Homework help!

Discussion in 'Homework Help' started by Sam1990, Feb 15, 2015.

  1. Sam1990

    Thread Starter New Member

    Feb 15, 2015
    2
    0
    Hi
    I am stuck at a problem in ASIC digital design: please help me out
    the problem is
    1]
    This is a design question. Please design a counter that counts the number of times the number “5” appears in a 4-bit input stream. The I/O is as follows:
    NumberIn: 4-bits wide (input)
    Start: Reset counter and overflow flag to zero while start is high (input)
    Count: 8-bit unsigned count (of the number of “5”s that have occurred since start went low (output)
    Overflow: Goes high if count overflows (count is unsigned, so you only need to monitor the adder carry out) and stays high until reset is asserted.
    I want to see a Register Transfer Level (RTL) schematic. Design this functional unit at the RTL level. An adder is required – you can represent this as a “+” unit – no need to design its detail. There is no need to optimize the design.
    The only flip-flop you can use is a D flip-flop, and its clock input can only be connected to “clock”. You can NOT use a flip-flop with preset or clear.
    An exemplar timing diagram can be found below (x=unknown).

    upload_2015-2-15_0-13-42.png
     
  2. WBahn

    Moderator

    Mar 31, 2012
    17,788
    4,808
    So.... what's your question?

    You need to show YOUR best attempt to solve YOUR homework problem.
     
  3. Sam1990

    Thread Starter New Member

    Feb 15, 2015
    2
    0
    Hi,
    i am beginner in this area, new to this subject
    and my question is how to approach the problem?
     
  4. WBahn

    Moderator

    Mar 31, 2012
    17,788
    4,808
    Break it into subproblems and then solve each of those in turn.

    You know that you need a circuit that counts whenever a particular event is seen. So make a circuit that counts only when a control signal is asserted and make another circuit that asserts a control signal only when the particular event is seen.
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,452
    3,371
    A title "Homework Help!" is no good to anyone.

    "How to count occurrences of a number in input stream?" is more descriptive of the thread.
     
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