How to get a fixed timesetp in hspice?

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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.
 

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?
 

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?
 

Add this option might help:

.options numdgt=4 (or higher)
 

No. Neither option numdgt nor option measdgt has the control to the ascii tr0 file.
 

joskin said:
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.
Click to expand...
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
)
 

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
 

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.
 

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.
 

maybe it is the problem of the circuit
 

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