PSpice sim time

[Active8]

hi:

let's say i have a circuit - any circuit - that needs say 20ms of
simulation run time to get to an event (like a output state/level
change) and i just want to probe a few ms or even us of output around
this event. do i have to run the simulation from the start every time,
or is there a way to save the first 18ms and start a new run from that
point in time up to (slightly past) the event?

probably not, i'm thinking, and if that's the case, maybe someone could
suggest another way to get the sim time down. i'd like to be able to do
this without losing resolution (i.e., be able to zoom in on a transition
of a 1ms wide pulse and still be able to see a few cycles of a 1us wide
pulse train)

what settings could i change to reduce the run time?

TIA,
mike

 

[Jim Thompson]

On Wed, 10 Sep 2003 03:24:21 GMT, Active8
<mcolasono@earthlink.net.invalid> wrote:

hi:

let's say i have a circuit - any circuit - that needs say 20ms of
simulation run time to get to an event (like a output state/level
change) and i just want to probe a few ms or even us of output around
this event. do i have to run the simulation from the start every time,
or is there a way to save the first 18ms and start a new run from that
point in time up to (slightly past) the event?

probably not, i'm thinking, and if that's the case, maybe someone could
suggest another way to get the sim time down. i'd like to be able to do
this without losing resolution (i.e., be able to zoom in on a transition
of a 1ms wide pulse and still be able to see a few cycles of a 1us wide
pulse train)

what settings could i change to reduce the run time?

TIA,
mike

You *can* pause a simulation, change the settings, then resume; but
you'll have to watch the progress and pause at the appropriate time.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Charles Edmondson]

Active8 wrote:

In article <l0pulv8s3v2bdpl5rqfi42v1vceunbefhr@4ax.com>, Jim-T@golana-
will-get-you.com says...


On Wed, 10 Sep 2003 03:24:21 GMT, Active8
mcolasono@earthlink.net.invalid> wrote:



hi:

let's say i have a circuit - any circuit - that needs say 20ms of
simulation run time to get to an event (like a output state/level
change) and i just want to probe a few ms or even us of output around
this event. do i have to run the simulation from the start every time,
or is there a way to save the first 18ms and start a new run from that
point in time up to (slightly past) the event?

probably not, i'm thinking, and if that's the case, maybe someone could
suggest another way to get the sim time down. i'd like to be able to do
this without losing resolution (i.e., be able to zoom in on a transition
of a 1ms wide pulse and still be able to see a few cycles of a 1us wide
pulse train)

what settings could i change to reduce the run time?

TIA,
mike


You *can* pause a simulation, change the settings, then resume; but
you'll have to watch the progress and pause at the appropriate time.

...Jim Thompson



it'd be nice to be able to programmatically change the timestep or what
ever speeds things up except for a specific range of TIME values around
the event of interest.

mike

I hate it when ya'll ask questions like that!

For instance, I know it is specifically possible to do what Mike asked,
to have the maximum time step change dynamically during a simulation. I
just wish I remembered how to do it! I know it involved using a
specific file to set these things in an option statement, and was added
to PSpice during the interactive simulation stuff (you know, the pause,
restart, whoops, we hit a convergence error, want to tweak a few things
feature... Of course, the guy I would ask about this isn't with
Cadence anymore,

Okay, now ya done it, went and looked Brian up. On the .tran statement,
you can add a schedule command! Syntax like
{schedule(time, value, time, value, time, value)}

You can do this for several different run time values to have things
change around.

As for stop and restart, I think they were looking in to it before the
pogrom. It was the next step in the pause - restart cycle but they
still had a few problems working it out.

Charlie
Edmondson Engineering
Unique Solutions to Unusual Problems

 

[John]

"Jim Thompson" <Jim-T@golana-will-get-you.com> wrote in message
news:gh47mvsdtusu5q3pfm12a4i60cm54541j1@4ax.com...

On Thu, 11 Sep 2003 15:21:44 -0700, Charles Edmondson
edmondson.ns@ieee.nw.org.invalid> wrote:

Active8 wrote:

There's a bodge way to alter the step time without using the statements.
This is easier than what the following explanation will make it sound.
Have a digital stimulus defined with a very high clock speed. The higher
the clock speed, the lower the min step will be.
Connect the stimulus to one input of an AND gate. Connect a resistor from
the gate output to ground.
Connect a HI or voltage source to the other input through two switches in
serial. These are the "timed" switches. One is normally open, the other is
normally closed. Just before the area where you need higher resolution,
close the normally open switch. After you ve crossed the trouble zone, open
the normally closed one.
This'll force the analogue simulator to do more calculations in this area
alone.

regards,
John

 

[Jim Thompson]

On Mon, 15 Sep 2003 15:08:42 +0200, "John" <John.Evans@cern.ch> wrote:

"Jim Thompson" <Jim-T@golana-will-get-you.com> wrote in message
news:gh47mvsdtusu5q3pfm12a4i60cm54541j1@4ax.com...
On Thu, 11 Sep 2003 15:21:44 -0700, Charles Edmondson
edmondson.ns@ieee.nw.org.invalid> wrote:

Active8 wrote:


There's a bodge way to alter the step time without using the statements.
This is easier than what the following explanation will make it sound.
Have a digital stimulus defined with a very high clock speed. The higher
the clock speed, the lower the min step will be.
Connect the stimulus to one input of an AND gate. Connect a resistor from
the gate output to ground.
Connect a HI or voltage source to the other input through two switches in
serial. These are the "timed" switches. One is normally open, the other is
normally closed. Just before the area where you need higher resolution,
close the normally open switch. After you ve crossed the trouble zone, open
the normally closed one.
This'll force the analogue simulator to do more calculations in this area
alone.

regards,
John

Clever!

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Active8]

In article <5v3cmv8vgp2da7l3fki8hdi3gqjkdtd3ri@4ax.com>, Jim-T@golana-
will-get-you.com says...

On Mon, 15 Sep 2003 07:52:16 -0700, Jim Thompson
Jim-T@golana-will-get-you.com> wrote:

On Mon, 15 Sep 2003 15:08:42 +0200, "John" <John.Evans@cern.ch> wrote:

[snip]
Just before the area where you need higher resolution,
close the normally open switch. After you ve crossed the trouble zone, open
the normally closed one.
This'll force the analogue simulator to do more calculations in this area
alone.

regards,
John

Clever!

...Jim Thompson

ooooh. delayed reactions. good thing i caught these posts.

sounds that way (clever), but right now my brain's too tired to figure
out how it works. i'll look into it later. thanks john.

It just occurred to me... make a PART with no pins, but with PARAMS:
visible to set the range(s) and drop it on your SIM page.



...Jim Thompson

same as above. and thank *you* too.

2 questions, if you 2 would, please:

1. what ranges are we setting with these Params? RELTOL and TMAX?

2. where do i find this timed switch? i only found V and I controlled
switches and the ideal switch. oh, there's the sentence. it says i
should make a timed switch by controlling it with a voltage source.
since i haven't used this question up yet, let me try another (multi-
part, this time) question. i found the switches in both the analog.lib
and the breakout.lib... the one in analog has all the params (in the
properties sheet) mentioned in the pspcref.pdf and i can't edit the
pspice model, but the switch in breakout has no params in the properties
sheet - i can edit the model and the params are defined there.

how'd they make this work this way (model/no model file) and what is the
deal with this breakout lib? i see the speil on breakout parts is
repeated for damned near every stock part in pspcref, but i'm not
understanding why/how this facilitates monte carlo/worst-case analysis.
haven't played with that yet except in CM, a monumental, unsupported,
POS, IMHO.


mike
>

 

[Charles Edmondson]

Active8 wrote:

In article <5v3cmv8vgp2da7l3fki8hdi3gqjkdtd3ri@4ax.com>, Jim-T@golana-
will-get-you.com says...


On Mon, 15 Sep 2003 07:52:16 -0700, Jim Thompson
Jim-T@golana-will-get-you.com> wrote:



On Mon, 15 Sep 2003 15:08:42 +0200, "John" <John.Evans@cern.ch> wrote:



[snip]


Just before the area where you need higher resolution,
close the normally open switch. After you ve crossed the trouble zone, open
the normally closed one.
This'll force the analogue simulator to do more calculations in this area
alone.

regards,
John


Clever!

...Jim Thompson



ooooh. delayed reactions. good thing i caught these posts.

sounds that way (clever), but right now my brain's too tired to figure
out how it works. i'll look into it later. thanks john.


It just occurred to me... make a PART with no pins, but with PARAMS:
visible to set the range(s) and drop it on your SIM page.



...Jim Thompson



same as above. and thank *you* too.

2 questions, if you 2 would, please:

1. what ranges are we setting with these Params? RELTOL and TMAX?

2. where do i find this timed switch? i only found V and I controlled
switches and the ideal switch. oh, there's the sentence. it says i
should make a timed switch by controlling it with a voltage source.
since i haven't used this question up yet, let me try another (multi-
part, this time) question. i found the switches in both the analog.lib
and the breakout.lib... the one in analog has all the params (in the
properties sheet) mentioned in the pspcref.pdf and i can't edit the
pspice model, but the switch in breakout has no params in the properties
sheet - i can edit the model and the params are defined there.

how'd they make this work this way (model/no model file) and what is the
deal with this breakout lib? i see the speil on breakout parts is
repeated for damned near every stock part in pspcref, but i'm not
understanding why/how this facilitates monte carlo/worst-case analysis.
haven't played with that yet except in CM, a monumental, unsupported,
POS, IMHO.


mike

Hi Mike,
Couple of questions there!

Okay, first, there IS a timed switch, like sw_tClose and sw_tOpen, that
you can just set to operate at a set time, but are probably not what you
want to use for this...

The reason for the two different voltage switches is for the two
different used. Breakout parts are for when you are creating a model,
or using a model created by someone else, and don't want to go to the
trouble of creating a new part. They start with nice, generic models
that you can customize, and then use multiple places on the schematic.
The other part with all the paramters is for use once instances, where
you just want to put one down and set it, not develop a model, etc. The
difference is in the PSpiceTemplate. One calls a model from the file,
the other creates the .model statement on the fly.

Hope that helps!

Charlie
Edmondson Engineering
Unique Solutions to Unusual Problems