Finding next state equation for UV flip flop?

Discussion in 'Homework Help' started by Gonzalo Armbrust, Oct 28, 2015.

  1. Gonzalo Armbrust

    Thread Starter New Member

    Jun 28, 2015
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    "A M-R flip-flop behaves as follows:
    If MR = 00, the flip-flop does not change state.
    If MR = 10, the flip-flop is reset; i.e. Q=0.
    If MR= 11, the flip-flop changes state.The input combination
    MR = 01 is not allowed.
    Give the next state equation for this flip flop"


    I have no idea how to solve this, could anyone provide any hints / clarifications that might help me out?
     
  2. WBahn

    Moderator

    Mar 31, 2012
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    Is this a "UV" flip flop or a "M-R" flip flop?

    Look at the next state equations for a JK flip flop. The idea is very similar.
     
  3. Gonzalo Armbrust

    Thread Starter New Member

    Jun 28, 2015
    16
    0

    It's an M-R flip flop, I apologize that was a typo. I have worked out a table for the solution and I think I may have gotten it:


    x's are labeled as don't cares

    M | R| Q | Q(+)
    x 0 0 0
    ------ 0 1
    1 x 1 0
    0 0 1 1

    when Q and Q(+) are both set to zero, this satisfies the condition in which MR = 00 and when MR = 10, since Q and Q(+) does not change state, and it also "resets" to 0, so m could be either 1 or 0, or just labeled as a don't care. The case of 01 is ignored since it is not allowed. The conditions are reversed for when Q = 1 and Q(+) = 0, this means MR = 10 and also equal to 11 since the values compliment. At Q and Q(+) = 1, MR has to be equal to 00 since it does not change state...

    is this correct?
     
  4. WBahn

    Moderator

    Mar 31, 2012
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    I have no idea what the line in your table is that has all the hyphens.

    Using TABLE tags might help.

    You are talking about Q(+) as thought it is one of your inputs.

    Your table doesn't cover the case where MR = 11 and Q = 0.
     
  5. Gonzalo Armbrust

    Thread Starter New Member

    Jun 28, 2015
    16
    0

    the line with the hyphens I used to show that the case in which MR = 01 is not allowed in the problem. For a certain part, I was asked to fill out the corresponding characteristic table with the correct MR inputs, so I was given:

    // MR are left blank for me to fill out

    Q | Q(+) | M | R
    0 | 0 | |
    0 | 1 | |
    1 | 0 | |
    1 | 1 | |

    I don't know how to use table tags.

    Since I was given this specific table to fill out, I need to find the U and V inputs that satisfy these conditions, so for example M = 0 and R= 0, when Q is 1 and Q(+) is 1, since the state does not change from Q, to Q(+). Would my table be correct for these circumstances?
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    4,796
    What are these 'U' and 'V' inputs that you keep talking about?
     
  7. Gonzalo Armbrust

    Thread Starter New Member

    Jun 28, 2015
    16
    0

    Nevermind! I solved it earlier today. Thank you for the help
     
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