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A general question about warnings and notices in Virtuoso

MohNaj

Hi,

I am using Cadence Virtuoso for and analog design and use Spectre (or its relatives such as APS, SpectreX,...) as the simulator. At the end of output log, I see the number of errors, warnings and notices. I understand errors and I know they stop simulations. I also know warnings do not stop simulations but they may affect the simulation results, accuracy and performance. However, I do not understand what notices are. Should I consider them more seriously? Can anyone introduce me a document that can briefly differentiate them. 

Moreover, I see some of the warnings are related to the simulator and convergence issues. However, some of them are reporting technology file related warnings (e.g. exceeding breakdown voltage of transistors). My questions is what warnings I should take serious. It seems that exceeding breakdown voltage is a serious warning as it may hurt the transistor. Or current density of a wire (in post layout simulation) is serious as it may burn the wire. However, they are warnings. Should I check every single warning after the simulation, which is a lot (for my PLL simulation, there is around 400 warnings and 100 notices)? or there is a better approach?

The technology is 45nm RFSOI and I am running tran analysis.

Any help is appreciated,

Mohammad

Parents
  • ShawnLogan

    Dear Mohammad,

    MohNaj said:
    However, some of them are reporting technology file related warnings (e.g. exceeding breakdown voltage of transistors). My questions is what warnings I should take serious. It seems that exceeding breakdown voltage is a serious warning as it may hurt the transistor. Or current density of a wire (in post layout simulation) is serious as it may burn the wire. However, they are warnings. Should I check every single warning after the simulation, which is a lot (for my PLL simulation, there is around 400 warnings and 100 notices)? or there is a better approach?

    If the warnings are "technology related", then they are likely a function of your PDK - which Cadence has no control over. Hence, I am not aware of any Cadence document that focuses on filtering log messages that are produced by your PDK.

    I would recommend writing a shell script or equivalent to post-process your simulator output log to allow you to more efficiently collate and then study which warnings may be important to you. As a start, to examine the warnings in a spectre.out file, the following UNIX command will locate all warnings and the lines just above and just below each and place them in a file "warnings.txt". I've attached an example output from a recent simulation output log I have.

    grep -C1 WARNING spectre.out > warnings.txt

    Others who monitor this Forum may have other or better answers...but this was my first thought Mohammad.

    Shawn

    Fullscreen warnings.txt Download 
    Warning from spectre during AHDL read-in.
    WARNING (VACOMP-2435): The environment variable CDS_AHDLCMI_ENABLE is no longer supported. Therefore, the simulator will use the default compiled C code flow.

--
Warning from spectre during hierarchy flattening.
    WARNING (SFE-884): "/projects/bcm/beta/tech/tsmc5ff/dmodels/spectre/1.2_2p4.0.0.0/log5ff.scs" 630: The option 'tmiage' is deleted because it is redefined at '/projects/sdd5e/users/sml/cds/src/simCases/apdser_spectre_model.scs':line '845'.

--
Warning from spectre during hierarchy flattening.
    WARNING (SPECTRE-17101): The value 'psf' specified for the 'checklimitdest' option will no longer be supported in future releases. Use 'spectre -h' to see other recommended values for the 'checklimitdest' option.

--
Warning from spectre during alter `alternwmc'.
    WARNING (SPECTRE-16518): An arithmetic exception occurred in analysis `alternwmc' . Use `+diagnose' command-line option to get more information.

Reply
  • ShawnLogan

    Dear Mohammad,

    MohNaj said:
    However, some of them are reporting technology file related warnings (e.g. exceeding breakdown voltage of transistors). My questions is what warnings I should take serious. It seems that exceeding breakdown voltage is a serious warning as it may hurt the transistor. Or current density of a wire (in post layout simulation) is serious as it may burn the wire. However, they are warnings. Should I check every single warning after the simulation, which is a lot (for my PLL simulation, there is around 400 warnings and 100 notices)? or there is a better approach?

    If the warnings are "technology related", then they are likely a function of your PDK - which Cadence has no control over. Hence, I am not aware of any Cadence document that focuses on filtering log messages that are produced by your PDK.

    I would recommend writing a shell script or equivalent to post-process your simulator output log to allow you to more efficiently collate and then study which warnings may be important to you. As a start, to examine the warnings in a spectre.out file, the following UNIX command will locate all warnings and the lines just above and just below each and place them in a file "warnings.txt". I've attached an example output from a recent simulation output log I have.

    grep -C1 WARNING spectre.out > warnings.txt

    Others who monitor this Forum may have other or better answers...but this was my first thought Mohammad.

    Shawn

    Fullscreen warnings.txt Download 
    Warning from spectre during AHDL read-in.
    WARNING (VACOMP-2435): The environment variable CDS_AHDLCMI_ENABLE is no longer supported. Therefore, the simulator will use the default compiled C code flow.

--
Warning from spectre during hierarchy flattening.
    WARNING (SFE-884): "/projects/bcm/beta/tech/tsmc5ff/dmodels/spectre/1.2_2p4.0.0.0/log5ff.scs" 630: The option 'tmiage' is deleted because it is redefined at '/projects/sdd5e/users/sml/cds/src/simCases/apdser_spectre_model.scs':line '845'.

--
Warning from spectre during hierarchy flattening.
    WARNING (SPECTRE-17101): The value 'psf' specified for the 'checklimitdest' option will no longer be supported in future releases. Use 'spectre -h' to see other recommended values for the 'checklimitdest' option.

--
Warning from spectre during alter `alternwmc'.
    WARNING (SPECTRE-16518): An arithmetic exception occurred in analysis `alternwmc' . Use `+diagnose' command-line option to get more information.

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