D flip flop

Discussion in 'Homework Help' started by MilK, Mar 9, 2008.

  1. MilK

    Thread Starter Member

    Mar 1, 2008
    25
    0
    Hi,

    How can i use a D flip flop 7474, to operate as a "memory" device?
    example: a user store some password into a system(using d flipflop). now, if he enter the password correctly, he have access to the system, if he enter 3 times wrong, its lock.

    for the 7474, clk signal must be connect to the clk input of chip only.

    any suggestion?

    The flipflop has a PR n CLR, should i make use of that?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,136
    1,786
    At one bit per FF you're going to need quite a few of them. You would be better off using a microcontroller for that purpose. If you still insist on a discrete logic implementation then I would suggest a gate array.
     
  3. razzler

    Member

    Feb 9, 2008
    16
    0
    how bits is the password?
     
  4. mik3ca

    Active Member

    Feb 11, 2007
    189
    0
    a bit can store 2 states.
    a byte stores 256 states.
    The ascii system is at least 7 bits long, typically 8.

    So to store 1 character, you need at least 4 7474's. you could use 1 74xxx73 (8-bit latch/flip-flop), but the best way to go is to use a microcontroller.
     
  5. MilK

    Thread Starter Member

    Mar 1, 2008
    25
    0
    Solved-:D thks
     
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