Delay problem

[yein]

I wonder why i use the clause like:
a<=b after 10 ns
there is no effect in the timing simulation.
why does it like this?
Is there any differences in the waveform if using the functional or timing simulation with above clause?
I am using quartus 2 web edition.

Thanks in advance..

 

[bonami172]

Hi,
I think this clause only work in functionnal simulation. The timing simulation will be done after the synthesis of your design but the synthesis don't support any assignment with "after ...

 

[jeandelfrigo]

Hi,


Bonami172 is correct.

after, wait for and other time related statements cannot be synthesized, they are purely for simulation.

When performing timing simulations your code needs to be synthesized, mapped, placed and routed, so that the complete component timing info is known and can be used by the simulator.

You can still use the statements in your testbench though.

A little tip try to write your code in a decent way and try to constrain it well, so that you meet timing with sufficient margin.

You do not want to completely timing simulate a complex design if you can avoid it, trust me on this.

regards

jeandelfrigo