Korchemny, Dmitry wrote: [...] > Particularly for an unassigned freevar, it seems that > there is no requirement for the freevar to ever change. > How much simulator implementation variability is valid? > > [Korchemny, Dmitry] This is correct, but if the variable changes, there > will be an event. If my suggestion is accepted, this problem becomes > irrelevant. But *when* does such an event occur? If a simulator can decide to change a freevar, is there a defined region during which such a change must take place? Assume for a moment that freevars are "assigned" in the Observed region; if that is the case then the next reactive region process set would see the change "before" the normal active region processes. Is that reasonable? If a freevar "glitches" due to multiple evaluations of an assertion, is it ever important to have observability of that glitch? > From what I think I've heard, it seems unlikely to me that > inspecting or using a freevar value during simulation would > be terribly useful, particularly given the lack of > constraints on the implementation behavior in assigning to > the unassigned freevars. Is that the case? > > [Korchemny, Dmitry] I agree. > > If so, should all non-checker use of a freevar just be made illegal? > > [Korchemny, Dmitry] Yes, it makes sense. That certainly would reduce areas in which LRM specified behavior could diverge. There are still end-user expectations with respect to non-HDL references to the freevars (ie. vpi access, "wave window" viewing, etc). For those cases, I think that either we need to disallow any external visibility of freevars (which is likely very unappealing due to vpi expression access), or we should be deal with the scheduling issues related to the region in which freevars may change. Gord. -- -------------------------------------------------------------------- Gordon Vreugdenhil 503-685-0808 Model Technology (Mentor Graphics) gordonv@model.com -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.Received on Thu Mar 20 07:54:51 2008
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