i need to build a comparator
of 2 numbers (each number has two bits)

i think that we should subtruct them
and if the last bit (sign bit) equals to one then the top number is smaller

but here i get a totaly different solution
i cant unerstand it:

http://s290.photobucket.com/albums/ll279/t...nt=IMG_8812.jpg

 

hi,
Get the datasheet for the HEF4585 4bit magnitude comparator i/c

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Eric
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i know that implementation

i am asking about the logic of FS implementation
??

personally i thought if we substract the two input numbers
then we should know who is bigger by looking at the last bit
(the sign bit)

but here they are doing some other thing
what are they doing here:

http://s290.photobucket.com/albums/l...t=IMG_8812.jpg

 

hi,
Looked at the link, I cannot identify what the square blocks are supposed to represent.????

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Eric
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this squares are only the background paper

 

I dont mean the paper grid.!

The blocks with Fs and Hs written in them...

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Eric
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its B (borrow) and D (the resolt)

 

hi.
This is an extract from the HEF4585 datasheet that I refered to earlier.

Its just the bottom two elements of the magnitude comparator.

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Eric
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i am femiliar with this implementation

i am looking for the FS implementation

 

By analogy with adders, where we have the half adder and the full adder, and going out on a limb I'm guessing that Fs stands for Full Subtractor.

I think it is fair to say that if you want help on this forum you might want to reconsider the churlish attitude you are displaying.

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Thanks PB, I thought it was just me who thought his manner a little brusque.

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Eric
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PIC tutorials:
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i have presented a question and the effort i tried to understand it



how to implement a comparator using FS(full substructor) components
???

in the top thread there is a circuit that suposedly implements it
but i cant understand the logic behind it

??????

 

FS=Full Subtractor??

 

fs=full substructor

 

Probably help if you could spell it right.

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