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Simulation time-advance cycle


Oct 1, 2022
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I am taking a course on digital design as part of my undergrad, and I am stuck on a homework problem. One part of the problem asks "explain how one should choose the simulation step size, if one does not just use a default value provided by the simulator."

I cannot find any mention of this in my digital design textbooks, the VHDL-2008 standard, or any search engine results. Can anyone tell me how the minimum simulation step size is determined and if a designer can have control over this value?

I read on a separate thread that the simulation can be either "event" simulation or "cycle" simulation. I am assuming that cycle simulation means the simulation step size is equal to 1/2 the clock rate. Would this then be the smallest useful step size?
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The time step should be brief enough so that changes are slight from one simulation frame to the next.

* To choose a reasonable length of time step, make it so between 100 and 10,000 of them fit into a frequency source you designate in your schematic.

* Certain events happen so fast that you need to choose a shorter time step in order to have detailed action show up in the simulation.

* Sometimes your scope trace is a lissajous figure. If the time step is too long then it causes a curve to appear to be drawn with straight lines. In that case try a shorter time step.

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