# o/p 4-bit comparator

Discussion in 'Homework Help' started by zulfi100, Mar 24, 2013.

1. ### zulfi100 Thread Starter Member

Jun 7, 2012
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0
Hi,
Kindly guide me with the output of 2 2-bit comparators (i think its a 4-bit magnitude comparator) constructed by combing 2 xnor gates whose o/p is connected to a AND gate. When input 11 and 00 is supplied, i am getting 1 output though 11 and 00 are not same. Kindly guide me.

Zulfi.

Mar 31, 2012
18,087
4,917

3. ### zulfi100 Thread Starter Member

Jun 7, 2012
320
0
Hi,
The expression can be:
(P1 xnor Q1) and (P2 xnor Q2)
The circuit is shown at:

Kindly guide me.
Zulfi.

4. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
Now, what is another name for the XNOR gate? Specifically, it is HI when both inputs are ...?

In the example you started with, the four bits that were applied, 11 and 00, how did those four bits map to the two 2-bit numbers being compared?

5. ### zulfi100 Thread Starter Member

Jun 7, 2012
320
0
Ans. When inputs are same. Sorry I dont know the other name (wiki says enor or exnor).
Sorry. I dont understand this mapping term. 1100 is mapped to 11 xnor 00.

Kindly guide me.

Zulfi.

6. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
It is also known as the EQ, or EQUALITY, gate.

Well, look at the slides that you linked. In particular, slide #6.

7. ### zulfi100 Thread Starter Member

Jun 7, 2012
320
0
Okay. Thanks. I got it now. I should be:
comparing 00 & 11
so (0 xnor 1) and (0 xnor 1)= 0 (not same).