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19984 Discussions

set_net_delay overwrite

Honored Contributor II



I am using the avalon_st_clock_crosser IP in my Design which has a net_delay constraint of 2ns. 

This is defined in the .../ip/altera/avalon_st/altera_avalon_st_handshake_clock_crosser folder. 


Unfortunately this constraint can't be met in all cases by some few ten pico seconds, which is not really a problem itself. 


I would like to modify the existing constrain (within my design) to get rid of the violation messages. 


Other timing exceptions like set_max_delay or set_max_skew have a precedence that the last assignments overwrite earlier assignments. 


"set_net_delay" seems to behave different. 

set_net_delay -from X -to Y 2.001 set_net_delay -from X -to Y 2.002 set_net_delay -from X -to Y 2.003  


.. results in having three additional timing violations instead of having only the one with the last setting. 


Some (partially ugly) workarounds i thought of: 

  • changing the IP in the intel component folder  

  • copying the IP to my Project folder, change the IP there,  

  • disable automatic test of net delay violations and live with the violations with the risk of overlook some real violation, additional effort in manual verification  



Is there a way to overwrite set_net_delay constraints that i am missing? 



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