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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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 07 Sep 2004 7:12 How to get a fixed timesetp in hspice? |
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hello all!
I need a fixed or approximate fixed timestep for .tran sim, who can tell me how to do?
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frankon_o2
Joined: 07 Sep 2004
Posts: 8
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| 07 Sep 2004 10:56 How to get a fixed timesetp in hspice? |
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for example:
.tran 1u 20m
then 1uSec is the time step of transient simulation
the length of simulation is 20mSec
Is that what u want to know?
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nathan
Joined: 17 May 2001
Posts: 307
Helped: 2
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| 07 Sep 2004 12:55 Re: How to get a fixed timesetp in hspice? |
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use delmax (maxdel ???)= ...
nathan
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 07 Sep 2004 13:06 Re: How to get a fixed timesetp in hspice? |
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| frankon_o2 wrote: |
for example:
.tran 1u 20m
then 1uSec is the time step of transient simulation
the length of simulation is 20mSec
Is that what u want to know? |
hspice will change the timestep, not always 1u
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 07 Sep 2004 13:09 Re: How to get a fixed timesetp in hspice? |
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| nathan wrote: |
use delmax (maxdel ???)= ...
nathan |
I use this opt:
.option post=2 accurate DELMAX=0.0u RMAX=1 DVDT=2 LVLTIM=2 FS=0.1 FT=0.1
it has a little benifit .
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always@smart
Joined: 08 Feb 2002
Posts: 308
Helped: 7
Location: ASIA
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| 07 Sep 2004 13:24 Re: How to get a fixed timesetp in hspice? |
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hi ysz,
how do u know that Hspice will change the timestep? sorry i;m new in using hspice.
can you please also explained the command u have shown us?
.option post=2 accurate DELMAX=0.0u RMAX=1 DVDT=2 LVLTIM=2 FS=0.1 FT=0.1
thanks in advance
regards,
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 07 Sep 2004 13:44 How to get a fixed timesetp in hspice? |
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Star-Hspice allows the selection of three dynamic timestep control algorithms:
n Iteration count
n Truncation
n DVDT
Each of these algorithms uses a dynamically changing timestep.
you can look it up in the manual.
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 07 Sep 2004 13:48 Re: How to get a fixed timesetp in hspice? |
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this is my ugly wave, who can help me?
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leo_o2
Joined: 03 Sep 2004
Posts: 330
Helped: 20
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| 07 Sep 2004 14:10 Re: How to get a fixed timesetp in hspice? |
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| Set DELMAX to a value smaller than the minimum pulse width. It might help. Avoid signals with steep edge.
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 08 Sep 2004 8:58 Re: How to get a fixed timesetp in hspice? |
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| leo_o2 wrote: |
| Set DELMAX to a value smaller than the minimum pulse width. It might help. Avoid signals with steep edge. |
I already set DelMax=0u
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leo_o2
Joined: 03 Sep 2004
Posts: 330
Helped: 20
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| 09 Sep 2004 3:20 Re: How to get a fixed timesetp in hspice? |
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| What is TStep that you used for .tran analysis?
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 09 Sep 2004 9:54 How to get a fixed timesetp in hspice? |
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.option post=2 accurate DELMAX=0.0u RMAX=1 DVDT=2 LVLTIM=2 FS=0.1 FT=0.1
.tran 10u 120m
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leo_o2
Joined: 03 Sep 2004
Posts: 330
Helped: 20
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| 10 Sep 2004 3:10 Re: How to get a fixed timesetp in hspice? |
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| Obviously, 10us for Tstep is too big. You must decrease it first in my opinion.
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 10 Sep 2004 5:27 How to get a fixed timesetp in hspice? |
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| I have changed it to 1us, the wave is same, I'm so doubt.
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leo_o2
Joined: 03 Sep 2004
Posts: 330
Helped: 20
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| 10 Sep 2004 10:21 Re: How to get a fixed timesetp in hspice? |
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| Try 10ns. However, it will be very slow.
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joskin
Joined: 26 Mar 2004
Posts: 39
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| 16 Sep 2004 6:10 Re: How to get a fixed timesetp in hspice? |
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The main problem is your simultion time is too long(bigger than 100ms).
Because in (*.tr#)transient sim result file,the valid digital number that describe simulation time is fixed,the wave can't show detailed information when the time exceeds 100ms.
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 16 Sep 2004 9:12 Re: How to get a fixed timesetp in hspice? |
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| joskin wrote: |
The main problem is your simultion time is too long(bigger than 100ms).
Because in (*.tr#)transient sim result file,the valid digital number that describe simulation time is fixed,the wave can't show detailed information when the time exceeds 100ms. |
really?
but if I can set a fixed timestep, I will set the timestep longer, so the number of steps are reduced, maybe I can have longer sim time. do you think so?
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 22 Sep 2004 8:28 How to get a fixed timesetp in hspice? |
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| Nobody can help me?
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Hughes
Joined: 10 Jun 2003
Posts: 712
Helped: 84
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| 24 Sep 2004 5:56 Re: How to get a fixed timesetp in hspice? |
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| ysz wrote: |
.option post=2 accurate DELMAX=0.0u RMAX=1 DVDT=2 LVLTIM=2 FS=0.1 FT=0.1
.tran 10u 120m |
Don't set DELMAX=0, set to a small value other than 0. For example:
.option delmax=0.1n
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fashion
Joined: 01 Sep 2004
Posts: 27
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| 28 Sep 2004 11:30 How to get a fixed timesetp in hspice? |
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| If you set more accurate, the speed of simulation will be very long, sometime set 1/10 of total time.
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 30 Sep 2004 19:23 Re: How to get a fixed timesetp in hspice? |
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| Hughes wrote: |
| ysz wrote: |
.option post=2 accurate DELMAX=0.0u RMAX=1 DVDT=2 LVLTIM=2 FS=0.1 FT=0.1
.tran 10u 120m |
Don't set DELMAX=0, set to a small value other than 0. For example:
.option delmax=0.1n |
Hughes, thank you!
I changed the parameter to:
.option post=2 DELMAX=10n RMAX=1.01 DVDT=2 LVLTIM=2 FS=0.1 FT=0.1
.tran 10u 120m
but the wave....
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Hughes
Joined: 10 Jun 2003
Posts: 712
Helped: 84
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| 01 Oct 2004 14:41 Re: How to get a fixed timesetp in hspice? |
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| ysz wrote: |
| Hughes wrote: |
| ysz wrote: |
.option post=2 accurate DELMAX=0.0u RMAX=1 DVDT=2 LVLTIM=2 FS=0.1 FT=0.1
.tran 10u 120m |
Don't set DELMAX=0, set to a small value other than 0. For example:
.option delmax=0.1n |
Hughes, thank you!
I changed the parameter to:
.option post=2 DELMAX=10n RMAX=1.01 DVDT=2 LVLTIM=2 FS=0.1 FT=0.1
.tran 10u 120m
but the wave.... |
Hi ysz,
Did you ever check the tr0 file size? Maybe the file size exceed some limit.
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 08 Oct 2004 4:06 Re: How to get a fixed timesetp in hspice? |
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The problem was solved by Hughes's help.
Just changes the parameter to :
.option post=1 accurate
.tran 0.5u 120m
but I am so doubt about the post parameter, post=1 saves file by binary format, post=2 saves file by ascii format, they are no relationship of the wave shapes, but there are really some difference, any body could explain this question to me?
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Hughes
Joined: 10 Jun 2003
Posts: 712
Helped: 84
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| 08 Oct 2004 5:47 How to get a fixed timesetp in hspice? |
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| I have reviewed the ascii .tr0 file and found that all data only had five effective digits. As a result, when simulation time is between 10ms and 100ms, the output time resolution is 1us. When simulation 10ms and 1000ms, the output time resolution is 10us. Thus, we got the ulgly waveform. The calculation resolution is not limited to 5 effective digits. I didn't find how to change the number of effective digits in ascii .tr0 files. Who knows?
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tlihu
Joined: 02 Jan 2002
Posts: 627
Helped: 5
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| 08 Oct 2004 7:47 How to get a fixed timesetp in hspice? |
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Add this option might help:
.options numdgt=4 (or higher)
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Hughes
Joined: 10 Jun 2003
Posts: 712
Helped: 84
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| 08 Oct 2004 8:24 How to get a fixed timesetp in hspice? |
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| No. Neither option numdgt nor option measdgt has the control to the ascii tr0 file.
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ysz
Joined: 14 Aug 2004
Posts: 44
Location: fujian china
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| 08 Oct 2004 17:32 Re: How to get a fixed timesetp in hspice? |
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| joskin wrote: |
The main problem is your simultion time is too long(bigger than 100ms).
Because in (*.tr#)transient sim result file,the valid digital number that describe simulation time is fixed,the wave can't show detailed information when the time exceeds 100ms. |
joskin is right!
by the data list below, we find if sim time more than 100ms, we will lost the last valid digital number, so the timestep will become incertitude.
when awaves shows the wave, the data will displayed at the same time, so we got the ugly wave:
TIME ---------- gnd ------------ neta ---------- vdd ----------- I(vdd
0.99992E-01 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.99993E-01 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.99994E-01 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.99995E-01 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.99996E-01 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.99997E-01 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.99998E-01 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.99999E-01 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******5rows*******
0.10000E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10000E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10000E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10000E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10000E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******11rows*******
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10001E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******10rows*******
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10002E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******10rows*******
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10003E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******9rows*******
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10004E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******5rows*******
0.10005E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10005E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10005E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10005E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10005E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******5rows*******
0.10006E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10006E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10006E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10006E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10006E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******5rows*******
0.10007E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10007E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10007E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10007E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10007E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******5rows*******
0.10008E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10008E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10008E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10008E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10008E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
******5rows*******
0.10009E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10009E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10009E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10009E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10009E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
0.10010E+00 0.00000E+00 0.18750E+01 0.50000E+01 -.62500E-04
(vdd vdd gnd 5v
.option post=2 accurate
.tran 0.5u 120m
R1 neta VDD 50K
R2 neta gnd 30k
.END
)
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morecode1234567890
Joined: 04 Oct 2003
Posts: 18
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| 15 Oct 2004 16:54 Re: How to get a fixed timesetp in hspice? |
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I daily work with hspice, and i usally find lot of convergence problems, no dc path to gound, time step to small, etc. most of the times this problems are becouse of short circuits, open circuits, etc... So, befoure spend a lot of time looking for an options that solves your problem you'd better to have a look, again, to your circuits, it is used to be bad human done thing.
sorry for my english
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tedchen
Joined: 13 Jan 2003
Posts: 19
Helped: 1
Location: United State
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| 22 Oct 2004 20:28 Re: How to get a fixed timesetp in hspice? |
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| You guys can check some books like "Inside SPICE" or "The SPICE Book." Those books got useful suggestions for solving simulation problems. They can also help you to setup your simulation properly.
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mit80
Joined: 29 Feb 2004
Posts: 4
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| 25 Oct 2004 18:43 How to get a fixed timesetp in hspice? |
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| in my opinion, set the option accurate can help you most of the time. Then check the circuit schematic, not to short circuit or "no dc path to ground", and so.
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