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Flip Flops

  1. Apr 6, 2005 #1
    Right now i am studying Introduction to Electronics and i am finding problem in understanding the Flip flops....
    I wanna know what purpose they solve ....
    Can some explain me edge triggered and jk flip flops..the basic purpose they solve and their applications and
    i have studied From Malvino and Leach but i could not grasp well..so i turn here to PF.
    Pls help
    Thx in advance
     
  2. jcsd
  3. Apr 6, 2005 #2
    Loads of stuff.......

    serial / parallel converters (shift register), counters, buffers, frequency dividers, multiplexers, encoders/decoders ...

    The JK basically has two inputs, two outputs and a clock. The outputs are inverted such that whatever is on Q is the opposite on Not Q. The inputs J and K define what the flip flop is to do to the outputs when there is an edge on the clock pin. This is to either make the outputs high, low, change from the current state or stay at the current state.
     
  4. Apr 6, 2005 #3
    I always liked it when flip flops were explained in terms of latches. Do you understand latches and their purpose for being? A latch can be thought of as a memory, it stores a value when a control signal is asserted. As you may guess, a memory has many, many applications.

    An edge triggered flip flop is similar to a latch except the write time can be considered instaneous. It only occurs on a control signal transition which is also instaneous in the ideal case. So an edge triggered flip flop is a memory with a zero write time. This is an advantage because now the input signal, the data to be written, only needs to be stable (or valid) for a minimum amount of time.

    Now before anybody gets too excited, there is no such thing as zero write time and for any flip flop there are two critical times that must be considered. The amount of time it takes the circuit to stabilize relative to the new input. Since the circuit should be stable before attempting the write this time occurs before the edge and is denoted as setup time, and the amount of time it takes to actually perform the write. This occurs after the edge and is called the hold time.

    So in reality a flip flop cannot operate at frequencies faster than the inverse of the sum of the setup and hold time. And technically as you go faster there is even more that you may have to consider, such as the rise time of the control and data signals. But that's another class...
     
  5. Apr 6, 2005 #4
    thx very muxh Delta and Egsmith for replying..
    yeah Egsmith i understand what Latch is.....and i understood initial statements but last some lines were hazy to me...
    Like u are referring to write andset up and hold time...i can't understood ..pls help.
     
  6. Apr 8, 2005 #5
    It's probably because I am using terms you are unfamiliar with. How would you describe a latch?
     
  7. Apr 9, 2005 #6
    i would describe latch as a device which sets or resets depending on the input and the output is connected to the s and output complement is connected to the r.
    there can be two types of it -clocked and unclocked .....

    i have read over it and i am finding their application in SWITCH DEBOUNCERS as confusing....i.e. what exactly they are doing in it and how to explain hold time and set up time..
     
  8. Apr 9, 2005 #7
    i think this is the type of multivibrator that is used in game shows too right?
     
  9. Apr 11, 2005 #8

    Astronuc

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