Cannot plot transient response (no graph/empty window)

Dear hikotoshi,

hikotoshi said:

Whenever I try to do a transient simulation of any circuit, I only get a black window, as seen below. DC and other simulations work fine. I've made a very simple inverter schematic as shown in the picture and I don't see any errors in the Spectre log. This problem occurs on any circuit, I've tried various. What could be the reason for this?

Did you check the CIW window for any issues? It sounds as if a netlist cannot be created -  possibly due to an invalid parameter in your transient input pulse. This will prevent spectre from simulating the circuit. In my limited experience, if a netlist cannot be generated, the response you describe is common. If there is no information in the CIW, You might try to enable the  +diagnose option to provide more information. If you have not done this before, some instructions are at Cadence On0line support at URL:

support.cadence.com/.../ArticleAttachmentPortal

It is a bit difficult for me to be certain on the issue as you have not included the netlist or input.scs file or the tools you are using...

Shawn

Hi,

Thanks for the reply, but the netlist seems fine to me. I've attached the input.scs. Tools are GF 22FDX-EXT.

input.scs:

// Generated for: spectre
// Generated on: Mar 7 22:12:24 2021
// Design library name: thesis
// Design cell name: test
// Design view name: schematic
simulator lang=spectre
global 0 VDD!
include "$SPECTRE_MODEL_PATH/design_wrapper_rf.lib.scs" section=tt_pre
parameters nfet=1 pfet=1 CL=10f F=2G vdd=1

// Library name: cmos22fdsoi
// Cell name: INV
// View name: schematic
subckt INV_pcell_0 A Y inh_hSup inh_lSup
parameters wfp=80n nfp=1 lp=20n p_lap=0 ulpp=0 wfn=80n nfn=1 ln=20n \
p_lan=0 ulpn=0
P0 (Y A inh_hSup inh_lSup) pfet w=(wfp)*(nfp) l=lp as=6.72f ad=6.72f \
ps=328n pd=328n nf=nfp par=(1) par_nf=(1) * (nfp) m=1 plorient=0 \
acv_opt=-1 ptwell=0 ngcon=1 nscon=1 ndcon=1 p_la=p_lap p_wa=0 \
ulp=ulpp lle_pcpc=84n tie_orient=0 swrfmhc_local=0 analog=0
N0 (Y A inh_lSup inh_lSup) nfet w=(wfn)*(nfn) l=ln as=6.72f ad=6.72f \
ps=328n pd=328n nf=nfn par=(1) par_nf=(1) * (nfn) m=1 plorient=0 \
acv_opt=-1 ptwell=0 ngcon=1 nscon=1 ndcon=1 p_la=p_lan p_wa=0 \
ulp=ulpn lle_pcpc=84n tie_orient=0 swrfmhc_local=0 analog=0
ends INV_pcell_0
// End of subcircuit definition.

// Library name: thesis
// Cell name: test
// View name: schematic
INV0 (INPUT OUTPUT VDD! 0) INV_pcell_0 wfp=80n nfp=1 lp=20n p_lap=0 ulpp=0 \
wfn=80n nfn=1 ln=20n p_lan=0 ulpn=0
V1 (INPUT 0) vsource type=pulse val0=0 val1=vdd period=1/F rise=0.1/F \
fall=0.1/F
V0 (VDD! 0) vsource dc=vdd type=dc
C0 (OUTPUT 0) capacitor c=CL
simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \
tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 vthmod=vthcc \
ivthn=300e-9 ivthp=70e-9 ivthw=0 ivthl=0 maxnotes=5 maxwarns=5 \
digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \
checklimitdest=psf vdsatmod=gds
tran tran stop=5n errpreset=conservative write="spectre.ic" \
writefinal="spectre.fc" annotate=status maxiters=5
finalTimeOP info what=oppoint where=rawfile
dc dc param=vdd start=0 stop=1 step=0.1 write="spectre.dc" oppoint=rawfile \
maxiters=150 maxsteps=10000 annotate=status
modelParameter info what=models where=rawfile
element info what=inst where=rawfile
outputParameter info what=output where=rawfile
designParamVals info what=parameters where=rawfile
primitives info what=primitives where=rawfile
subckts info what=subckts where=rawfile
save INPUT OUTPUT
saveOptions options save=allpub

I have noticed the following in the CDS.log file:

net /INPUT selected but not highlighted

net /OUTPUT selected but not highlighted

No valid waveforms for plotting

No image saved: Possible reasons could be that none of the windows

or subwindows are visible or are non-empty.

Could this indicate the source of the problem? Both signals are set to plot & save.

I would advise you to contact customer support - I don't think it's a netlisting issue (since you wouldn't the dc sweep results either in that case). It does seem a bit strange, although you didn't mention anything about the versions used. It would be interesting to see if you can see the results in the results browser, and whether you can plot from there. However, I think the best thing would be to work with colleagues in support - a screen sharing session is likely to get the bottom of this quickly.

Andrew.

Dear hikotoshi,

hikotoshi said:

I've attached the input.scs. Tools are GF 22FDX-EXT.

input.scs:

Thank you for providing your input.scs file! This is quite helpful - to me anyway!

If you have not followed through with Andrew's suggestion to contact customer support, I think I may have found an issue that will preclude spectre from performing the transient simulation.

Examining your input.scs file, the input pulse statement to your inverter is defined as follows:

hikotoshi said:

V1 (INPUT 0) vsource type=pulse val0=0 val1=vdd period=1/F rise=0.1/F \
fall=0.1/F

However, it is missing the "width" attribute. Without the "width" atttribute, it is not clear how spectre can establish the pulse width. From the UNIX spectre -h vsource command, an example vpulse statement is provided below. Note the parameter "width" which is missing from the vpulse statement in your input.scs

Sample Instance Statement:
vpulse1 (1 0) vsource type=pulse val0=0 val1=5 period=100n rise=10n fall=10n width=40n

Did you specificy a width in the ADE setup GUI highlighted in Figure 1 hikotoshi?

Shawn

Figure 1

That still wouldn't cause only the dc sweep results to appear - it would most likely cause either a non-pulse waveform or an error. In practice though, if the width is omitted, it is inferred from the period and the rise/fall times (i.e. I think it's (period-rise-fall)/2). I just tried the netlist (with some made up models rather than looking for the right model files) and it runs OK, and I can plot INPUT and OUTPUT (from command line).

So that's not it...

The issue is very unlikely to be related to an error in the netlist - I'm struggling to think of what it might be though, since it doesn't sound like symptoms I've seen before...

Andrew

Thanks, I'll try contacting them, however since I'm using cadence provided by my university I do not have access to the license key required to unlock support capabilities. How do I go about contacting support in this case?

Yeah I did not but as Andrew suggested this was sadly not the cause of the issue, as even after specifying a width the graph is still blank. Thanks for the idea anyway.

Dear hikotoshi and Andrew,

Thank you, Andrew, for alerting me about the default width setting. I actually examined the analogLib reference for the independent pulse source to see if there was a default width value. From the reference manual, in Figure 2, it suggests there is not a default value - which is what prompted me to include myu comment - sorry! Perhaps, if you think it worth it, I can open a case to request the document I accessed might be updated to reflect the default value's existence?

hikotoshi said:

eah I did not but as Andrew suggested this was sadly not the cause of the issue, as even after specifying a width the graph is still blank. T

Rats!

Thank you anyway, hikotoshi, in any case for trying my suggestion!

hikotoshi said:

I do not have access to the license key required to unlock support capabilities. How do I go about contacting support in this case?

I think if you contact your IT or professor/teaching assistant (or whomever installs your Cadence tools), that individual can provide you with the license key.

Shawn

Figure 2

analogLib_ref_p400.pdf

Unknown said:

I can open a case to request the document I accessed might be updated to reflect the default value's existence?

It doesn't mention in "spectre -h vsource" that the width is calculated when period is given (if period is not given, then width defaults to infinity) - that's probably the first thing that should be fixed. By all means please do file a case on that.

To hikotoshi, I'd suggest first seeing if you can access the latest IC6.1.8 or ICADVM20.1 hotfix to see if that solves your problem (you still didn't mention which version you're using) - the latest is IC6.1.8.64b.500;16 (ISR 16) - i.e. with .16 at the end. If that doesn't work, follow Shawn's suggestion in order to contact support through you university link.

Andrew