Does a Flip flop store data or move data or both

Discussion in 'Homework Help' started by Yami, May 23, 2016.

  1. Yami

    Thread Starter Member

    Jan 18, 2016
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    Hi I've got exams tomorrow and I've been doing some exercises. I've got this multiple choice question for :- A flip flop can a)store data b)Move data c)Both a and b ....... I thought it was "c" but doing some searches on the internet I'm confused. This was not clearly explained to us in class.
     
  2. WBahn

    Moderator

    Mar 31, 2012
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    Well, give an example in which you think a flip flop stores data and then give an example in which you think a flip flop moves data.
     
  3. Yami

    Thread Starter Member

    Jan 18, 2016
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    shift register - data movement
    shift register - data storage
    shift registers are made up of flips flops. That's what I had in mind? am I on the right track?
     
  4. Yami

    Thread Starter Member

    Jan 18, 2016
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    Partly related to this is I've got this other question about "Another name of standard ring counter is ?" Its my understanding that Johnson counter is a variation of the ring counter not another name for it. I did some google searches no luck. Is there another name for Ring counters?
     
  5. WBahn

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    Mar 31, 2012
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    But the question isn't asking about what circuits that are made up of flip flops do. Otherwise you could answer that they count, for instance.

    It is asking what the flip-flop, by itself, can do.
     
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  6. Yami

    Thread Starter Member

    Jan 18, 2016
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    Ah! So it should be stores data
     
  7. WBahn

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    Mar 31, 2012
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    Yes.
     
  8. Yami

    Thread Starter Member

    Jan 18, 2016
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    Cool, thanks so much for the help.
    Also could you please shed some light into my next question
    Appreciate the help very much
     
  9. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    I am confused too then :)

    If we have a short pipe with water flowing through it, the water gets from one end to the other. If we put ten of these together end to end, we have a longer pipe. We do not however say that each section is not able to transfer water anymore just because it is connected to the other short sections now.

    In a shift register, each flip flop acts as part of the whole thing, but each one transfers one bit at a time as well as acts as storage. There are a lot of kinds of flip flops too. The D flip flop is sometimes said to 'transfer' the bit on the D input to the Q output when the clock goes high (or low).

    This leads me to think that they can both store and move data. Of course this also assumes that you have already studied shift registers or something like that in the course.
     
  10. WBahn

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    Mar 31, 2012
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    The question isn't asking about shift registers, it is asking about a specific device known as a flip flop.

    If you are going to say that a flip flop moves data because a circuit that is composed of flip flops can data, then why couldn't you say that a flip flop counts since a circuit composed of flip flops can count?

    The notion that a flip flop moves data from its input to its output is somewhat spurious -- what logic circuit can't be said to move something from its input to its output?
     
  11. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hello again,

    Well, counting off some integers:
    0,1,2,3,4,5,...

    If you want to say that a single flip flop does not actually count anything then you have to state that transitioning from 0 to 1 is not counting while going beyond that is counting. I happen to view going from 0 to 1 as counting as well as farther up the line. Therefore i have to view a flip flop as a 1 bit counter.

    There are a lot of 1 bit devices really. A one bit adder will add:
    0+0=0
    1+0=1
    0+1=1
    1+1=0

    It looks like this last entry isnt adding, but it's only a 1 bit adder so the msb gets truncated.

    I tried to show how the short pipe was transferring something when it was part of the larger pipe, but that means it must be transferring something on it's own too, so the short pipe is viewed as a microcosm of the full width pipe...it's the same thing just smaller.

    The D flip flop is interesting because it takes the input on the D and transfers it to the output, but only on the clock transition. So the data on D can be there for a year but not transferred, then all of a sudden a clock transition happens and the data is now on the output. That seems to behave as data movement.

    I dont know about an amplifier though, if we could consider that to move data, but a multiplexer seems to 'enable' data. So what i am saying here is that i dont think we should disqualify the Flip Flop as moving data just because other things might seem to move data too. I suspect this could be more a question of philosophy than electronics.

    Defining MOVE:
    verb
    1. go in a specified direction or manner; change position. change the place or position of.
    2. change or cause to change from one state, opinion, sphere, or activity to another.
    Depending on how we interpret this, i think we could say either way. However, if we can find one definition that says that we can call it a 'move' then it's hard to say that we can never say that it 'moved'.

    Flip flop data movement is not restricted to shift registers either. Suppose we have an 8 bit wide register of flip flops, and a 'buffer' set on the output of those 8 (8 more). When we clock the second buffer set, the data moves from the D inputs to the Q outputs, all 8 at the same time. It's hard to say that it did not move because the D inputs could be internal to the IC chip while the Q outputs are accessible to the user on the output pins of the IC chip. Thus, the data 'moved' from the internal storage to the external pins. This happens sometimes when the internal data can change while the user is reading the output pins, and if there was no buffer the user might read some bits that changed and some that didnt change yet. With the buffer, the internal clock is responsible for the "data transfer" which makes a stable copy available on the outputs (which is a different physical place than the internal D inputs). So it appears to both store and move data.
     
  12. WBahn

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    Mar 31, 2012
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    But you keep talking about circuits that USE flip flops as a part of them. For example, your description of a single flip flop counting from 0 to 1 is not something that a single flip flop does -- this behavior is the result of a larger circuit (even if that larger circuit consists of how the flip flop is wired) that uses the flip flop as one element of it. Also, if changing from a 0 to a 1 qualifies as "counting", then when asked what an inverter does we would need to say that it counts. The same with your register example -- it behaves that way not because of how a flip flop behaves, but because of how a larger circuit that uses flip flops behaves. If that is the criteria, then we have to conclude that a flip flop does anything any computer that uses flip flops does.

    It could be argued that a DFF "moves" data from its input to its output, though I think that that is a rather trivial and specious claim. But what about other flip flops, such as a TFF. What data is being moved there? But ALL flip flops (which is what the question appears to be asking about) store one bit of information, with the specific bit of information being a function of the inputs to the flip flop and possibly the current piece of information stored.
     
  13. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    In order to understand the operation of anything you have to look at the circuits it is used in. If not, then a flip flop does nothing because it has no input excitation :)

    Seriously? You must know the difference between an inverter and a T flip flop :)
    A "T" flip flop can count 0, 1, 0, 1, but it's counting things, which are the positive transitions of the T input and there is a delay in response as it does not change state again until the next rising edge. The inverter changes state as soon as the input changes LEVEL, so there is no counting action going on. Totally different actions.

    I used the D flip flop because it is easy to understand. I was going to progress to the JK type next if needed. Since you went to the T flip flop we can talk about that also.

    So we look at all the Trees in the woods, and we see Oak and Maple and Redwood. When someone asks us if a tree in those woods can be Maple, do we say "no" because they are not all maple? Only if they ask us if ALL the trees are maple do we have to say "no" because they are not all maple only some of them are.

    The D flip flop appears to move 1 bit of data from it's D input to it's Q output, and this appears to be a realistic physical movement because the two pins could be on opposite sides of the IC package. The T flip flop does not appear to be moving anything because it's outputs change state as the clock goes high, so the function there appears more like counting or dividing than moving. So we cant say that all flip flops move data, but some do appear to move data.
    So back to the question, "Can a flip flop move data?", and the answer could be "yes" because we found "a flip flop" and it was moving data :)
    If you wanted to specify what type could do this, i guess you would be free to do so.

    I have also read articles on the web about flip flops moving data. We could look around more too if you would like to see what we could find.
     
  14. Yami

    Thread Starter Member

    Jan 18, 2016
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    The same question poped up at exam yesterday. After the exam I had a bit of discussion with my teacher and he said that the answer would be that a flip flop can move data and store data. I tried to explain the reasons that's explained here and even showed him this forum topic. He didn't buy it.
     
  15. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Obviously your teacher made up his lesson plan and promptly closed his mind. Sad, you seem to know what you are doing and still got a fail for having a better answer than he does.

    The only way I know of that a flip flop can move data by itself is if I put it in my pocket and drive to Cleveland.
     
    Last edited: May 25, 2016
  16. WBahn

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    Mar 31, 2012
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    The question DID as about ALL flip flops! At least that is my reading of it -- and maybe that is where the mismatch is coming. If asked about flip flops, I interpret that as being asked to describe those features that the class of things called "flip flop" share. I do not interpret as asking me describe the possibly unique characteristics of one particular flip flop.

    Using your tree example, if I were taking a biology class and I was asked to describe a tree, I would not expect to get good marks if I said trees have apples on them.

    So I think we are going to have to agree to disagree.

    It would be interesting to see what the "correct" answer was on this exam.
     
  17. MrAl

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    Jun 17, 2014
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    Hi again,

    Yes the exact wording comes into play, and i do agree with you in part also.

    I do see one more thing here though, and that is that i think you should notice that there is no 'correct' answer to this, if by that you mean that there is some universally accepted correct answer. If you just mean that the correct answer is the one the professor happened to like and declares himself (acting as King of the class) as correct, then i agree there would only be one correct answer. But in general this seems to fall into the domain of the purely philosophical where sometimes there is no one correct answer (the tree falling in the woods, is a hole in the ground real, etc.). This would mean that whoever read the question might interpret it differently or just come up with different answers depending on the application.

    So i believe we have reached what is sometimes called an impasse, but on the other hand i dont disagree completely either :)
     
  18. WBahn

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    Oh, I agree that there often isn't an absolute correct answer to a question like this. Nor do I say that I would necessarily agree with the instructor's chosen answer. Part of that would depend on the way they had presented the material -- in particular how they described the flow of data in a component and a system.
     
  19. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    https://en.wikipedia.org/wiki/Ring_counter

    ak
     
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