RE: [sv-bc] Verilog Std Ambiguity

From: Steven Sharp <sharp_at_.....>
Date: Thu Oct 15 2009 - 15:25:01 PDT
>From: "Bresticker, Shalom" <shalom.bresticker@intel.com>

>Another and logical alternative would have been to calculate the delay on each 
bit of the vector separately, as in a parallel connection module path in a 
specify block.


This would certainly be the most realistic alternative.  The difference in
rise/fall delay that is being modeled is dependent on the high/low drive
characteristics of the driver on that bit.  Selecting the delay based on
the value of any other bit is unrealistic, whether it is based on the LSB
or the reduction-OR of all the bits.  (While there may be some effects
of one driver on another, such as extra delays for simultaneous switching,
those are secondary effects that are more complex than these delays are
trying to model).

The problem is that it would effectively require the vector net to be
expanded or "scalared", so that the individual bits could be scheduled
independently at different times.  That would have a significant cost in
simulation performance.  I presume that is why it was not done that way.


Steven Sharp
sharp@cadence.com


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Received on Thu Oct 15 15:25:52 2009

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