Shift register implementation of CRC- Please help!

Discussion in 'Homework Help' started by ferrero, May 16, 2009.

  1. ferrero

    ferrero Thread Starter New Member

    Joined:
    May 16, 2009
    Messages:
    5

    Hi guys... new here

    I have a problem with the following and hope all the gurus here can help me out on this


    Consider a transmission system using Cyclic Redundancy Check (CRC) technique with a
    generator polynomial ​
    10101. The receiver receives the following bit pattern:

    100111011000.
    (a) Draw a digital logic circuit for a shift register implementation of CRC.
    [8 marks]



    (b) Use the logic to evaluate the received bit pattern to see whether the bit pattern
    is error-free.​
    [12 marks]


    thank!:D
  2. hgmjr

    hgmjr Moderator Staff Member

    Joined:
    Jan 28, 2005
    Messages:
    9,030
    Location:
    Tennessee, USA (GMT-6)
    There are a number of very good articles on the Internet that present a solution that uses gates. Here is a pretty thorough article on CRC that covers the subject.

    hgmjr
  3. ferrero

    ferrero Thread Starter New Member

    Joined:
    May 16, 2009
    Messages:
    5
    :eek: thanks for the link hgmjr!


    so base on that article 10101 = 1*x0 + 0*x1 + 1*x2 + 0*x3 +1*x4

    therefore = 1 + x2 + x4

    but is the circuit like this?


    A<---B + C<---D +




    :confused::confused:
    Last edited: May 16, 2009
  4. ferrero

    ferrero Thread Starter New Member

    Joined:
    May 16, 2009
    Messages:
    5
    Please help to see if this is correct becoz the 12 mark question is ok for me... juz need to get the circuit right... pls?
  5. hgmjr

    hgmjr Moderator Staff Member

    Joined:
    Jan 28, 2005
    Messages:
    9,030
    Location:
    Tennessee, USA (GMT-6)
    Go ahead and take a stab at drawing up the CRC circuit and post it here. We can then make suggestions on what you need to adjust should a correction be needed.

    hgmjr
  6. hgmjr

    hgmjr Moderator Staff Member

    Joined:
    Jan 28, 2005
    Messages:
    9,030
    Location:
    Tennessee, USA (GMT-6)
    Did you use the "MANAGE ATTACHMENTS" button to attach your diagram?

    hgmjr
  7. ferrero

    ferrero Thread Starter New Member

    Joined:
    May 16, 2009
    Messages:
    5
    here you go... :D

    Attached Files:

  8. hgmjr

    hgmjr Moderator Staff Member

    Joined:
    Jan 28, 2005
    Messages:
    9,030
    Location:
    Tennessee, USA (GMT-6)
    I would imagine that you would need 5 stages rather that just 4, since there are five bits in your CRC term.

    hgmjr
  9. ferrero

    ferrero Thread Starter New Member

    Joined:
    May 16, 2009
    Messages:
    5
    i look at my coure notes and they only have A B C D for 5 bit 11001

    and this is how they drew it


    can you kindly enlighten me directly??... i am really confused now :confused::confused:

    thanks...

    Attached Files:

  10. hgmjr

    hgmjr Moderator Staff Member

    Joined:
    Jan 28, 2005
    Messages:
    9,030
    Location:
    Tennessee, USA (GMT-6)
    I stand corrected.

    You wrote the correct equation in your earlier post.

    I am used to the flow shown like the article that I linked you to earlier.

    One thing for sure, your vertical arrows should be pointing into the circled + signs rather than the flip/flops.

    hgmjr
Similar Threads
Forum Title Date
Homework Help Using shift registers to implement a stack Wednesday at 3:04 PM
Homework Help Help Needed in Shift Register Assignment.. Nov 11, 2014
Homework Help Bidirectional Shift Registers Sep 27, 2014
Homework Help Shift Registers Sep 15, 2014
Homework Help subtraction with shift register Sep 1, 2014

Share This Page