MESSAGE
| DATE | 2014-12-15 |
| FROM | Ruben Safir
|
| SUBJECT | Subject: [LIU Comp Sci] [Samir.Iabbassen@liu.edu: RE: NOTE ERROR:****Error in the Hamming
|
From owner-learn-outgoing-at-mrbrklyn.com Mon Dec 15 09:07:47 2014
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Date: Mon, 15 Dec 2014 09:07:45 -0500
From: Ruben Safir
To: learn-at-nylxs.com
Subject: [LIU Comp Sci] [Samir.Iabbassen-at-liu.edu: RE: NOTE ERROR:****Error in the Hamming
notes on the final review]
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----- Forwarded message from Samir Iabbassen -----
Date: Mon, 15 Dec 2014 01:02:12 +0000
From: Samir Iabbassen
To: Ruben Safir
Subject: RE: NOTE ERROR:****Error in the Hamming notes on the final review
I have no idea which specifications you are referring to, but if you want references from material we used please check the power point presentation on page 22 and chapter 5.
Regards,
Samir
________________________________________
From: Ruben Safir [mrbrklyn-at-panix.com]
Sent: Sunday, December 14, 2014 5:18 AM
To: Samir Iabbassen
Cc: learn-at-nylxs.com
Subject: NOTE ERROR:****Error in the Hamming notes on the final review
I'm looking at the hamming notes and I don't think it is right.
P4=P4 (x)? 0 (x)? 1 (x)??0 =1
Not accoding to how I see it
d8 d7 d6 d5 p4 d4 d3 d2 p3 d1 p2 p1
1100 1011 1010 1001 1000 0111 0110 0101 0100 0011 0010 0001 (r = 4)
1 0 1 0 1 0 0 1
P4 is 1 (x) 0 (x) 1 (x) 0 which is 0 (not 1)
The origianl party writen p4 -> p1
0010
After the flip of 5
0111
0010
0111
_____
0101
which is the 5th position...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I don't understand why this is being done BACKWARD though.
According to the Specification why are you not counting from
left to right from position 1 -> 12. It should look like this:
Draw the diagram
p1 p2 d1 p3 d2 d3 d4 p4 d5 d6 d7 d8
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 (r = 4)
1 0 1 0 1 0 0 1
p1 ~ xor(d1,d2,d4,d5,d7) all 0001 positions
1 xor 0 xor 0 xor 1 xor 0 = 0
p2 ~ d1 d3 d4 d6 d7
1 xor 1 xor 0 xor 0 xor 0 = 0
p3 ~ d2 d3 d4 d8
0 1 0 1 = 0
p4 ~ d5 d6 d7 d8
1 0 0 1 = 0
Parity Bits are 0000
Total Message is
0010010001001
if 5 flips
p1 p2 d1 p3 d2 d3 d4 p4 d5 d6 d7 d8
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 (r = 4)
1 0 1 0 0 0 0 1
the calculated parity is now
p1 10000 = 1
p2 11000 =0
p3 0101 = 0
p4 0001 = 1
0000
1001
____
1001 = d5
which means I need to read the question better because you asked to flip
posiiton 5 in the stream and not position 5 of the data .... but the
math all works.
NOTE: I couldn't understand why you reverse the order? Maybe this was
an IBM Bigended bits problem. I don't know but it makes it a PIA to map
out. And I thought it was inconstitant with the textbook but then I
notices that although the text maps the data data like I do, he then, at
the last step says
"Let us verify that this scheme works with an example. Assume that
the 8-bit input word is 00111001, with data bit D1 in the rightmost
position."
Damn - why do this backwards!
----- End forwarded message -----
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