasional Contributorset_max_skew giving path not found warning
Hello,
I have a set of signals passing between asynchronous clock domains in an spi slave module.
I get the following warning when i try to add the max skew constraint
Warning (332182): No path is found satisfying assignment "set_max_skew -from [get_keepers {*spi*shift_reg*}] -to [get_keepers {*spi*rx_data_reg*}] -get_skew_value_from_clock_period min_clock_period -skew_value_multiplier 0.800 ". This assignment will be ignored.
The exact command from the sdc file is also included
set_max_skew -from [get_keepers {*spi*shift_reg*}] -to [get_keepers {*spi*rx_data_reg*}] -get_skew_value_from_clock_period min_clock_period -skew_value_multiplier 0.8
Thanks
Jay
Hey,
I have the exact same problem. https://community.intel.com/t5/Intel-Quartus-Prime-Software/Crossing-Clock-Domain-Problems-Timing-Analyser-ignores-set-max/td-p/1308590 .
However it works during the place and route and also the designs output is correct. I can not detect any metastability.Am I right assuming that this error just occurs while using the Timing Analyser and no error is thrown during compilation?
Sadly I also got no answer as do other people with the same question (looking through the forum it gets asked at least once a week I would say).
Best regard
Christian
13 Replies
SyafieqSSuper Contributor
Hi Jaya,
You might need to see below KDB which affect 20.4 and prior Quartus user. This may affect the source destination when trying to set the skew of your constraint. Can you try instead of specify get_value_from_clock_period dst_clock_period -value_multiplier 0.8, you put the value straight away but this time applied to set_max_skew constraint and see if it applicable. The reason is set net delay are able to work for above KDB when specify the value directly.
https://www.intel.com/content/www/us/en/support/programmable/articles/000085880.html
JoseTdeSousaNew Contributor
I had a similar issue: it happens in Standard Edition 18.1 -- 20.1, but does not happen in Quartus Pro 22.2
set_clock_groups -asynchronous *does* impact set_max_skew on Standard 18.1-20.1 but not on Pro 22.2
