questions..???

Discussion in 'General Electronics Chat' started by sunil_r_sp, May 20, 2007.

  1. sunil_r_sp

    Thread Starter Member

    Feb 18, 2007
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    1) I hav seen some text's mention XOR gate as a universal gate...Is it true ?
    2) Does an edge triggered circuit have race around problem......Isn't it applicable only to level triggered circuits..?
     
  2. Dave

    Retired Moderator

    Nov 17, 2003
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    Can you show us the texts where you have seen this information?

    As a suggestion, why don't you give us what you think are the answers to these questions and we can help you from there. Learning on here is a two way process.

    Dave
     
  3. Papabravo

    Expert

    Feb 24, 2006
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    1) No
    2) Race conditions happen in asyncronous circuits. Edge triggered and level triggered circuits are both syncronous. Syncronous circuits have a related problem called metastability, which is related to setup and hold time violations.
     
  4. sunil_r_sp

    Thread Starter Member

    Feb 18, 2007
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    I saw this as a question in the text "Digital Design Principles and Practices"
    by John F. Wakerly
    .......
    it was given in the text in the form of a question .........the question was......Is there any other gate other than XOR, NAND & NOR that can be configured as a universal gate....:)
     
  5. Dave

    Retired Moderator

    Nov 17, 2003
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    Looking at an XOR gate, you can make a NOT gate by tying one of the inputs to Vdd, but I can't see you can make an AND or OR gate.

    As a curiosity, in the "Digital Design Principles and Practices" textbook, can you tell us how the author expresses the concept of Universal Gate?

    Thanks.

    If the hold-time is large and the contamination delay is small, then data in an edge-triggered pipeline (for example back-to-back registers) can become corrupted. This is the race condition, also known as a hold-time failure, and is only overcome through logic-system redesign and not by alteration of the clock-rate.

    Dave
     
  6. sunil_r_sp

    Thread Starter Member

    Feb 18, 2007
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    the concept of universal gate is the same "a gate which can be used to realize the basic gate (AND,OR,NOT), as well as any other logic"........if it possible to realize a NAND or NOR using XOR then the job is done....
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
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    I have to start graveyard shift on Monday night, so I'm staying up as late as I can tonight. I just spent about 2.5 hours playing with XOR gates in Eagle Light, trying to get a NOR or NAND result. No dice.

    I got several combinations which would follow one input or the inverse while ignoring the other input. I got many which were simply XOR or XNOR. I got a few which always output a zero or a one, regardless of i/p.

    I won't say it can't be done just because I couldn't do it, but I will say that it won't be done my me.:D I'm going for a walk now.
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    From experience with older computers, I would sugest that the NOR gate is quite universal, as is the NAND. Like thingmaker, I can't see how to make much of anything out of an XOR gate, or combinations thereof.

    As an exersize, try making a 2 input AND gate using the XOR function.
     
  9. Papabravo

    Expert

    Feb 24, 2006
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