Feedback Frenzy

[SercoSteveB]

What are the values of Boolean Out 1, 2 & 3 following execution of the VI?

a) Boolean Out 1 = FALSE, Boolean Out 2 = FALSE, Boolean Out 3 = FALSE

b) Boolean Out 1 = TRUE, Boolean Out 2 = FALSE, Boolean Out 3 = TRUE

c) Boolean Out 1 = FALSE, Boolean Out 2 = TRUE, Boolean Out 3 = FALSE

d) Boolean Out 1 = TRUE, Boolean Out 2 = TRUE, Boolean Out 3 = TRUE

[nik35324]

D.

Pen and paper required to solve Feedback Frenzy. 

[crossrulz]

D

No pen and paper required.  You just have to understand that shift registers and feedback nodes are almost exactly the same thing and count the value delays.  It should become obvious (after about 30 seconds) that all three options are doing the same thing.

Now just to throw a kink into this.  Call this VI inside of a FOR loop that will run twice...

Spoiler

You will get all FALSE since the feedback nodes are initializing at start up (on first call) while the shift registers are initializing each time the FOR loop starts.  This can be fixed by moving the initialization of the feedback nodes to the loop.

[Matt-A.]

Yes.  I had to draw this one out. 

D

[MrStevenUND]

D.  You should be able to do this by inspection if you know how shifts and feedback nodes work.  The bottom one did trip me up a bit though, but T, T, F isn't an option.

[jwscs]

thank you, that was very informative!

now i understand shift registers .. i mean feedback nodes

[Tsjabrantes]

Letter D is the correct answer. You have to set in your mind that feedback node is like a shift register.

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SercoSteveB escreveu:

What are the values of Boolean Out 1, 2 & 3 following execution of the VI?

a) Boolean Out 1 = FALSE, Boolean Out 2 = FALSE, Boolean Out 3 = FALSE

b) Boolean Out 1 = TRUE, Boolean Out 2 = FALSE, Boolean Out 3 = TRUE

c) Boolean Out 1 = FALSE, Boolean Out 2 = TRUE, Boolean Out 3 = FALSE

d) Boolean Out 1 = TRUE, Boolean Out 2 = TRUE, Boolean Out 3 = TRUE

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[SercoSteveB]

Answer: D,  nice one all.  

Does anyone have any rules around when they decide to use a Feedback Node over a Shift Register or visa-versa?

[crossrulz]

My general rule is that if the value is needed after the loop, use a shift register.  Otherwise I find the Feedback Node simplifies wiring.

The other time for shift registers is in State Machines and Queued Message Handlers.  The shift register is holding state information that all cases need, so a shift register will make the wiring cleaner here.

[Sprats]

I am taking CLAD exam on sep 7th and I am preparing myself without coaching. .. I am so tense. Any simple tips to review whole topics and also any materials related to the newly added syllabus ( Hardware).. please let me know. That would be a great help......I like this blog a lot.learned many new concepts 

[levonsg]

D