delay measurement with modelsim

[dhanasingaraja]

Hi,

I wanna measure delay of a ripple carry adder from modelsim simulation.program works fine.I can see the output waveforms also.but i can't find any delay between inputs and output even with zoom view also.i have attached my output screenshot


pls..... help me

 

[shaiko]

Of course you can't.
The simulation MODEL is IDEAL with zero delay time.

 

[ljxpjpjljx]

If you don't use SDF back annotate, you won't have any delay between input and output!

 

[dhanasingaraja]

How can i use SDF back annotation in modelsim?

 

[nisshith]

first you need to generate the SDF file, it is a very complicated process.
I suggest you take the gate level design and quantify delays of each gate (like delay of INV1X=1 and model delays of larger gates as multiple of these using the formula d=p+g*h) and calculate the approximate delay.