07-22-2009 12:58 AM
i have made a simple ADR,and done the post_simulation in modelsim.but the result is indeterminate state.
and i found there was a warning when i execute "generate post_map simulation model" in ise.the warning is :
"NCD is not completely routed, some delays may be inaccurate".
so how can i do with the warning?can it be the reason of the wrong result of post_simulation in modelsim?
07-22-2009 06:11 AM
I think you always get this warning with post-map simulation. Basically it says your timing
won't be as accurate as a post P&R simulation. If your behavioral simulation was running
properly, you may have some timing problems, including possibly setup or hold violations
due to testbench timing.
07-22-2009 06:31 PM
do you mean it's may be the problem of my testbench ? sorry it's the first time for me to do the post_time simulation ,i have much thing to learn.
thank you for your help ! :)
07-23-2009 05:57 AM
It's possible for a testbench to work with behavioral simulation but not with timing
simulation. For example if you have synchronous inputs to the unit under test
and the test bench changes them one "delta" after the rising clock edge, the
behavioral simulation will always capture these signals properly, however a timing
simulation may require some non-zero amount of hold time and the "delta"
really represents zero hold time. Setup and hold violations should show up as
warning messages during simulation.
Theoretically if you have constrained all paths in your design (this is a rare case)
and have met timing constraints, the timing simulation should match the behavioral
simulation IF the test bench timing conforms to the constraints as well.