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Aborting transient analysis after desired value is found

JayJetz

I am simulating a floating gate memory model custom made in verilog.  I am running several simulations using an Ocean script with varying parameters to determine total charge, time to reach total charge, retention time, etc.  All of these must be done with transient analysis.

 My question is how do I abort a transient analysis once the maximum charge is reached (there is a node in the model that displays the charge that can be read as a voltage).  The problem is when I run transient analysis, it takes an incredibly long time because the charge is constantly changing due to thermal effects and my time step is in the picosecond range.  I have tried setting the step to a larger value using the ?step parameter for the analysis command, but that did not change anything.

 Once the simulation is complete, I have the code to scan the waveform, find the maximum charge, how long it took to reach this value, print the information to a text file, change parameters and repeat.  The only problem is the time to run the simulation.  It takes up to 5 minutes and I have thousands of simulations to run for each data point.   Also, the time it takes to reach the maximum charge varies with the parameters so I can not just set the transient analysis to a very small value.  Right now it is at 1 microsecond.

  So, I am looking for the analysis parameters that would allow me to stop after reaching the maximum charge.  This could be found by a simple if statement that says if the same maximum is reached twice, stop the experiment.  The charge on the floating gate changes by 1 due to thermal effects every few picoseconds and this is why the simulation takes so long.

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  • Several ways you could do this. One is to use SpectreMDL to run the analyses and make the measurements, and then use the "autostop" facility to stop the simulation. Look in the simulator documentation for the Measurement Description Language info.

    The other approach (which will probably work better if you are using OCEAN or ADE for simulation) is to have a VerilogA block in your schematic which checks for the condition having been met, and then calls $finish_current_analysis when met. See Solution 11488490 .

    An example:

     `include "disciplines.vams"
    module stopearly (a);

    input a;
    electrical a;

    analog

       @(cross(V(a)-0.9)) $finish_current_analysis;

    endmodule

    Regards,

    Andrew

Reply

  • Several ways you could do this. One is to use SpectreMDL to run the analyses and make the measurements, and then use the "autostop" facility to stop the simulation. Look in the simulator documentation for the Measurement Description Language info.

    The other approach (which will probably work better if you are using OCEAN or ADE for simulation) is to have a VerilogA block in your schematic which checks for the condition having been met, and then calls $finish_current_analysis when met. See Solution 11488490 .

    An example:

     `include "disciplines.vams"
    module stopearly (a);

    input a;
    electrical a;

    analog

       @(cross(V(a)-0.9)) $finish_current_analysis;

    endmodule

    Regards,

    Andrew

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