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How to simulate full custom digital circuit digitally in virtuoso(spectre)

wenxuzhao

 I've built a full custom digital circuit in virtuoso, suppose to run at 3GHz. I tried to simulate it for 1ms, which takes several days... Actually I just need digital behavior of it and do not care about the transistor level things. Is there any way that I can simulate it digitally, ie, reducing the simulation time? Thanks a lot!

Wenxu

  • Hi Wenxu

    You can use AMS Designer to do a mixed-signal simulation. It will be able to use the original verilog/vhdl RTL file of the digital circuitry instead of the actual transistor level circuits.

    Best regards
    Quek

  • Quek,

     

    Thank you! Right now, I have to build the entire circuit in transistor level, it performs digital behavior, I wonder if I can do something to speedup the simulation, while it is still transistor level. 

     

    Thank you!

     

    Wenxu

  • Hi Wenxu

    You can use aps mode of spectre to speed up transistor level simulations. It is really very fast but retains full accuracy of spectre. You can enable it in ADE-L in "Setup->High Performance Simulation".


    Best regards
    Quek

  • Hi Wenxu

    You can also use our ultrasim fastspice simulator to do the simulation. It allows you to set different accuracy modes on your blocks. E.g. set "digital_fast" mode for the custom digital block and use default mode for the other blocks.


    Best regards
    Quek

  •  Hi Quek,

     It really helps, thank you!

    Besides, I found that "aps" is also a "simulator" choise under Simulator/Directory/Host, should I change from "spectre" to "aps" when I enable APS mode in  "Setup->High Performance Simulation"? Or, what's the difference between "spectre" simulator with APS mode and "aps" simulator with APS mode?

     And Ultrasim simulator is the best way to simulate a full custom digital circuit digitally, right?

    Thank you!

     

    Wenxu

  • Hi Wenxu,

    You should not use "aps" as the choice of simulator under Simulator/Directory/Host - that is obsolete and was the initial interface to the APS technology. In fact in later IC615 ISRs it has been removed. The correct interface is the Setup->High Performance Simulation.

    In both modes the simulator is the same - but the interface via "aps" as  the simulator is more limited because it dates from when APS had just been implemented and only supported a subset of spectre's capability.

    Ultrasim has the benefit of being able to trade off accuracy versus speed for particular blocks, and if it's custom digital you probably don't need full spectre accuracy - and hence can get speed improvements that way.

    Regards,

    Andrew.

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