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Simulators >> Timing Simulators >> increase accuracy for a sub-block in Ultrasim ?
https://designers-guide.org/forum/YaBB.pl?num=1159305433

Message started by richard88 on Sep 26^th, 2006, 2:17pm

Title: increase accuracy for a sub-block in Ultrasim ?
Post by richard88 on Sep 26^th, 2006, 2:17pm

Hi,
I ran a switching regulator simulation but found out one of the schmitt trigger not functioning. increasing the accuracy to from level 5 to 4 works. However the simulation time tremendous slow down. I have another similar circuit using level5 accuracy works well and pretty fast. Is there a way we can increase the accuracy in Ultrasim just for a small sub-block ?

Thanks.
Richard

Title: Re: increase accuracy for a sub-block in Ultrasim
Post by byang on Sep 26^th, 2006, 3:59pm

Hi, Richard,

As I remember, you can add instance name after speed to specify it for that sub-block. There should be explanation in the Ultrasim manual.

However, I think the slowdown may be due to the fact that the sub-block is functioning now and Ultrasim has to take smallter time step. Changing speed from 5 to 4 shouldn't cause such a big slowdown. Are you using sim_mode=ms? Have you tried other simulation mode such as amr or a? How big is the whole circuit (number of transistors)?

Baolin

Title: Re: increase accuracy for a sub-block in Ultrasim
Post by bernd on Sep 27^th, 2006, 2:51am

Quote:

Is there a way we can increase the accuracy in Ultrasim just for a small sub-block ?

You can use the Hierarchy Editor (HED) with a config view to assign
'sim_mode' or 'speed' for UltraSim for every cell or instance,
no mater how small.
Just enable 'View -> Properties' in the HED,
you will get two additional columns for 'sim_mode' or 'speed' in the HED.
And 'Allow usim_opt on HED' form the 'Simulation ->
Options -> Analog' in the Analog Environment (Artist), to get the stuff netlisted.

Bernd

Title: Re: increase accuracy for a sub-block in Ultrasim
Post by richard88 on Sep 27^th, 2006, 3:37am

Thanks,
I checked on the simulation option "allow usim opt on schematics" and then "Q" on properties on the subblock and then "add" the speed string on the query box.
What I found out is that it is slightly faster, not a whole lot.
This test circuit A contains 3 blocks : bandgap and eprom and switching regulator. I have another similar test circuit B but all the 3 blocks (in ctr A) are hier. contained in a big cell. I just do a default option simulation, the sim speed is at least 4X faster (than ctr A) and the schmitt trigger in the oscillator subblock is working. I'm just puzzled by this. For ctr A, if using default sim option, the schmitt trigger would not work but it is fast.

Thanks,
Richard

bernd wrote on Sep 27^th, 2006, 2:51am:

Quote:

Is there a way we can increase the accuracy in Ultrasim just for a small sub-block ?