[SI-LIST] Re: flight time and propagation delay in Hspice
- From: Steve Horne <sch@xxxxxxxxxxxxxx>
- To: a.ingraham@xxxxxxxx
- Date: Thu, 4 Dec 2003 12:33:31 -0600
Actually, HSPICE and Smartspice (and, undoubtedly, other SPICE
tools) are both quite capable of making relative timing
measurements (prOpagation delays, rise times, etc.). You would
need to include the reference circuit in the simulation or,
alternativelym, write a script to compare delays from two
different SPICE runs.
Steve
Ingraham, Andrew writes:
> My recollection of the .measure function in (H)Spice, is that it simply
> lists the signal-crossings (at some threshold voltage of your choosing)
> relative to the simulation time. By itself, it doesn't even show you simple
> delay, though you can use it to show signal crossings at two points in the
> circuit and then compare them with one another, which would give you the
> apparent signal delay from point A to point B.
>
> In Spice (as opposed to some more advanced tools that may or may not be
> based on the Spice engine), if you want a delay that is expressed with
> respect to a reference test load, then you need to set up a simulation with
> that test load, and make the subtraction yourself. Spice won't do it for
> you.
>
> Re: doing the test load simulation just once ... actually, it's once per set
> of process and environmental conditions (temperature, supply voltage, driver
> model). You just don't need to repeat it every time you do a simulation
> with those same conditions.
>
> Regards,
> Andy
>
>
> > one question regarding to flight time and propagation delay when using
> > Hspice simulation, In most GUI simulation tool such as candence
> > specctraquest, there's a test load as a reference to measure "flight time"
> > while in Hspice ,there's meas. syntax provied for us to measure
> > propagation
> > delay, I wonder if this propagation delay is as same as the fligth time we
> > measure in GUI tools(specctraquest)???
> > or.. we still need to add test load circuit into Hspice netlist for
> > simulate
> > the "flight time"??
> > anyone who please could enlighten me on this issue. thanks a lot!
>
>
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