advance simulation time without running

[anupam.jain21]

How can i stop a simulation and then advance the simulation time
without running my simulations and then re run the simulation from the
advanced value ?

regards,
Anupam Jain

 

[backhus]

How can i stop a simulation and then advance the simulation time
without running my simulations and then re run the simulation from the
advanced value ?

regards,
Anupam Jain

Hi Anupam,
easy answer: You can't!

Because most circuits have an unpredictable behavior, and change
internal states with each clock.

And if you have a simpler circuit that either has nothing like a clock,
or idles in its states, then why would you want to skip over some
simulation time? Just continue with your testbench after the simulation
arrives in the idle state.

have a nice simulation

Eilert

 

[HT-Lab]

How can i stop a simulation and then advance the simulation time
without running my simulations and then re run the simulation from the
advanced value ?

regards,
Anupam Jain

As Eilert already mentioned, you can't. However, Modelsim SE/Questa has a
feature called Checkpoint & Restore (VCS/Aldec/NC-Sim/ probably have
something similar) . This feature enables you to save your simulation result
and restart at that point at a later time, perhaps this can help you out?

Hans
www.ht-lab.com

 

[anupam.jain21]

As Eilert already mentioned, you can't. However, Modelsim SE/Questa has a
feature called Checkpoint & Restore (VCS/Aldec/NC-Sim/ probably have
something similar) . This feature enables you to save your simulation result
and restart at that point at a later time, perhaps this can help you out?

Hanswww.ht-lab.com

Ok ..bad luck there...
I just wanted to dump the values at a time and then advance the
simulation time(when i know there is no major activity going on) and
then re run the simulation form the advanced time in order to save
some simulation time.

The saving and restoring feature won't help as each test case is
totally different.

Anyway... thanks



regards,
Anupam Jain

 

[Jonathan Bromley]

I just wanted to dump the values at a time and then advance the
simulation time(when i know there is no major activity going on) and
then re run the simulation form the advanced time in order to save
some simulation time.

Oh dear... very strange assumptions here!

If there is truly *no* activity, then advancing simulation time
is FREE and consumes essentially no simulator CPU! VHDL simulation
is event-driven. If there is no scheduled activity for the
next (let's say) 1us of simulated time, then the only thing the
simulator needs to do is to add 1us to the current time (NOW) and
then do whatever the next scheduled event may be. All the
simulation activity takes place in delta cycles; making time
progress costs nothing.

On the other hand, as others have pointed out, if there is *any*
activity then you *must* simulate it because you can't predict
what its effects are going to be.

If you are so sure about the state of the system after your long
period of time, then why not use the simulator's command-line
"force" command to put the entire sim into that state and then
re-start simulation? The absolute value of simulated time will
be wrong, but otherwise everything will be set up the way you
want it. Personally, though, I wouldn't trust myself to be
able to force the sim into a future state with sufficient
accuracy.
--
Jonathan Bromley, Consultant

DOULOS - Developing Design Know-how
VHDL * Verilog * SystemC * e * Perl * Tcl/Tk * Project Services

Doulos Ltd., 22 Market Place, Ringwood, BH24 1AW, UK
(e-mail address removed)
http://www.MYCOMPANY.com

The contents of this message may contain personal views which
are not the views of Doulos Ltd., unless specifically stated.

 

[HT-Lab]

Ok ..bad luck there...
I just wanted to dump the values at a time and then advance the
simulation time(when i know there is no major activity going on) and
then re run the simulation form the advanced time in order to save
some simulation time.

Not sure what simulator you are using but what you can do is to turn the
logging off (log/nolog command in Modelsim) during the "non-interesting"
period. Depending on how many signals you log this might save you a bit of
time.

As Jonathan just mentioned you could use the force command but this is very
tricky. If you want to go down this route I would suggest you investigate
doing this automatically. I have never tried this but what might work is if
you log all your signals, then export them to a textfile (e.g. in Modelsim
using the list window) and then create a massive force file from this
textfile using a bit of Tcl. As I mentioned I have never tried this so your
mileage may vary as they say

Hans.

www.ht-lab.com

 

[anupam.jain21]

Not sure what simulator you are using but what you can do is to turn the
logging off (log/nolog command in Modelsim) during the "non-interesting"
period. Depending on how many signals you log this might save you a bit of
time.

As Jonathan just mentioned you could use the force command but this is very
tricky. If you want to go down this route I would suggest you investigate
doing this automatically. I have never tried this but what might work is if
you log all your signals, then export them to a textfile (e.g. in Modelsim
using the list window) and then create a massive force file from this
textfile using a bit of Tcl. As I mentioned I have never tried this so your
mileage may vary as they say

Hans.

www.ht-lab.com

Thank you for all those quick responses...
I used "force" and i think this is what i wanted...

regards,
Anupam Jain