Re: last_crossing()

Hi Geoffrey,
No, last_crossing() doesn't control the analog timestep. It simply uses 
interpolation to determine where the value crossed. That is why I commonly see 
it used in conjunction with cross() as well, cross will control the time step 
to get the crossing within tolerance, and then last_crossing() will use 
interpolation to get the most accurate crossing time.

Dave


Geoffrey.Coram wrote:
> I thought last_crossing() controlled the timestep in the analog solver
> so that the crossing could be resolved accurately.  Thus, it doesn't
> seem to make sense in a digital context.  If the digital event happens
> a long time after the crossing, the simulator may not be able to
> "back up" to make an accurate measurement.
> 
> Can you make the measurement in the analog domain, and "sample" the
> result when you want it in the event-driven context?  I guess this
> would slow the performance if you don't need the accurate
> measurement most of the time.
> 
> -Geoffrey
> 
> 
> 
> Ken Kundert wrote:
>> All,
>>     Just noticed a deficiency in Verilog-AMS. I went to use
>> last_crossing() to make a very accurate time measurement in an always
>> block, and I could not do it. last_crossing() is only allowed in the
>> analog block. It would be really helpful to also have access to it in
>> the event-driven context.
>>
>> Comments?
>>
>> -Ken
>>
> 

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-- David Miller
-- Design Technology (Austin)
-- Freescale Semiconductor
-- Ph : 512 996-7377 Fax: x7755
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