How can I construct a flip flop or other similar VI?

Hi all,
I am trying to develop a hardware simulator and the hardware has some feedback in it. For starters, I'm trying to make a simple D flip flop. I can do this using a while loop and shift registers or a feedback node, but I have to make the module non-reentrant so that it stores the internal state between calls.
The problem with this is that I want to be able to put multiple flip flops on a diagram and if the VI is non-reentrant, which I have to do to use functional global variables, they all wind up sharing the same internal state, which is unacceptable. But of course, I can't make it reentrant, otherwise the next time I excute the flip flop VI, it won't be in the right state.
It seems that LabView needs a way to generate a VI that is re-entrant, but yet holds it's internal state on a PER-INSTANTIATION basis.
Any ideas?
Thanks,
Jason

JasonWB wrote:
Thanks - this seems to be working. I have an associate who claims he needs to change the name of the VI, even if it IS reentrant - I am looking into that. Thanks much for the help! I was getting confused with functional globals, thinking that was what I needed. So, I assume that as long as the particular instantiation is loaded into memory, it will hold all internal values in shift registers?
Your associate may be seeing something that could be tricking him into thinking that. Like if he is initializing the shift registers outside the loop, then the registers will not hold the previous value because they get re-initialized on each run. This has nothing to do with it being reentrant, it's just doing what it's wired to do.
Functional Globals are actually just subVIs that are not reentrant so that they can share data the same way a regular variable does.
And you're correct in that as long as the reentrant is in memory, the values in it's shift registers will hold.
Ed
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.

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