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

1. ### ferrero Thread Starter New Member

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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 ​

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!

2. ### hgmjr Moderator

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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 Thread Starter New Member

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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 +

Last edited: May 16, 2009
4. ### ferrero Thread Starter New Member

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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 Moderator

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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 Moderator

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Did you use the "MANAGE ATTACHMENTS" button to attach your diagram?

hgmjr

7. ### ferrero Thread Starter New Member

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here you go...

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8. ### hgmjr Moderator

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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 Thread Starter New Member

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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

thanks...

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10. ### hgmjr Moderator

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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