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Ocean/Spectre measurement question

Octavian

Hello,

I'm trying to setup an ocean expression for measuring the delay between two events. I want something like "measure the delay between when clock goes high and when output crosses a threshold (i.e. 50mV) ". In hspice I would use the trig-targ construct but I could not find something similar for ocean/spectre.

I tried using the cross function but that starts counting events at the beginning of the simulation and gets tripped by glitches which occur before the clock edge. I guess I'm looking for a way to delay the start of the search until the clock signal has toggled. Is there something like this available?

Thanks,

--Tavi 

  • Hi Tavi,

    I think that you can use something like the clip function to restrict the input between a certain time, and then you can apply the cross function to the output.

    Hopefully this is what you were looking for?

    Regards,

    Lawrence.

  • Hi Tavi,

    Just to add to Lawrence's good answer, you might want to use the cross function in combination with the clip function. Since you are looking to start your measurement after a clock has started, you could clip the waveform you want to measure starting at the N'th crossing of your clock (N is the threshold crossing you want to start looking at the waveform to measure). The resulting expression might look like the following with the two waveforms called "clockin" and "output_wave", a simulation stop time of TSTOP, and a switching threshold of "vthreshold".

    cross(clip( output_wave cross( clockin vthreshold N 'rising) TSTOP) vthreshold 1 'rising)

    Shawn

  • Thanks everybody. This answers my question.

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