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Homework Help: Modulo 2 long division attempts

  1. Mar 22, 2013 #1
    Hello, could someone please confirm if have done the modulo 2 division in order to find the CRC code word for these two correctly.

    1) using the CRC polynominal 1011, for the information word 0101 1001
    (attached image 1 is my attempt)

    2) using the CRC polynominal 1101, for the information word 0100 1101
    (attached image 2 is my attempt)

    Thank you kindly for any confirmation.

    Attached Files:

  2. jcsd
  3. Mar 22, 2013 #2


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    Homework Helper

    You can check these by converting to decimal. For the first one, 1011001000 is 712, 1011 is 11. 712/11 is 64 remainder 8. You got 65 remainder 3. I'll give you a hint where you went wrong. 1000-1011 isn't 11. It's negative.
  4. Mar 22, 2013 #3
    hello, thanks kindly for your help.
    However, I just can't see what I have done wrong with that final operation on the first question.
    I ended up with remainder 11 after I performed the XOR operation on 1000 and 1011.
    How could I get another result. I thought the rule with modulo 2 division was to use XOR ?

    Thanks for any clarification.
  5. Mar 23, 2013 #4


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    Homework Helper

    It is, and CRC's use the same type of math. Your answers look OK to me.
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