Adexl - dynamically stop transient run on event trigger

You're lucky that I responded to this given that the MDL script is in Comic Sans. That's a cardinal sin (I probably should state that in the forum guidelines!). Just kidding...

If you read the documentation (Spectre Circuit Simulator Measurement Description Language Reference), in the section on autostop, it says:

Only functions that determine specific events, such as delay and event measurements, can cause an automatic stop.

Well, your rise2=rise1+10e-6 is not going to create an event. It's just an addition. Even if it did create an event, it's adding 10u to the rise time, not the time at which the rise time was measured. You also didn't declare rise1 in your MDL code either. I think you want something like this:

alias measurement tran_autostop
 {
    export real rise1
    real tcross
    real clkDel

    run tran
    rise1=risetime(sig=V(clk_en), initval=0, inittype='y, finalval=1.8, finaltype='y, theta1=10, theta2=90)
    // find the time at which the risetime was measured - 90% of the finalval
    tcross=cross(sig=V(clk_en), dir='rise, thresh=0.9*1.8)
    // measure something 10us later
    clkDel=V(clk_en)@(tcross+10u)
  }

run tran_autostop

This will run for 10us beyond the point at which the rise time was measured (I tested it). The @ is an event operator, and is measuring the clk_en signal 10u after the time of the crossing.

Regards,

Andrew

Thanks Andrew. It's working. My first mistake was adding 10u to risetime to stop simualtion. That's not correct. tcross is correct one. Operator @ really helped me. Sorry about font, I will stick to default one.

Can vdd value be variable? Autostop is not working with VAR("vdd"). 

Is it possible to make stoptime=clkdel? Because expressions depending on stoptime like clip, are failing.

alias measurement tran_autostop
 {
 export
 real tcross
 real clkDel

run tran
 tcross=cross(sig=V(clk_en), dir='rise, thresh=VAR("vdd")/2)
 clkDel=V(clk_en)@(tcross+10u)
 }
run tran_autostop

Yes. This is covered in the MDL manual that I mentioned earlier in the section headed Accessing Netlist or Model Parameters. You wouldn't use a SKILL function (VAR("vdd")) in an MDL file; SpectreMDL knows about Spectre parameters, and since the vdd parameter would be in a parameters statement in the netlist - like this:

parameters vdd=1.8

you can simply reference it in the MDL:

alias measurement tran_autostop
 {
    export real rise1
    real tcross
    real clkDel

    run tran
    rise1=risetime(sig=V(clk_en), initval=0, inittype='y, finalval=vdd, finaltype='y, theta1=10, theta2=90)
    // find the time at which the risetime was measured - 90% of the finalval
    tcross=cross(sig=V(clk_en), dir='rise, thresh=0.9*vdd)
    // measure something 10us later
    clkDel=V(clk_en)@(tcross+10u)
  }

run tran_autostop

Regards,

Andrew

Parameter is working. How to assign new stop_time to output expressions? For e.g., I have clip(vout meas_start stop_time). Tried below code. It's not working. Please help.

alias measurement tran_autostop
 {
 export
 real tcross
 real clkdelay
 real stop_time

run tran
 tcross=cross(sig=V(ok_hv), dir='rise, thresh=vdd/2)
 clkdelay=V(ok_hv)@(tcross+2000/myfreq)
 stop_time=clkdelay
 }
run tran_autostop

That's not going to work. I'm assuming you're talking about adjusting an ADE output expression (using clip). For a start, you're not exporting clkdelay or stop_time, and even if you were, the dimensions are completely wrong (clkdelay is a voltage not a time, and hence so is stop_time). You could use the mechanism described in How to use an MDL script within ADE (remembering to set the mdlpsfoutput setting in current versions) to use an expression to read the exported results back into ADE, but in this case it's unnecessary.

The clip() function (see the documentation) accepts nil as the third argument which means that it will be the final x-value of the waveform. 

If you really need to know what the final x-value is in an ADE output expression, you can use lastVal(VT("/vout")) (use an appropriate signal name that you have in the design). As I said though, with clip() this is unnecessary you can just do: clip(VT("/vout") 13u nil) or something like that.

Andrew

I am injecting noise at noise_start=stop_time-20u. Is there a way to make noise_start as a function of some trigger? say, after clkok_rise, start noise.

By "injecting noise" what do you mean? How are you injecting it?

By the way, you're lucky I saw this, since nobody gets notifiers on post edits - only on the initial post which didn't include this additional question.

Andrew

Adding vsouce vdd noise by delaying it to stop_time-20u

I don't think you can alter the delay on a source on the fly based on a measurement. It's not obvious to me how that could be done anyway.

I had originally been assuming that you might be talking about turning transient noise on or off based on a measurement event; this ought to work (it works with .measure statements and asserts), but it doesn't work (for me) if the measurement is defined in MDL. I created a CCR earlier today about that.

Regards,

Andrew