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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.

Parents

  • I feel more clarification is needed.  Here is the output for a 1 second long simulation that I aborted after it reached 30 microseconds (which took more than 10 minutes to run the simulation):

     

        tran: time = 17.72 ps   (1.77 n%), step = 298.4 as    (29.8 f%)
        tran: time = 109 ps     (10.9 n%), step = 106.6 fs    (10.7 p%)
        tran: time = 1.145 ns    (114 n%), step = 891.6 fs    (89.2 p%)
        tran: time = 10.4 ns    (1.04 u%), step = 5.085 ps     (509 p%)
        tran: time = 2.667 us    (267 u%), step = 11.28 ns    (1.13 u%)
        tran: time = 3.373 us    (337 u%), step = 26.15 ps    (2.62 n%)
        tran: time = 4.683 us    (468 u%), step = 21.92 ps    (2.19 n%)
        tran: time = 6.609 us    (661 u%), step = 183.6 ps    (18.4 n%)
        tran: time = 8.076 us    (808 u%), step = 546.5 ps    (54.7 n%)
        tran: time = 10.56 us   (1.06 m%), step = 3.132 ns     (313 n%)
        tran: time = 11.91 us   (1.19 m%), step = 1.13 ns      (113 n%)
        tran: time = 14.02 us    (1.4 m%), step = 89.52 ps    (8.95 n%)
        tran: time = 17.12 us   (1.71 m%), step = 339.6 ps      (34 n%)
        tran: time = 18 us       (1.8 m%), step = 8.234 ps     (823 p%)
        tran: time = 20.87 us   (2.09 m%), step = 9.58 ns      (958 n%)
        tran: time = 22.94 us   (2.29 m%), step = 743.4 ps    (74.3 n%)
        tran: time = 24.04 us    (2.4 m%), step = 89.32 ps    (8.93 n%)
        tran: time = 24.83 us   (2.48 m%), step = 49 ps        (4.9 n%)
        tran: time = 26.18 us   (2.62 m%), step = 401.1 ps    (40.1 n%)
        tran: time = 27.26 us   (2.73 m%), step = 5.733 ns     (573 n%)
        tran: time = 28.01 us    (2.8 m%), step = 2.069 ns     (207 n%)
        tran: time = 29.13 us   (2.91 m%), step = 117.2 ps    (11.7 n%)

     

    The maximum charge was reached at 71 nanoseconds.  I would like the simulation to automatically stop around this time.  The rest of the simulation is updating the waveform when the charge changes from one below the maximum charge back to the maximum charge.  Is there some way to set the minmum step to 10 nanoseconds?  Are there other methods that I could use to abort the simulation?

    Or perhaps is there a way to run a transient simulation manually one step at a time?  For example, step 1 nanosecond, check value, step 5 nanoseconds, check value, etc. 

    Thank you for your help. 

Reply

  • I feel more clarification is needed.  Here is the output for a 1 second long simulation that I aborted after it reached 30 microseconds (which took more than 10 minutes to run the simulation):

     

        tran: time = 17.72 ps   (1.77 n%), step = 298.4 as    (29.8 f%)
        tran: time = 109 ps     (10.9 n%), step = 106.6 fs    (10.7 p%)
        tran: time = 1.145 ns    (114 n%), step = 891.6 fs    (89.2 p%)
        tran: time = 10.4 ns    (1.04 u%), step = 5.085 ps     (509 p%)
        tran: time = 2.667 us    (267 u%), step = 11.28 ns    (1.13 u%)
        tran: time = 3.373 us    (337 u%), step = 26.15 ps    (2.62 n%)
        tran: time = 4.683 us    (468 u%), step = 21.92 ps    (2.19 n%)
        tran: time = 6.609 us    (661 u%), step = 183.6 ps    (18.4 n%)
        tran: time = 8.076 us    (808 u%), step = 546.5 ps    (54.7 n%)
        tran: time = 10.56 us   (1.06 m%), step = 3.132 ns     (313 n%)
        tran: time = 11.91 us   (1.19 m%), step = 1.13 ns      (113 n%)
        tran: time = 14.02 us    (1.4 m%), step = 89.52 ps    (8.95 n%)
        tran: time = 17.12 us   (1.71 m%), step = 339.6 ps      (34 n%)
        tran: time = 18 us       (1.8 m%), step = 8.234 ps     (823 p%)
        tran: time = 20.87 us   (2.09 m%), step = 9.58 ns      (958 n%)
        tran: time = 22.94 us   (2.29 m%), step = 743.4 ps    (74.3 n%)
        tran: time = 24.04 us    (2.4 m%), step = 89.32 ps    (8.93 n%)
        tran: time = 24.83 us   (2.48 m%), step = 49 ps        (4.9 n%)
        tran: time = 26.18 us   (2.62 m%), step = 401.1 ps    (40.1 n%)
        tran: time = 27.26 us   (2.73 m%), step = 5.733 ns     (573 n%)
        tran: time = 28.01 us    (2.8 m%), step = 2.069 ns     (207 n%)
        tran: time = 29.13 us   (2.91 m%), step = 117.2 ps    (11.7 n%)

     

    The maximum charge was reached at 71 nanoseconds.  I would like the simulation to automatically stop around this time.  The rest of the simulation is updating the waveform when the charge changes from one below the maximum charge back to the maximum charge.  Is there some way to set the minmum step to 10 nanoseconds?  Are there other methods that I could use to abort the simulation?

    Or perhaps is there a way to run a transient simulation manually one step at a time?  For example, step 1 nanosecond, check value, step 5 nanoseconds, check value, etc. 

    Thank you for your help. 

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