Building A Comparator Using Fs

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transgalactic

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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:

**broken link removed**
 

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

**broken link removed**
 
hi,
Looked at the link, I cannot identify what the square blocks are supposed to represent.????
 
transgalactic said:
its B (borrow) and D (the resolt)
Click to expand...

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

Its just the bottom two elements of the magnitude comparator.
 
Last edited:
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.
 
Papabravo said:
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.
Click to expand...

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

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

??????
 
Last edited:
transgalactic said:
i have presented a question and the effort i tried to understand it
how to implement a comparator using FS(full substructor) components
???
??????
Click to expand...

Hi,
It was difficult to follow your question, the problem is that many abbreviations, like Fs, can mean different things when no context is given.

I Googled for Full subtractor got these results.
Do they answer your question,?

**broken link removed**

**broken link removed**

**broken link removed**
 
in those links there is no implementation of a comparator using Full subtractor components.

so i need to decide that by the least digit of their subtraction which on is bigger?????????

cause i need to build it using "full subtractor " components

and i cant understand the circuit of the solution
which i presented in the first thread
 
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