I need Urgent Help PLEASE

Discussion in 'Homework Help' started by nadia23, Sep 29, 2013.

  1. nadia23

    Thread Starter New Member

    Sep 29, 2013
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    I am not sure I am posting my question in right place or not sorry for that in advance, I got and assignment which is due tomorrow:( in Computer System, I will be so thank full if anyone can help me please.:)

    You have a sensor that outputs a logic level to indicate that a warm object (presumed to be a human) is in the surveyed area. There is also a pulse every second. Produce a circuit that outputs a logic signal to an alarm if the sensor has been outputting and occupied signal for more than 4 seconds. Only concern yourself with the sensor output at the time of the second pulses – it is assumed that nothing of interest could change during the one second between pulses. Your design should provide for a reset signal that turns the alarm off and you can assume that this will be done as soon as the unit is turned on. Your alarm should continue to sound until the reset signal is given.

    The Hint Which is given:
    One is to count the clock pulses that occur while the input is set to one and to reset the count to zero should the input be zero at pulse time. If the count ever reaches 4 set a flip flop the Q output of which is the alarm output. The reset should zero the counter and reset the alarm flip flop.

    • The second is to shift the input states into a three bit shift register, with the three shift register Q outputs and the input signal and the timing pulses going to a 5 bit AND gate. The output of this gate goes to a flip flop whose Q output drives the alarm. On reset this flip flop and the shift register should be cleared (actually only one bit of the shift register needs to be cleared as this will ensure that the output of the AND gate ceases to be true).
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    This goes under Homework Help.

    As the forum title says, we help with homework, not do your homework for you.
     
  3. nadia23

    Thread Starter New Member

    Sep 29, 2013
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    Thanks For your reply, but I didn't ask to do my all homework I asked about general help like giving me an idea how should I design the circuit in cedar or some other software.
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Then start.
    Show us what u have got so far.

    Q !!
    What is cedar ?

    Do you have any experience in any design software ?
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    The Hints give you two options. Which do you want to use?
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    Actually, you didn't ask anything at all. You stated that your homework was due tomorrow and that you would be thankful if anyone could help you. Then you simply posted the problem and the hints you were given.

    You need to show YOUR efforts to work YOUR homework. That then serves as a starting point for discussions in which we can see where you are getting stuck and how we might be able to nudge you in the right direction.
     
  7. nadia23

    Thread Starter New Member

    Sep 29, 2013
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    I was confused how to elaborate the hint to start the assignment.
    The problem is I can't start the assignment till I don't know the design.


    Cedar is a software that we can draw the circuits anc can check it.

    My question in here is:

    What is 5 bit And Gate?
     
    Last edited: Sep 30, 2013
  8. nadia23

    Thread Starter New Member

    Sep 29, 2013
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    and according hint one, How can I count the clock pulses to reach up to 4 then set a flipflop.
     
    Last edited: Sep 30, 2013
  9. WBahn

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    Mar 31, 2012
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    Strictly speaking, it could refer to one of two things. It could refer to five 2-input AND gates configured so that two 5-bit values are applied to the inputs and the result is a 5-bit output in which each bit in the output is the AND of the corresponding bits from each input. Or, it could refer to a finve-input AND gate that has five inputs and a single output in which the output is the logical AND of all five inputs. The latter is what is meant here.
     
    nadia23 likes this.
  10. WBahn

    Moderator

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    With a counter.
     
  11. nadia23

    Thread Starter New Member

    Sep 29, 2013
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    Hey, I did as you suggested. But I'm getting this blue wire. I'm not sure how to fix it. Could you please help me? I have posted a screenshot below.[​IMG]
     
  12. WBahn

    Moderator

    Mar 31, 2012
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    So... what does a blue wire mean?

    Don't assume that everyone knows anything about the particular software tool you are using?

    My guess is that it has something to do with leaving unused inputs floating, which is something you should never do. And this goes for the reset/preset inputs on your flipflops, too.

    You should also, unless you have a darn good reason (which do exist), avoid doing asynchronous logic design. Thus, ALL of your flipflops should be clocked by the same clock signal. Otherwise, the onus is on you to properly analyze the design for critical race conditions and deal with any that exist.
     
  13. nadia23

    Thread Starter New Member

    Sep 29, 2013
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    I assume blue line means that the wiring not working properly that is it. I did connect the reset part as well but it didn't work too.
     
  14. nadia23

    Thread Starter New Member

    Sep 29, 2013
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    I am just following to do the second hint which they provided us, I am not very good with computer system
     
  15. WBahn

    Moderator

    Mar 31, 2012
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    Again, don't leave unused inputs floating. You have three inputs to the 8-input AND gate that are not connected to anything? Are they a logic False or a logic True?

    You don't know?

    Well, neither does the simulator.
     
    nadia23 likes this.
  16. nadia23

    Thread Starter New Member

    Sep 29, 2013
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    Thanks for your response but I already submit my assignment. I am using cedar which is software can design the gates there weren't anything 5 bits And gate so I used this one. I did connect the K out put with the D flip flop but nothing else with other three pins, lets see what will happen
     
  17. WBahn

    Moderator

    Mar 31, 2012
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    Well, then what will happen on this assignment will happen. In the future you will hopefully not wait until so late to start working on your assignment so that we can have the time necessary to help you find a complete solution.

    But hopefully you are sufficiently interested in the field you are studying to want to continue understanding how to solve this problem.
     
    nadia23 likes this.
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