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[SDF]Delay Calculation

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maulin sheth

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Hello All,

I have doubt for SDF file.
Suppose I have an 2 input AND gate.
Now in SDF file,For this cell :

Two calculation are given : 1) A input to Output Z and
2) B input to Output Z.

So what is the actual delay of And Gate : means It is that which one is maximum from A to Z or B to Z?

Thanks in advance.
 

Depending on the input pattern, one or both paths from input to output can get excited. For example, if B input stays at 1, and A input change from 0 to 1, then Z changes from 0 to 1. In this case the A to Z path is chosen. If both A and B change from 0 to 1, then both paths are chosen and i think the worst path (please double check this) from input to output is the actual delay of the and gate.

You can simulate with SDF annotation to see what happens when both inputs change from 0 to 1.

Other senior members can correct me if i am wrong.
 

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