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Design Languages >> Verilog-AMS >> Enforcing event driven analog simulation point
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Message started by CADGuy on Oct 26^th, 2016, 1:01am

Title: Enforcing event driven analog simulation point
Post by CADGuy on Oct 26^th, 2016, 1:01am

I am facing an issue with simulator (APS liberal) missing intermediate points on the edge for edge-triggered D flipflops.

I have a design with sequences of D-Flipflops, which effect the state of the outputs. These flipflops are edge triggered.

With Transient liberal settings, the timestep taken by APS(spectre) are not capturing the minimum three points in the input of the D-flipflops everytime. It is giving many times just two points of the changing state and missing an intermediate point. This proves that the time-step algorithm is not able to resolve the points needed to correct operation correctly.

As a solution of this, I am attaching a dummy verilog-A to the inputs of D-flipflops and enforcing a point by @cross event. With Verilog-A, I dont have to change simulator settings and hence I am saving simulation points that way.

Is there a better solution than using the dummy Verilog-A?
Please no answers on updating relref/lteratio.

Title: Re: Enforcing event driven analog simulation point
Post by kemiyun on Oct 26^th, 2016, 5:07am

It sounds like what you're looking for is "strobe" option. It allows you to put simulation steps periodically.

If you don't want to go into sim settings I guess verilogA is an alternative, but cross event also has a tolerance you need to set tight tolerances for max accuracy whereas strobe just calculates a point accurately.

Edit: I think I misunderstood your problem, if you don't know when to strobe accurate verilogA is the only solution I can think of. You can also run a preliminary simulation, note the crossing using last_crossing function in verilogA and then strobe on those points. This can also be scripted actually.